Actual source code: snes.c

  1: #include <petsc/private/snesimpl.h>
  2: #include <petscdmshell.h>
  3: #include <petscdraw.h>
  4: #include <petscds.h>
  5: #include <petscdmadaptor.h>
  6: #include <petscconvest.h>

  8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
  9: PetscFunctionList SNESList              = NULL;

 11: /* Logging support */
 12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
 13: PetscLogEvent SNES_Solve, SNES_SetUp, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NewtonALEval, SNES_NPCSolve, SNES_ObjectiveEval;

 15: /*@
 16:   SNESSetErrorIfNotConverged - Causes `SNESSolve()` to generate an error immediately if the solver has not converged.

 18:   Logically Collective

 20:   Input Parameters:
 21: + snes - iterative context obtained from `SNESCreate()`
 22: - flg  - `PETSC_TRUE` indicates you want the error generated

 24:   Options Database Key:
 25: . -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

 27:   Level: intermediate

 29:   Note:
 30:   Normally PETSc continues if a solver fails to converge, you can call `SNESGetConvergedReason()` after a `SNESSolve()`
 31:   to determine if it has converged. Otherwise the solution may be inaccurate or wrong

 33: .seealso: [](ch_snes), `SNES`, `SNESGetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 34: @*/
 35: PetscErrorCode SNESSetErrorIfNotConverged(SNES snes, PetscBool flg)
 36: {
 37:   PetscFunctionBegin;
 40:   snes->errorifnotconverged = flg;
 41:   PetscFunctionReturn(PETSC_SUCCESS);
 42: }

 44: /*@
 45:   SNESGetErrorIfNotConverged - Indicates if `SNESSolve()` will generate an error if the solver does not converge?

 47:   Not Collective

 49:   Input Parameter:
 50: . snes - iterative context obtained from `SNESCreate()`

 52:   Output Parameter:
 53: . flag - `PETSC_TRUE` if it will generate an error, else `PETSC_FALSE`

 55:   Level: intermediate

 57: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetErrorIfNotConverged()`, `KSPGetErrorIfNotConverged()`, `KSPSetErrorIfNotConverged()`
 58: @*/
 59: PetscErrorCode SNESGetErrorIfNotConverged(SNES snes, PetscBool *flag)
 60: {
 61:   PetscFunctionBegin;
 63:   PetscAssertPointer(flag, 2);
 64:   *flag = snes->errorifnotconverged;
 65:   PetscFunctionReturn(PETSC_SUCCESS);
 66: }

 68: /*@
 69:   SNESSetAlwaysComputesFinalResidual - tells the `SNES` to always compute the residual (nonlinear function value) at the final solution

 71:   Logically Collective

 73:   Input Parameters:
 74: + snes - the shell `SNES`
 75: - flg  - `PETSC_TRUE` to always compute the residual

 77:   Level: advanced

 79:   Note:
 80:   Some solvers (such as smoothers in a `SNESFAS`) do not need the residual computed at the final solution so skip computing it
 81:   to save time.

 83: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESGetAlwaysComputesFinalResidual()`
 84: @*/
 85: PetscErrorCode SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
 86: {
 87:   PetscFunctionBegin;
 89:   snes->alwayscomputesfinalresidual = flg;
 90:   PetscFunctionReturn(PETSC_SUCCESS);
 91: }

 93: /*@
 94:   SNESGetAlwaysComputesFinalResidual - checks if the `SNES` always computes the residual at the final solution

 96:   Logically Collective

 98:   Input Parameter:
 99: . snes - the `SNES` context

101:   Output Parameter:
102: . flg - `PETSC_TRUE` if the residual is computed

104:   Level: advanced

106: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSolve()`, `SNESSetAlwaysComputesFinalResidual()`
107: @*/
108: PetscErrorCode SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
109: {
110:   PetscFunctionBegin;
112:   *flg = snes->alwayscomputesfinalresidual;
113:   PetscFunctionReturn(PETSC_SUCCESS);
114: }

116: /*@
117:   SNESSetFunctionDomainError - tells `SNES` that the input vector, a proposed new solution, to your function you provided to `SNESSetFunction()` is not
118:   in the functions domain. For example, a step with negative pressure.

120:   Not Collective

122:   Input Parameter:
123: . snes - the `SNES` context

125:   Level: advanced

127:   Notes:
128:   This does not need to be called by all processes in the `SNES` MPI communicator.

130:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

132:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

134:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
135:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

137:   You can call `SNESSetJacobianDomainError()` during a Jacobian computation to indicate the proposed solution is not in the domain.

139:   Developer Note:
140:   This value is used by `SNESCheckFunctionNorm()` to determine if the `SNESConvergedReason` is set to `SNES_DIVERGED_FUNCTION_DOMAIN`

142: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetJacobianDomainError()`, `SNESVISetVariableBounds()`,
143:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`,
144:           `SNES_DIVERGED_FUNCTION_DOMAIN`
145: @*/
146: PetscErrorCode SNESSetFunctionDomainError(SNES snes)
147: {
148:   PetscFunctionBegin;
150:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates input vector is not in the function domain");
151:   snes->domainerror = PETSC_TRUE;
152:   PetscFunctionReturn(PETSC_SUCCESS);
153: }

155: /*@
156:   SNESSetJacobianDomainError - tells `SNES` that the function you provided to `SNESSetJacobian()` at the proposed step. For example there is a negative element transformation.

158:   Logically Collective

160:   Input Parameter:
161: . snes - the `SNES` context

163:   Level: advanced

165:   Notes:
166:   If this is called the `SNESSolve()` stops iterating and returns with a `SNESConvergedReason` of `SNES_DIVERGED_FUNCTION_DOMAIN`

168:   You should always call `SNESGetConvergedReason()` after each `SNESSolve()` and verify if the iteration converged (positive result) or diverged (negative result).

170:   You can direct `SNES` to avoid certain steps by using `SNESVISetVariableBounds()`, `SNESVISetComputeVariableBounds()` or
171:   `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`

173: .seealso: [](ch_snes), `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESVISetVariableBounds()`,
174:           `SNESVISetComputeVariableBounds()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESConvergedReason`, `SNESGetConvergedReason()`
175: @*/
176: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
177: {
178:   PetscFunctionBegin;
180:   PetscCheck(!snes->errorifnotconverged, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "User code indicates computeJacobian does not make sense");
181:   snes->jacobiandomainerror = PETSC_TRUE;
182:   PetscFunctionReturn(PETSC_SUCCESS);
183: }

185: /*@
186:   SNESSetCheckJacobianDomainError - tells `SNESSolve()` whether to check if the user called `SNESSetJacobianDomainError()` Jacobian domain error after
187:   each Jacobian evaluation. By default, it checks for the Jacobian domain error in the debug mode, and does not check it in the optimized mode.

189:   Logically Collective

191:   Input Parameters:
192: + snes - the `SNES` context
193: - flg  - indicates if or not to check Jacobian domain error after each Jacobian evaluation

195:   Level: advanced

197:   Note:
198:   Checks require one extra parallel synchronization for each Jacobian evaluation

200: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESGetCheckJacobianDomainError()`
201: @*/
202: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
203: {
204:   PetscFunctionBegin;
206:   snes->checkjacdomainerror = flg;
207:   PetscFunctionReturn(PETSC_SUCCESS);
208: }

210: /*@
211:   SNESGetCheckJacobianDomainError - Get an indicator whether or not `SNES` is checking Jacobian domain errors after each Jacobian evaluation.

213:   Logically Collective

215:   Input Parameter:
216: . snes - the `SNES` context

218:   Output Parameter:
219: . flg - `PETSC_FALSE` indicates that it is not checking Jacobian domain errors after each Jacobian evaluation

221:   Level: advanced

223: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSetFunction()`, `SNESFunctionFn`, `SNESSetFunctionDomainError()`, `SNESSetCheckJacobianDomainError()`
224: @*/
225: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
226: {
227:   PetscFunctionBegin;
229:   PetscAssertPointer(flg, 2);
230:   *flg = snes->checkjacdomainerror;
231:   PetscFunctionReturn(PETSC_SUCCESS);
232: }

234: /*@
235:   SNESGetFunctionDomainError - Gets the status of the domain error after a call to `SNESComputeFunction()`

237:   Not Collective, different MPI processes may return different values

239:   Input Parameter:
240: . snes - the `SNES` context

242:   Output Parameter:
243: . domainerror - Set to `PETSC_TRUE` if there's a domain error; `PETSC_FALSE` otherwise.

245:   Level: developer

247:   Notes:
248:   The value will only be true on those MPI processes that called `SNESSetFunctionDomainError()`

250:   The value is reset to `PETSC_FALSE` when `SNESCheckFunctionNorm()` is called.

252: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`
253: @*/
254: PetscErrorCode SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
255: {
256:   PetscFunctionBegin;
258:   PetscAssertPointer(domainerror, 2);
259:   *domainerror = snes->domainerror;
260:   PetscFunctionReturn(PETSC_SUCCESS);
261: }

263: /*@
264:   SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to `SNESComputeJacobian()`

266:   Not Collective, different MPI processes may return different values

268:   Input Parameter:
269: . snes - the `SNES` context

271:   Output Parameter:
272: . domainerror - Set to `PETSC_TRUE` if there's a Jacobian domain error; `PETSC_FALSE` otherwise.

274:   Level: advanced

276:   Notes:
277:   The value will only be true on those MPI processes that called `SNESSetJacobianDomainError()`

279:   The value is reset to `PETSC_FALSE` when `SNESCheckJacobianDomainerror()` is called but only `SNESSetCheckJacobianDomainError()` was called

281: .seealso: [](ch_snes), `SNES`, `SNESSetFunctionDomainError()`, `SNESComputeFunction()`, `SNESGetFunctionDomainError()`
282: @*/
283: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
284: {
285:   PetscFunctionBegin;
287:   PetscAssertPointer(domainerror, 2);
288:   *domainerror = snes->jacobiandomainerror;
289:   PetscFunctionReturn(PETSC_SUCCESS);
290: }

292: /*@
293:   SNESLoad - Loads a `SNES` that has been stored in `PETSCVIEWERBINARY` with `SNESView()`.

295:   Collective

297:   Input Parameters:
298: + snes   - the newly loaded `SNES`, this needs to have been created with `SNESCreate()` or
299:            some related function before a call to `SNESLoad()`.
300: - viewer - binary file viewer, obtained from `PetscViewerBinaryOpen()`

302:   Level: intermediate

304:   Note:
305:   The `SNESType` is determined by the data in the file, any type set into the `SNES` before this call is ignored.

307: .seealso: [](ch_snes), `SNES`, `PetscViewer`, `SNESCreate()`, `SNESType`, `PetscViewerBinaryOpen()`, `SNESView()`, `MatLoad()`, `VecLoad()`
308: @*/
309: PetscErrorCode SNESLoad(SNES snes, PetscViewer viewer)
310: {
311:   PetscBool isbinary;
312:   PetscInt  classid;
313:   char      type[256];
314:   KSP       ksp;
315:   DM        dm;
316:   DMSNES    dmsnes;

318:   PetscFunctionBegin;
321:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
322:   PetscCheck(isbinary, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Invalid viewer; open viewer with PetscViewerBinaryOpen()");

324:   PetscCall(PetscViewerBinaryRead(viewer, &classid, 1, NULL, PETSC_INT));
325:   PetscCheck(classid == SNES_FILE_CLASSID, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Not SNES next in file");
326:   PetscCall(PetscViewerBinaryRead(viewer, type, 256, NULL, PETSC_CHAR));
327:   PetscCall(SNESSetType(snes, type));
328:   PetscTryTypeMethod(snes, load, viewer);
329:   PetscCall(SNESGetDM(snes, &dm));
330:   PetscCall(DMGetDMSNES(dm, &dmsnes));
331:   PetscCall(DMSNESLoad(dmsnes, viewer));
332:   PetscCall(SNESGetKSP(snes, &ksp));
333:   PetscCall(KSPLoad(ksp, viewer));
334:   PetscFunctionReturn(PETSC_SUCCESS);
335: }

337: #include <petscdraw.h>
338: #if defined(PETSC_HAVE_SAWS)
339: #include <petscviewersaws.h>
340: #endif

342: /*@
343:   SNESViewFromOptions - View a `SNES` based on values in the options database

345:   Collective

347:   Input Parameters:
348: + A    - the `SNES` context
349: . obj  - Optional object that provides the options prefix for the checks
350: - name - command line option

352:   Level: intermediate

354: .seealso: [](ch_snes), `SNES`, `SNESView`, `PetscObjectViewFromOptions()`, `SNESCreate()`
355: @*/
356: PetscErrorCode SNESViewFromOptions(SNES A, PetscObject obj, const char name[])
357: {
358:   PetscFunctionBegin;
360:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
361:   PetscFunctionReturn(PETSC_SUCCESS);
362: }

364: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES, Vec, Mat, Mat, void *);

366: /*@
367:   SNESView - Prints or visualizes the `SNES` data structure.

369:   Collective

371:   Input Parameters:
372: + snes   - the `SNES` context
373: - viewer - the `PetscViewer`

375:   Options Database Key:
376: . -snes_view - Calls `SNESView()` at end of `SNESSolve()`

378:   Level: beginner

380:   Notes:
381:   The available visualization contexts include
382: +     `PETSC_VIEWER_STDOUT_SELF` - standard output (default)
383: -     `PETSC_VIEWER_STDOUT_WORLD` - synchronized standard
384:   output where only the first processor opens
385:   the file.  All other processors send their
386:   data to the first processor to print.

388:   The available formats include
389: +     `PETSC_VIEWER_DEFAULT` - standard output (default)
390: -     `PETSC_VIEWER_ASCII_INFO_DETAIL` - more verbose output for `SNESNASM`

392:   The user can open an alternative visualization context with
393:   `PetscViewerASCIIOpen()` - output to a specified file.

395:   In the debugger you can do "call `SNESView`(snes,0)" to display the `SNES` solver. (The same holds for any PETSc object viewer).

397: .seealso: [](ch_snes), `SNES`, `SNESLoad()`, `SNESCreate()`, `PetscViewerASCIIOpen()`
398: @*/
399: PetscErrorCode SNESView(SNES snes, PetscViewer viewer)
400: {
401:   SNESKSPEW     *kctx;
402:   KSP            ksp;
403:   SNESLineSearch linesearch;
404:   PetscBool      iascii, isstring, isbinary, isdraw;
405:   DMSNES         dmsnes;
406: #if defined(PETSC_HAVE_SAWS)
407:   PetscBool issaws;
408: #endif

410:   PetscFunctionBegin;
412:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &viewer));
414:   PetscCheckSameComm(snes, 1, viewer, 2);

416:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
417:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
418:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &isbinary));
419:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
420: #if defined(PETSC_HAVE_SAWS)
421:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
422: #endif
423:   if (iascii) {
424:     SNESNormSchedule normschedule;
425:     DM               dm;
426:     SNESJacobianFn  *cJ;
427:     void            *ctx;
428:     const char      *pre = "";

430:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)snes, viewer));
431:     if (!snes->setupcalled) PetscCall(PetscViewerASCIIPrintf(viewer, "  SNES has not been set up so information may be incomplete\n"));
432:     if (snes->ops->view) {
433:       PetscCall(PetscViewerASCIIPushTab(viewer));
434:       PetscUseTypeMethod(snes, view, viewer);
435:       PetscCall(PetscViewerASCIIPopTab(viewer));
436:     }
437:     if (snes->max_funcs == PETSC_UNLIMITED) {
438:       PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=unlimited\n", snes->max_its));
439:     } else {
440:       PetscCall(PetscViewerASCIIPrintf(viewer, "  maximum iterations=%" PetscInt_FMT ", maximum function evaluations=%" PetscInt_FMT "\n", snes->max_its, snes->max_funcs));
441:     }
442:     PetscCall(PetscViewerASCIIPrintf(viewer, "  tolerances: relative=%g, absolute=%g, solution=%g\n", (double)snes->rtol, (double)snes->abstol, (double)snes->stol));
443:     if (snes->usesksp) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of linear solver iterations=%" PetscInt_FMT "\n", snes->linear_its));
444:     PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of function evaluations=%" PetscInt_FMT "\n", snes->nfuncs));
445:     PetscCall(SNESGetNormSchedule(snes, &normschedule));
446:     if (normschedule > 0) PetscCall(PetscViewerASCIIPrintf(viewer, "  norm schedule %s\n", SNESNormSchedules[normschedule]));
447:     if (snes->gridsequence) PetscCall(PetscViewerASCIIPrintf(viewer, "  total number of grid sequence refinements=%" PetscInt_FMT "\n", snes->gridsequence));
448:     if (snes->ksp_ewconv) {
449:       kctx = (SNESKSPEW *)snes->kspconvctx;
450:       if (kctx) {
451:         PetscCall(PetscViewerASCIIPrintf(viewer, "  Eisenstat-Walker computation of KSP relative tolerance (version %" PetscInt_FMT ")\n", kctx->version));
452:         PetscCall(PetscViewerASCIIPrintf(viewer, "    rtol_0=%g, rtol_max=%g, threshold=%g\n", (double)kctx->rtol_0, (double)kctx->rtol_max, (double)kctx->threshold));
453:         PetscCall(PetscViewerASCIIPrintf(viewer, "    gamma=%g, alpha=%g, alpha2=%g\n", (double)kctx->gamma, (double)kctx->alpha, (double)kctx->alpha2));
454:       }
455:     }
456:     if (snes->lagpreconditioner == -1) {
457:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is never rebuilt\n"));
458:     } else if (snes->lagpreconditioner > 1) {
459:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Preconditioned is rebuilt every %" PetscInt_FMT " new Jacobians\n", snes->lagpreconditioner));
460:     }
461:     if (snes->lagjacobian == -1) {
462:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is never rebuilt\n"));
463:     } else if (snes->lagjacobian > 1) {
464:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is rebuilt every %" PetscInt_FMT " SNES iterations\n", snes->lagjacobian));
465:     }
466:     PetscCall(SNESGetDM(snes, &dm));
467:     PetscCall(DMSNESGetJacobian(dm, &cJ, &ctx));
468:     if (snes->mf_operator) {
469:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing\n"));
470:       pre = "Preconditioning ";
471:     }
472:     if (cJ == SNESComputeJacobianDefault) {
473:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences one column at a time\n", pre));
474:     } else if (cJ == SNESComputeJacobianDefaultColor) {
475:       PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using finite differences with coloring\n", pre));
476:       /* it slightly breaks data encapsulation for access the DMDA information directly */
477:     } else if (cJ == SNESComputeJacobian_DMDA) {
478:       MatFDColoring fdcoloring;
479:       PetscCall(PetscObjectQuery((PetscObject)dm, "DMDASNES_FDCOLORING", (PetscObject *)&fdcoloring));
480:       if (fdcoloring) {
481:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using colored finite differences on a DMDA\n", pre));
482:       } else {
483:         PetscCall(PetscViewerASCIIPrintf(viewer, "  %sJacobian is built using a DMDA local Jacobian\n", pre));
484:       }
485:     } else if (snes->mf && !snes->mf_operator) {
486:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n"));
487:     }
488:   } else if (isstring) {
489:     const char *type;
490:     PetscCall(SNESGetType(snes, &type));
491:     PetscCall(PetscViewerStringSPrintf(viewer, " SNESType: %-7.7s", type));
492:     PetscTryTypeMethod(snes, view, viewer);
493:   } else if (isbinary) {
494:     PetscInt    classid = SNES_FILE_CLASSID;
495:     MPI_Comm    comm;
496:     PetscMPIInt rank;
497:     char        type[256];

499:     PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
500:     PetscCallMPI(MPI_Comm_rank(comm, &rank));
501:     if (rank == 0) {
502:       PetscCall(PetscViewerBinaryWrite(viewer, &classid, 1, PETSC_INT));
503:       PetscCall(PetscStrncpy(type, ((PetscObject)snes)->type_name, sizeof(type)));
504:       PetscCall(PetscViewerBinaryWrite(viewer, type, sizeof(type), PETSC_CHAR));
505:     }
506:     PetscTryTypeMethod(snes, view, viewer);
507:   } else if (isdraw) {
508:     PetscDraw draw;
509:     char      str[36];
510:     PetscReal x, y, bottom, h;

512:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
513:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
514:     PetscCall(PetscStrncpy(str, "SNES: ", sizeof(str)));
515:     PetscCall(PetscStrlcat(str, ((PetscObject)snes)->type_name, sizeof(str)));
516:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_BLUE, PETSC_DRAW_BLACK, str, NULL, &h));
517:     bottom = y - h;
518:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
519:     PetscTryTypeMethod(snes, view, viewer);
520: #if defined(PETSC_HAVE_SAWS)
521:   } else if (issaws) {
522:     PetscMPIInt rank;
523:     const char *name;

525:     PetscCall(PetscObjectGetName((PetscObject)snes, &name));
526:     PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));
527:     if (!((PetscObject)snes)->amsmem && rank == 0) {
528:       char dir[1024];

530:       PetscCall(PetscObjectViewSAWs((PetscObject)snes, viewer));
531:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/its", name));
532:       PetscCallSAWs(SAWs_Register, (dir, &snes->iter, 1, SAWs_READ, SAWs_INT));
533:       if (!snes->conv_hist) PetscCall(SNESSetConvergenceHistory(snes, NULL, NULL, PETSC_DECIDE, PETSC_TRUE));
534:       PetscCall(PetscSNPrintf(dir, 1024, "/PETSc/Objects/%s/conv_hist", name));
535:       PetscCallSAWs(SAWs_Register, (dir, snes->conv_hist, 10, SAWs_READ, SAWs_DOUBLE));
536:     }
537: #endif
538:   }
539:   if (snes->linesearch) {
540:     PetscCall(SNESGetLineSearch(snes, &linesearch));
541:     PetscCall(PetscViewerASCIIPushTab(viewer));
542:     PetscCall(SNESLineSearchView(linesearch, viewer));
543:     PetscCall(PetscViewerASCIIPopTab(viewer));
544:   }
545:   if (snes->npc && snes->usesnpc) {
546:     PetscCall(PetscViewerASCIIPushTab(viewer));
547:     PetscCall(SNESView(snes->npc, viewer));
548:     PetscCall(PetscViewerASCIIPopTab(viewer));
549:   }
550:   PetscCall(PetscViewerASCIIPushTab(viewer));
551:   PetscCall(DMGetDMSNES(snes->dm, &dmsnes));
552:   PetscCall(DMSNESView(dmsnes, viewer));
553:   PetscCall(PetscViewerASCIIPopTab(viewer));
554:   if (snes->usesksp) {
555:     PetscCall(SNESGetKSP(snes, &ksp));
556:     PetscCall(PetscViewerASCIIPushTab(viewer));
557:     PetscCall(KSPView(ksp, viewer));
558:     PetscCall(PetscViewerASCIIPopTab(viewer));
559:   }
560:   if (isdraw) {
561:     PetscDraw draw;
562:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
563:     PetscCall(PetscDrawPopCurrentPoint(draw));
564:   }
565:   PetscFunctionReturn(PETSC_SUCCESS);
566: }

568: /*
569:   We retain a list of functions that also take SNES command
570:   line options. These are called at the end SNESSetFromOptions()
571: */
572: #define MAXSETFROMOPTIONS 5
573: static PetscInt numberofsetfromoptions;
574: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

576: /*@C
577:   SNESAddOptionsChecker - Adds an additional function to check for `SNES` options.

579:   Not Collective

581:   Input Parameter:
582: . snescheck - function that checks for options

584:   Calling sequence of `snescheck`:
585: . snes - the `SNES` object for which it is checking options

587:   Level: developer

589: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`
590: @*/
591: PetscErrorCode SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES snes))
592: {
593:   PetscFunctionBegin;
594:   PetscCheck(numberofsetfromoptions < MAXSETFROMOPTIONS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %d allowed", MAXSETFROMOPTIONS);
595:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
596:   PetscFunctionReturn(PETSC_SUCCESS);
597: }

599: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
600: {
601:   Mat          J;
602:   MatNullSpace nullsp;

604:   PetscFunctionBegin;

607:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
608:     Mat A = snes->jacobian, B = snes->jacobian_pre;
609:     PetscCall(MatCreateVecs(A ? A : B, NULL, &snes->vec_func));
610:   }

612:   PetscCheck(version == 1 || version == 2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");
613:   if (version == 1) {
614:     PetscCall(MatCreateSNESMF(snes, &J));
615:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
616:     PetscCall(MatSetFromOptions(J));
617:     /* TODO: the version 2 code should be merged into the MatCreateSNESMF() and MatCreateMFFD() infrastructure and then removed */
618:   } else /* if (version == 2) */ {
619:     PetscCheck(snes->vec_func, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "SNESSetFunction() must be called first");
620: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
621:     PetscCall(MatCreateSNESMFMore(snes, snes->vec_func, &J));
622: #else
623:     SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
624: #endif
625:   }

627:   /* attach any user provided null space that was on Amat to the newly created matrix-free matrix */
628:   if (snes->jacobian) {
629:     PetscCall(MatGetNullSpace(snes->jacobian, &nullsp));
630:     if (nullsp) PetscCall(MatSetNullSpace(J, nullsp));
631:   }

633:   PetscCall(PetscInfo(snes, "Setting default matrix-free operator routines (version %" PetscInt_FMT ")\n", version));
634:   if (hasOperator) {
635:     /* This version replaces the user provided Jacobian matrix with a
636:        matrix-free version but still employs the user-provided matrix used for computing the preconditioner. */
637:     PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
638:   } else {
639:     /* This version replaces both the user-provided Jacobian and the user-
640:      provided preconditioner Jacobian with the default matrix-free version. */
641:     if (snes->npcside == PC_LEFT && snes->npc) {
642:       if (!snes->jacobian) PetscCall(SNESSetJacobian(snes, J, NULL, NULL, NULL));
643:     } else {
644:       KSP       ksp;
645:       PC        pc;
646:       PetscBool match;

648:       PetscCall(SNESSetJacobian(snes, J, J, MatMFFDComputeJacobian, NULL));
649:       /* Force no preconditioner */
650:       PetscCall(SNESGetKSP(snes, &ksp));
651:       PetscCall(KSPGetPC(ksp, &pc));
652:       PetscCall(PetscObjectTypeCompareAny((PetscObject)pc, &match, PCSHELL, PCH2OPUS, ""));
653:       if (!match) {
654:         PetscCall(PetscInfo(snes, "Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n"));
655:         PetscCall(PCSetType(pc, PCNONE));
656:       }
657:     }
658:   }
659:   PetscCall(MatDestroy(&J));
660:   PetscFunctionReturn(PETSC_SUCCESS);
661: }

663: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine, Mat Restrict, Vec Rscale, Mat Inject, DM dmcoarse, void *ctx)
664: {
665:   SNES snes = (SNES)ctx;
666:   Vec  Xfine, Xfine_named = NULL, Xcoarse;

668:   PetscFunctionBegin;
669:   if (PetscLogPrintInfo) {
670:     PetscInt finelevel, coarselevel, fineclevel, coarseclevel;
671:     PetscCall(DMGetRefineLevel(dmfine, &finelevel));
672:     PetscCall(DMGetCoarsenLevel(dmfine, &fineclevel));
673:     PetscCall(DMGetRefineLevel(dmcoarse, &coarselevel));
674:     PetscCall(DMGetCoarsenLevel(dmcoarse, &coarseclevel));
675:     PetscCall(PetscInfo(dmfine, "Restricting SNES solution vector from level %" PetscInt_FMT "-%" PetscInt_FMT " to level %" PetscInt_FMT "-%" PetscInt_FMT "\n", finelevel, fineclevel, coarselevel, coarseclevel));
676:   }
677:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
678:   else {
679:     PetscCall(DMGetNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
680:     Xfine = Xfine_named;
681:   }
682:   PetscCall(DMGetNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
683:   if (Inject) {
684:     PetscCall(MatRestrict(Inject, Xfine, Xcoarse));
685:   } else {
686:     PetscCall(MatRestrict(Restrict, Xfine, Xcoarse));
687:     PetscCall(VecPointwiseMult(Xcoarse, Xcoarse, Rscale));
688:   }
689:   PetscCall(DMRestoreNamedGlobalVector(dmcoarse, "SNESVecSol", &Xcoarse));
690:   if (Xfine_named) PetscCall(DMRestoreNamedGlobalVector(dmfine, "SNESVecSol", &Xfine_named));
691:   PetscFunctionReturn(PETSC_SUCCESS);
692: }

694: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm, DM dmc, void *ctx)
695: {
696:   PetscFunctionBegin;
697:   PetscCall(DMCoarsenHookAdd(dmc, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, ctx));
698:   PetscFunctionReturn(PETSC_SUCCESS);
699: }

701: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
702:  * safely call SNESGetDM() in their residual evaluation routine. */
703: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp, Mat A, Mat B, void *ctx)
704: {
705:   SNES            snes = (SNES)ctx;
706:   DMSNES          sdm;
707:   Vec             X, Xnamed = NULL;
708:   DM              dmsave;
709:   void           *ctxsave;
710:   SNESJacobianFn *jac = NULL;

712:   PetscFunctionBegin;
713:   dmsave = snes->dm;
714:   PetscCall(KSPGetDM(ksp, &snes->dm));
715:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
716:   else {
717:     PetscBool has;

719:     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
720:     PetscCall(DMHasNamedGlobalVector(snes->dm, "SNESVecSol", &has));
721:     PetscCheck(has, PetscObjectComm((PetscObject)snes->dm), PETSC_ERR_PLIB, "Missing SNESVecSol");
722:     PetscCall(DMGetNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
723:     X = Xnamed;
724:     PetscCall(SNESGetJacobian(snes, NULL, NULL, &jac, &ctxsave));
725:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
726:     if (jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, SNESComputeJacobianDefaultColor, NULL));
727:   }

729:   /* Compute the operators */
730:   PetscCall(DMGetDMSNES(snes->dm, &sdm));
731:   if (Xnamed && sdm->ops->computefunction) {
732:     /* The SNES contract with the user is that ComputeFunction is always called before ComputeJacobian.
733:        We make sure of this here. Disable affine shift since it is for the finest level */
734:     Vec F, saverhs = snes->vec_rhs;

736:     snes->vec_rhs = NULL;
737:     PetscCall(DMGetGlobalVector(snes->dm, &F));
738:     PetscCall(SNESComputeFunction(snes, X, F));
739:     PetscCall(DMRestoreGlobalVector(snes->dm, &F));
740:     snes->vec_rhs = saverhs;
741:     snes->nfuncs--; /* Do not log coarser level evaluations */
742:   }
743:   /* Make sure KSP DM has the Jacobian computation routine */
744:   if (!sdm->ops->computejacobian) PetscCall(DMCopyDMSNES(dmsave, snes->dm));
745:   PetscCall(SNESComputeJacobian(snes, X, A, B));

747:   /* Put the previous context back */
748:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) PetscCall(SNESSetJacobian(snes, NULL, NULL, jac, ctxsave));

750:   if (Xnamed) PetscCall(DMRestoreNamedGlobalVector(snes->dm, "SNESVecSol", &Xnamed));
751:   snes->dm = dmsave;
752:   PetscFunctionReturn(PETSC_SUCCESS);
753: }

755: /*@
756:   SNESSetUpMatrices - ensures that matrices are available for `SNES` Newton-like methods, this is called by `SNESSetUp_XXX()`

758:   Collective

760:   Input Parameter:
761: . snes - `SNES` object to configure

763:   Level: developer

765:   Note:
766:   If the matrices do not yet exist it attempts to create them based on options previously set for the `SNES` such as `-snes_mf`

768:   Developer Note:
769:   The functionality of this routine overlaps in a confusing way with the functionality of `SNESSetUpMatrixFree_Private()` which is called by
770:   `SNESSetUp()` but sometimes `SNESSetUpMatrices()` is called without `SNESSetUp()` being called. A refactorization to simplify the
771:   logic that handles the matrix-free case is desirable.

773: .seealso: [](ch_snes), `SNES`, `SNESSetUp()`
774: @*/
775: PetscErrorCode SNESSetUpMatrices(SNES snes)
776: {
777:   DM     dm;
778:   DMSNES sdm;

780:   PetscFunctionBegin;
781:   PetscCall(SNESGetDM(snes, &dm));
782:   PetscCall(DMGetDMSNES(dm, &sdm));
783:   if (!snes->jacobian && snes->mf && !snes->mf_operator && !snes->jacobian_pre) {
784:     Mat   J;
785:     void *functx;
786:     PetscCall(MatCreateSNESMF(snes, &J));
787:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
788:     PetscCall(MatSetFromOptions(J));
789:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
790:     PetscCall(SNESSetJacobian(snes, J, J, NULL, NULL));
791:     PetscCall(MatDestroy(&J));
792:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
793:     Mat J, B;
794:     PetscCall(MatCreateSNESMF(snes, &J));
795:     PetscCall(MatMFFDSetOptionsPrefix(J, ((PetscObject)snes)->prefix));
796:     PetscCall(MatSetFromOptions(J));
797:     PetscCall(DMCreateMatrix(snes->dm, &B));
798:     /* sdm->computejacobian was already set to reach here */
799:     PetscCall(SNESSetJacobian(snes, J, B, NULL, NULL));
800:     PetscCall(MatDestroy(&J));
801:     PetscCall(MatDestroy(&B));
802:   } else if (!snes->jacobian_pre) {
803:     PetscDS   prob;
804:     Mat       J, B;
805:     PetscBool hasPrec = PETSC_FALSE;

807:     J = snes->jacobian;
808:     PetscCall(DMGetDS(dm, &prob));
809:     if (prob) PetscCall(PetscDSHasJacobianPreconditioner(prob, &hasPrec));
810:     if (J) PetscCall(PetscObjectReference((PetscObject)J));
811:     else if (hasPrec) PetscCall(DMCreateMatrix(snes->dm, &J));
812:     PetscCall(DMCreateMatrix(snes->dm, &B));
813:     PetscCall(SNESSetJacobian(snes, J ? J : B, B, NULL, NULL));
814:     PetscCall(MatDestroy(&J));
815:     PetscCall(MatDestroy(&B));
816:   }
817:   {
818:     KSP ksp;
819:     PetscCall(SNESGetKSP(snes, &ksp));
820:     PetscCall(KSPSetComputeOperators(ksp, KSPComputeOperators_SNES, snes));
821:     PetscCall(DMCoarsenHookAdd(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
822:   }
823:   PetscFunctionReturn(PETSC_SUCCESS);
824: }

826: PETSC_EXTERN PetscErrorCode PetscMonitorPauseFinal_Internal(PetscInt, void *);

828: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
829: {
830:   PetscFunctionBegin;
831:   if (!snes->pauseFinal) PetscFunctionReturn(PETSC_SUCCESS);
832:   PetscCall(PetscMonitorPauseFinal_Internal(snes->numbermonitors, snes->monitorcontext));
833:   PetscFunctionReturn(PETSC_SUCCESS);
834: }

836: /*@C
837:   SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

839:   Collective

841:   Input Parameters:
842: + snes         - `SNES` object you wish to monitor
843: . name         - the monitor type one is seeking
844: . help         - message indicating what monitoring is done
845: . manual       - manual page for the monitor
846: . monitor      - the monitor function, this must use a `PetscViewerFormat` as its context
847: - monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the `SNES` or `PetscViewer` objects

849:   Calling sequence of `monitor`:
850: + snes - the nonlinear solver context
851: . it   - the current iteration
852: . r    - the current function norm
853: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

855:   Calling sequence of `monitorsetup`:
856: + snes - the nonlinear solver context
857: - vf   - a `PetscViewerAndFormat` struct that contains the `PetscViewer` and `PetscViewerFormat` to use

859:   Options Database Key:
860: . -name - trigger the use of this monitor in `SNESSetFromOptions()`

862:   Level: advanced

864: .seealso: [](ch_snes), `PetscOptionsCreateViewer()`, `PetscOptionsGetReal()`, `PetscOptionsHasName()`, `PetscOptionsGetString()`,
865:           `PetscOptionsGetIntArray()`, `PetscOptionsGetRealArray()`, `PetscOptionsBool()`
866:           `PetscOptionsInt()`, `PetscOptionsString()`, `PetscOptionsReal()`,
867:           `PetscOptionsName()`, `PetscOptionsBegin()`, `PetscOptionsEnd()`, `PetscOptionsHeadBegin()`,
868:           `PetscOptionsStringArray()`, `PetscOptionsRealArray()`, `PetscOptionsScalar()`,
869:           `PetscOptionsBoolGroupBegin()`, `PetscOptionsBoolGroup()`, `PetscOptionsBoolGroupEnd()`,
870:           `PetscOptionsFList()`, `PetscOptionsEList()`
871: @*/
872: PetscErrorCode SNESMonitorSetFromOptions(SNES snes, const char name[], const char help[], const char manual[], PetscErrorCode (*monitor)(SNES snes, PetscInt it, PetscReal r, PetscViewerAndFormat *vf), PetscErrorCode (*monitorsetup)(SNES snes, PetscViewerAndFormat *vf))
873: {
874:   PetscViewer       viewer;
875:   PetscViewerFormat format;
876:   PetscBool         flg;

878:   PetscFunctionBegin;
879:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, name, &viewer, &format, &flg));
880:   if (flg) {
881:     PetscViewerAndFormat *vf;
882:     PetscCall(PetscViewerAndFormatCreate(viewer, format, &vf));
883:     PetscCall(PetscViewerDestroy(&viewer));
884:     if (monitorsetup) PetscCall((*monitorsetup)(snes, vf));
885:     PetscCall(SNESMonitorSet(snes, (PetscErrorCode (*)(SNES, PetscInt, PetscReal, void *))monitor, vf, (PetscCtxDestroyFn *)PetscViewerAndFormatDestroy));
886:   }
887:   PetscFunctionReturn(PETSC_SUCCESS);
888: }

890: PetscErrorCode SNESEWSetFromOptions_Private(SNESKSPEW *kctx, PetscBool print_api, MPI_Comm comm, const char *prefix)
891: {
892:   const char *api = print_api ? "SNESKSPSetParametersEW" : NULL;

894:   PetscFunctionBegin;
895:   PetscOptionsBegin(comm, prefix, "Eisenstat and Walker type forcing options", "KSP");
896:   PetscCall(PetscOptionsInt("-ksp_ew_version", "Version 1, 2 or 3", api, kctx->version, &kctx->version, NULL));
897:   PetscCall(PetscOptionsReal("-ksp_ew_rtol0", "0 <= rtol0 < 1", api, kctx->rtol_0, &kctx->rtol_0, NULL));
898:   kctx->rtol_max = PetscMax(kctx->rtol_0, kctx->rtol_max);
899:   PetscCall(PetscOptionsReal("-ksp_ew_rtolmax", "0 <= rtolmax < 1", api, kctx->rtol_max, &kctx->rtol_max, NULL));
900:   PetscCall(PetscOptionsReal("-ksp_ew_gamma", "0 <= gamma <= 1", api, kctx->gamma, &kctx->gamma, NULL));
901:   PetscCall(PetscOptionsReal("-ksp_ew_alpha", "1 < alpha <= 2", api, kctx->alpha, &kctx->alpha, NULL));
902:   PetscCall(PetscOptionsReal("-ksp_ew_alpha2", "alpha2", NULL, kctx->alpha2, &kctx->alpha2, NULL));
903:   PetscCall(PetscOptionsReal("-ksp_ew_threshold", "0 < threshold < 1", api, kctx->threshold, &kctx->threshold, NULL));
904:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p1", "p1", NULL, kctx->v4_p1, &kctx->v4_p1, NULL));
905:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p2", "p2", NULL, kctx->v4_p2, &kctx->v4_p2, NULL));
906:   PetscCall(PetscOptionsReal("-ksp_ew_v4_p3", "p3", NULL, kctx->v4_p3, &kctx->v4_p3, NULL));
907:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m1", "Scaling when rk-1 in [p2,p3)", NULL, kctx->v4_m1, &kctx->v4_m1, NULL));
908:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m2", "Scaling when rk-1 in [p3,+infty)", NULL, kctx->v4_m2, &kctx->v4_m2, NULL));
909:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m3", "Threshold for successive rtol (0.1 in Eq.7)", NULL, kctx->v4_m3, &kctx->v4_m3, NULL));
910:   PetscCall(PetscOptionsReal("-ksp_ew_v4_m4", "Adaptation scaling (0.5 in Eq.7)", NULL, kctx->v4_m4, &kctx->v4_m4, NULL));
911:   PetscOptionsEnd();
912:   PetscFunctionReturn(PETSC_SUCCESS);
913: }

915: /*@
916:   SNESSetFromOptions - Sets various `SNES` and `KSP` parameters from user options.

918:   Collective

920:   Input Parameter:
921: . snes - the `SNES` context

923:   Options Database Keys:
924: + -snes_type <type>                                                            - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, `SNESType` for complete list
925: . -snes_rtol <rtol>                                                            - relative decrease in tolerance norm from initial
926: . -snes_atol <abstol>                                                          - absolute tolerance of residual norm
927: . -snes_stol <stol>                                                            - convergence tolerance in terms of the norm of the change in the solution between steps
928: . -snes_divergence_tolerance <divtol>                                          - if the residual goes above divtol*rnorm0, exit with divergence
929: . -snes_max_it <max_it>                                                        - maximum number of iterations
930: . -snes_max_funcs <max_funcs>                                                  - maximum number of function evaluations
931: . -snes_force_iteration <force>                                                - force `SNESSolve()` to take at least one iteration
932: . -snes_max_fail <max_fail>                                                    - maximum number of line search failures allowed before stopping, default is none
933: . -snes_max_linear_solve_fail                                                  - number of linear solver failures before SNESSolve() stops
934: . -snes_lag_preconditioner <lag>                                               - how often preconditioner is rebuilt (use -1 to never rebuild)
935: . -snes_lag_preconditioner_persists <true,false>                               - retains the -snes_lag_preconditioner information across multiple SNESSolve()
936: . -snes_lag_jacobian <lag>                                                     - how often Jacobian is rebuilt (use -1 to never rebuild)
937: . -snes_lag_jacobian_persists <true,false>                                     - retains the -snes_lag_jacobian information across multiple SNESSolve()
938: . -snes_convergence_test <default,skip,correct_pressure>                       - convergence test in nonlinear solver. default `SNESConvergedDefault()`. skip `SNESConvergedSkip()` means continue iterating until max_it or some other criterion is reached, saving expense of convergence test. correct_pressure `SNESConvergedCorrectPressure()` has special handling of a pressure null space.
939: . -snes_monitor [ascii][:filename][:viewer format]                             - prints residual norm at each iteration. if no filename given prints to stdout
940: . -snes_monitor_solution [ascii binary draw][:filename][:viewer format]        - plots solution at each iteration
941: . -snes_monitor_residual [ascii binary draw][:filename][:viewer format]        - plots residual (not its norm) at each iteration
942: . -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
943: . -snes_monitor_lg_residualnorm                                                - plots residual norm at each iteration
944: . -snes_monitor_lg_range                                                       - plots residual norm at each iteration
945: . -snes_monitor_pause_final                                                    - Pauses all monitor drawing after the solver ends
946: . -snes_fd                                                                     - use finite differences to compute Jacobian; very slow, only for testing
947: . -snes_fd_color                                                               - use finite differences with coloring to compute Jacobian
948: . -snes_mf_ksp_monitor                                                         - if using matrix-free multiply then print h at each `KSP` iteration
949: . -snes_converged_reason                                                       - print the reason for convergence/divergence after each solve
950: . -npc_snes_type <type>                                                        - the `SNES` type to use as a nonlinear preconditioner
951: . -snes_test_jacobian <optional threshold>                                     - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
952: - -snes_test_jacobian_view                                                     - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

954:   Options Database Keys for Eisenstat-Walker method:
955: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
956: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
957: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
958: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
959: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
960: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
961: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
962: - -snes_ksp_ew_threshold <threshold> - Sets threshold

964:   Level: beginner

966:   Notes:
967:   To see all options, run your program with the -help option or consult the users manual

969:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
970:   and computing explicitly with
971:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

973: .seealso: [](ch_snes), `SNESType`, `SNESSetOptionsPrefix()`, `SNESResetFromOptions()`, `SNES`, `SNESCreate()`, `MatCreateSNESMF()`, `MatFDColoring`
974: @*/
975: PetscErrorCode SNESSetFromOptions(SNES snes)
976: {
977:   PetscBool   flg, pcset, persist, set;
978:   PetscInt    i, indx, lag, grids, max_its, max_funcs;
979:   const char *deft        = SNESNEWTONLS;
980:   const char *convtests[] = {"default", "skip", "correct_pressure"};
981:   SNESKSPEW  *kctx        = NULL;
982:   char        type[256], monfilename[PETSC_MAX_PATH_LEN], ewprefix[256];
983:   PCSide      pcside;
984:   const char *optionsprefix;
985:   PetscReal   rtol, abstol, stol;

987:   PetscFunctionBegin;
989:   PetscCall(SNESRegisterAll());
990:   PetscObjectOptionsBegin((PetscObject)snes);
991:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
992:   PetscCall(PetscOptionsFList("-snes_type", "Nonlinear solver method", "SNESSetType", SNESList, deft, type, 256, &flg));
993:   if (flg) {
994:     PetscCall(SNESSetType(snes, type));
995:   } else if (!((PetscObject)snes)->type_name) {
996:     PetscCall(SNESSetType(snes, deft));
997:   }

999:   abstol    = snes->abstol;
1000:   rtol      = snes->rtol;
1001:   stol      = snes->stol;
1002:   max_its   = snes->max_its;
1003:   max_funcs = snes->max_funcs;
1004:   PetscCall(PetscOptionsReal("-snes_rtol", "Stop if decrease in function norm less than", "SNESSetTolerances", snes->rtol, &rtol, NULL));
1005:   PetscCall(PetscOptionsReal("-snes_atol", "Stop if function norm less than", "SNESSetTolerances", snes->abstol, &abstol, NULL));
1006:   PetscCall(PetscOptionsReal("-snes_stol", "Stop if step length less than", "SNESSetTolerances", snes->stol, &stol, NULL));
1007:   PetscCall(PetscOptionsInt("-snes_max_it", "Maximum iterations", "SNESSetTolerances", snes->max_its, &max_its, NULL));
1008:   PetscCall(PetscOptionsInt("-snes_max_funcs", "Maximum function evaluations", "SNESSetTolerances", snes->max_funcs, &max_funcs, NULL));
1009:   PetscCall(SNESSetTolerances(snes, abstol, rtol, stol, max_its, max_funcs));

1011:   PetscCall(PetscOptionsReal("-snes_divergence_tolerance", "Stop if residual norm increases by this factor", "SNESSetDivergenceTolerance", snes->divtol, &snes->divtol, &flg));
1012:   if (flg) PetscCall(SNESSetDivergenceTolerance(snes, snes->divtol));

1014:   PetscCall(PetscOptionsInt("-snes_max_fail", "Maximum nonlinear step failures", "SNESSetMaxNonlinearStepFailures", snes->maxFailures, &snes->maxFailures, &flg));
1015:   if (flg) PetscCall(SNESSetMaxNonlinearStepFailures(snes, snes->maxFailures));

1017:   PetscCall(PetscOptionsInt("-snes_max_linear_solve_fail", "Maximum failures in linear solves allowed", "SNESSetMaxLinearSolveFailures", snes->maxLinearSolveFailures, &snes->maxLinearSolveFailures, &flg));
1018:   if (flg) PetscCall(SNESSetMaxLinearSolveFailures(snes, snes->maxLinearSolveFailures));

1020:   PetscCall(PetscOptionsBool("-snes_error_if_not_converged", "Generate error if solver does not converge", "SNESSetErrorIfNotConverged", snes->errorifnotconverged, &snes->errorifnotconverged, NULL));
1021:   PetscCall(PetscOptionsBool("-snes_force_iteration", "Force SNESSolve() to take at least one iteration", "SNESSetForceIteration", snes->forceiteration, &snes->forceiteration, NULL));
1022:   PetscCall(PetscOptionsBool("-snes_check_jacobian_domain_error", "Check Jacobian domain error after Jacobian evaluation", "SNESCheckJacobianDomainError", snes->checkjacdomainerror, &snes->checkjacdomainerror, NULL));

1024:   PetscCall(PetscOptionsInt("-snes_lag_preconditioner", "How often to rebuild preconditioner", "SNESSetLagPreconditioner", snes->lagpreconditioner, &lag, &flg));
1025:   if (flg) {
1026:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
1027:     PetscCall(SNESSetLagPreconditioner(snes, lag));
1028:   }
1029:   PetscCall(PetscOptionsBool("-snes_lag_preconditioner_persists", "Preconditioner lagging through multiple SNES solves", "SNESSetLagPreconditionerPersists", snes->lagjac_persist, &persist, &flg));
1030:   if (flg) PetscCall(SNESSetLagPreconditionerPersists(snes, persist));
1031:   PetscCall(PetscOptionsInt("-snes_lag_jacobian", "How often to rebuild Jacobian", "SNESSetLagJacobian", snes->lagjacobian, &lag, &flg));
1032:   if (flg) {
1033:     PetscCheck(lag != -1, PetscObjectComm((PetscObject)snes), PETSC_ERR_USER, "Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
1034:     PetscCall(SNESSetLagJacobian(snes, lag));
1035:   }
1036:   PetscCall(PetscOptionsBool("-snes_lag_jacobian_persists", "Jacobian lagging through multiple SNES solves", "SNESSetLagJacobianPersists", snes->lagjac_persist, &persist, &flg));
1037:   if (flg) PetscCall(SNESSetLagJacobianPersists(snes, persist));

1039:   PetscCall(PetscOptionsInt("-snes_grid_sequence", "Use grid sequencing to generate initial guess", "SNESSetGridSequence", snes->gridsequence, &grids, &flg));
1040:   if (flg) PetscCall(SNESSetGridSequence(snes, grids));

1042:   PetscCall(PetscOptionsEList("-snes_convergence_test", "Convergence test", "SNESSetConvergenceTest", convtests, PETSC_STATIC_ARRAY_LENGTH(convtests), "default", &indx, &flg));
1043:   if (flg) {
1044:     switch (indx) {
1045:     case 0:
1046:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedDefault, NULL, NULL));
1047:       break;
1048:     case 1:
1049:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedSkip, NULL, NULL));
1050:       break;
1051:     case 2:
1052:       PetscCall(SNESSetConvergenceTest(snes, SNESConvergedCorrectPressure, NULL, NULL));
1053:       break;
1054:     }
1055:   }

1057:   PetscCall(PetscOptionsEList("-snes_norm_schedule", "SNES Norm schedule", "SNESSetNormSchedule", SNESNormSchedules, 5, "function", &indx, &flg));
1058:   if (flg) PetscCall(SNESSetNormSchedule(snes, (SNESNormSchedule)indx));

1060:   PetscCall(PetscOptionsEList("-snes_function_type", "SNES Norm schedule", "SNESSetFunctionType", SNESFunctionTypes, 2, "unpreconditioned", &indx, &flg));
1061:   if (flg) PetscCall(SNESSetFunctionType(snes, (SNESFunctionType)indx));

1063:   kctx = (SNESKSPEW *)snes->kspconvctx;

1065:   PetscCall(PetscOptionsBool("-snes_ksp_ew", "Use Eisentat-Walker linear system convergence test", "SNESKSPSetUseEW", snes->ksp_ewconv, &snes->ksp_ewconv, NULL));

1067:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1068:   PetscCall(PetscSNPrintf(ewprefix, sizeof(ewprefix), "%s%s", optionsprefix ? optionsprefix : "", "snes_"));
1069:   PetscCall(SNESEWSetFromOptions_Private(kctx, PETSC_TRUE, PetscObjectComm((PetscObject)snes), ewprefix));

1071:   flg = PETSC_FALSE;
1072:   PetscCall(PetscOptionsBool("-snes_monitor_cancel", "Remove all monitors", "SNESMonitorCancel", flg, &flg, &set));
1073:   if (set && flg) PetscCall(SNESMonitorCancel(snes));

1075:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor", "Monitor norm of function", "SNESMonitorDefault", SNESMonitorDefault, SNESMonitorDefaultSetUp));
1076:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_short", "Monitor norm of function with fewer digits", "SNESMonitorDefaultShort", SNESMonitorDefaultShort, NULL));
1077:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_range", "Monitor range of elements of function", "SNESMonitorRange", SNESMonitorRange, NULL));

1079:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_ratio", "Monitor ratios of the norm of function for consecutive steps", "SNESMonitorRatio", SNESMonitorRatio, SNESMonitorRatioSetUp));
1080:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_field", "Monitor norm of function (split into fields)", "SNESMonitorDefaultField", SNESMonitorDefaultField, NULL));
1081:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution", "View solution at each iteration", "SNESMonitorSolution", SNESMonitorSolution, NULL));
1082:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_solution_update", "View correction at each iteration", "SNESMonitorSolutionUpdate", SNESMonitorSolutionUpdate, NULL));
1083:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_residual", "View residual at each iteration", "SNESMonitorResidual", SNESMonitorResidual, NULL));
1084:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_jacupdate_spectrum", "Print the change in the spectrum of the Jacobian", "SNESMonitorJacUpdateSpectrum", SNESMonitorJacUpdateSpectrum, NULL));
1085:   PetscCall(SNESMonitorSetFromOptions(snes, "-snes_monitor_fields", "Monitor norm of function per field", "SNESMonitorSet", SNESMonitorFields, NULL));
1086:   PetscCall(PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL));

1088:   PetscCall(PetscOptionsString("-snes_monitor_python", "Use Python function", "SNESMonitorSet", NULL, monfilename, sizeof(monfilename), &flg));
1089:   if (flg) PetscCall(PetscPythonMonitorSet((PetscObject)snes, monfilename));

1091:   flg = PETSC_FALSE;
1092:   PetscCall(PetscOptionsBool("-snes_monitor_lg_range", "Plot function range at each iteration", "SNESMonitorLGRange", flg, &flg, NULL));
1093:   if (flg) {
1094:     PetscViewer ctx;

1096:     PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, NULL, PETSC_DECIDE, PETSC_DECIDE, 400, 300, &ctx));
1097:     PetscCall(SNESMonitorSet(snes, SNESMonitorLGRange, ctx, (PetscCtxDestroyFn *)PetscViewerDestroy));
1098:   }

1100:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
1101:   PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_converged_reason", &snes->convergedreasonviewer, &snes->convergedreasonformat, NULL));
1102:   flg = PETSC_FALSE;
1103:   PetscCall(PetscOptionsBool("-snes_converged_reason_view_cancel", "Remove all converged reason viewers", "SNESConvergedReasonViewCancel", flg, &flg, &set));
1104:   if (set && flg) PetscCall(SNESConvergedReasonViewCancel(snes));

1106:   flg = PETSC_FALSE;
1107:   PetscCall(PetscOptionsBool("-snes_fd", "Use finite differences (slow) to compute Jacobian", "SNESComputeJacobianDefault", flg, &flg, NULL));
1108:   if (flg) {
1109:     void *functx;
1110:     DM    dm;
1111:     PetscCall(SNESGetDM(snes, &dm));
1112:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1113:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
1114:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefault, functx));
1115:     PetscCall(PetscInfo(snes, "Setting default finite difference Jacobian matrix\n"));
1116:   }

1118:   flg = PETSC_FALSE;
1119:   PetscCall(PetscOptionsBool("-snes_fd_function", "Use finite differences (slow) to compute function from user objective", "SNESObjectiveComputeFunctionDefaultFD", flg, &flg, NULL));
1120:   if (flg) PetscCall(SNESSetFunction(snes, NULL, SNESObjectiveComputeFunctionDefaultFD, NULL));

1122:   flg = PETSC_FALSE;
1123:   PetscCall(PetscOptionsBool("-snes_fd_color", "Use finite differences with coloring to compute Jacobian", "SNESComputeJacobianDefaultColor", flg, &flg, NULL));
1124:   if (flg) {
1125:     DM dm;
1126:     PetscCall(SNESGetDM(snes, &dm));
1127:     PetscCall(DMSNESUnsetJacobianContext_Internal(dm));
1128:     PetscCall(SNESSetJacobian(snes, snes->jacobian, snes->jacobian_pre, SNESComputeJacobianDefaultColor, NULL));
1129:     PetscCall(PetscInfo(snes, "Setting default finite difference coloring Jacobian matrix\n"));
1130:   }

1132:   flg = PETSC_FALSE;
1133:   PetscCall(PetscOptionsBool("-snes_mf_operator", "Use a Matrix-Free Jacobian with user-provided matrix for computing the preconditioner", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf_operator, &flg));
1134:   if (flg && snes->mf_operator) {
1135:     snes->mf_operator = PETSC_TRUE;
1136:     snes->mf          = PETSC_TRUE;
1137:   }
1138:   flg = PETSC_FALSE;
1139:   PetscCall(PetscOptionsBool("-snes_mf", "Use a Matrix-Free Jacobian with no matrix for computing the preconditioner", "SNESSetUseMatrixFree", PETSC_FALSE, &snes->mf, &flg));
1140:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
1141:   PetscCall(PetscOptionsInt("-snes_mf_version", "Matrix-Free routines version 1 or 2", "None", snes->mf_version, &snes->mf_version, NULL));

1143:   flg = PETSC_FALSE;
1144:   PetscCall(SNESGetNPCSide(snes, &pcside));
1145:   PetscCall(PetscOptionsEnum("-snes_npc_side", "SNES nonlinear preconditioner side", "SNESSetNPCSide", PCSides, (PetscEnum)pcside, (PetscEnum *)&pcside, &flg));
1146:   if (flg) PetscCall(SNESSetNPCSide(snes, pcside));

1148: #if defined(PETSC_HAVE_SAWS)
1149:   /*
1150:     Publish convergence information using SAWs
1151:   */
1152:   flg = PETSC_FALSE;
1153:   PetscCall(PetscOptionsBool("-snes_monitor_saws", "Publish SNES progress using SAWs", "SNESMonitorSet", flg, &flg, NULL));
1154:   if (flg) {
1155:     void *ctx;
1156:     PetscCall(SNESMonitorSAWsCreate(snes, &ctx));
1157:     PetscCall(SNESMonitorSet(snes, SNESMonitorSAWs, ctx, SNESMonitorSAWsDestroy));
1158:   }
1159: #endif
1160: #if defined(PETSC_HAVE_SAWS)
1161:   {
1162:     PetscBool set;
1163:     flg = PETSC_FALSE;
1164:     PetscCall(PetscOptionsBool("-snes_saws_block", "Block for SAWs at end of SNESSolve", "PetscObjectSAWsBlock", ((PetscObject)snes)->amspublishblock, &flg, &set));
1165:     if (set) PetscCall(PetscObjectSAWsSetBlock((PetscObject)snes, flg));
1166:   }
1167: #endif

1169:   for (i = 0; i < numberofsetfromoptions; i++) PetscCall((*othersetfromoptions[i])(snes));

1171:   PetscTryTypeMethod(snes, setfromoptions, PetscOptionsObject);

1173:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
1174:   PetscCall(PetscObjectProcessOptionsHandlers((PetscObject)snes, PetscOptionsObject));
1175:   PetscOptionsEnd();

1177:   if (snes->linesearch) {
1178:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
1179:     PetscCall(SNESLineSearchSetFromOptions(snes->linesearch));
1180:   }

1182:   if (snes->usesksp) {
1183:     if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
1184:     PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
1185:     PetscCall(KSPSetFromOptions(snes->ksp));
1186:   }

1188:   /* if user has set the SNES NPC type via options database, create it. */
1189:   PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
1190:   PetscCall(PetscOptionsHasName(((PetscObject)snes)->options, optionsprefix, "-npc_snes_type", &pcset));
1191:   if (pcset && (!snes->npc)) PetscCall(SNESGetNPC(snes, &snes->npc));
1192:   if (snes->npc) PetscCall(SNESSetFromOptions(snes->npc));
1193:   snes->setfromoptionscalled++;
1194:   PetscFunctionReturn(PETSC_SUCCESS);
1195: }

1197: /*@
1198:   SNESResetFromOptions - Sets various `SNES` and `KSP` parameters from user options ONLY if the `SNESSetFromOptions()` was previously called

1200:   Collective

1202:   Input Parameter:
1203: . snes - the `SNES` context

1205:   Level: advanced

1207: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESSetOptionsPrefix()`
1208: @*/
1209: PetscErrorCode SNESResetFromOptions(SNES snes)
1210: {
1211:   PetscFunctionBegin;
1212:   if (snes->setfromoptionscalled) PetscCall(SNESSetFromOptions(snes));
1213:   PetscFunctionReturn(PETSC_SUCCESS);
1214: }

1216: /*@C
1217:   SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
1218:   the nonlinear solvers.

1220:   Logically Collective; No Fortran Support

1222:   Input Parameters:
1223: + snes    - the `SNES` context
1224: . compute - function to compute the context
1225: - destroy - function to destroy the context, see `PetscCtxDestroyFn` for the calling sequence

1227:   Calling sequence of `compute`:
1228: + snes - the `SNES` context
1229: - ctx  - context to be computed

1231:   Level: intermediate

1233:   Note:
1234:   This routine is useful if you are performing grid sequencing or using `SNESFAS` and need the appropriate context generated for each level.

1236:   Use `SNESSetApplicationContext()` to see the context immediately

1238: .seealso: [](ch_snes), `SNESGetApplicationContext()`, `SNESSetApplicationContext()`, `PetscCtxDestroyFn`
1239: @*/
1240: PetscErrorCode SNESSetComputeApplicationContext(SNES snes, PetscErrorCode (*compute)(SNES snes, void **ctx), PetscCtxDestroyFn *destroy)
1241: {
1242:   PetscFunctionBegin;
1244:   snes->ops->usercompute = compute;
1245:   snes->ops->ctxdestroy  = destroy;
1246:   PetscFunctionReturn(PETSC_SUCCESS);
1247: }

1249: /*@
1250:   SNESSetApplicationContext - Sets the optional user-defined context for the nonlinear solvers.

1252:   Logically Collective

1254:   Input Parameters:
1255: + snes - the `SNES` context
1256: - ctx  - the user context

1258:   Level: intermediate

1260:   Notes:
1261:   Users can provide a context when constructing the `SNES` options and then access it inside their function, Jacobian computation, or other evaluation function
1262:   with `SNESGetApplicationContext()`

1264:   To provide a function that computes the context for you use `SNESSetComputeApplicationContext()`

1266:   Fortran Note:
1267:   This only works when `ctx` is a Fortran derived type (it cannot be a `PetscObject`), we recommend writing a Fortran interface definition for this
1268:   function that tells the Fortran compiler the derived data type that is passed in as the `ctx` argument. See `SNESGetApplicationContext()` for
1269:   an example.

1271: .seealso: [](ch_snes), `SNES`, `SNESSetComputeApplicationContext()`, `SNESGetApplicationContext()`
1272: @*/
1273: PetscErrorCode SNESSetApplicationContext(SNES snes, void *ctx)
1274: {
1275:   KSP ksp;

1277:   PetscFunctionBegin;
1279:   PetscCall(SNESGetKSP(snes, &ksp));
1280:   PetscCall(KSPSetApplicationContext(ksp, ctx));
1281:   snes->ctx = ctx;
1282:   PetscFunctionReturn(PETSC_SUCCESS);
1283: }

1285: /*@
1286:   SNESGetApplicationContext - Gets the user-defined context for the
1287:   nonlinear solvers set with `SNESGetApplicationContext()` or `SNESSetComputeApplicationContext()`

1289:   Not Collective

1291:   Input Parameter:
1292: . snes - `SNES` context

1294:   Output Parameter:
1295: . ctx - user context

1297:   Level: intermediate

1299:   Fortran Notes:
1300:   This only works when the context is a Fortran derived type (it cannot be a `PetscObject`) and you **must** write a Fortran interface definition for this
1301:   function that tells the Fortran compiler the derived data type that is returned as the `ctx` argument. For example,
1302: .vb
1303:   Interface SNESGetApplicationContext
1304:     Subroutine SNESGetApplicationContext(snes,ctx,ierr)
1305:   #include <petsc/finclude/petscsnes.h>
1306:       use petscsnes
1307:       SNES snes
1308:       type(tUsertype), pointer :: ctx
1309:       PetscErrorCode ierr
1310:     End Subroutine
1311:   End Interface SNESGetApplicationContext
1312: .ve

1314:   The prototype for `ctx` must be
1315: .vb
1316:   type(tUsertype), pointer :: ctx
1317: .ve

1319: .seealso: [](ch_snes), `SNESSetApplicationContext()`, `SNESSetComputeApplicationContext()`
1320: @*/
1321: PetscErrorCode SNESGetApplicationContext(SNES snes, PeCtx ctx)
1322: {
1323:   PetscFunctionBegin;
1325:   *(void **)ctx = snes->ctx;
1326:   PetscFunctionReturn(PETSC_SUCCESS);
1327: }

1329: /*@
1330:   SNESSetUseMatrixFree - indicates that `SNES` should use matrix-free finite difference matrix-vector products to apply the Jacobian.

1332:   Logically Collective

1334:   Input Parameters:
1335: + snes        - `SNES` context
1336: . mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1337: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored. With
1338:                 this option no matrix-element based preconditioners can be used in the linear solve since the matrix won't be explicitly available

1340:   Options Database Keys:
1341: + -snes_mf_operator - use matrix-free only for the mat operator
1342: . -snes_mf          - use matrix-free for both the mat and pmat operator
1343: . -snes_fd_color    - compute the Jacobian via coloring and finite differences.
1344: - -snes_fd          - compute the Jacobian via finite differences (slow)

1346:   Level: intermediate

1348:   Note:
1349:   `SNES` supports three approaches for computing (approximate) Jacobians: user provided via `SNESSetJacobian()`, matrix-free using `MatCreateSNESMF()`,
1350:   and computing explicitly with
1351:   finite differences and coloring using `MatFDColoring`. It is also possible to use automatic differentiation and the `MatFDColoring` object.

1353: .seealso: [](ch_snes), `SNES`, `SNESGetUseMatrixFree()`, `MatCreateSNESMF()`, `SNESComputeJacobianDefaultColor()`, `MatFDColoring`
1354: @*/
1355: PetscErrorCode SNESSetUseMatrixFree(SNES snes, PetscBool mf_operator, PetscBool mf)
1356: {
1357:   PetscFunctionBegin;
1361:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
1362:   snes->mf_operator = mf_operator;
1363:   PetscFunctionReturn(PETSC_SUCCESS);
1364: }

1366: /*@
1367:   SNESGetUseMatrixFree - indicates if the `SNES` uses matrix-free finite difference matrix vector products to apply the Jacobian.

1369:   Not Collective, but the resulting flags will be the same on all MPI processes

1371:   Input Parameter:
1372: . snes - `SNES` context

1374:   Output Parameters:
1375: + mf_operator - use matrix-free only for the Amat used by `SNESSetJacobian()`, this means the user provided Pmat will continue to be used
1376: - mf          - use matrix-free for both the Amat and Pmat used by `SNESSetJacobian()`, both the Amat and Pmat set in `SNESSetJacobian()` will be ignored

1378:   Level: intermediate

1380: .seealso: [](ch_snes), `SNES`, `SNESSetUseMatrixFree()`, `MatCreateSNESMF()`
1381: @*/
1382: PetscErrorCode SNESGetUseMatrixFree(SNES snes, PetscBool *mf_operator, PetscBool *mf)
1383: {
1384:   PetscFunctionBegin;
1386:   if (mf) *mf = snes->mf;
1387:   if (mf_operator) *mf_operator = snes->mf_operator;
1388:   PetscFunctionReturn(PETSC_SUCCESS);
1389: }

1391: /*@
1392:   SNESGetIterationNumber - Gets the number of nonlinear iterations completed in the current or most recent `SNESSolve()`

1394:   Not Collective

1396:   Input Parameter:
1397: . snes - `SNES` context

1399:   Output Parameter:
1400: . iter - iteration number

1402:   Level: intermediate

1404:   Notes:
1405:   For example, during the computation of iteration 2 this would return 1.

1407:   This is useful for using lagged Jacobians (where one does not recompute the
1408:   Jacobian at each `SNES` iteration). For example, the code
1409: .vb
1410:       ierr = SNESGetIterationNumber(snes,&it);
1411:       if (!(it % 2)) {
1412:         [compute Jacobian here]
1413:       }
1414: .ve
1415:   can be used in your function that computes the Jacobian to cause the Jacobian to be
1416:   recomputed every second `SNES` iteration. See also `SNESSetLagJacobian()`

1418:   After the `SNES` solve is complete this will return the number of nonlinear iterations used.

1420: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetLagJacobian()`, `SNESGetLinearSolveIterations()`, `SNESSetMonitor()`
1421: @*/
1422: PetscErrorCode SNESGetIterationNumber(SNES snes, PetscInt *iter)
1423: {
1424:   PetscFunctionBegin;
1426:   PetscAssertPointer(iter, 2);
1427:   *iter = snes->iter;
1428:   PetscFunctionReturn(PETSC_SUCCESS);
1429: }

1431: /*@
1432:   SNESSetIterationNumber - Sets the current iteration number.

1434:   Not Collective

1436:   Input Parameters:
1437: + snes - `SNES` context
1438: - iter - iteration number

1440:   Level: developer

1442:   Note:
1443:   This should only be called inside a `SNES` nonlinear solver.

1445: .seealso: [](ch_snes), `SNESGetLinearSolveIterations()`
1446: @*/
1447: PetscErrorCode SNESSetIterationNumber(SNES snes, PetscInt iter)
1448: {
1449:   PetscFunctionBegin;
1451:   PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
1452:   snes->iter = iter;
1453:   PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
1454:   PetscFunctionReturn(PETSC_SUCCESS);
1455: }

1457: /*@
1458:   SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1459:   attempted by the nonlinear solver in the current or most recent `SNESSolve()` .

1461:   Not Collective

1463:   Input Parameter:
1464: . snes - `SNES` context

1466:   Output Parameter:
1467: . nfails - number of unsuccessful steps attempted

1469:   Level: intermediate

1471:   Note:
1472:   This counter is reset to zero for each successive call to `SNESSolve()`.

1474: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1475:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetMaxNonlinearStepFailures()`
1476: @*/
1477: PetscErrorCode SNESGetNonlinearStepFailures(SNES snes, PetscInt *nfails)
1478: {
1479:   PetscFunctionBegin;
1481:   PetscAssertPointer(nfails, 2);
1482:   *nfails = snes->numFailures;
1483:   PetscFunctionReturn(PETSC_SUCCESS);
1484: }

1486: /*@
1487:   SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1488:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1490:   Not Collective

1492:   Input Parameters:
1493: + snes     - `SNES` context
1494: - maxFails - maximum of unsuccessful steps allowed, use `PETSC_UNLIMITED` to have no limit on the number of failures

1496:   Options Database Key:
1497: . -snes_max_fail <n> - maximum number of unsuccessful steps allowed

1499:   Level: intermediate

1501:   Developer Note:
1502:   The options database key is wrong for this function name

1504: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1505:           `SNESGetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1506: @*/
1507: PetscErrorCode SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1508: {
1509:   PetscFunctionBegin;

1512:   if (maxFails == PETSC_UNLIMITED) {
1513:     snes->maxFailures = PETSC_INT_MAX;
1514:   } else {
1515:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1516:     snes->maxFailures = maxFails;
1517:   }
1518:   PetscFunctionReturn(PETSC_SUCCESS);
1519: }

1521: /*@
1522:   SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1523:   attempted by the nonlinear solver before it gives up and returns unconverged or generates an error

1525:   Not Collective

1527:   Input Parameter:
1528: . snes - `SNES` context

1530:   Output Parameter:
1531: . maxFails - maximum of unsuccessful steps

1533:   Level: intermediate

1535: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`,
1536:           `SNESSetMaxNonlinearStepFailures()`, `SNESGetNonlinearStepFailures()`
1537: @*/
1538: PetscErrorCode SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1539: {
1540:   PetscFunctionBegin;
1542:   PetscAssertPointer(maxFails, 2);
1543:   *maxFails = snes->maxFailures;
1544:   PetscFunctionReturn(PETSC_SUCCESS);
1545: }

1547: /*@
1548:   SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1549:   done by the `SNES` object in the current or most recent `SNESSolve()`

1551:   Not Collective

1553:   Input Parameter:
1554: . snes - `SNES` context

1556:   Output Parameter:
1557: . nfuncs - number of evaluations

1559:   Level: intermediate

1561:   Note:
1562:   Reset every time `SNESSolve()` is called unless `SNESSetCountersReset()` is used.

1564: .seealso: [](ch_snes), `SNES`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`, `SNESGetLinearSolveFailures()`, `SNESSetCountersReset()`
1565: @*/
1566: PetscErrorCode SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1567: {
1568:   PetscFunctionBegin;
1570:   PetscAssertPointer(nfuncs, 2);
1571:   *nfuncs = snes->nfuncs;
1572:   PetscFunctionReturn(PETSC_SUCCESS);
1573: }

1575: /*@
1576:   SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1577:   linear solvers in the current or most recent `SNESSolve()`

1579:   Not Collective

1581:   Input Parameter:
1582: . snes - `SNES` context

1584:   Output Parameter:
1585: . nfails - number of failed solves

1587:   Options Database Key:
1588: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1590:   Level: intermediate

1592:   Note:
1593:   This counter is reset to zero for each successive call to `SNESSolve()`.

1595: .seealso: [](ch_snes), `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`
1596: @*/
1597: PetscErrorCode SNESGetLinearSolveFailures(SNES snes, PetscInt *nfails)
1598: {
1599:   PetscFunctionBegin;
1601:   PetscAssertPointer(nfails, 2);
1602:   *nfails = snes->numLinearSolveFailures;
1603:   PetscFunctionReturn(PETSC_SUCCESS);
1604: }

1606: /*@
1607:   SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1608:   allowed before `SNES` returns with a diverged reason of `SNES_DIVERGED_LINEAR_SOLVE`

1610:   Logically Collective

1612:   Input Parameters:
1613: + snes     - `SNES` context
1614: - maxFails - maximum allowed linear solve failures, use `PETSC_UNLIMITED` to have no limit on the number of failures

1616:   Options Database Key:
1617: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

1619:   Level: intermediate

1621:   Note:
1622:   By default this is 0; that is `SNES` returns on the first failed linear solve

1624:   Developer Note:
1625:   The options database key is wrong for this function name

1627: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESGetLinearSolveIterations()`
1628: @*/
1629: PetscErrorCode SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1630: {
1631:   PetscFunctionBegin;

1635:   if (maxFails == PETSC_UNLIMITED) {
1636:     snes->maxLinearSolveFailures = PETSC_INT_MAX;
1637:   } else {
1638:     PetscCheck(maxFails >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Cannot have a negative maximum number of failures");
1639:     snes->maxLinearSolveFailures = maxFails;
1640:   }
1641:   PetscFunctionReturn(PETSC_SUCCESS);
1642: }

1644: /*@
1645:   SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1646:   are allowed before `SNES` returns as unsuccessful

1648:   Not Collective

1650:   Input Parameter:
1651: . snes - `SNES` context

1653:   Output Parameter:
1654: . maxFails - maximum of unsuccessful solves allowed

1656:   Level: intermediate

1658:   Note:
1659:   By default this is 1; that is `SNES` returns on the first failed linear solve

1661: .seealso: [](ch_snes), `SNESSetErrorIfNotConverged()`, `SNESGetLinearSolveFailures()`, `SNESGetLinearSolveIterations()`, `SNESSetMaxLinearSolveFailures()`,
1662: @*/
1663: PetscErrorCode SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1664: {
1665:   PetscFunctionBegin;
1667:   PetscAssertPointer(maxFails, 2);
1668:   *maxFails = snes->maxLinearSolveFailures;
1669:   PetscFunctionReturn(PETSC_SUCCESS);
1670: }

1672: /*@
1673:   SNESGetLinearSolveIterations - Gets the total number of linear iterations
1674:   used by the nonlinear solver in the most recent `SNESSolve()`

1676:   Not Collective

1678:   Input Parameter:
1679: . snes - `SNES` context

1681:   Output Parameter:
1682: . lits - number of linear iterations

1684:   Level: intermediate

1686:   Notes:
1687:   This counter is reset to zero for each successive call to `SNESSolve()` unless `SNESSetCountersReset()` is used.

1689:   If the linear solver fails inside the `SNESSolve()` the iterations for that call to the linear solver are not included. If you wish to count them
1690:   then call `KSPGetIterationNumber()` after the failed solve.

1692: .seealso: [](ch_snes), `SNES`, `SNESGetIterationNumber()`, `SNESGetLinearSolveFailures()`, `SNESGetMaxLinearSolveFailures()`, `SNESSetCountersReset()`
1693: @*/
1694: PetscErrorCode SNESGetLinearSolveIterations(SNES snes, PetscInt *lits)
1695: {
1696:   PetscFunctionBegin;
1698:   PetscAssertPointer(lits, 2);
1699:   *lits = snes->linear_its;
1700:   PetscFunctionReturn(PETSC_SUCCESS);
1701: }

1703: /*@
1704:   SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1705:   are reset every time `SNESSolve()` is called.

1707:   Logically Collective

1709:   Input Parameters:
1710: + snes  - `SNES` context
1711: - reset - whether to reset the counters or not, defaults to `PETSC_TRUE`

1713:   Level: developer

1715: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1716: @*/
1717: PetscErrorCode SNESSetCountersReset(SNES snes, PetscBool reset)
1718: {
1719:   PetscFunctionBegin;
1722:   snes->counters_reset = reset;
1723:   PetscFunctionReturn(PETSC_SUCCESS);
1724: }

1726: /*@
1727:   SNESResetCounters - Reset counters for linear iterations and function evaluations.

1729:   Logically Collective

1731:   Input Parameters:
1732: . snes - `SNES` context

1734:   Level: developer

1736:   Note:
1737:   It honors the flag set with `SNESSetCountersReset()`

1739: .seealso: [](ch_snes), `SNESGetNumberFunctionEvals()`, `SNESGetLinearSolveIterations()`, `SNESGetNPC()`
1740: @*/
1741: PetscErrorCode SNESResetCounters(SNES snes)
1742: {
1743:   PetscFunctionBegin;
1745:   if (snes->counters_reset) {
1746:     snes->nfuncs      = 0;
1747:     snes->linear_its  = 0;
1748:     snes->numFailures = 0;
1749:   }
1750:   PetscFunctionReturn(PETSC_SUCCESS);
1751: }

1753: /*@
1754:   SNESSetKSP - Sets a `KSP` context for the `SNES` object to use

1756:   Not Collective, but the `SNES` and `KSP` objects must live on the same `MPI_Comm`

1758:   Input Parameters:
1759: + snes - the `SNES` context
1760: - ksp  - the `KSP` context

1762:   Level: developer

1764:   Notes:
1765:   The `SNES` object already has its `KSP` object, you can obtain with `SNESGetKSP()`
1766:   so this routine is rarely needed.

1768:   The `KSP` object that is already in the `SNES` object has its reference count
1769:   decreased by one when this is called.

1771: .seealso: [](ch_snes), `SNES`, `KSP`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`
1772: @*/
1773: PetscErrorCode SNESSetKSP(SNES snes, KSP ksp)
1774: {
1775:   PetscFunctionBegin;
1778:   PetscCheckSameComm(snes, 1, ksp, 2);
1779:   PetscCall(PetscObjectReference((PetscObject)ksp));
1780:   if (snes->ksp) PetscCall(PetscObjectDereference((PetscObject)snes->ksp));
1781:   snes->ksp = ksp;
1782:   PetscFunctionReturn(PETSC_SUCCESS);
1783: }

1785: /*@
1786:   SNESParametersInitialize - Sets all the parameters in `snes` to their default value (when `SNESCreate()` was called) if they
1787:   currently contain default values

1789:   Collective

1791:   Input Parameter:
1792: . snes - the `SNES` object

1794:   Level: developer

1796:   Developer Note:
1797:   This is called by all the `SNESCreate_XXX()` routines.

1799: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`,
1800:           `PetscObjectParameterSetDefault()`
1801: @*/
1802: PetscErrorCode SNESParametersInitialize(SNES snes)
1803: {
1804:   PetscObjectParameterSetDefault(snes, max_its, 50);
1805:   PetscObjectParameterSetDefault(snes, max_funcs, 10000);
1806:   PetscObjectParameterSetDefault(snes, rtol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1807:   PetscObjectParameterSetDefault(snes, abstol, PetscDefined(USE_REAL_SINGLE) ? 1.e-25 : 1.e-50);
1808:   PetscObjectParameterSetDefault(snes, stol, PetscDefined(USE_REAL_SINGLE) ? 1.e-5 : 1.e-8);
1809:   PetscObjectParameterSetDefault(snes, divtol, 1.e4);
1810:   return PETSC_SUCCESS;
1811: }

1813: /*@
1814:   SNESCreate - Creates a nonlinear solver context used to manage a set of nonlinear solves

1816:   Collective

1818:   Input Parameter:
1819: . comm - MPI communicator

1821:   Output Parameter:
1822: . outsnes - the new `SNES` context

1824:   Options Database Keys:
1825: + -snes_mf          - Activates default matrix-free Jacobian-vector products, and no matrix to construct a preconditioner
1826: . -snes_mf_operator - Activates default matrix-free Jacobian-vector products, and a user-provided matrix as set by `SNESSetJacobian()`
1827: . -snes_fd_coloring - uses a relative fast computation of the Jacobian using finite differences and a graph coloring
1828: - -snes_fd          - Uses (slow!) finite differences to compute Jacobian

1830:   Level: beginner

1832:   Developer Notes:
1833:   `SNES` always creates a `KSP` object even though many `SNES` methods do not use it. This is
1834:   unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
1835:   particular method does use `KSP` and regulates if the information about the `KSP` is printed
1836:   in `SNESView()`.

1838:   `TSSetFromOptions()` does call `SNESSetFromOptions()` which can lead to users being confused
1839:   by help messages about meaningless `SNES` options.

1841:   `SNES` always creates the `snes->kspconvctx` even though it is used by only one type. This should be fixed.

1843: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESDestroy()`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
1844: @*/
1845: PetscErrorCode SNESCreate(MPI_Comm comm, SNES *outsnes)
1846: {
1847:   SNES       snes;
1848:   SNESKSPEW *kctx;

1850:   PetscFunctionBegin;
1851:   PetscAssertPointer(outsnes, 2);
1852:   PetscCall(SNESInitializePackage());

1854:   PetscCall(PetscHeaderCreate(snes, SNES_CLASSID, "SNES", "Nonlinear solver", "SNES", comm, SNESDestroy, SNESView));
1855:   snes->ops->converged = SNESConvergedDefault;
1856:   snes->usesksp        = PETSC_TRUE;
1857:   snes->norm           = 0.0;
1858:   snes->xnorm          = 0.0;
1859:   snes->ynorm          = 0.0;
1860:   snes->normschedule   = SNES_NORM_ALWAYS;
1861:   snes->functype       = SNES_FUNCTION_DEFAULT;
1862:   snes->ttol           = 0.0;

1864:   snes->rnorm0               = 0;
1865:   snes->nfuncs               = 0;
1866:   snes->numFailures          = 0;
1867:   snes->maxFailures          = 1;
1868:   snes->linear_its           = 0;
1869:   snes->lagjacobian          = 1;
1870:   snes->jac_iter             = 0;
1871:   snes->lagjac_persist       = PETSC_FALSE;
1872:   snes->lagpreconditioner    = 1;
1873:   snes->pre_iter             = 0;
1874:   snes->lagpre_persist       = PETSC_FALSE;
1875:   snes->numbermonitors       = 0;
1876:   snes->numberreasonviews    = 0;
1877:   snes->data                 = NULL;
1878:   snes->setupcalled          = PETSC_FALSE;
1879:   snes->ksp_ewconv           = PETSC_FALSE;
1880:   snes->nwork                = 0;
1881:   snes->work                 = NULL;
1882:   snes->nvwork               = 0;
1883:   snes->vwork                = NULL;
1884:   snes->conv_hist_len        = 0;
1885:   snes->conv_hist_max        = 0;
1886:   snes->conv_hist            = NULL;
1887:   snes->conv_hist_its        = NULL;
1888:   snes->conv_hist_reset      = PETSC_TRUE;
1889:   snes->counters_reset       = PETSC_TRUE;
1890:   snes->vec_func_init_set    = PETSC_FALSE;
1891:   snes->reason               = SNES_CONVERGED_ITERATING;
1892:   snes->npcside              = PC_RIGHT;
1893:   snes->setfromoptionscalled = 0;

1895:   snes->mf          = PETSC_FALSE;
1896:   snes->mf_operator = PETSC_FALSE;
1897:   snes->mf_version  = 1;

1899:   snes->numLinearSolveFailures = 0;
1900:   snes->maxLinearSolveFailures = 1;

1902:   snes->vizerotolerance     = 1.e-8;
1903:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

1905:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
1906:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

1908:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1909:   PetscCall(PetscNew(&kctx));

1911:   snes->kspconvctx  = kctx;
1912:   kctx->version     = 2;
1913:   kctx->rtol_0      = 0.3; /* Eisenstat and Walker suggest rtol_0=.5, but
1914:                              this was too large for some test cases */
1915:   kctx->rtol_last   = 0.0;
1916:   kctx->rtol_max    = 0.9;
1917:   kctx->gamma       = 1.0;
1918:   kctx->alpha       = 0.5 * (1.0 + PetscSqrtReal(5.0));
1919:   kctx->alpha2      = kctx->alpha;
1920:   kctx->threshold   = 0.1;
1921:   kctx->lresid_last = 0.0;
1922:   kctx->norm_last   = 0.0;

1924:   kctx->rk_last     = 0.0;
1925:   kctx->rk_last_2   = 0.0;
1926:   kctx->rtol_last_2 = 0.0;
1927:   kctx->v4_p1       = 0.1;
1928:   kctx->v4_p2       = 0.4;
1929:   kctx->v4_p3       = 0.7;
1930:   kctx->v4_m1       = 0.8;
1931:   kctx->v4_m2       = 0.5;
1932:   kctx->v4_m3       = 0.1;
1933:   kctx->v4_m4       = 0.5;

1935:   PetscCall(SNESParametersInitialize(snes));
1936:   *outsnes = snes;
1937:   PetscFunctionReturn(PETSC_SUCCESS);
1938: }

1940: /*@C
1941:   SNESSetFunction - Sets the function evaluation routine and function
1942:   vector for use by the `SNES` routines in solving systems of nonlinear
1943:   equations.

1945:   Logically Collective

1947:   Input Parameters:
1948: + snes - the `SNES` context
1949: . r    - vector to store function values, may be `NULL`
1950: . f    - function evaluation routine;  for calling sequence see `SNESFunctionFn`
1951: - ctx  - [optional] user-defined context for private data for the
1952:          function evaluation routine (may be `NULL`)

1954:   Level: beginner

1956: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetPicard()`, `SNESFunctionFn`
1957: @*/
1958: PetscErrorCode SNESSetFunction(SNES snes, Vec r, SNESFunctionFn *f, void *ctx)
1959: {
1960:   DM dm;

1962:   PetscFunctionBegin;
1964:   if (r) {
1966:     PetscCheckSameComm(snes, 1, r, 2);
1967:     PetscCall(PetscObjectReference((PetscObject)r));
1968:     PetscCall(VecDestroy(&snes->vec_func));
1969:     snes->vec_func = r;
1970:   }
1971:   PetscCall(SNESGetDM(snes, &dm));
1972:   PetscCall(DMSNESSetFunction(dm, f, ctx));
1973:   if (f == SNESPicardComputeFunction) PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
1974:   PetscFunctionReturn(PETSC_SUCCESS);
1975: }

1977: /*@C
1978:   SNESSetInitialFunction - Set an already computed function evaluation at the initial guess to be reused by `SNESSolve()`.

1980:   Logically Collective

1982:   Input Parameters:
1983: + snes - the `SNES` context
1984: - f    - vector to store function value

1986:   Level: developer

1988:   Notes:
1989:   This should not be modified during the solution procedure.

1991:   This is used extensively in the `SNESFAS` hierarchy and in nonlinear preconditioning.

1993: .seealso: [](ch_snes), `SNES`, `SNESFAS`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetInitialFunctionNorm()`
1994: @*/
1995: PetscErrorCode SNESSetInitialFunction(SNES snes, Vec f)
1996: {
1997:   Vec vec_func;

1999:   PetscFunctionBegin;
2002:   PetscCheckSameComm(snes, 1, f, 2);
2003:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2004:     snes->vec_func_init_set = PETSC_FALSE;
2005:     PetscFunctionReturn(PETSC_SUCCESS);
2006:   }
2007:   PetscCall(SNESGetFunction(snes, &vec_func, NULL, NULL));
2008:   PetscCall(VecCopy(f, vec_func));

2010:   snes->vec_func_init_set = PETSC_TRUE;
2011:   PetscFunctionReturn(PETSC_SUCCESS);
2012: }

2014: /*@
2015:   SNESSetNormSchedule - Sets the `SNESNormSchedule` used in convergence and monitoring
2016:   of the `SNES` method, when norms are computed in the solving process

2018:   Logically Collective

2020:   Input Parameters:
2021: + snes         - the `SNES` context
2022: - normschedule - the frequency of norm computation

2024:   Options Database Key:
2025: . -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

2027:   Level: advanced

2029:   Notes:
2030:   Only certain `SNES` methods support certain `SNESNormSchedules`.  Most require evaluation
2031:   of the nonlinear function and the taking of its norm at every iteration to
2032:   even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
2033:   `SNESNGS` and the like do not require the norm of the function to be computed, and therefore
2034:   may either be monitored for convergence or not.  As these are often used as nonlinear
2035:   preconditioners, monitoring the norm of their error is not a useful enterprise within
2036:   their solution.

2038: .seealso: [](ch_snes), `SNESNormSchedule`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`
2039: @*/
2040: PetscErrorCode SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
2041: {
2042:   PetscFunctionBegin;
2044:   snes->normschedule = normschedule;
2045:   PetscFunctionReturn(PETSC_SUCCESS);
2046: }

2048: /*@
2049:   SNESGetNormSchedule - Gets the `SNESNormSchedule` used in convergence and monitoring
2050:   of the `SNES` method.

2052:   Logically Collective

2054:   Input Parameters:
2055: + snes         - the `SNES` context
2056: - normschedule - the type of the norm used

2058:   Level: advanced

2060: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2061: @*/
2062: PetscErrorCode SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
2063: {
2064:   PetscFunctionBegin;
2066:   *normschedule = snes->normschedule;
2067:   PetscFunctionReturn(PETSC_SUCCESS);
2068: }

2070: /*@
2071:   SNESSetFunctionNorm - Sets the last computed residual norm.

2073:   Logically Collective

2075:   Input Parameters:
2076: + snes - the `SNES` context
2077: - norm - the value of the norm

2079:   Level: developer

2081: .seealso: [](ch_snes), `SNES`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2082: @*/
2083: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
2084: {
2085:   PetscFunctionBegin;
2087:   snes->norm = norm;
2088:   PetscFunctionReturn(PETSC_SUCCESS);
2089: }

2091: /*@
2092:   SNESGetFunctionNorm - Gets the last computed norm of the residual

2094:   Not Collective

2096:   Input Parameter:
2097: . snes - the `SNES` context

2099:   Output Parameter:
2100: . norm - the last computed residual norm

2102:   Level: developer

2104: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2105: @*/
2106: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
2107: {
2108:   PetscFunctionBegin;
2110:   PetscAssertPointer(norm, 2);
2111:   *norm = snes->norm;
2112:   PetscFunctionReturn(PETSC_SUCCESS);
2113: }

2115: /*@
2116:   SNESGetUpdateNorm - Gets the last computed norm of the solution update

2118:   Not Collective

2120:   Input Parameter:
2121: . snes - the `SNES` context

2123:   Output Parameter:
2124: . ynorm - the last computed update norm

2126:   Level: developer

2128:   Note:
2129:   The new solution is the current solution plus the update, so this norm is an indication of the size of the update

2131: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`
2132: @*/
2133: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
2134: {
2135:   PetscFunctionBegin;
2137:   PetscAssertPointer(ynorm, 2);
2138:   *ynorm = snes->ynorm;
2139:   PetscFunctionReturn(PETSC_SUCCESS);
2140: }

2142: /*@
2143:   SNESGetSolutionNorm - Gets the last computed norm of the solution

2145:   Not Collective

2147:   Input Parameter:
2148: . snes - the `SNES` context

2150:   Output Parameter:
2151: . xnorm - the last computed solution norm

2153:   Level: developer

2155: .seealso: [](ch_snes), `SNES`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `SNESGetFunctionNorm()`, `SNESGetUpdateNorm()`
2156: @*/
2157: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
2158: {
2159:   PetscFunctionBegin;
2161:   PetscAssertPointer(xnorm, 2);
2162:   *xnorm = snes->xnorm;
2163:   PetscFunctionReturn(PETSC_SUCCESS);
2164: }

2166: /*@
2167:   SNESSetFunctionType - Sets the `SNESFunctionType`
2168:   of the `SNES` method.

2170:   Logically Collective

2172:   Input Parameters:
2173: + snes - the `SNES` context
2174: - type - the function type

2176:   Level: developer

2178:   Values of the function type\:
2179: +  `SNES_FUNCTION_DEFAULT`          - the default for the given `SNESType`
2180: .  `SNES_FUNCTION_UNPRECONDITIONED` - an unpreconditioned function evaluation (this is the function provided with `SNESSetFunction()`
2181: -  `SNES_FUNCTION_PRECONDITIONED`   - a transformation of the function provided with `SNESSetFunction()`

2183:   Note:
2184:   Different `SNESType`s use this value in different ways

2186: .seealso: [](ch_snes), `SNES`, `SNESFunctionType`, `SNESGetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2187: @*/
2188: PetscErrorCode SNESSetFunctionType(SNES snes, SNESFunctionType type)
2189: {
2190:   PetscFunctionBegin;
2192:   snes->functype = type;
2193:   PetscFunctionReturn(PETSC_SUCCESS);
2194: }

2196: /*@
2197:   SNESGetFunctionType - Gets the `SNESFunctionType` used in convergence and monitoring set with `SNESSetFunctionType()`
2198:   of the SNES method.

2200:   Logically Collective

2202:   Input Parameters:
2203: + snes - the `SNES` context
2204: - type - the type of the function evaluation, see `SNESSetFunctionType()`

2206:   Level: advanced

2208: .seealso: [](ch_snes), `SNESSetFunctionType()`, `SNESFunctionType`, `SNESSetNormSchedule()`, `SNESComputeFunction()`, `VecNorm()`, `SNESSetFunction()`, `SNESSetInitialFunction()`, `SNESNormSchedule`
2209: @*/
2210: PetscErrorCode SNESGetFunctionType(SNES snes, SNESFunctionType *type)
2211: {
2212:   PetscFunctionBegin;
2214:   *type = snes->functype;
2215:   PetscFunctionReturn(PETSC_SUCCESS);
2216: }

2218: /*@C
2219:   SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
2220:   use with composed nonlinear solvers.

2222:   Input Parameters:
2223: + snes - the `SNES` context, usually of the `SNESType` `SNESNGS`
2224: . f    - function evaluation routine to apply Gauss-Seidel, see `SNESNGSFn` for calling sequence
2225: - ctx  - [optional] user-defined context for private data for the smoother evaluation routine (may be `NULL`)

2227:   Level: intermediate

2229:   Note:
2230:   The `SNESNGS` routines are used by the composed nonlinear solver to generate
2231:   a problem appropriate update to the solution, particularly `SNESFAS`.

2233: .seealso: [](ch_snes), `SNESNGS`, `SNESGetNGS()`, `SNESNCG`, `SNESGetFunction()`, `SNESComputeNGS()`, `SNESNGSFn`
2234: @*/
2235: PetscErrorCode SNESSetNGS(SNES snes, SNESNGSFn *f, void *ctx)
2236: {
2237:   DM dm;

2239:   PetscFunctionBegin;
2241:   PetscCall(SNESGetDM(snes, &dm));
2242:   PetscCall(DMSNESSetNGS(dm, f, ctx));
2243:   PetscFunctionReturn(PETSC_SUCCESS);
2244: }

2246: /*
2247:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
2248:    changed during the KSPSolve()
2249: */
2250: PetscErrorCode SNESPicardComputeMFFunction(SNES snes, Vec x, Vec f, void *ctx)
2251: {
2252:   DM     dm;
2253:   DMSNES sdm;

2255:   PetscFunctionBegin;
2256:   PetscCall(SNESGetDM(snes, &dm));
2257:   PetscCall(DMGetDMSNES(dm, &sdm));
2258:   /*  A(x)*x - b(x) */
2259:   if (sdm->ops->computepfunction) {
2260:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2261:     PetscCall(VecScale(f, -1.0));
2262:     /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
2263:     if (!snes->picard) PetscCall(MatDuplicate(snes->jacobian_pre, MAT_DO_NOT_COPY_VALUES, &snes->picard));
2264:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2265:     PetscCall(MatMultAdd(snes->picard, x, f, f));
2266:   } else {
2267:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->picard, snes->picard, sdm->pctx));
2268:     PetscCall(MatMult(snes->picard, x, f));
2269:   }
2270:   PetscFunctionReturn(PETSC_SUCCESS);
2271: }

2273: PetscErrorCode SNESPicardComputeFunction(SNES snes, Vec x, Vec f, void *ctx)
2274: {
2275:   DM     dm;
2276:   DMSNES sdm;

2278:   PetscFunctionBegin;
2279:   PetscCall(SNESGetDM(snes, &dm));
2280:   PetscCall(DMGetDMSNES(dm, &sdm));
2281:   /*  A(x)*x - b(x) */
2282:   if (sdm->ops->computepfunction) {
2283:     PetscCallBack("SNES Picard callback function", (*sdm->ops->computepfunction)(snes, x, f, sdm->pctx));
2284:     PetscCall(VecScale(f, -1.0));
2285:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2286:     PetscCall(MatMultAdd(snes->jacobian_pre, x, f, f));
2287:   } else {
2288:     PetscCallBack("SNES Picard callback Jacobian", (*sdm->ops->computepjacobian)(snes, x, snes->jacobian, snes->jacobian_pre, sdm->pctx));
2289:     PetscCall(MatMult(snes->jacobian_pre, x, f));
2290:   }
2291:   PetscFunctionReturn(PETSC_SUCCESS);
2292: }

2294: PetscErrorCode SNESPicardComputeJacobian(SNES snes, Vec x1, Mat J, Mat B, void *ctx)
2295: {
2296:   PetscFunctionBegin;
2297:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
2298:   /* must assembly if matrix-free to get the last SNES solution */
2299:   PetscCall(MatAssemblyBegin(J, MAT_FINAL_ASSEMBLY));
2300:   PetscCall(MatAssemblyEnd(J, MAT_FINAL_ASSEMBLY));
2301:   PetscFunctionReturn(PETSC_SUCCESS);
2302: }

2304: /*@C
2305:   SNESSetPicard - Use `SNES` to solve the system $A(x) x = bp(x) + b $ via a Picard type iteration (Picard linearization)

2307:   Logically Collective

2309:   Input Parameters:
2310: + snes - the `SNES` context
2311: . r    - vector to store function values, may be `NULL`
2312: . bp   - function evaluation routine, may be `NULL`, for the calling sequence see `SNESFunctionFn`
2313: . Amat - matrix with which $A(x) x - bp(x) - b$ is to be computed
2314: . Pmat - matrix from which preconditioner is computed (usually the same as `Amat`)
2315: . J    - function to compute matrix values, for the calling sequence see `SNESJacobianFn`
2316: - ctx  - [optional] user-defined context for private data for the function evaluation routine (may be `NULL`)

2318:   Level: intermediate

2320:   Notes:
2321:   It is often better to provide the nonlinear function $F()$ and some approximation to its Jacobian directly and use
2322:   an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

2324:   One can call `SNESSetPicard()` or `SNESSetFunction()` (and possibly `SNESSetJacobian()`) but cannot call both

2326:   Solves the equation $A(x) x = bp(x) - b$ via the defect correction algorithm $A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}$.
2327:   When an exact solver is used this corresponds to the "classic" Picard $A(x^{n}) x^{n+1} = bp(x^{n}) + b$ iteration.

2329:   Run with `-snes_mf_operator` to solve the system with Newton's method using $A(x^{n})$ to construct the preconditioner.

2331:   We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
2332:   the direct Picard iteration $A(x^n) x^{n+1} = bp(x^n) + b$

2334:   There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
2335:   believe it is the iteration  $A(x^{n}) x^{n+1} = b(x^{n})$ hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
2336:   different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument \:-).

2338:   When used with `-snes_mf_operator` this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of $A(x)x - bp(x) - b$ and
2339:   $A(x^{n})$ is used to build the preconditioner

2341:   When used with `-snes_fd` this will compute the true Jacobian (very slowly one column at a time) and thus represent Newton's method.

2343:   When used with `-snes_fd_coloring` this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
2344:   the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix $A$ so you must provide in $A$ the needed nonzero structure for the correct
2345:   coloring. When using `DMDA` this may mean creating the matrix $A$ with `DMCreateMatrix()` using a wider stencil than strictly needed for $A$ or with a `DMDA_STENCIL_BOX`.
2346:   See the comment in src/snes/tutorials/ex15.c.

2348: .seealso: [](ch_snes), `SNES`, `SNESGetFunction()`, `SNESSetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESGetPicard()`, `SNESLineSearchPreCheckPicard()`,
2349:           `SNESFunctionFn`, `SNESJacobianFn`
2350: @*/
2351: PetscErrorCode SNESSetPicard(SNES snes, Vec r, SNESFunctionFn *bp, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
2352: {
2353:   DM dm;

2355:   PetscFunctionBegin;
2357:   PetscCall(SNESGetDM(snes, &dm));
2358:   PetscCall(DMSNESSetPicard(dm, bp, J, ctx));
2359:   PetscCall(DMSNESSetMFFunction(dm, SNESPicardComputeMFFunction, ctx));
2360:   PetscCall(SNESSetFunction(snes, r, SNESPicardComputeFunction, ctx));
2361:   PetscCall(SNESSetJacobian(snes, Amat, Pmat, SNESPicardComputeJacobian, ctx));
2362:   PetscFunctionReturn(PETSC_SUCCESS);
2363: }

2365: /*@C
2366:   SNESGetPicard - Returns the context for the Picard iteration

2368:   Not Collective, but `Vec` is parallel if `SNES` is parallel. Collective if `Vec` is requested, but has not been created yet.

2370:   Input Parameter:
2371: . snes - the `SNES` context

2373:   Output Parameters:
2374: + r    - the function (or `NULL`)
2375: . f    - the function (or `NULL`);  for calling sequence see `SNESFunctionFn`
2376: . Amat - the matrix used to defined the operation A(x) x - b(x) (or `NULL`)
2377: . Pmat - the matrix from which the preconditioner will be constructed (or `NULL`)
2378: . J    - the function for matrix evaluation (or `NULL`);  for calling sequence see `SNESJacobianFn`
2379: - ctx  - the function context (or `NULL`)

2381:   Level: advanced

2383: .seealso: [](ch_snes), `SNESSetFunction()`, `SNESSetPicard()`, `SNESGetFunction()`, `SNESGetJacobian()`, `SNESGetDM()`, `SNESFunctionFn`, `SNESJacobianFn`
2384: @*/
2385: PetscErrorCode SNESGetPicard(SNES snes, Vec *r, SNESFunctionFn **f, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
2386: {
2387:   DM dm;

2389:   PetscFunctionBegin;
2391:   PetscCall(SNESGetFunction(snes, r, NULL, NULL));
2392:   PetscCall(SNESGetJacobian(snes, Amat, Pmat, NULL, NULL));
2393:   PetscCall(SNESGetDM(snes, &dm));
2394:   PetscCall(DMSNESGetPicard(dm, f, J, ctx));
2395:   PetscFunctionReturn(PETSC_SUCCESS);
2396: }

2398: /*@C
2399:   SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the nonlinear problem

2401:   Logically Collective

2403:   Input Parameters:
2404: + snes - the `SNES` context
2405: . func - function evaluation routine, see `SNESInitialGuessFn` for the calling sequence
2406: - ctx  - [optional] user-defined context for private data for the
2407:          function evaluation routine (may be `NULL`)

2409:   Level: intermediate

2411: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESInitialGuessFn`
2412: @*/
2413: PetscErrorCode SNESSetComputeInitialGuess(SNES snes, SNESInitialGuessFn *func, void *ctx)
2414: {
2415:   PetscFunctionBegin;
2417:   if (func) snes->ops->computeinitialguess = func;
2418:   if (ctx) snes->initialguessP = ctx;
2419:   PetscFunctionReturn(PETSC_SUCCESS);
2420: }

2422: /*@C
2423:   SNESGetRhs - Gets the vector for solving F(x) = `rhs`. If `rhs` is not set
2424:   it assumes a zero right-hand side.

2426:   Logically Collective

2428:   Input Parameter:
2429: . snes - the `SNES` context

2431:   Output Parameter:
2432: . rhs - the right-hand side vector or `NULL` if there is no right-hand side vector

2434:   Level: intermediate

2436: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`, `SNESComputeFunction()`, `SNESSetJacobian()`, `SNESSetFunction()`
2437: @*/
2438: PetscErrorCode SNESGetRhs(SNES snes, Vec *rhs)
2439: {
2440:   PetscFunctionBegin;
2442:   PetscAssertPointer(rhs, 2);
2443:   *rhs = snes->vec_rhs;
2444:   PetscFunctionReturn(PETSC_SUCCESS);
2445: }

2447: /*@
2448:   SNESComputeFunction - Calls the function that has been set with `SNESSetFunction()`.

2450:   Collective

2452:   Input Parameters:
2453: + snes - the `SNES` context
2454: - x    - input vector

2456:   Output Parameter:
2457: . y - function vector, as set by `SNESSetFunction()`

2459:   Level: developer

2461:   Notes:
2462:   `SNESComputeFunction()` is typically used within nonlinear solvers
2463:   implementations, so users would not generally call this routine themselves.

2465:   When solving for $F(x) = b$, this routine computes $y = F(x) - b$.

2467: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeMFFunction()`
2468: @*/
2469: PetscErrorCode SNESComputeFunction(SNES snes, Vec x, Vec y)
2470: {
2471:   DM     dm;
2472:   DMSNES sdm;

2474:   PetscFunctionBegin;
2478:   PetscCheckSameComm(snes, 1, x, 2);
2479:   PetscCheckSameComm(snes, 1, y, 3);
2480:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2482:   PetscCall(SNESGetDM(snes, &dm));
2483:   PetscCall(DMGetDMSNES(dm, &sdm));
2484:   PetscCheck(sdm->ops->computefunction || snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2485:   if (sdm->ops->computefunction) {
2486:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2487:     PetscCall(VecLockReadPush(x));
2488:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2489:     snes->domainerror = PETSC_FALSE;
2490:     {
2491:       void           *ctx;
2492:       SNESFunctionFn *computefunction;
2493:       PetscCall(DMSNESGetFunction(dm, &computefunction, &ctx));
2494:       PetscCallBack("SNES callback function", (*computefunction)(snes, x, y, ctx));
2495:     }
2496:     PetscCall(VecLockReadPop(x));
2497:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2498:   } else /* if (snes->vec_rhs) */ {
2499:     PetscCall(MatMult(snes->jacobian, x, y));
2500:   }
2501:   if (snes->vec_rhs) PetscCall(VecAXPY(y, -1.0, snes->vec_rhs));
2502:   snes->nfuncs++;
2503:   /*
2504:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2505:      propagate the value to all processes
2506:   */
2507:   PetscCall(VecFlag(y, snes->domainerror));
2508:   PetscFunctionReturn(PETSC_SUCCESS);
2509: }

2511: /*@
2512:   SNESComputeMFFunction - Calls the function that has been set with `DMSNESSetMFFunction()`.

2514:   Collective

2516:   Input Parameters:
2517: + snes - the `SNES` context
2518: - x    - input vector

2520:   Output Parameter:
2521: . y - output vector

2523:   Level: developer

2525:   Notes:
2526:   `SNESComputeMFFunction()` is used within the matrix-vector products called by the matrix created with `MatCreateSNESMF()`
2527:   so users would not generally call this routine themselves.

2529:   Since this function is intended for use with finite differencing it does not subtract the right-hand side vector provided with `SNESSolve()`
2530:   while `SNESComputeFunction()` does. As such, this routine cannot be used with  `MatMFFDSetBase()` with a provided F function value even if it applies the
2531:   same function as `SNESComputeFunction()` if a `SNESSolve()` right-hand side vector is use because the two functions difference would include this right hand side function.

2533: .seealso: [](ch_snes), `SNES`, `SNESSetFunction()`, `SNESGetFunction()`, `SNESComputeFunction()`, `MatCreateSNESMF()`, `DMSNESSetMFFunction()`
2534: @*/
2535: PetscErrorCode SNESComputeMFFunction(SNES snes, Vec x, Vec y)
2536: {
2537:   DM     dm;
2538:   DMSNES sdm;

2540:   PetscFunctionBegin;
2544:   PetscCheckSameComm(snes, 1, x, 2);
2545:   PetscCheckSameComm(snes, 1, y, 3);
2546:   PetscCall(VecValidValues_Internal(x, 2, PETSC_TRUE));

2548:   PetscCall(SNESGetDM(snes, &dm));
2549:   PetscCall(DMGetDMSNES(dm, &sdm));
2550:   PetscCall(PetscLogEventBegin(SNES_FunctionEval, snes, x, y, 0));
2551:   PetscCall(VecLockReadPush(x));
2552:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
2553:   snes->domainerror = PETSC_FALSE;
2554:   PetscCallBack("SNES callback function", (*sdm->ops->computemffunction)(snes, x, y, sdm->mffunctionctx));
2555:   PetscCall(VecLockReadPop(x));
2556:   PetscCall(PetscLogEventEnd(SNES_FunctionEval, snes, x, y, 0));
2557:   snes->nfuncs++;
2558:   /*
2559:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2560:      propagate the value to all processes
2561:   */
2562:   PetscCall(VecFlag(y, snes->domainerror));
2563:   PetscFunctionReturn(PETSC_SUCCESS);
2564: }

2566: /*@
2567:   SNESComputeNGS - Calls the Gauss-Seidel function that has been set with `SNESSetNGS()`.

2569:   Collective

2571:   Input Parameters:
2572: + snes - the `SNES` context
2573: . x    - input vector
2574: - b    - rhs vector

2576:   Output Parameter:
2577: . x - new solution vector

2579:   Level: developer

2581:   Note:
2582:   `SNESComputeNGS()` is typically used within composed nonlinear solver
2583:   implementations, so most users would not generally call this routine
2584:   themselves.

2586: .seealso: [](ch_snes), `SNESNGSFn`, `SNESSetNGS()`, `SNESComputeFunction()`, `SNESNGS`
2587: @*/
2588: PetscErrorCode SNESComputeNGS(SNES snes, Vec b, Vec x)
2589: {
2590:   DM     dm;
2591:   DMSNES sdm;

2593:   PetscFunctionBegin;
2597:   PetscCheckSameComm(snes, 1, x, 3);
2598:   if (b) PetscCheckSameComm(snes, 1, b, 2);
2599:   if (b) PetscCall(VecValidValues_Internal(b, 2, PETSC_TRUE));
2600:   PetscCall(PetscLogEventBegin(SNES_NGSEval, snes, x, b, 0));
2601:   PetscCall(SNESGetDM(snes, &dm));
2602:   PetscCall(DMGetDMSNES(dm, &sdm));
2603:   PetscCheck(sdm->ops->computegs, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2604:   if (b) PetscCall(VecLockReadPush(b));
2605:   PetscCallBack("SNES callback NGS", (*sdm->ops->computegs)(snes, x, b, sdm->gsctx));
2606:   if (b) PetscCall(VecLockReadPop(b));
2607:   PetscCall(PetscLogEventEnd(SNES_NGSEval, snes, x, b, 0));
2608:   PetscFunctionReturn(PETSC_SUCCESS);
2609: }

2611: static PetscErrorCode SNESComputeFunction_FD(SNES snes, Vec Xin, Vec G)
2612: {
2613:   Vec          X;
2614:   PetscScalar *g;
2615:   PetscReal    f, f2;
2616:   PetscInt     low, high, N, i;
2617:   PetscBool    flg;
2618:   PetscReal    h = .5 * PETSC_SQRT_MACHINE_EPSILON;

2620:   PetscFunctionBegin;
2621:   PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_fd_delta", &h, &flg));
2622:   PetscCall(VecDuplicate(Xin, &X));
2623:   PetscCall(VecCopy(Xin, X));
2624:   PetscCall(VecGetSize(X, &N));
2625:   PetscCall(VecGetOwnershipRange(X, &low, &high));
2626:   PetscCall(VecSetOption(X, VEC_IGNORE_OFF_PROC_ENTRIES, PETSC_TRUE));
2627:   PetscCall(VecGetArray(G, &g));
2628:   for (i = 0; i < N; i++) {
2629:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2630:     PetscCall(VecAssemblyBegin(X));
2631:     PetscCall(VecAssemblyEnd(X));
2632:     PetscCall(SNESComputeObjective(snes, X, &f));
2633:     PetscCall(VecSetValue(X, i, 2.0 * h, ADD_VALUES));
2634:     PetscCall(VecAssemblyBegin(X));
2635:     PetscCall(VecAssemblyEnd(X));
2636:     PetscCall(SNESComputeObjective(snes, X, &f2));
2637:     PetscCall(VecSetValue(X, i, -h, ADD_VALUES));
2638:     PetscCall(VecAssemblyBegin(X));
2639:     PetscCall(VecAssemblyEnd(X));
2640:     if (i >= low && i < high) g[i - low] = (f2 - f) / (2.0 * h);
2641:   }
2642:   PetscCall(VecRestoreArray(G, &g));
2643:   PetscCall(VecDestroy(&X));
2644:   PetscFunctionReturn(PETSC_SUCCESS);
2645: }

2647: PetscErrorCode SNESTestFunction(SNES snes)
2648: {
2649:   Vec               x, g1, g2, g3;
2650:   PetscBool         complete_print = PETSC_FALSE, test = PETSC_FALSE;
2651:   PetscReal         hcnorm, fdnorm, hcmax, fdmax, diffmax, diffnorm;
2652:   PetscScalar       dot;
2653:   MPI_Comm          comm;
2654:   PetscViewer       viewer, mviewer;
2655:   PetscViewerFormat format;
2656:   PetscInt          tabs;
2657:   static PetscBool  directionsprinted = PETSC_FALSE;
2658:   SNESObjectiveFn  *objective;

2660:   PetscFunctionBegin;
2661:   PetscCall(SNESGetObjective(snes, &objective, NULL));
2662:   if (!objective) PetscFunctionReturn(PETSC_SUCCESS);

2664:   PetscObjectOptionsBegin((PetscObject)snes);
2665:   PetscCall(PetscOptionsName("-snes_test_function", "Compare hand-coded and finite difference function", "None", &test));
2666:   PetscCall(PetscOptionsViewer("-snes_test_function_view", "View difference between hand-coded and finite difference function element entries", "None", &mviewer, &format, &complete_print));
2667:   PetscOptionsEnd();
2668:   if (!test) {
2669:     if (complete_print) PetscCall(PetscViewerDestroy(&mviewer));
2670:     PetscFunctionReturn(PETSC_SUCCESS);
2671:   }

2673:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2674:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2675:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2676:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2677:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Function -------------\n"));
2678:   if (!complete_print && !directionsprinted) {
2679:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_function_view and optionally -snes_test_function <threshold> to show difference\n"));
2680:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference function entries greater than <threshold>.\n"));
2681:   }
2682:   if (!directionsprinted) {
2683:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Function, if (for double precision runs) ||F - Ffd||/||F|| is\n"));
2684:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Function is probably correct.\n"));
2685:     directionsprinted = PETSC_TRUE;
2686:   }
2687:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2689:   PetscCall(SNESGetSolution(snes, &x));
2690:   PetscCall(VecDuplicate(x, &g1));
2691:   PetscCall(VecDuplicate(x, &g2));
2692:   PetscCall(VecDuplicate(x, &g3));
2693:   PetscCall(SNESComputeFunction(snes, x, g1));
2694:   PetscCall(SNESComputeFunction_FD(snes, x, g2));

2696:   PetscCall(VecNorm(g2, NORM_2, &fdnorm));
2697:   PetscCall(VecNorm(g1, NORM_2, &hcnorm));
2698:   PetscCall(VecNorm(g2, NORM_INFINITY, &fdmax));
2699:   PetscCall(VecNorm(g1, NORM_INFINITY, &hcmax));
2700:   PetscCall(VecDot(g1, g2, &dot));
2701:   PetscCall(VecCopy(g1, g3));
2702:   PetscCall(VecAXPY(g3, -1.0, g2));
2703:   PetscCall(VecNorm(g3, NORM_2, &diffnorm));
2704:   PetscCall(VecNorm(g3, NORM_INFINITY, &diffmax));
2705:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ||Ffd|| %g, ||F|| = %g, angle cosine = (Ffd'F)/||Ffd||||F|| = %g\n", (double)fdnorm, (double)hcnorm, (double)(PetscRealPart(dot) / (fdnorm * hcnorm))));
2706:   PetscCall(PetscViewerASCIIPrintf(viewer, "  2-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffnorm / PetscMax(hcnorm, fdnorm)), (double)diffnorm));
2707:   PetscCall(PetscViewerASCIIPrintf(viewer, "  max-norm ||F - Ffd||/||F|| = %g, ||F - Ffd|| = %g\n", (double)(diffmax / PetscMax(hcmax, fdmax)), (double)diffmax));

2709:   if (complete_print) {
2710:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded function ----------\n"));
2711:     PetscCall(VecView(g1, mviewer));
2712:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference function ----------\n"));
2713:     PetscCall(VecView(g2, mviewer));
2714:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference function ----------\n"));
2715:     PetscCall(VecView(g3, mviewer));
2716:   }
2717:   PetscCall(VecDestroy(&g1));
2718:   PetscCall(VecDestroy(&g2));
2719:   PetscCall(VecDestroy(&g3));

2721:   if (complete_print) {
2722:     PetscCall(PetscViewerPopFormat(mviewer));
2723:     PetscCall(PetscViewerDestroy(&mviewer));
2724:   }
2725:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2726:   PetscFunctionReturn(PETSC_SUCCESS);
2727: }

2729: PetscErrorCode SNESTestJacobian(SNES snes)
2730: {
2731:   Mat               A, B, C, D, jacobian;
2732:   Vec               x = snes->vec_sol, f;
2733:   PetscReal         nrm, gnorm;
2734:   PetscReal         threshold = 1.e-5;
2735:   MatType           mattype;
2736:   PetscInt          m, n, M, N;
2737:   void             *functx;
2738:   PetscBool         complete_print = PETSC_FALSE, threshold_print = PETSC_FALSE, test = PETSC_FALSE, flg, istranspose;
2739:   PetscViewer       viewer, mviewer;
2740:   MPI_Comm          comm;
2741:   PetscInt          tabs;
2742:   static PetscBool  directionsprinted = PETSC_FALSE;
2743:   PetscViewerFormat format;

2745:   PetscFunctionBegin;
2746:   PetscObjectOptionsBegin((PetscObject)snes);
2747:   PetscCall(PetscOptionsName("-snes_test_jacobian", "Compare hand-coded and finite difference Jacobians", "None", &test));
2748:   PetscCall(PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold, NULL));
2749:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display", "-snes_test_jacobian_view", "3.13", NULL));
2750:   PetscCall(PetscOptionsViewer("-snes_test_jacobian_view", "View difference between hand-coded and finite difference Jacobians element entries", "None", &mviewer, &format, &complete_print));
2751:   PetscCall(PetscOptionsDeprecated("-snes_test_jacobian_display_threshold", "-snes_test_jacobian", "3.13", "-snes_test_jacobian accepts an optional threshold (since v3.10)"));
2752:   PetscCall(PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print));
2753:   PetscOptionsEnd();
2754:   if (!test) PetscFunctionReturn(PETSC_SUCCESS);

2756:   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
2757:   PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
2758:   PetscCall(PetscViewerASCIIGetTab(viewer, &tabs));
2759:   PetscCall(PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel));
2760:   PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian -------------\n"));
2761:   if (!complete_print && !directionsprinted) {
2762:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n"));
2763:     PetscCall(PetscViewerASCIIPrintf(viewer, "    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n"));
2764:   }
2765:   if (!directionsprinted) {
2766:     PetscCall(PetscViewerASCIIPrintf(viewer, "  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n"));
2767:     PetscCall(PetscViewerASCIIPrintf(viewer, "    O(1.e-8), the hand-coded Jacobian is probably correct.\n"));
2768:     directionsprinted = PETSC_TRUE;
2769:   }
2770:   if (complete_print) PetscCall(PetscViewerPushFormat(mviewer, format));

2772:   PetscCall(PetscObjectTypeCompare((PetscObject)snes->jacobian, MATMFFD, &flg));
2773:   if (!flg) jacobian = snes->jacobian;
2774:   else jacobian = snes->jacobian_pre;

2776:   if (!x) PetscCall(MatCreateVecs(jacobian, &x, NULL));
2777:   else PetscCall(PetscObjectReference((PetscObject)x));
2778:   PetscCall(VecDuplicate(x, &f));

2780:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
2781:   PetscCall(SNESComputeFunction(snes, x, f));
2782:   PetscCall(VecDestroy(&f));
2783:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, SNESKSPTRANSPOSEONLY, &istranspose));
2784:   while (jacobian) {
2785:     Mat JT = NULL, Jsave = NULL;

2787:     if (istranspose) {
2788:       PetscCall(MatCreateTranspose(jacobian, &JT));
2789:       Jsave    = jacobian;
2790:       jacobian = JT;
2791:     }
2792:     PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)jacobian, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPISBAIJ, ""));
2793:     if (flg) {
2794:       A = jacobian;
2795:       PetscCall(PetscObjectReference((PetscObject)A));
2796:     } else {
2797:       PetscCall(MatComputeOperator(jacobian, MATAIJ, &A));
2798:     }

2800:     PetscCall(MatGetType(A, &mattype));
2801:     PetscCall(MatGetSize(A, &M, &N));
2802:     PetscCall(MatGetLocalSize(A, &m, &n));
2803:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &B));
2804:     PetscCall(MatSetType(B, mattype));
2805:     PetscCall(MatSetSizes(B, m, n, M, N));
2806:     PetscCall(MatSetBlockSizesFromMats(B, A, A));
2807:     PetscCall(MatSetUp(B));
2808:     PetscCall(MatSetOption(B, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2810:     PetscCall(SNESGetFunction(snes, NULL, NULL, &functx));
2811:     PetscCall(SNESComputeJacobianDefault(snes, x, B, B, functx));

2813:     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &D));
2814:     PetscCall(MatAYPX(D, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2815:     PetscCall(MatNorm(D, NORM_FROBENIUS, &nrm));
2816:     PetscCall(MatNorm(A, NORM_FROBENIUS, &gnorm));
2817:     PetscCall(MatDestroy(&D));
2818:     if (!gnorm) gnorm = 1; /* just in case */
2819:     PetscCall(PetscViewerASCIIPrintf(viewer, "  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n", (double)(nrm / gnorm), (double)nrm));

2821:     if (complete_print) {
2822:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded Jacobian ----------\n"));
2823:       PetscCall(MatView(A, mviewer));
2824:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Finite difference Jacobian ----------\n"));
2825:       PetscCall(MatView(B, mviewer));
2826:     }

2828:     if (threshold_print || complete_print) {
2829:       PetscInt           Istart, Iend, *ccols, bncols, cncols, j, row;
2830:       PetscScalar       *cvals;
2831:       const PetscInt    *bcols;
2832:       const PetscScalar *bvals;

2834:       PetscCall(MatCreate(PetscObjectComm((PetscObject)A), &C));
2835:       PetscCall(MatSetType(C, mattype));
2836:       PetscCall(MatSetSizes(C, m, n, M, N));
2837:       PetscCall(MatSetBlockSizesFromMats(C, A, A));
2838:       PetscCall(MatSetUp(C));
2839:       PetscCall(MatSetOption(C, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE));

2841:       PetscCall(MatAYPX(B, -1.0, A, DIFFERENT_NONZERO_PATTERN));
2842:       PetscCall(MatGetOwnershipRange(B, &Istart, &Iend));

2844:       for (row = Istart; row < Iend; row++) {
2845:         PetscCall(MatGetRow(B, row, &bncols, &bcols, &bvals));
2846:         PetscCall(PetscMalloc2(bncols, &ccols, bncols, &cvals));
2847:         for (j = 0, cncols = 0; j < bncols; j++) {
2848:           if (PetscAbsScalar(bvals[j]) > threshold) {
2849:             ccols[cncols] = bcols[j];
2850:             cvals[cncols] = bvals[j];
2851:             cncols += 1;
2852:           }
2853:         }
2854:         if (cncols) PetscCall(MatSetValues(C, 1, &row, cncols, ccols, cvals, INSERT_VALUES));
2855:         PetscCall(MatRestoreRow(B, row, &bncols, &bcols, &bvals));
2856:         PetscCall(PetscFree2(ccols, cvals));
2857:       }
2858:       PetscCall(MatAssemblyBegin(C, MAT_FINAL_ASSEMBLY));
2859:       PetscCall(MatAssemblyEnd(C, MAT_FINAL_ASSEMBLY));
2860:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n", (double)threshold));
2861:       PetscCall(MatView(C, complete_print ? mviewer : viewer));
2862:       PetscCall(MatDestroy(&C));
2863:     }
2864:     PetscCall(MatDestroy(&A));
2865:     PetscCall(MatDestroy(&B));
2866:     PetscCall(MatDestroy(&JT));
2867:     if (Jsave) jacobian = Jsave;
2868:     if (jacobian != snes->jacobian_pre) {
2869:       jacobian = snes->jacobian_pre;
2870:       PetscCall(PetscViewerASCIIPrintf(viewer, "  ---------- Testing Jacobian for preconditioner -------------\n"));
2871:     } else jacobian = NULL;
2872:   }
2873:   PetscCall(VecDestroy(&x));
2874:   if (complete_print) PetscCall(PetscViewerPopFormat(mviewer));
2875:   if (mviewer) PetscCall(PetscViewerDestroy(&mviewer));
2876:   PetscCall(PetscViewerASCIISetTab(viewer, tabs));
2877:   PetscFunctionReturn(PETSC_SUCCESS);
2878: }

2880: /*@
2881:   SNESComputeJacobian - Computes the Jacobian matrix that has been set with `SNESSetJacobian()`.

2883:   Collective

2885:   Input Parameters:
2886: + snes - the `SNES` context
2887: - X    - input vector

2889:   Output Parameters:
2890: + A - Jacobian matrix
2891: - B - optional matrix for building the preconditioner, usually the same as `A`

2893:   Options Database Keys:
2894: + -snes_lag_preconditioner <lag>           - how often to rebuild preconditioner
2895: . -snes_lag_jacobian <lag>                 - how often to rebuild Jacobian
2896: . -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
2897: . -snes_test_jacobian_view                 - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
2898: . -snes_compare_explicit                   - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2899: . -snes_compare_explicit_draw              - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2900: . -snes_compare_explicit_contour           - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2901: . -snes_compare_operator                   - Make the comparison options above use the operator instead of the matrix used to construct the preconditioner
2902: . -snes_compare_coloring                   - Compute the finite difference Jacobian using coloring and display norms of difference
2903: . -snes_compare_coloring_display           - Compute the finite difference Jacobian using coloring and display verbose differences
2904: . -snes_compare_coloring_threshold         - Display only those matrix entries that differ by more than a given threshold
2905: . -snes_compare_coloring_threshold_atol    - Absolute tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2906: . -snes_compare_coloring_threshold_rtol    - Relative tolerance for difference in matrix entries to be displayed by `-snes_compare_coloring_threshold`
2907: . -snes_compare_coloring_draw              - Compute the finite difference Jacobian using coloring and draw differences
2908: - -snes_compare_coloring_draw_contour      - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

2910:   Level: developer

2912:   Note:
2913:   Most users should not need to explicitly call this routine, as it
2914:   is used internally within the nonlinear solvers.

2916:   Developer Note:
2917:   This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine `SNESTestJacobian()` use to used
2918:   with the `SNESType` of test that has been removed.

2920: .seealso: [](ch_snes), `SNESSetJacobian()`, `KSPSetOperators()`, `MatStructure`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobian()`
2921: @*/
2922: PetscErrorCode SNESComputeJacobian(SNES snes, Vec X, Mat A, Mat B)
2923: {
2924:   PetscBool flag;
2925:   DM        dm;
2926:   DMSNES    sdm;
2927:   KSP       ksp;

2929:   PetscFunctionBegin;
2932:   PetscCheckSameComm(snes, 1, X, 2);
2933:   PetscCall(VecValidValues_Internal(X, 2, PETSC_TRUE));
2934:   PetscCall(SNESGetDM(snes, &dm));
2935:   PetscCall(DMGetDMSNES(dm, &sdm));

2937:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix-free */
2938:   if (snes->lagjacobian == -2) {
2939:     snes->lagjacobian = -1;

2941:     PetscCall(PetscInfo(snes, "Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n"));
2942:   } else if (snes->lagjacobian == -1) {
2943:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is -1\n"));
2944:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2945:     if (flag) {
2946:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2947:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2948:     }
2949:     PetscFunctionReturn(PETSC_SUCCESS);
2950:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2951:     PetscCall(PetscInfo(snes, "Reusing Jacobian/preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagjacobian, snes->iter));
2952:     PetscCall(PetscObjectTypeCompare((PetscObject)A, MATMFFD, &flag));
2953:     if (flag) {
2954:       PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2955:       PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2956:     }
2957:     PetscFunctionReturn(PETSC_SUCCESS);
2958:   }
2959:   if (snes->npc && snes->npcside == PC_LEFT) {
2960:     PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
2961:     PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
2962:     PetscFunctionReturn(PETSC_SUCCESS);
2963:   }

2965:   PetscCall(PetscLogEventBegin(SNES_JacobianEval, snes, X, A, B));
2966:   PetscCall(VecLockReadPush(X));
2967:   {
2968:     void           *ctx;
2969:     SNESJacobianFn *J;
2970:     PetscCall(DMSNESGetJacobian(dm, &J, &ctx));
2971:     PetscCallBack("SNES callback Jacobian", (*J)(snes, X, A, B, ctx));
2972:   }
2973:   PetscCall(VecLockReadPop(X));
2974:   PetscCall(PetscLogEventEnd(SNES_JacobianEval, snes, X, A, B));

2976:   /* attach latest linearization point to the matrix used to construct the preconditioner */
2977:   PetscCall(PetscObjectCompose((PetscObject)B, "__SNES_latest_X", (PetscObject)X));

2979:   /* the next line ensures that snes->ksp exists */
2980:   PetscCall(SNESGetKSP(snes, &ksp));
2981:   if (snes->lagpreconditioner == -2) {
2982:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner exactly once since lag is -2\n"));
2983:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2984:     snes->lagpreconditioner = -1;
2985:   } else if (snes->lagpreconditioner == -1) {
2986:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is -1\n"));
2987:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2988:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2989:     PetscCall(PetscInfo(snes, "Reusing preconditioner because lag is %" PetscInt_FMT " and SNES iteration is %" PetscInt_FMT "\n", snes->lagpreconditioner, snes->iter));
2990:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_TRUE));
2991:   } else {
2992:     PetscCall(PetscInfo(snes, "Rebuilding preconditioner\n"));
2993:     PetscCall(KSPSetReusePreconditioner(snes->ksp, PETSC_FALSE));
2994:   }

2996:   /* monkey business to allow testing Jacobians in multilevel solvers.
2997:      This is needed because the SNESTestXXX interface does not accept vectors and matrices */
2998:   {
2999:     Vec xsave            = snes->vec_sol;
3000:     Mat jacobiansave     = snes->jacobian;
3001:     Mat jacobian_presave = snes->jacobian_pre;

3003:     snes->vec_sol      = X;
3004:     snes->jacobian     = A;
3005:     snes->jacobian_pre = B;
3006:     PetscCall(SNESTestFunction(snes));
3007:     PetscCall(SNESTestJacobian(snes));

3009:     snes->vec_sol      = xsave;
3010:     snes->jacobian     = jacobiansave;
3011:     snes->jacobian_pre = jacobian_presave;
3012:   }

3014:   {
3015:     PetscBool flag = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_operator = PETSC_FALSE;
3016:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit", NULL, NULL, &flag));
3017:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw", NULL, NULL, &flag_draw));
3018:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_explicit_draw_contour", NULL, NULL, &flag_contour));
3019:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_operator", NULL, NULL, &flag_operator));
3020:     if (flag || flag_draw || flag_contour) {
3021:       Mat         Bexp_mine = NULL, Bexp, FDexp;
3022:       PetscViewer vdraw, vstdout;
3023:       PetscBool   flg;
3024:       if (flag_operator) {
3025:         PetscCall(MatComputeOperator(A, MATAIJ, &Bexp_mine));
3026:         Bexp = Bexp_mine;
3027:       } else {
3028:         /* See if the matrix used to construct the preconditioner can be viewed and added directly */
3029:         PetscCall(PetscObjectBaseTypeCompareAny((PetscObject)B, &flg, MATSEQAIJ, MATMPIAIJ, MATSEQDENSE, MATMPIDENSE, MATSEQBAIJ, MATMPIBAIJ, MATSEQSBAIJ, MATMPIBAIJ, ""));
3030:         if (flg) Bexp = B;
3031:         else {
3032:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
3033:           PetscCall(MatComputeOperator(B, MATAIJ, &Bexp_mine));
3034:           Bexp = Bexp_mine;
3035:         }
3036:       }
3037:       PetscCall(MatConvert(Bexp, MATSAME, MAT_INITIAL_MATRIX, &FDexp));
3038:       PetscCall(SNESComputeJacobianDefault(snes, X, FDexp, FDexp, NULL));
3039:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3040:       if (flag_draw || flag_contour) {
3041:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Explicit Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3042:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3043:       } else vdraw = NULL;
3044:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit %s\n", flag_operator ? "Jacobian" : "preconditioning Jacobian"));
3045:       if (flag) PetscCall(MatView(Bexp, vstdout));
3046:       if (vdraw) PetscCall(MatView(Bexp, vdraw));
3047:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Finite difference Jacobian\n"));
3048:       if (flag) PetscCall(MatView(FDexp, vstdout));
3049:       if (vdraw) PetscCall(MatView(FDexp, vdraw));
3050:       PetscCall(MatAYPX(FDexp, -1.0, Bexp, SAME_NONZERO_PATTERN));
3051:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian\n"));
3052:       if (flag) PetscCall(MatView(FDexp, vstdout));
3053:       if (vdraw) { /* Always use contour for the difference */
3054:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3055:         PetscCall(MatView(FDexp, vdraw));
3056:         PetscCall(PetscViewerPopFormat(vdraw));
3057:       }
3058:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));
3059:       PetscCall(PetscViewerDestroy(&vdraw));
3060:       PetscCall(MatDestroy(&Bexp_mine));
3061:       PetscCall(MatDestroy(&FDexp));
3062:     }
3063:   }
3064:   {
3065:     PetscBool flag = PETSC_FALSE, flag_display = PETSC_FALSE, flag_draw = PETSC_FALSE, flag_contour = PETSC_FALSE, flag_threshold = PETSC_FALSE;
3066:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON, threshold_rtol = 10 * PETSC_SQRT_MACHINE_EPSILON;
3067:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring", NULL, NULL, &flag));
3068:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_display", NULL, NULL, &flag_display));
3069:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw", NULL, NULL, &flag_draw));
3070:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_draw_contour", NULL, NULL, &flag_contour));
3071:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold", NULL, NULL, &flag_threshold));
3072:     if (flag_threshold) {
3073:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_rtol", &threshold_rtol, NULL));
3074:       PetscCall(PetscOptionsGetReal(((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_compare_coloring_threshold_atol", &threshold_atol, NULL));
3075:     }
3076:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
3077:       Mat             Bfd;
3078:       PetscViewer     vdraw, vstdout;
3079:       MatColoring     coloring;
3080:       ISColoring      iscoloring;
3081:       MatFDColoring   matfdcoloring;
3082:       SNESFunctionFn *func;
3083:       void           *funcctx;
3084:       PetscReal       norm1, norm2, normmax;

3086:       PetscCall(MatDuplicate(B, MAT_DO_NOT_COPY_VALUES, &Bfd));
3087:       PetscCall(MatColoringCreate(Bfd, &coloring));
3088:       PetscCall(MatColoringSetType(coloring, MATCOLORINGSL));
3089:       PetscCall(MatColoringSetFromOptions(coloring));
3090:       PetscCall(MatColoringApply(coloring, &iscoloring));
3091:       PetscCall(MatColoringDestroy(&coloring));
3092:       PetscCall(MatFDColoringCreate(Bfd, iscoloring, &matfdcoloring));
3093:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3094:       PetscCall(MatFDColoringSetUp(Bfd, iscoloring, matfdcoloring));
3095:       PetscCall(ISColoringDestroy(&iscoloring));

3097:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
3098:       PetscCall(SNESGetFunction(snes, NULL, &func, &funcctx));
3099:       PetscCall(MatFDColoringSetFunction(matfdcoloring, (PetscErrorCode (*)(void))func, funcctx));
3100:       PetscCall(PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring, ((PetscObject)snes)->prefix));
3101:       PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring, "coloring_"));
3102:       PetscCall(MatFDColoringSetFromOptions(matfdcoloring));
3103:       PetscCall(MatFDColoringApply(Bfd, matfdcoloring, X, snes));
3104:       PetscCall(MatFDColoringDestroy(&matfdcoloring));

3106:       PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes), &vstdout));
3107:       if (flag_draw || flag_contour) {
3108:         PetscCall(PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes), NULL, "Colored Jacobians", PETSC_DECIDE, PETSC_DECIDE, 300, 300, &vdraw));
3109:         if (flag_contour) PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3110:       } else vdraw = NULL;
3111:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Explicit preconditioning Jacobian\n"));
3112:       if (flag_display) PetscCall(MatView(B, vstdout));
3113:       if (vdraw) PetscCall(MatView(B, vdraw));
3114:       PetscCall(PetscViewerASCIIPrintf(vstdout, "Colored Finite difference Jacobian\n"));
3115:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3116:       if (vdraw) PetscCall(MatView(Bfd, vdraw));
3117:       PetscCall(MatAYPX(Bfd, -1.0, B, SAME_NONZERO_PATTERN));
3118:       PetscCall(MatNorm(Bfd, NORM_1, &norm1));
3119:       PetscCall(MatNorm(Bfd, NORM_FROBENIUS, &norm2));
3120:       PetscCall(MatNorm(Bfd, NORM_MAX, &normmax));
3121:       PetscCall(PetscViewerASCIIPrintf(vstdout, "User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n", (double)norm1, (double)norm2, (double)normmax));
3122:       if (flag_display) PetscCall(MatView(Bfd, vstdout));
3123:       if (vdraw) { /* Always use contour for the difference */
3124:         PetscCall(PetscViewerPushFormat(vdraw, PETSC_VIEWER_DRAW_CONTOUR));
3125:         PetscCall(MatView(Bfd, vdraw));
3126:         PetscCall(PetscViewerPopFormat(vdraw));
3127:       }
3128:       if (flag_contour) PetscCall(PetscViewerPopFormat(vdraw));

3130:       if (flag_threshold) {
3131:         PetscInt bs, rstart, rend, i;
3132:         PetscCall(MatGetBlockSize(B, &bs));
3133:         PetscCall(MatGetOwnershipRange(B, &rstart, &rend));
3134:         for (i = rstart; i < rend; i++) {
3135:           const PetscScalar *ba, *ca;
3136:           const PetscInt    *bj, *cj;
3137:           PetscInt           bn, cn, j, maxentrycol = -1, maxdiffcol = -1, maxrdiffcol = -1;
3138:           PetscReal          maxentry = 0, maxdiff = 0, maxrdiff = 0;
3139:           PetscCall(MatGetRow(B, i, &bn, &bj, &ba));
3140:           PetscCall(MatGetRow(Bfd, i, &cn, &cj, &ca));
3141:           PetscCheck(bn == cn, ((PetscObject)A)->comm, PETSC_ERR_PLIB, "Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
3142:           for (j = 0; j < bn; j++) {
3143:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3144:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
3145:               maxentrycol = bj[j];
3146:               maxentry    = PetscRealPart(ba[j]);
3147:             }
3148:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
3149:               maxdiffcol = bj[j];
3150:               maxdiff    = PetscRealPart(ca[j]);
3151:             }
3152:             if (rdiff > maxrdiff) {
3153:               maxrdiffcol = bj[j];
3154:               maxrdiff    = rdiff;
3155:             }
3156:           }
3157:           if (maxrdiff > 1) {
3158:             PetscCall(PetscViewerASCIIPrintf(vstdout, "row %" PetscInt_FMT " (maxentry=%g at %" PetscInt_FMT ", maxdiff=%g at %" PetscInt_FMT ", maxrdiff=%g at %" PetscInt_FMT "):", i, (double)maxentry, maxentrycol, (double)maxdiff, maxdiffcol, (double)maxrdiff, maxrdiffcol));
3159:             for (j = 0; j < bn; j++) {
3160:               PetscReal rdiff;
3161:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol * PetscAbsScalar(ba[j]));
3162:               if (rdiff > 1) PetscCall(PetscViewerASCIIPrintf(vstdout, " (%" PetscInt_FMT ",%g:%g)", bj[j], (double)PetscRealPart(ba[j]), (double)PetscRealPart(ca[j])));
3163:             }
3164:             PetscCall(PetscViewerASCIIPrintf(vstdout, "\n"));
3165:           }
3166:           PetscCall(MatRestoreRow(B, i, &bn, &bj, &ba));
3167:           PetscCall(MatRestoreRow(Bfd, i, &cn, &cj, &ca));
3168:         }
3169:       }
3170:       PetscCall(PetscViewerDestroy(&vdraw));
3171:       PetscCall(MatDestroy(&Bfd));
3172:     }
3173:   }
3174:   PetscFunctionReturn(PETSC_SUCCESS);
3175: }

3177: /*@C
3178:   SNESSetJacobian - Sets the function to compute Jacobian as well as the
3179:   location to store the matrix.

3181:   Logically Collective

3183:   Input Parameters:
3184: + snes - the `SNES` context
3185: . Amat - the matrix that defines the (approximate) Jacobian
3186: . Pmat - the matrix to be used in constructing the preconditioner, usually the same as `Amat`.
3187: . J    - Jacobian evaluation routine (if `NULL` then `SNES` retains any previously set value), see `SNESJacobianFn` for details
3188: - ctx  - [optional] user-defined context for private data for the
3189:          Jacobian evaluation routine (may be `NULL`) (if `NULL` then `SNES` retains any previously set value)

3191:   Level: beginner

3193:   Notes:
3194:   If the `Amat` matrix and `Pmat` matrix are different you must call `MatAssemblyBegin()`/`MatAssemblyEnd()` on
3195:   each matrix.

3197:   If you know the operator `Amat` has a null space you can use `MatSetNullSpace()` and `MatSetTransposeNullSpace()` to supply the null
3198:   space to `Amat` and the `KSP` solvers will automatically use that null space as needed during the solution process.

3200:   If using `SNESComputeJacobianDefaultColor()` to assemble a Jacobian, the `ctx` argument
3201:   must be a `MatFDColoring`.

3203:   Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
3204:   example is to use the "Picard linearization" which only differentiates through the highest order parts of each term using `SNESSetPicard()`

3206: .seealso: [](ch_snes), `SNES`, `KSPSetOperators()`, `SNESSetFunction()`, `MatMFFDComputeJacobian()`, `SNESComputeJacobianDefaultColor()`, `MatStructure`,
3207:           `SNESSetPicard()`, `SNESJacobianFn`, `SNESFunctionFn`
3208: @*/
3209: PetscErrorCode SNESSetJacobian(SNES snes, Mat Amat, Mat Pmat, SNESJacobianFn *J, void *ctx)
3210: {
3211:   DM dm;

3213:   PetscFunctionBegin;
3217:   if (Amat) PetscCheckSameComm(snes, 1, Amat, 2);
3218:   if (Pmat) PetscCheckSameComm(snes, 1, Pmat, 3);
3219:   PetscCall(SNESGetDM(snes, &dm));
3220:   PetscCall(DMSNESSetJacobian(dm, J, ctx));
3221:   if (Amat) {
3222:     PetscCall(PetscObjectReference((PetscObject)Amat));
3223:     PetscCall(MatDestroy(&snes->jacobian));

3225:     snes->jacobian = Amat;
3226:   }
3227:   if (Pmat) {
3228:     PetscCall(PetscObjectReference((PetscObject)Pmat));
3229:     PetscCall(MatDestroy(&snes->jacobian_pre));

3231:     snes->jacobian_pre = Pmat;
3232:   }
3233:   PetscFunctionReturn(PETSC_SUCCESS);
3234: }

3236: /*@C
3237:   SNESGetJacobian - Returns the Jacobian matrix and optionally the user
3238:   provided context for evaluating the Jacobian.

3240:   Not Collective, but `Mat` object will be parallel if `SNES` is

3242:   Input Parameter:
3243: . snes - the nonlinear solver context

3245:   Output Parameters:
3246: + Amat - location to stash (approximate) Jacobian matrix (or `NULL`)
3247: . Pmat - location to stash matrix used to compute the preconditioner (or `NULL`)
3248: . J    - location to put Jacobian function (or `NULL`), for calling sequence see `SNESJacobianFn`
3249: - ctx  - location to stash Jacobian ctx (or `NULL`)

3251:   Level: advanced

3253: .seealso: [](ch_snes), `SNES`, `Mat`, `SNESSetJacobian()`, `SNESComputeJacobian()`, `SNESJacobianFn`, `SNESGetFunction()`
3254: @*/
3255: PetscErrorCode SNESGetJacobian(SNES snes, Mat *Amat, Mat *Pmat, SNESJacobianFn **J, void **ctx)
3256: {
3257:   DM dm;

3259:   PetscFunctionBegin;
3261:   if (Amat) *Amat = snes->jacobian;
3262:   if (Pmat) *Pmat = snes->jacobian_pre;
3263:   PetscCall(SNESGetDM(snes, &dm));
3264:   PetscCall(DMSNESGetJacobian(dm, J, ctx));
3265:   PetscFunctionReturn(PETSC_SUCCESS);
3266: }

3268: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
3269: {
3270:   DM     dm;
3271:   DMSNES sdm;

3273:   PetscFunctionBegin;
3274:   PetscCall(SNESGetDM(snes, &dm));
3275:   PetscCall(DMGetDMSNES(dm, &sdm));
3276:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
3277:     DM        dm;
3278:     PetscBool isdense, ismf;

3280:     PetscCall(SNESGetDM(snes, &dm));
3281:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &isdense, MATSEQDENSE, MATMPIDENSE, MATDENSE, NULL));
3282:     PetscCall(PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre, &ismf, MATMFFD, MATSHELL, NULL));
3283:     if (isdense) {
3284:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefault, NULL));
3285:     } else if (!ismf) {
3286:       PetscCall(DMSNESSetJacobian(dm, SNESComputeJacobianDefaultColor, NULL));
3287:     }
3288:   }
3289:   PetscFunctionReturn(PETSC_SUCCESS);
3290: }

3292: /*@
3293:   SNESSetUp - Sets up the internal data structures for the later use
3294:   of a nonlinear solver `SNESSolve()`.

3296:   Collective

3298:   Input Parameter:
3299: . snes - the `SNES` context

3301:   Level: advanced

3303:   Note:
3304:   For basic use of the `SNES` solvers the user does not need to explicitly call
3305:   `SNESSetUp()`, since these actions will automatically occur during
3306:   the call to `SNESSolve()`.  However, if one wishes to control this
3307:   phase separately, `SNESSetUp()` should be called after `SNESCreate()`
3308:   and optional routines of the form SNESSetXXX(), but before `SNESSolve()`.

3310: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`, `SNESDestroy()`, `SNESSetFromOptions()`
3311: @*/
3312: PetscErrorCode SNESSetUp(SNES snes)
3313: {
3314:   DM             dm;
3315:   DMSNES         sdm;
3316:   SNESLineSearch linesearch, pclinesearch;
3317:   void          *lsprectx, *lspostctx;
3318:   PetscBool      mf_operator, mf;
3319:   Vec            f, fpc;
3320:   void          *funcctx;
3321:   void          *jacctx, *appctx;
3322:   Mat            j, jpre;
3323:   PetscErrorCode (*precheck)(SNESLineSearch, Vec, Vec, PetscBool *, void *);
3324:   PetscErrorCode (*postcheck)(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
3325:   SNESFunctionFn *func;
3326:   SNESJacobianFn *jac;

3328:   PetscFunctionBegin;
3330:   if (snes->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
3331:   PetscCall(PetscLogEventBegin(SNES_SetUp, snes, 0, 0, 0));

3333:   if (!((PetscObject)snes)->type_name) PetscCall(SNESSetType(snes, SNESNEWTONLS));

3335:   PetscCall(SNESGetFunction(snes, &snes->vec_func, NULL, NULL));

3337:   PetscCall(SNESGetDM(snes, &dm));
3338:   PetscCall(DMGetDMSNES(dm, &sdm));
3339:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3341:   if (!snes->vec_func) PetscCall(DMCreateGlobalVector(dm, &snes->vec_func));

3343:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));

3345:   if (snes->linesearch) {
3346:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
3347:     PetscCall(SNESLineSearchSetFunction(snes->linesearch, SNESComputeFunction));
3348:   }

3350:   PetscCall(SNESGetUseMatrixFree(snes, &mf_operator, &mf));
3351:   if (snes->npc && snes->npcside == PC_LEFT) {
3352:     snes->mf          = PETSC_TRUE;
3353:     snes->mf_operator = PETSC_FALSE;
3354:   }

3356:   if (snes->npc) {
3357:     /* copy the DM over */
3358:     PetscCall(SNESGetDM(snes, &dm));
3359:     PetscCall(SNESSetDM(snes->npc, dm));

3361:     PetscCall(SNESGetFunction(snes, &f, &func, &funcctx));
3362:     PetscCall(VecDuplicate(f, &fpc));
3363:     PetscCall(SNESSetFunction(snes->npc, fpc, func, funcctx));
3364:     PetscCall(SNESGetJacobian(snes, &j, &jpre, &jac, &jacctx));
3365:     PetscCall(SNESSetJacobian(snes->npc, j, jpre, jac, jacctx));
3366:     PetscCall(SNESGetApplicationContext(snes, &appctx));
3367:     PetscCall(SNESSetApplicationContext(snes->npc, appctx));
3368:     PetscCall(SNESSetUseMatrixFree(snes->npc, mf_operator, mf));
3369:     PetscCall(VecDestroy(&fpc));

3371:     /* copy the function pointers over */
3372:     PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)snes->npc));

3374:     /* default to 1 iteration */
3375:     PetscCall(SNESSetTolerances(snes->npc, 0.0, 0.0, 0.0, 1, snes->npc->max_funcs));
3376:     if (snes->npcside == PC_RIGHT) {
3377:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_FINAL_ONLY));
3378:     } else {
3379:       PetscCall(SNESSetNormSchedule(snes->npc, SNES_NORM_NONE));
3380:     }
3381:     PetscCall(SNESSetFromOptions(snes->npc));

3383:     /* copy the line search context over */
3384:     if (snes->linesearch && snes->npc->linesearch) {
3385:       PetscCall(SNESGetLineSearch(snes, &linesearch));
3386:       PetscCall(SNESGetLineSearch(snes->npc, &pclinesearch));
3387:       PetscCall(SNESLineSearchGetPreCheck(linesearch, &precheck, &lsprectx));
3388:       PetscCall(SNESLineSearchGetPostCheck(linesearch, &postcheck, &lspostctx));
3389:       PetscCall(SNESLineSearchSetPreCheck(pclinesearch, precheck, lsprectx));
3390:       PetscCall(SNESLineSearchSetPostCheck(pclinesearch, postcheck, lspostctx));
3391:       PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch));
3392:     }
3393:   }
3394:   if (snes->mf) PetscCall(SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version));
3395:   if (snes->ops->usercompute && !snes->ctx) PetscCallBack("SNES callback compute application context", (*snes->ops->usercompute)(snes, &snes->ctx));

3397:   snes->jac_iter = 0;
3398:   snes->pre_iter = 0;

3400:   PetscTryTypeMethod(snes, setup);

3402:   PetscCall(SNESSetDefaultComputeJacobian(snes));

3404:   if (snes->npc && snes->npcside == PC_LEFT) {
3405:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
3406:       if (snes->linesearch) {
3407:         PetscCall(SNESGetLineSearch(snes, &linesearch));
3408:         PetscCall(SNESLineSearchSetFunction(linesearch, SNESComputeFunctionDefaultNPC));
3409:       }
3410:     }
3411:   }
3412:   PetscCall(PetscLogEventEnd(SNES_SetUp, snes, 0, 0, 0));
3413:   snes->setupcalled = PETSC_TRUE;
3414:   PetscFunctionReturn(PETSC_SUCCESS);
3415: }

3417: /*@
3418:   SNESReset - Resets a `SNES` context to the state it was in before `SNESSetUp()` was called and removes any allocated `Vec` and `Mat` from its data structures

3420:   Collective

3422:   Input Parameter:
3423: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3425:   Level: intermediate

3427:   Notes:
3428:   Any options set on the `SNES` object, including those set with `SNESSetFromOptions()` remain.

3430:   Call this if you wish to reuse a `SNES` but with different size vectors

3432:   Also calls the application context destroy routine set with `SNESSetComputeApplicationContext()`

3434: .seealso: [](ch_snes), `SNES`, `SNESDestroy()`, `SNESCreate()`, `SNESSetUp()`, `SNESSolve()`
3435: @*/
3436: PetscErrorCode SNESReset(SNES snes)
3437: {
3438:   PetscFunctionBegin;
3440:   if (snes->ops->ctxdestroy && snes->ctx) {
3441:     PetscCallBack("SNES callback destroy application context", (*snes->ops->ctxdestroy)(&snes->ctx));
3442:     snes->ctx = NULL;
3443:   }
3444:   if (snes->npc) PetscCall(SNESReset(snes->npc));

3446:   PetscTryTypeMethod(snes, reset);
3447:   if (snes->ksp) PetscCall(KSPReset(snes->ksp));

3449:   if (snes->linesearch) PetscCall(SNESLineSearchReset(snes->linesearch));

3451:   PetscCall(VecDestroy(&snes->vec_rhs));
3452:   PetscCall(VecDestroy(&snes->vec_sol));
3453:   PetscCall(VecDestroy(&snes->vec_sol_update));
3454:   PetscCall(VecDestroy(&snes->vec_func));
3455:   PetscCall(MatDestroy(&snes->jacobian));
3456:   PetscCall(MatDestroy(&snes->jacobian_pre));
3457:   PetscCall(MatDestroy(&snes->picard));
3458:   PetscCall(VecDestroyVecs(snes->nwork, &snes->work));
3459:   PetscCall(VecDestroyVecs(snes->nvwork, &snes->vwork));

3461:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

3463:   snes->nwork = snes->nvwork = 0;
3464:   snes->setupcalled          = PETSC_FALSE;
3465:   PetscFunctionReturn(PETSC_SUCCESS);
3466: }

3468: /*@
3469:   SNESConvergedReasonViewCancel - Clears all the reason view functions for a `SNES` object provided with `SNESConvergedReasonViewSet()` also
3470:   removes the default viewer.

3472:   Collective

3474:   Input Parameter:
3475: . snes - the nonlinear iterative solver context obtained from `SNESCreate()`

3477:   Level: intermediate

3479: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESReset()`, `SNESConvergedReasonViewSet()`
3480: @*/
3481: PetscErrorCode SNESConvergedReasonViewCancel(SNES snes)
3482: {
3483:   PetscInt i;

3485:   PetscFunctionBegin;
3487:   for (i = 0; i < snes->numberreasonviews; i++) {
3488:     if (snes->reasonviewdestroy[i]) PetscCall((*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]));
3489:   }
3490:   snes->numberreasonviews = 0;
3491:   PetscCall(PetscViewerDestroy(&snes->convergedreasonviewer));
3492:   PetscFunctionReturn(PETSC_SUCCESS);
3493: }

3495: /*@
3496:   SNESDestroy - Destroys the nonlinear solver context that was created
3497:   with `SNESCreate()`.

3499:   Collective

3501:   Input Parameter:
3502: . snes - the `SNES` context

3504:   Level: beginner

3506: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESSolve()`
3507: @*/
3508: PetscErrorCode SNESDestroy(SNES *snes)
3509: {
3510:   DM dm;

3512:   PetscFunctionBegin;
3513:   if (!*snes) PetscFunctionReturn(PETSC_SUCCESS);
3515:   if (--((PetscObject)*snes)->refct > 0) {
3516:     *snes = NULL;
3517:     PetscFunctionReturn(PETSC_SUCCESS);
3518:   }

3520:   PetscCall(SNESReset(*snes));
3521:   PetscCall(SNESDestroy(&(*snes)->npc));

3523:   /* if memory was published with SAWs then destroy it */
3524:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*snes));
3525:   PetscTryTypeMethod(*snes, destroy);

3527:   dm = (*snes)->dm;
3528:   while (dm) {
3529:     PetscCall(DMCoarsenHookRemove(dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, *snes));
3530:     PetscCall(DMGetCoarseDM(dm, &dm));
3531:   }

3533:   PetscCall(DMDestroy(&(*snes)->dm));
3534:   PetscCall(KSPDestroy(&(*snes)->ksp));
3535:   PetscCall(SNESLineSearchDestroy(&(*snes)->linesearch));

3537:   PetscCall(PetscFree((*snes)->kspconvctx));
3538:   if ((*snes)->ops->convergeddestroy) PetscCall((*(*snes)->ops->convergeddestroy)((*snes)->cnvP));
3539:   if ((*snes)->conv_hist_alloc) PetscCall(PetscFree2((*snes)->conv_hist, (*snes)->conv_hist_its));
3540:   PetscCall(SNESMonitorCancel(*snes));
3541:   PetscCall(SNESConvergedReasonViewCancel(*snes));
3542:   PetscCall(PetscHeaderDestroy(snes));
3543:   PetscFunctionReturn(PETSC_SUCCESS);
3544: }

3546: /* ----------- Routines to set solver parameters ---------- */

3548: /*@
3549:   SNESSetLagPreconditioner - Sets when the preconditioner is rebuilt in the nonlinear solve `SNESSolve()`.

3551:   Logically Collective

3553:   Input Parameters:
3554: + snes - the `SNES` context
3555: - lag  - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3556:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3558:   Options Database Keys:
3559: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple `SNESSolve()`
3560: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3561: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple `SNESSolve()`
3562: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3564:   Level: intermediate

3566:   Notes:
3567:   The default is 1

3569:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagPreconditionerPersists()` was called

3571:   `SNESSetLagPreconditionerPersists()` allows using the same uniform lagging (for example every second linear solve) across multiple nonlinear solves.

3573: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetLagPreconditionerPersists()`,
3574:           `SNESSetLagJacobianPersists()`, `SNES`, `SNESSolve()`
3575: @*/
3576: PetscErrorCode SNESSetLagPreconditioner(SNES snes, PetscInt lag)
3577: {
3578:   PetscFunctionBegin;
3580:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3581:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3583:   snes->lagpreconditioner = lag;
3584:   PetscFunctionReturn(PETSC_SUCCESS);
3585: }

3587: /*@
3588:   SNESSetGridSequence - sets the number of steps of grid sequencing that `SNES` will do

3590:   Logically Collective

3592:   Input Parameters:
3593: + snes  - the `SNES` context
3594: - steps - the number of refinements to do, defaults to 0

3596:   Options Database Key:
3597: . -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

3599:   Level: intermediate

3601:   Notes:
3602:   Once grid sequencing is turned on `SNESSolve()` will automatically perform the solve on each grid refinement.

3604:   Use `SNESGetSolution()` to extract the fine grid solution after grid sequencing.

3606: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetGridSequence()`,
3607:           `SNESSetDM()`, `SNESSolve()`
3608: @*/
3609: PetscErrorCode SNESSetGridSequence(SNES snes, PetscInt steps)
3610: {
3611:   PetscFunctionBegin;
3614:   snes->gridsequence = steps;
3615:   PetscFunctionReturn(PETSC_SUCCESS);
3616: }

3618: /*@
3619:   SNESGetGridSequence - gets the number of steps of grid sequencing that `SNES` will do

3621:   Logically Collective

3623:   Input Parameter:
3624: . snes - the `SNES` context

3626:   Output Parameter:
3627: . steps - the number of refinements to do, defaults to 0

3629:   Level: intermediate

3631: .seealso: [](ch_snes), `SNESGetLagPreconditioner()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESSetGridSequence()`
3632: @*/
3633: PetscErrorCode SNESGetGridSequence(SNES snes, PetscInt *steps)
3634: {
3635:   PetscFunctionBegin;
3637:   *steps = snes->gridsequence;
3638:   PetscFunctionReturn(PETSC_SUCCESS);
3639: }

3641: /*@
3642:   SNESGetLagPreconditioner - Return how often the preconditioner is rebuilt

3644:   Not Collective

3646:   Input Parameter:
3647: . snes - the `SNES` context

3649:   Output Parameter:
3650: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3651:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

3653:   Level: intermediate

3655:   Notes:
3656:   The default is 1

3658:   The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3660: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3661: @*/
3662: PetscErrorCode SNESGetLagPreconditioner(SNES snes, PetscInt *lag)
3663: {
3664:   PetscFunctionBegin;
3666:   *lag = snes->lagpreconditioner;
3667:   PetscFunctionReturn(PETSC_SUCCESS);
3668: }

3670: /*@
3671:   SNESSetLagJacobian - Set when the Jacobian is rebuilt in the nonlinear solve. See `SNESSetLagPreconditioner()` for determining how
3672:   often the preconditioner is rebuilt.

3674:   Logically Collective

3676:   Input Parameters:
3677: + snes - the `SNES` context
3678: - lag  - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3679:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

3681:   Options Database Keys:
3682: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3683: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3684: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3685: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag.

3687:   Level: intermediate

3689:   Notes:
3690:   The default is 1

3692:   The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

3694:   If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
3695:   at the next Newton step but never again (unless it is reset to another value)

3697: .seealso: [](ch_snes), `SNES`, `SNESGetLagPreconditioner()`, `SNESSetLagPreconditioner()`, `SNESGetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`
3698: @*/
3699: PetscErrorCode SNESSetLagJacobian(SNES snes, PetscInt lag)
3700: {
3701:   PetscFunctionBegin;
3703:   PetscCheck(lag >= -2, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag must be -2, -1, 1 or greater");
3704:   PetscCheck(lag, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Lag cannot be 0");
3706:   snes->lagjacobian = lag;
3707:   PetscFunctionReturn(PETSC_SUCCESS);
3708: }

3710: /*@
3711:   SNESGetLagJacobian - Get how often the Jacobian is rebuilt. See `SNESGetLagPreconditioner()` to determine when the preconditioner is rebuilt

3713:   Not Collective

3715:   Input Parameter:
3716: . snes - the `SNES` context

3718:   Output Parameter:
3719: . lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
3720:          the Jacobian is built etc.

3722:   Level: intermediate

3724:   Notes:
3725:   The default is 1

3727:   The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or `SNESSetLagJacobianPersists()` was called.

3729: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobian()`, `SNESSetLagPreconditioner()`, `SNESGetLagPreconditioner()`, `SNESSetLagJacobianPersists()`, `SNESSetLagPreconditionerPersists()`

3731: @*/
3732: PetscErrorCode SNESGetLagJacobian(SNES snes, PetscInt *lag)
3733: {
3734:   PetscFunctionBegin;
3736:   *lag = snes->lagjacobian;
3737:   PetscFunctionReturn(PETSC_SUCCESS);
3738: }

3740: /*@
3741:   SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple nonlinear solves

3743:   Logically collective

3745:   Input Parameters:
3746: + snes - the `SNES` context
3747: - flg  - jacobian lagging persists if true

3749:   Options Database Keys:
3750: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3751: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3752: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3753: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3755:   Level: advanced

3757:   Notes:
3758:   Normally when `SNESSetLagJacobian()` is used, the Jacobian is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3760:   This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3761:   several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3762:   timesteps may present huge efficiency gains.

3764: .seealso: [](ch_snes), `SNES`, `SNESSetLagPreconditionerPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`
3765: @*/
3766: PetscErrorCode SNESSetLagJacobianPersists(SNES snes, PetscBool flg)
3767: {
3768:   PetscFunctionBegin;
3771:   snes->lagjac_persist = flg;
3772:   PetscFunctionReturn(PETSC_SUCCESS);
3773: }

3775: /*@
3776:   SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

3778:   Logically Collective

3780:   Input Parameters:
3781: + snes - the `SNES` context
3782: - flg  - preconditioner lagging persists if true

3784:   Options Database Keys:
3785: + -snes_lag_jacobian_persists <true,false>       - sets the persistence through multiple SNES solves
3786: . -snes_lag_jacobian <-2,1,2,...>                - sets the lag
3787: . -snes_lag_preconditioner_persists <true,false> - sets the persistence through multiple SNES solves
3788: - -snes_lag_preconditioner <-2,1,2,...>          - sets the lag

3790:   Level: developer

3792:   Notes:
3793:   Normally when `SNESSetLagPreconditioner()` is used, the preconditioner is always rebuilt at the beginning of each new nonlinear solve, this removes that behavior

3795:   This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3796:   by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3797:   several timesteps may present huge efficiency gains.

3799: .seealso: [](ch_snes), `SNES`, `SNESSetLagJacobianPersists()`, `SNESSetLagJacobian()`, `SNESGetLagJacobian()`, `SNESGetNPC()`, `SNESSetLagPreconditioner()`
3800: @*/
3801: PetscErrorCode SNESSetLagPreconditionerPersists(SNES snes, PetscBool flg)
3802: {
3803:   PetscFunctionBegin;
3806:   snes->lagpre_persist = flg;
3807:   PetscFunctionReturn(PETSC_SUCCESS);
3808: }

3810: /*@
3811:   SNESSetForceIteration - force `SNESSolve()` to take at least one iteration regardless of the initial residual norm

3813:   Logically Collective

3815:   Input Parameters:
3816: + snes  - the `SNES` context
3817: - force - `PETSC_TRUE` require at least one iteration

3819:   Options Database Key:
3820: . -snes_force_iteration <force> - Sets forcing an iteration

3822:   Level: intermediate

3824:   Note:
3825:   This is used sometimes with `TS` to prevent `TS` from detecting a false steady state solution

3827: .seealso: [](ch_snes), `SNES`, `TS`, `SNESSetDivergenceTolerance()`
3828: @*/
3829: PetscErrorCode SNESSetForceIteration(SNES snes, PetscBool force)
3830: {
3831:   PetscFunctionBegin;
3833:   snes->forceiteration = force;
3834:   PetscFunctionReturn(PETSC_SUCCESS);
3835: }

3837: /*@
3838:   SNESGetForceIteration - Check whether or not `SNESSolve()` take at least one iteration regardless of the initial residual norm

3840:   Logically Collective

3842:   Input Parameter:
3843: . snes - the `SNES` context

3845:   Output Parameter:
3846: . force - `PETSC_TRUE` requires at least one iteration.

3848:   Level: intermediate

3850: .seealso: [](ch_snes), `SNES`, `SNESSetForceIteration()`, `SNESSetDivergenceTolerance()`
3851: @*/
3852: PetscErrorCode SNESGetForceIteration(SNES snes, PetscBool *force)
3853: {
3854:   PetscFunctionBegin;
3856:   *force = snes->forceiteration;
3857:   PetscFunctionReturn(PETSC_SUCCESS);
3858: }

3860: /*@
3861:   SNESSetTolerances - Sets various parameters used in `SNES` convergence tests.

3863:   Logically Collective

3865:   Input Parameters:
3866: + snes   - the `SNES` context
3867: . abstol - the absolute convergence tolerance, $ F(x^n) \le abstol $
3868: . rtol   - the relative convergence tolerance, $ F(x^n) \le reltol * F(x^0) $
3869: . stol   - convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3870: . maxit  - the maximum number of iterations allowed in the solver, default 50.
3871: - maxf   - the maximum number of function evaluations allowed in the solver (use `PETSC_UNLIMITED` indicates no limit), default 10,000

3873:   Options Database Keys:
3874: + -snes_atol <abstol>    - Sets `abstol`
3875: . -snes_rtol <rtol>      - Sets `rtol`
3876: . -snes_stol <stol>      - Sets `stol`
3877: . -snes_max_it <maxit>   - Sets `maxit`
3878: - -snes_max_funcs <maxf> - Sets `maxf` (use `unlimited` to have no maximum)

3880:   Level: intermediate

3882:   Note:
3883:   All parameters must be non-negative

3885:   Use `PETSC_CURRENT` to retain the current value of any parameter and `PETSC_DETERMINE` to use the default value for the given `SNES`.
3886:   The default value is the value in the object when its type is set.

3888:   Use `PETSC_UNLIMITED` on `maxit` or `maxf` to indicate there is no bound on the number of iterations or number of function evaluations.

3890:   Fortran Note:
3891:   Use `PETSC_CURRENT_INTEGER`, `PETSC_CURRENT_REAL`, `PETSC_UNLIMITED_INTEGER`, `PETSC_DETERMINE_INTEGER`, or `PETSC_DETERMINE_REAL`

3893: .seealso: [](ch_snes), `SNESSolve()`, `SNES`, `SNESSetDivergenceTolerance()`, `SNESSetForceIteration()`
3894: @*/
3895: PetscErrorCode SNESSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit, PetscInt maxf)
3896: {
3897:   PetscFunctionBegin;

3905:   if (abstol == (PetscReal)PETSC_DETERMINE) {
3906:     snes->abstol = snes->default_abstol;
3907:   } else if (abstol != (PetscReal)PETSC_CURRENT) {
3908:     PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
3909:     snes->abstol = abstol;
3910:   }

3912:   if (rtol == (PetscReal)PETSC_DETERMINE) {
3913:     snes->rtol = snes->default_rtol;
3914:   } else if (rtol != (PetscReal)PETSC_CURRENT) {
3915:     PetscCheck(rtol >= 0.0 && 1.0 > rtol, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
3916:     snes->rtol = rtol;
3917:   }

3919:   if (stol == (PetscReal)PETSC_DETERMINE) {
3920:     snes->stol = snes->default_stol;
3921:   } else if (stol != (PetscReal)PETSC_CURRENT) {
3922:     PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
3923:     snes->stol = stol;
3924:   }

3926:   if (maxit == PETSC_DETERMINE) {
3927:     snes->max_its = snes->default_max_its;
3928:   } else if (maxit == PETSC_UNLIMITED) {
3929:     snes->max_its = PETSC_INT_MAX;
3930:   } else if (maxit != PETSC_CURRENT) {
3931:     PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
3932:     snes->max_its = maxit;
3933:   }

3935:   if (maxf == PETSC_DETERMINE) {
3936:     snes->max_funcs = snes->default_max_funcs;
3937:   } else if (maxf == PETSC_UNLIMITED || maxf == -1) {
3938:     snes->max_funcs = PETSC_UNLIMITED;
3939:   } else if (maxf != PETSC_CURRENT) {
3940:     PetscCheck(maxf >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of function evaluations %" PetscInt_FMT " must be nonnegative", maxf);
3941:     snes->max_funcs = maxf;
3942:   }
3943:   PetscFunctionReturn(PETSC_SUCCESS);
3944: }

3946: /*@
3947:   SNESSetDivergenceTolerance - Sets the divergence tolerance used for the `SNES` divergence test.

3949:   Logically Collective

3951:   Input Parameters:
3952: + snes   - the `SNES` context
3953: - divtol - the divergence tolerance. Use `PETSC_UNLIMITED` to deactivate the test. If the residual norm $ F(x^n) \ge divtol * F(x^0) $ the solver
3954:            is stopped due to divergence.

3956:   Options Database Key:
3957: . -snes_divergence_tolerance <divtol> - Sets `divtol`

3959:   Level: intermediate

3961:   Notes:
3962:   Use `PETSC_DETERMINE` to use the default value from when the object's type was set.

3964:   Fortran Note:
3965:   Use ``PETSC_DETERMINE_REAL` or `PETSC_UNLIMITED_REAL`

3967: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetTolerances()`, `SNESGetDivergenceTolerance()`
3968: @*/
3969: PetscErrorCode SNESSetDivergenceTolerance(SNES snes, PetscReal divtol)
3970: {
3971:   PetscFunctionBegin;

3975:   if (divtol == (PetscReal)PETSC_DETERMINE) {
3976:     snes->divtol = snes->default_divtol;
3977:   } else if (divtol == (PetscReal)PETSC_UNLIMITED || divtol == -1) {
3978:     snes->divtol = PETSC_UNLIMITED;
3979:   } else if (divtol != (PetscReal)PETSC_CURRENT) {
3980:     PetscCheck(divtol >= 1.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Divergence tolerance %g must be greater than 1.0", (double)divtol);
3981:     snes->divtol = divtol;
3982:   }
3983:   PetscFunctionReturn(PETSC_SUCCESS);
3984: }

3986: /*@
3987:   SNESGetTolerances - Gets various parameters used in `SNES` convergence tests.

3989:   Not Collective

3991:   Input Parameter:
3992: . snes - the `SNES` context

3994:   Output Parameters:
3995: + atol  - the absolute convergence tolerance
3996: . rtol  - the relative convergence tolerance
3997: . stol  - convergence tolerance in terms of the norm of the change in the solution between steps
3998: . maxit - the maximum number of iterations allowed
3999: - maxf  - the maximum number of function evaluations allowed, `PETSC_UNLIMITED` indicates no bound

4001:   Level: intermediate

4003:   Notes:
4004:   See `SNESSetTolerances()` for details on the parameters.

4006:   The user can specify `NULL` for any parameter that is not needed.

4008: .seealso: [](ch_snes), `SNES`, `SNESSetTolerances()`
4009: @*/
4010: PetscErrorCode SNESGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit, PetscInt *maxf)
4011: {
4012:   PetscFunctionBegin;
4014:   if (atol) *atol = snes->abstol;
4015:   if (rtol) *rtol = snes->rtol;
4016:   if (stol) *stol = snes->stol;
4017:   if (maxit) *maxit = snes->max_its;
4018:   if (maxf) *maxf = snes->max_funcs;
4019:   PetscFunctionReturn(PETSC_SUCCESS);
4020: }

4022: /*@
4023:   SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

4025:   Not Collective

4027:   Input Parameters:
4028: + snes   - the `SNES` context
4029: - divtol - divergence tolerance

4031:   Level: intermediate

4033: .seealso: [](ch_snes), `SNES`, `SNESSetDivergenceTolerance()`
4034: @*/
4035: PetscErrorCode SNESGetDivergenceTolerance(SNES snes, PetscReal *divtol)
4036: {
4037:   PetscFunctionBegin;
4039:   if (divtol) *divtol = snes->divtol;
4040:   PetscFunctionReturn(PETSC_SUCCESS);
4041: }

4043: PETSC_INTERN PetscErrorCode SNESMonitorRange_Private(SNES, PetscInt, PetscReal *);

4045: PetscErrorCode SNESMonitorLGRange(SNES snes, PetscInt n, PetscReal rnorm, void *monctx)
4046: {
4047:   PetscDrawLG      lg;
4048:   PetscReal        x, y, per;
4049:   PetscViewer      v = (PetscViewer)monctx;
4050:   static PetscReal prev; /* should be in the context */
4051:   PetscDraw        draw;

4053:   PetscFunctionBegin;
4055:   PetscCall(PetscViewerDrawGetDrawLG(v, 0, &lg));
4056:   if (!n) PetscCall(PetscDrawLGReset(lg));
4057:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4058:   PetscCall(PetscDrawSetTitle(draw, "Residual norm"));
4059:   x = (PetscReal)n;
4060:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
4061:   else y = -15.0;
4062:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4063:   if (n < 20 || !(n % 5) || snes->reason) {
4064:     PetscCall(PetscDrawLGDraw(lg));
4065:     PetscCall(PetscDrawLGSave(lg));
4066:   }

4068:   PetscCall(PetscViewerDrawGetDrawLG(v, 1, &lg));
4069:   if (!n) PetscCall(PetscDrawLGReset(lg));
4070:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4071:   PetscCall(PetscDrawSetTitle(draw, "% elements > .2*max element"));
4072:   PetscCall(SNESMonitorRange_Private(snes, n, &per));
4073:   x = (PetscReal)n;
4074:   y = 100.0 * per;
4075:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4076:   if (n < 20 || !(n % 5) || snes->reason) {
4077:     PetscCall(PetscDrawLGDraw(lg));
4078:     PetscCall(PetscDrawLGSave(lg));
4079:   }

4081:   PetscCall(PetscViewerDrawGetDrawLG(v, 2, &lg));
4082:   if (!n) {
4083:     prev = rnorm;
4084:     PetscCall(PetscDrawLGReset(lg));
4085:   }
4086:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4087:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm"));
4088:   x = (PetscReal)n;
4089:   y = (prev - rnorm) / prev;
4090:   PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4091:   if (n < 20 || !(n % 5) || snes->reason) {
4092:     PetscCall(PetscDrawLGDraw(lg));
4093:     PetscCall(PetscDrawLGSave(lg));
4094:   }

4096:   PetscCall(PetscViewerDrawGetDrawLG(v, 3, &lg));
4097:   if (!n) PetscCall(PetscDrawLGReset(lg));
4098:   PetscCall(PetscDrawLGGetDraw(lg, &draw));
4099:   PetscCall(PetscDrawSetTitle(draw, "(norm -oldnorm)/oldnorm*(% > .2 max)"));
4100:   x = (PetscReal)n;
4101:   y = (prev - rnorm) / (prev * per);
4102:   if (n > 2) { /*skip initial crazy value */
4103:     PetscCall(PetscDrawLGAddPoint(lg, &x, &y));
4104:   }
4105:   if (n < 20 || !(n % 5) || snes->reason) {
4106:     PetscCall(PetscDrawLGDraw(lg));
4107:     PetscCall(PetscDrawLGSave(lg));
4108:   }
4109:   prev = rnorm;
4110:   PetscFunctionReturn(PETSC_SUCCESS);
4111: }

4113: /*@
4114:   SNESConverged - Run the convergence test and update the `SNESConvergedReason`.

4116:   Collective

4118:   Input Parameters:
4119: + snes  - the `SNES` context
4120: . it    - current iteration
4121: . xnorm - 2-norm of current iterate
4122: . snorm - 2-norm of current step
4123: - fnorm - 2-norm of function

4125:   Level: developer

4127:   Note:
4128:   This routine is called by the `SNESSolve()` implementations.
4129:   It does not typically need to be called by the user.

4131: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4132: @*/
4133: PetscErrorCode SNESConverged(SNES snes, PetscInt it, PetscReal xnorm, PetscReal snorm, PetscReal fnorm)
4134: {
4135:   PetscFunctionBegin;
4136:   if (!snes->reason) {
4137:     if (snes->normschedule == SNES_NORM_ALWAYS) PetscUseTypeMethod(snes, converged, it, xnorm, snorm, fnorm, &snes->reason, snes->cnvP);
4138:     if (it == snes->max_its && !snes->reason) {
4139:       if (snes->normschedule == SNES_NORM_ALWAYS) {
4140:         PetscCall(PetscInfo(snes, "Maximum number of iterations has been reached: %" PetscInt_FMT "\n", snes->max_its));
4141:         snes->reason = SNES_DIVERGED_MAX_IT;
4142:       } else snes->reason = SNES_CONVERGED_ITS;
4143:     }
4144:   }
4145:   PetscFunctionReturn(PETSC_SUCCESS);
4146: }

4148: /*@
4149:   SNESMonitor - runs any `SNES` monitor routines provided with `SNESMonitor()` or the options database

4151:   Collective

4153:   Input Parameters:
4154: + snes  - nonlinear solver context obtained from `SNESCreate()`
4155: . iter  - current iteration number
4156: - rnorm - current relative norm of the residual

4158:   Level: developer

4160:   Note:
4161:   This routine is called by the `SNESSolve()` implementations.
4162:   It does not typically need to be called by the user.

4164: .seealso: [](ch_snes), `SNES`, `SNESMonitorSet()`
4165: @*/
4166: PetscErrorCode SNESMonitor(SNES snes, PetscInt iter, PetscReal rnorm)
4167: {
4168:   PetscInt i, n = snes->numbermonitors;

4170:   PetscFunctionBegin;
4171:   if (n > 0) SNESCheckFunctionNorm(snes, rnorm);
4172:   PetscCall(VecLockReadPush(snes->vec_sol));
4173:   for (i = 0; i < n; i++) PetscCall((*snes->monitor[i])(snes, iter, rnorm, snes->monitorcontext[i]));
4174:   PetscCall(VecLockReadPop(snes->vec_sol));
4175:   PetscFunctionReturn(PETSC_SUCCESS);
4176: }

4178: /* ------------ Routines to set performance monitoring options ----------- */

4180: /*MC
4181:     SNESMonitorFunction - functional form passed to `SNESMonitorSet()` to monitor convergence of nonlinear solver

4183:      Synopsis:
4184: #include <petscsnes.h>
4185:     PetscErrorCode SNESMonitorFunction(SNES snes, PetscInt its, PetscReal norm, void *mctx)

4187:      Collective

4189:     Input Parameters:
4190: +    snes - the `SNES` context
4191: .    its - iteration number
4192: .    norm - 2-norm function value (may be estimated)
4193: -    mctx - [optional] monitoring context

4195:    Level: advanced

4197: .seealso: [](ch_snes), `SNESMonitorSet()`, `SNESMonitorSet()`, `SNESMonitorGet()`
4198: M*/

4200: /*@C
4201:   SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
4202:   iteration of the `SNES` nonlinear solver to display the iteration's
4203:   progress.

4205:   Logically Collective

4207:   Input Parameters:
4208: + snes           - the `SNES` context
4209: . f              - the monitor function,  for the calling sequence see `SNESMonitorFunction`
4210: . mctx           - [optional] user-defined context for private data for the monitor routine (use `NULL` if no context is desired)
4211: - monitordestroy - [optional] routine that frees monitor context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4213:   Options Database Keys:
4214: + -snes_monitor               - sets `SNESMonitorDefault()`
4215: . -snes_monitor draw::draw_lg - sets line graph monitor,
4216: - -snes_monitor_cancel        - cancels all monitors that have been hardwired into a code by calls to `SNESMonitorSet()`, but does not cancel those set via
4217:                                 the options database.

4219:   Level: intermediate

4221:   Note:
4222:   Several different monitoring routines may be set by calling
4223:   `SNESMonitorSet()` multiple times; all will be called in the
4224:   order in which they were set.

4226:   Fortran Note:
4227:   Only a single monitor function can be set for each `SNES` object

4229: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESMonitorDefault()`, `SNESMonitorCancel()`, `SNESMonitorFunction`, `PetscCtxDestroyFn`
4230: @*/
4231: PetscErrorCode SNESMonitorSet(SNES snes, PetscErrorCode (*f)(SNES, PetscInt, PetscReal, void *), void *mctx, PetscCtxDestroyFn *monitordestroy)
4232: {
4233:   PetscInt  i;
4234:   PetscBool identical;

4236:   PetscFunctionBegin;
4238:   for (i = 0; i < snes->numbermonitors; i++) {
4239:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))f, mctx, monitordestroy, (PetscErrorCode (*)(void))snes->monitor[i], snes->monitorcontext[i], snes->monitordestroy[i], &identical));
4240:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4241:   }
4242:   PetscCheck(snes->numbermonitors < MAXSNESMONITORS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many monitors set");
4243:   snes->monitor[snes->numbermonitors]          = f;
4244:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
4245:   snes->monitorcontext[snes->numbermonitors++] = mctx;
4246:   PetscFunctionReturn(PETSC_SUCCESS);
4247: }

4249: /*@
4250:   SNESMonitorCancel - Clears all the monitor functions for a `SNES` object.

4252:   Logically Collective

4254:   Input Parameter:
4255: . snes - the `SNES` context

4257:   Options Database Key:
4258: . -snes_monitor_cancel - cancels all monitors that have been hardwired
4259:                          into a code by calls to `SNESMonitorSet()`, but does not cancel those
4260:                          set via the options database

4262:   Level: intermediate

4264:   Note:
4265:   There is no way to clear one specific monitor from a `SNES` object.

4267: .seealso: [](ch_snes), `SNES`, `SNESMonitorGet()`, `SNESMonitorDefault()`, `SNESMonitorSet()`
4268: @*/
4269: PetscErrorCode SNESMonitorCancel(SNES snes)
4270: {
4271:   PetscInt i;

4273:   PetscFunctionBegin;
4275:   for (i = 0; i < snes->numbermonitors; i++) {
4276:     if (snes->monitordestroy[i]) PetscCall((*snes->monitordestroy[i])(&snes->monitorcontext[i]));
4277:   }
4278:   snes->numbermonitors = 0;
4279:   PetscFunctionReturn(PETSC_SUCCESS);
4280: }

4282: /*MC
4283:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

4285:      Synopsis:
4286: #include <petscsnes.h>
4287:      PetscErrorCode SNESConvergenceTest(SNES snes, PetscInt it, PetscReal xnorm, PetscReal gnorm, PetscReal f, SNESConvergedReason *reason, void *cctx)

4289:      Collective

4291:     Input Parameters:
4292: +    snes - the `SNES` context
4293: .    it - current iteration (0 is the first and is before any Newton step)
4294: .    xnorm - 2-norm of current iterate
4295: .    gnorm - 2-norm of current step
4296: .    f - 2-norm of function
4297: -    cctx - [optional] convergence context

4299:     Output Parameter:
4300: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

4302:    Level: intermediate

4304: .seealso: [](ch_snes), `SNES`, `SNESSolve`, `SNESSetConvergenceTest()`
4305: M*/

4307: /*@C
4308:   SNESSetConvergenceTest - Sets the function that is to be used
4309:   to test for convergence of the nonlinear iterative solution.

4311:   Logically Collective

4313:   Input Parameters:
4314: + snes                        - the `SNES` context
4315: . SNESConvergenceTestFunction - routine to test for convergence
4316: . cctx                        - [optional] context for private data for the convergence routine  (may be `NULL`)
4317: - destroy                     - [optional] destructor for the context (may be `NULL`; `PETSC_NULL_FUNCTION` in Fortran)

4319:   Level: advanced

4321: .seealso: [](ch_snes), `SNES`, `SNESConvergedDefault()`, `SNESConvergedSkip()`, `SNESConvergenceTestFunction`
4322: @*/
4323: PetscErrorCode SNESSetConvergenceTest(SNES snes, PetscErrorCode (*SNESConvergenceTestFunction)(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason *, void *), void *cctx, PetscErrorCode (*destroy)(void *))
4324: {
4325:   PetscFunctionBegin;
4327:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
4328:   if (snes->ops->convergeddestroy) PetscCall((*snes->ops->convergeddestroy)(snes->cnvP));
4329:   snes->ops->converged        = SNESConvergenceTestFunction;
4330:   snes->ops->convergeddestroy = destroy;
4331:   snes->cnvP                  = cctx;
4332:   PetscFunctionReturn(PETSC_SUCCESS);
4333: }

4335: /*@
4336:   SNESGetConvergedReason - Gets the reason the `SNES` iteration was stopped, which may be due to convergence, divergence, or stagnation

4338:   Not Collective

4340:   Input Parameter:
4341: . snes - the `SNES` context

4343:   Output Parameter:
4344: . reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` for the individual convergence tests for complete lists

4346:   Options Database Key:
4347: . -snes_converged_reason - prints the reason to standard out

4349:   Level: intermediate

4351:   Note:
4352:   Should only be called after the call the `SNESSolve()` is complete, if it is called earlier it returns the value `SNES__CONVERGED_ITERATING`.

4354: .seealso: [](ch_snes), `SNESSolve()`, `SNESSetConvergenceTest()`, `SNESSetConvergedReason()`, `SNESConvergedReason`, `SNESGetConvergedReasonString()`
4355: @*/
4356: PetscErrorCode SNESGetConvergedReason(SNES snes, SNESConvergedReason *reason)
4357: {
4358:   PetscFunctionBegin;
4360:   PetscAssertPointer(reason, 2);
4361:   *reason = snes->reason;
4362:   PetscFunctionReturn(PETSC_SUCCESS);
4363: }

4365: /*@C
4366:   SNESGetConvergedReasonString - Return a human readable string for `SNESConvergedReason`

4368:   Not Collective

4370:   Input Parameter:
4371: . snes - the `SNES` context

4373:   Output Parameter:
4374: . strreason - a human readable string that describes `SNES` converged reason

4376:   Level: beginner

4378: .seealso: [](ch_snes), `SNES`, `SNESGetConvergedReason()`
4379: @*/
4380: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char **strreason)
4381: {
4382:   PetscFunctionBegin;
4384:   PetscAssertPointer(strreason, 2);
4385:   *strreason = SNESConvergedReasons[snes->reason];
4386:   PetscFunctionReturn(PETSC_SUCCESS);
4387: }

4389: /*@
4390:   SNESSetConvergedReason - Sets the reason the `SNES` iteration was stopped.

4392:   Not Collective

4394:   Input Parameters:
4395: + snes   - the `SNES` context
4396: - reason - negative value indicates diverged, positive value converged, see `SNESConvergedReason` or the
4397:             manual pages for the individual convergence tests for complete lists

4399:   Level: developer

4401:   Developer Note:
4402:   Called inside the various `SNESSolve()` implementations

4404: .seealso: [](ch_snes), `SNESGetConvergedReason()`, `SNESSetConvergenceTest()`, `SNESConvergedReason`
4405: @*/
4406: PetscErrorCode SNESSetConvergedReason(SNES snes, SNESConvergedReason reason)
4407: {
4408:   PetscFunctionBegin;
4410:   PetscCheck(!snes->errorifnotconverged || reason > 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_PLIB, "SNES code should have previously errored due to negative reason");
4411:   snes->reason = reason;
4412:   PetscFunctionReturn(PETSC_SUCCESS);
4413: }

4415: /*@
4416:   SNESSetConvergenceHistory - Sets the arrays used to hold the convergence history.

4418:   Logically Collective

4420:   Input Parameters:
4421: + snes  - iterative context obtained from `SNESCreate()`
4422: . a     - array to hold history, this array will contain the function norms computed at each step
4423: . its   - integer array holds the number of linear iterations for each solve.
4424: . na    - size of `a` and `its`
4425: - reset - `PETSC_TRUE` indicates each new nonlinear solve resets the history counter to zero,
4426:           else it continues storing new values for new nonlinear solves after the old ones

4428:   Level: intermediate

4430:   Notes:
4431:   If 'a' and 'its' are `NULL` then space is allocated for the history. If 'na' is `PETSC_DECIDE` (or, deprecated, `PETSC_DEFAULT`) then a
4432:   default array of length 1,000 is allocated.

4434:   This routine is useful, e.g., when running a code for purposes
4435:   of accurate performance monitoring, when no I/O should be done
4436:   during the section of code that is being timed.

4438:   If the arrays run out of space after a number of iterations then the later values are not saved in the history

4440: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetConvergenceHistory()`
4441: @*/
4442: PetscErrorCode SNESSetConvergenceHistory(SNES snes, PetscReal a[], PetscInt its[], PetscInt na, PetscBool reset)
4443: {
4444:   PetscFunctionBegin;
4446:   if (a) PetscAssertPointer(a, 2);
4447:   if (its) PetscAssertPointer(its, 3);
4448:   if (!a) {
4449:     if (na == PETSC_DECIDE) na = 1000;
4450:     PetscCall(PetscCalloc2(na, &a, na, &its));
4451:     snes->conv_hist_alloc = PETSC_TRUE;
4452:   }
4453:   snes->conv_hist       = a;
4454:   snes->conv_hist_its   = its;
4455:   snes->conv_hist_max   = (size_t)na;
4456:   snes->conv_hist_len   = 0;
4457:   snes->conv_hist_reset = reset;
4458:   PetscFunctionReturn(PETSC_SUCCESS);
4459: }

4461: #if defined(PETSC_HAVE_MATLAB)
4462:   #include <engine.h> /* MATLAB include file */
4463:   #include <mex.h>    /* MATLAB include file */

4465: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
4466: {
4467:   mxArray   *mat;
4468:   PetscInt   i;
4469:   PetscReal *ar;

4471:   mat = mxCreateDoubleMatrix(snes->conv_hist_len, 1, mxREAL);
4472:   ar  = (PetscReal *)mxGetData(mat);
4473:   for (i = 0; i < snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
4474:   return mat;
4475: }
4476: #endif

4478: /*@C
4479:   SNESGetConvergenceHistory - Gets the arrays used to hold the convergence history.

4481:   Not Collective

4483:   Input Parameter:
4484: . snes - iterative context obtained from `SNESCreate()`

4486:   Output Parameters:
4487: + a   - array to hold history, usually was set with `SNESSetConvergenceHistory()`
4488: . its - integer array holds the number of linear iterations (or
4489:          negative if not converged) for each solve.
4490: - na  - size of `a` and `its`

4492:   Level: intermediate

4494:   Note:
4495:   This routine is useful, e.g., when running a code for purposes
4496:   of accurate performance monitoring, when no I/O should be done
4497:   during the section of code that is being timed.

4499:   Fortran Notes:
4500:   Return the arrays with ``SNESRestoreConvergenceHistory()`

4502:   Use the arguments
4503: .vb
4504:   PetscReal, pointer :: a(:)
4505:   PetscInt, pointer :: its(:)
4506: .ve

4508: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetConvergenceHistory()`
4509: @*/
4510: PetscErrorCode SNESGetConvergenceHistory(SNES snes, PetscReal *a[], PetscInt *its[], PetscInt *na)
4511: {
4512:   PetscFunctionBegin;
4514:   if (a) *a = snes->conv_hist;
4515:   if (its) *its = snes->conv_hist_its;
4516:   if (na) *na = (PetscInt)snes->conv_hist_len;
4517:   PetscFunctionReturn(PETSC_SUCCESS);
4518: }

4520: /*@C
4521:   SNESSetUpdate - Sets the general-purpose update function called
4522:   at the beginning of every iteration of the nonlinear solve. Specifically
4523:   it is called just before the Jacobian is "evaluated" and after the function
4524:   evaluation.

4526:   Logically Collective

4528:   Input Parameters:
4529: + snes - The nonlinear solver context
4530: - func - The update function; for calling sequence see `SNESUpdateFn`

4532:   Level: advanced

4534:   Notes:
4535:   This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your function provided
4536:   to `SNESSetFunction()`, or `SNESSetPicard()`
4537:   This is not used by most users, and it is intended to provide a general hook that is run
4538:   right before the direction step is computed.

4540:   Users are free to modify the current residual vector,
4541:   the current linearization point, or any other vector associated to the specific solver used.
4542:   If such modifications take place, it is the user responsibility to update all the relevant
4543:   vectors. For example, if one is adjusting the model parameters at each Newton step their code may look like
4544: .vb
4545:   PetscErrorCode update(SNES snes, PetscInt iteration)
4546:   {
4547:     PetscFunctionBeginUser;
4548:     if (iteration > 0) {
4549:       // update the model parameters here
4550:       Vec x,f;
4551:       PetscCall(SNESGetSolution(snes,&x));
4552:       PetcCall(SNESGetFunction(snes,&f,NULL,NULL));
4553:       PetscCall(SNESComputeFunction(snes,x,f));
4554:     }
4555:     PetscFunctionReturn(PETSC_SUCCESS);
4556:   }
4557: .ve

4559:   There are a variety of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

4561: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetJacobian()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchSetPostCheck()`, `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRSetPostCheck()`,
4562:          `SNESMonitorSet()`
4563: @*/
4564: PetscErrorCode SNESSetUpdate(SNES snes, SNESUpdateFn *func)
4565: {
4566:   PetscFunctionBegin;
4568:   snes->ops->update = func;
4569:   PetscFunctionReturn(PETSC_SUCCESS);
4570: }

4572: /*@
4573:   SNESConvergedReasonView - Displays the reason a `SNES` solve converged or diverged to a viewer

4575:   Collective

4577:   Input Parameters:
4578: + snes   - iterative context obtained from `SNESCreate()`
4579: - viewer - the viewer to display the reason

4581:   Options Database Keys:
4582: + -snes_converged_reason          - print reason for converged or diverged, also prints number of iterations
4583: - -snes_converged_reason ::failed - only print reason and number of iterations when diverged

4585:   Level: beginner

4587:   Note:
4588:   To change the format of the output call `PetscViewerPushFormat`(viewer,format) before this call. Use `PETSC_VIEWER_DEFAULT` for the default,
4589:   use `PETSC_VIEWER_FAILED` to only display a reason if it fails.

4591: .seealso: [](ch_snes), `SNESConvergedReason`, `PetscViewer`, `SNES`,
4592:           `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`, `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`,
4593:           `SNESConvergedReasonViewFromOptions()`,
4594:           `PetscViewerPushFormat()`, `PetscViewerPopFormat()`
4595: @*/
4596: PetscErrorCode SNESConvergedReasonView(SNES snes, PetscViewer viewer)
4597: {
4598:   PetscViewerFormat format;
4599:   PetscBool         isAscii;

4601:   PetscFunctionBegin;
4602:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
4603:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &isAscii));
4604:   if (isAscii) {
4605:     PetscCall(PetscViewerGetFormat(viewer, &format));
4606:     PetscCall(PetscViewerASCIIAddTab(viewer, ((PetscObject)snes)->tablevel + 1));
4607:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
4608:       DM       dm;
4609:       Vec      u;
4610:       PetscDS  prob;
4611:       PetscInt Nf, f;
4612:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
4613:       void    **exactCtx;
4614:       PetscReal error;

4616:       PetscCall(SNESGetDM(snes, &dm));
4617:       PetscCall(SNESGetSolution(snes, &u));
4618:       PetscCall(DMGetDS(dm, &prob));
4619:       PetscCall(PetscDSGetNumFields(prob, &Nf));
4620:       PetscCall(PetscMalloc2(Nf, &exactSol, Nf, &exactCtx));
4621:       for (f = 0; f < Nf; ++f) PetscCall(PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]));
4622:       PetscCall(DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error));
4623:       PetscCall(PetscFree2(exactSol, exactCtx));
4624:       if (error < 1.0e-11) PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n"));
4625:       else PetscCall(PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", (double)error));
4626:     }
4627:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
4628:       if (((PetscObject)snes)->prefix) {
4629:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve converged due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4630:       } else {
4631:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve converged due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4632:       }
4633:     } else if (snes->reason <= 0) {
4634:       if (((PetscObject)snes)->prefix) {
4635:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear %s solve did not converge due to %s iterations %" PetscInt_FMT "\n", ((PetscObject)snes)->prefix, SNESConvergedReasons[snes->reason], snes->iter));
4636:       } else {
4637:         PetscCall(PetscViewerASCIIPrintf(viewer, "Nonlinear solve did not converge due to %s iterations %" PetscInt_FMT "\n", SNESConvergedReasons[snes->reason], snes->iter));
4638:       }
4639:     }
4640:     PetscCall(PetscViewerASCIISubtractTab(viewer, ((PetscObject)snes)->tablevel + 1));
4641:   }
4642:   PetscFunctionReturn(PETSC_SUCCESS);
4643: }

4645: /*@C
4646:   SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
4647:   end of the nonlinear solver to display the convergence reason of the nonlinear solver.

4649:   Logically Collective

4651:   Input Parameters:
4652: + snes              - the `SNES` context
4653: . f                 - the `SNESConvergedReason` view function
4654: . vctx              - [optional] user-defined context for private data for the `SNESConvergedReason` view function (use `NULL` if no context is desired)
4655: - reasonviewdestroy - [optional] routine that frees the context (may be `NULL`), see `PetscCtxDestroyFn` for the calling sequence

4657:   Calling sequence of `f`:
4658: + snes - the `SNES` context
4659: - vctx - [optional] context for private data for the function

4661:   Options Database Keys:
4662: + -snes_converged_reason             - sets a default `SNESConvergedReasonView()`
4663: - -snes_converged_reason_view_cancel - cancels all converged reason viewers that have been hardwired into a code by
4664:                                        calls to `SNESConvergedReasonViewSet()`, but does not cancel those set via the options database.

4666:   Level: intermediate

4668:   Note:
4669:   Several different converged reason view routines may be set by calling
4670:   `SNESConvergedReasonViewSet()` multiple times; all will be called in the
4671:   order in which they were set.

4673: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESConvergedReason`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`, `SNESConvergedReasonViewCancel()`,
4674:           `PetscCtxDestroyFn`
4675: @*/
4676: PetscErrorCode SNESConvergedReasonViewSet(SNES snes, PetscErrorCode (*f)(SNES snes, void *vctx), void *vctx, PetscCtxDestroyFn *reasonviewdestroy)
4677: {
4678:   PetscInt  i;
4679:   PetscBool identical;

4681:   PetscFunctionBegin;
4683:   for (i = 0; i < snes->numberreasonviews; i++) {
4684:     PetscCall(PetscMonitorCompare((PetscErrorCode (*)(void))f, vctx, reasonviewdestroy, (PetscErrorCode (*)(void))snes->reasonview[i], snes->reasonviewcontext[i], snes->reasonviewdestroy[i], &identical));
4685:     if (identical) PetscFunctionReturn(PETSC_SUCCESS);
4686:   }
4687:   PetscCheck(snes->numberreasonviews < MAXSNESREASONVIEWS, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Too many SNES reasonview set");
4688:   snes->reasonview[snes->numberreasonviews]          = f;
4689:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
4690:   snes->reasonviewcontext[snes->numberreasonviews++] = vctx;
4691:   PetscFunctionReturn(PETSC_SUCCESS);
4692: }

4694: /*@
4695:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a `SNESConvergedReason` is to be viewed at the end of `SNESSolve()`
4696:   All the user-provided viewer routines set with `SNESConvergedReasonViewSet()` will be called, if they exist.

4698:   Collective

4700:   Input Parameter:
4701: . snes - the `SNES` object

4703:   Level: advanced

4705: .seealso: [](ch_snes), `SNES`, `SNESConvergedReason`, `SNESConvergedReasonViewSet()`, `SNESCreate()`, `SNESSetUp()`, `SNESDestroy()`,
4706:           `SNESSetTolerances()`, `SNESConvergedDefault()`, `SNESGetConvergedReason()`, `SNESConvergedReasonView()`
4707: @*/
4708: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
4709: {
4710:   static PetscBool incall = PETSC_FALSE;

4712:   PetscFunctionBegin;
4713:   if (incall) PetscFunctionReturn(PETSC_SUCCESS);
4714:   incall = PETSC_TRUE;

4716:   /* All user-provided viewers are called first, if they exist. */
4717:   for (PetscInt i = 0; i < snes->numberreasonviews; i++) PetscCall((*snes->reasonview[i])(snes, snes->reasonviewcontext[i]));

4719:   /* Call PETSc default routine if users ask for it */
4720:   if (snes->convergedreasonviewer) {
4721:     PetscCall(PetscViewerPushFormat(snes->convergedreasonviewer, snes->convergedreasonformat));
4722:     PetscCall(SNESConvergedReasonView(snes, snes->convergedreasonviewer));
4723:     PetscCall(PetscViewerPopFormat(snes->convergedreasonviewer));
4724:   }
4725:   incall = PETSC_FALSE;
4726:   PetscFunctionReturn(PETSC_SUCCESS);
4727: }

4729: /*@
4730:   SNESSolve - Solves a nonlinear system $F(x) = b $ associated with a `SNES` object

4732:   Collective

4734:   Input Parameters:
4735: + snes - the `SNES` context
4736: . b    - the constant part of the equation $F(x) = b$, or `NULL` to use zero.
4737: - x    - the solution vector.

4739:   Level: beginner

4741:   Note:
4742:   The user should initialize the vector, `x`, with the initial guess
4743:   for the nonlinear solve prior to calling `SNESSolve()` .

4745: .seealso: [](ch_snes), `SNES`, `SNESCreate()`, `SNESDestroy()`, `SNESSetFunction()`, `SNESSetJacobian()`, `SNESSetGridSequence()`, `SNESGetSolution()`,
4746:           `SNESNewtonTRSetPreCheck()`, `SNESNewtonTRGetPreCheck()`, `SNESNewtonTRSetPostCheck()`, `SNESNewtonTRGetPostCheck()`,
4747:           `SNESLineSearchSetPostCheck()`, `SNESLineSearchGetPostCheck()`, `SNESLineSearchSetPreCheck()`, `SNESLineSearchGetPreCheck()`
4748: @*/
4749: PetscErrorCode SNESSolve(SNES snes, Vec b, Vec x)
4750: {
4751:   PetscBool flg;
4752:   PetscInt  grid;
4753:   Vec       xcreated = NULL;
4754:   DM        dm;

4756:   PetscFunctionBegin;
4759:   if (x) PetscCheckSameComm(snes, 1, x, 3);
4761:   if (b) PetscCheckSameComm(snes, 1, b, 2);

4763:   /* High level operations using the nonlinear solver */
4764:   {
4765:     PetscViewer       viewer;
4766:     PetscViewerFormat format;
4767:     PetscInt          num;
4768:     PetscBool         flg;
4769:     static PetscBool  incall = PETSC_FALSE;

4771:     if (!incall) {
4772:       /* Estimate the convergence rate of the discretization */
4773:       PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg));
4774:       if (flg) {
4775:         PetscConvEst conv;
4776:         DM           dm;
4777:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
4778:         PetscInt     Nf;

4780:         incall = PETSC_TRUE;
4781:         PetscCall(SNESGetDM(snes, &dm));
4782:         PetscCall(DMGetNumFields(dm, &Nf));
4783:         PetscCall(PetscCalloc1(Nf, &alpha));
4784:         PetscCall(PetscConvEstCreate(PetscObjectComm((PetscObject)snes), &conv));
4785:         PetscCall(PetscConvEstSetSolver(conv, (PetscObject)snes));
4786:         PetscCall(PetscConvEstSetFromOptions(conv));
4787:         PetscCall(PetscConvEstSetUp(conv));
4788:         PetscCall(PetscConvEstGetConvRate(conv, alpha));
4789:         PetscCall(PetscViewerPushFormat(viewer, format));
4790:         PetscCall(PetscConvEstRateView(conv, alpha, viewer));
4791:         PetscCall(PetscViewerPopFormat(viewer));
4792:         PetscCall(PetscViewerDestroy(&viewer));
4793:         PetscCall(PetscConvEstDestroy(&conv));
4794:         PetscCall(PetscFree(alpha));
4795:         incall = PETSC_FALSE;
4796:       }
4797:       /* Adaptively refine the initial grid */
4798:       num = 1;
4799:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_initial", &num, &flg));
4800:       if (flg) {
4801:         DMAdaptor adaptor;

4803:         incall = PETSC_TRUE;
4804:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4805:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4806:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4807:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4808:         PetscCall(DMAdaptorSetUp(adaptor));
4809:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x));
4810:         PetscCall(DMAdaptorDestroy(&adaptor));
4811:         incall = PETSC_FALSE;
4812:       }
4813:       /* Use grid sequencing to adapt */
4814:       num = 0;
4815:       PetscCall(PetscOptionsGetInt(NULL, ((PetscObject)snes)->prefix, "-snes_adapt_sequence", &num, NULL));
4816:       if (num) {
4817:         DMAdaptor   adaptor;
4818:         const char *prefix;

4820:         incall = PETSC_TRUE;
4821:         PetscCall(DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor));
4822:         PetscCall(SNESGetOptionsPrefix(snes, &prefix));
4823:         PetscCall(DMAdaptorSetOptionsPrefix(adaptor, prefix));
4824:         PetscCall(DMAdaptorSetSolver(adaptor, snes));
4825:         PetscCall(DMAdaptorSetSequenceLength(adaptor, num));
4826:         PetscCall(DMAdaptorSetFromOptions(adaptor));
4827:         PetscCall(DMAdaptorSetUp(adaptor));
4828:         PetscCall(PetscObjectViewFromOptions((PetscObject)adaptor, NULL, "-snes_adapt_view"));
4829:         PetscCall(DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x));
4830:         PetscCall(DMAdaptorDestroy(&adaptor));
4831:         incall = PETSC_FALSE;
4832:       }
4833:     }
4834:   }
4835:   if (!x) x = snes->vec_sol;
4836:   if (!x) {
4837:     PetscCall(SNESGetDM(snes, &dm));
4838:     PetscCall(DMCreateGlobalVector(dm, &xcreated));
4839:     x = xcreated;
4840:   }
4841:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view_pre"));

4843:   for (grid = 0; grid < snes->gridsequence; grid++) PetscCall(PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4844:   for (grid = 0; grid < snes->gridsequence + 1; grid++) {
4845:     /* set solution vector */
4846:     if (!grid) PetscCall(PetscObjectReference((PetscObject)x));
4847:     PetscCall(VecDestroy(&snes->vec_sol));
4848:     snes->vec_sol = x;
4849:     PetscCall(SNESGetDM(snes, &dm));

4851:     /* set affine vector if provided */
4852:     if (b) PetscCall(PetscObjectReference((PetscObject)b));
4853:     PetscCall(VecDestroy(&snes->vec_rhs));
4854:     snes->vec_rhs = b;

4856:     if (snes->vec_rhs) PetscCheck(snes->vec_func != snes->vec_rhs, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Right hand side vector cannot be function vector");
4857:     PetscCheck(snes->vec_func != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be function vector");
4858:     PetscCheck(snes->vec_rhs != snes->vec_sol, PETSC_COMM_SELF, PETSC_ERR_ARG_IDN, "Solution vector cannot be right-hand side vector");
4859:     if (!snes->vec_sol_update /* && snes->vec_sol */) PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_sol_update));
4860:     PetscCall(DMShellSetGlobalVector(dm, snes->vec_sol));
4861:     PetscCall(SNESSetUp(snes));

4863:     if (!grid) {
4864:       if (snes->ops->computeinitialguess) PetscCallBack("SNES callback compute initial guess", (*snes->ops->computeinitialguess)(snes, snes->vec_sol, snes->initialguessP));
4865:     }

4867:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
4868:     PetscCall(SNESResetCounters(snes));
4869:     snes->reason = SNES_CONVERGED_ITERATING;
4870:     PetscCall(PetscLogEventBegin(SNES_Solve, snes, 0, 0, 0));
4871:     PetscUseTypeMethod(snes, solve);
4872:     PetscCall(PetscLogEventEnd(SNES_Solve, snes, 0, 0, 0));
4873:     PetscCheck(snes->reason, PETSC_COMM_SELF, PETSC_ERR_PLIB, "Internal error, solver %s returned without setting converged reason", ((PetscObject)snes)->type_name);
4874:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

4876:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
4877:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

4879:     PetscCall(PetscOptionsCreateViewer(PetscObjectComm((PetscObject)snes), ((PetscObject)snes)->options, ((PetscObject)snes)->prefix, "-snes_test_local_min", NULL, NULL, &flg));
4880:     if (flg && !PetscPreLoadingOn) PetscCall(SNESTestLocalMin(snes));
4881:     /* Call converged reason views. This may involve user-provided viewers as well */
4882:     PetscCall(SNESConvergedReasonViewFromOptions(snes));

4884:     if (snes->errorifnotconverged) PetscCheck(snes->reason >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_NOT_CONVERGED, "SNESSolve has not converged");
4885:     if (snes->reason < 0) break;
4886:     if (grid < snes->gridsequence) {
4887:       DM  fine;
4888:       Vec xnew;
4889:       Mat interp;

4891:       PetscCall(DMRefine(snes->dm, PetscObjectComm((PetscObject)snes), &fine));
4892:       PetscCheck(fine, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_INCOMP, "DMRefine() did not perform any refinement, cannot continue grid sequencing");
4893:       PetscCall(DMGetCoordinatesLocalSetUp(fine));
4894:       PetscCall(DMCreateInterpolation(snes->dm, fine, &interp, NULL));
4895:       PetscCall(DMCreateGlobalVector(fine, &xnew));
4896:       PetscCall(MatInterpolate(interp, x, xnew));
4897:       PetscCall(DMInterpolate(snes->dm, interp, fine));
4898:       PetscCall(MatDestroy(&interp));
4899:       x = xnew;

4901:       PetscCall(SNESReset(snes));
4902:       PetscCall(SNESSetDM(snes, fine));
4903:       PetscCall(SNESResetFromOptions(snes));
4904:       PetscCall(DMDestroy(&fine));
4905:       PetscCall(PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes))));
4906:     }
4907:   }
4908:   PetscCall(SNESViewFromOptions(snes, NULL, "-snes_view"));
4909:   PetscCall(VecViewFromOptions(snes->vec_sol, (PetscObject)snes, "-snes_view_solution"));
4910:   PetscCall(DMMonitor(snes->dm));
4911:   PetscCall(SNESMonitorPauseFinal_Internal(snes));

4913:   PetscCall(VecDestroy(&xcreated));
4914:   PetscCall(PetscObjectSAWsBlock((PetscObject)snes));
4915:   PetscFunctionReturn(PETSC_SUCCESS);
4916: }

4918: /* --------- Internal routines for SNES Package --------- */

4920: /*@
4921:   SNESSetType - Sets the algorithm/method to be used to solve the nonlinear system with the given `SNES`

4923:   Collective

4925:   Input Parameters:
4926: + snes - the `SNES` context
4927: - type - a known method

4929:   Options Database Key:
4930: . -snes_type <type> - Sets the method; use -help for a list
4931:    of available methods (for instance, newtonls or newtontr)

4933:   Level: intermediate

4935:   Notes:
4936:   See `SNESType` for available methods (for instance)
4937: +    `SNESNEWTONLS` - Newton's method with line search
4938:   (systems of nonlinear equations)
4939: -    `SNESNEWTONTR` - Newton's method with trust region
4940:   (systems of nonlinear equations)

4942:   Normally, it is best to use the `SNESSetFromOptions()` command and then
4943:   set the `SNES` solver type from the options database rather than by using
4944:   this routine.  Using the options database provides the user with
4945:   maximum flexibility in evaluating the many nonlinear solvers.
4946:   The `SNESSetType()` routine is provided for those situations where it
4947:   is necessary to set the nonlinear solver independently of the command
4948:   line or options database.  This might be the case, for example, when
4949:   the choice of solver changes during the execution of the program,
4950:   and the user's application is taking responsibility for choosing the
4951:   appropriate method.

4953:   Developer Note:
4954:   `SNESRegister()` adds a constructor for a new `SNESType` to `SNESList`, `SNESSetType()` locates
4955:   the constructor in that list and calls it to create the specific object.

4957: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESType`, `SNESCreate()`, `SNESDestroy()`, `SNESGetType()`, `SNESSetFromOptions()`
4958: @*/
4959: PetscErrorCode SNESSetType(SNES snes, SNESType type)
4960: {
4961:   PetscBool match;
4962:   PetscErrorCode (*r)(SNES);

4964:   PetscFunctionBegin;
4966:   PetscAssertPointer(type, 2);

4968:   PetscCall(PetscObjectTypeCompare((PetscObject)snes, type, &match));
4969:   if (match) PetscFunctionReturn(PETSC_SUCCESS);

4971:   PetscCall(PetscFunctionListFind(SNESList, type, &r));
4972:   PetscCheck(r, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_UNKNOWN_TYPE, "Unable to find requested SNES type %s", type);
4973:   /* Destroy the previous private SNES context */
4974:   PetscTryTypeMethod(snes, destroy);
4975:   /* Reinitialize type-specific function pointers in SNESOps structure */
4976:   snes->ops->reset          = NULL;
4977:   snes->ops->setup          = NULL;
4978:   snes->ops->solve          = NULL;
4979:   snes->ops->view           = NULL;
4980:   snes->ops->setfromoptions = NULL;
4981:   snes->ops->destroy        = NULL;

4983:   /* It may happen the user has customized the line search before calling SNESSetType */
4984:   if (((PetscObject)snes)->type_name) PetscCall(SNESLineSearchDestroy(&snes->linesearch));

4986:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
4987:   snes->setupcalled = PETSC_FALSE;

4989:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, type));
4990:   PetscCall((*r)(snes));
4991:   PetscFunctionReturn(PETSC_SUCCESS);
4992: }

4994: /*@
4995:   SNESGetType - Gets the `SNES` method type and name (as a string).

4997:   Not Collective

4999:   Input Parameter:
5000: . snes - nonlinear solver context

5002:   Output Parameter:
5003: . type - `SNES` method (a character string)

5005:   Level: intermediate

5007: .seealso: [](ch_snes), `SNESSetType()`, `SNESType`, `SNESSetFromOptions()`, `SNES`
5008: @*/
5009: PetscErrorCode SNESGetType(SNES snes, SNESType *type)
5010: {
5011:   PetscFunctionBegin;
5013:   PetscAssertPointer(type, 2);
5014:   *type = ((PetscObject)snes)->type_name;
5015:   PetscFunctionReturn(PETSC_SUCCESS);
5016: }

5018: /*@
5019:   SNESSetSolution - Sets the solution vector for use by the `SNES` routines.

5021:   Logically Collective

5023:   Input Parameters:
5024: + snes - the `SNES` context obtained from `SNESCreate()`
5025: - u    - the solution vector

5027:   Level: beginner

5029: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESGetSolution()`, `Vec`
5030: @*/
5031: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
5032: {
5033:   DM dm;

5035:   PetscFunctionBegin;
5038:   PetscCall(PetscObjectReference((PetscObject)u));
5039:   PetscCall(VecDestroy(&snes->vec_sol));

5041:   snes->vec_sol = u;

5043:   PetscCall(SNESGetDM(snes, &dm));
5044:   PetscCall(DMShellSetGlobalVector(dm, u));
5045:   PetscFunctionReturn(PETSC_SUCCESS);
5046: }

5048: /*@
5049:   SNESGetSolution - Returns the vector where the approximate solution is
5050:   stored. This is the fine grid solution when using `SNESSetGridSequence()`.

5052:   Not Collective, but `x` is parallel if `snes` is parallel

5054:   Input Parameter:
5055: . snes - the `SNES` context

5057:   Output Parameter:
5058: . x - the solution

5060:   Level: intermediate

5062: .seealso: [](ch_snes), `SNESSetSolution()`, `SNESSolve()`, `SNES`, `SNESGetSolutionUpdate()`, `SNESGetFunction()`
5063: @*/
5064: PetscErrorCode SNESGetSolution(SNES snes, Vec *x)
5065: {
5066:   PetscFunctionBegin;
5068:   PetscAssertPointer(x, 2);
5069:   *x = snes->vec_sol;
5070:   PetscFunctionReturn(PETSC_SUCCESS);
5071: }

5073: /*@
5074:   SNESGetSolutionUpdate - Returns the vector where the solution update is
5075:   stored.

5077:   Not Collective, but `x` is parallel if `snes` is parallel

5079:   Input Parameter:
5080: . snes - the `SNES` context

5082:   Output Parameter:
5083: . x - the solution update

5085:   Level: advanced

5087: .seealso: [](ch_snes), `SNES`, `SNESGetSolution()`, `SNESGetFunction()`
5088: @*/
5089: PetscErrorCode SNESGetSolutionUpdate(SNES snes, Vec *x)
5090: {
5091:   PetscFunctionBegin;
5093:   PetscAssertPointer(x, 2);
5094:   *x = snes->vec_sol_update;
5095:   PetscFunctionReturn(PETSC_SUCCESS);
5096: }

5098: /*@C
5099:   SNESGetFunction - Returns the function that defines the nonlinear system set with `SNESSetFunction()`

5101:   Not Collective, but `r` is parallel if `snes` is parallel. Collective if `r` is requested, but has not been created yet.

5103:   Input Parameter:
5104: . snes - the `SNES` context

5106:   Output Parameters:
5107: + r   - the vector that is used to store residuals (or `NULL` if you don't want it)
5108: . f   - the function (or `NULL` if you don't want it);  for calling sequence see `SNESFunctionFn`
5109: - ctx - the function context (or `NULL` if you don't want it)

5111:   Level: advanced

5113:   Note:
5114:   The vector `r` DOES NOT, in general, contain the current value of the `SNES` nonlinear function

5116: .seealso: [](ch_snes), `SNES`, `SNESSolve()`, `SNESSetFunction()`, `SNESGetSolution()`, `SNESFunctionFn`
5117: @*/
5118: PetscErrorCode SNESGetFunction(SNES snes, Vec *r, SNESFunctionFn **f, void **ctx)
5119: {
5120:   DM dm;

5122:   PetscFunctionBegin;
5124:   if (r) {
5125:     if (!snes->vec_func) {
5126:       if (snes->vec_rhs) {
5127:         PetscCall(VecDuplicate(snes->vec_rhs, &snes->vec_func));
5128:       } else if (snes->vec_sol) {
5129:         PetscCall(VecDuplicate(snes->vec_sol, &snes->vec_func));
5130:       } else if (snes->dm) {
5131:         PetscCall(DMCreateGlobalVector(snes->dm, &snes->vec_func));
5132:       }
5133:     }
5134:     *r = snes->vec_func;
5135:   }
5136:   PetscCall(SNESGetDM(snes, &dm));
5137:   PetscCall(DMSNESGetFunction(dm, f, ctx));
5138:   PetscFunctionReturn(PETSC_SUCCESS);
5139: }

5141: /*@C
5142:   SNESGetNGS - Returns the function and context set with `SNESSetNGS()`

5144:   Input Parameter:
5145: . snes - the `SNES` context

5147:   Output Parameters:
5148: + f   - the function (or `NULL`) see `SNESNGSFn` for calling sequence
5149: - ctx - the function context (or `NULL`)

5151:   Level: advanced

5153: .seealso: [](ch_snes), `SNESSetNGS()`, `SNESGetFunction()`, `SNESNGSFn`
5154: @*/
5155: PetscErrorCode SNESGetNGS(SNES snes, SNESNGSFn **f, void **ctx)
5156: {
5157:   DM dm;

5159:   PetscFunctionBegin;
5161:   PetscCall(SNESGetDM(snes, &dm));
5162:   PetscCall(DMSNESGetNGS(dm, f, ctx));
5163:   PetscFunctionReturn(PETSC_SUCCESS);
5164: }

5166: /*@
5167:   SNESSetOptionsPrefix - Sets the prefix used for searching for all
5168:   `SNES` options in the database.

5170:   Logically Collective

5172:   Input Parameters:
5173: + snes   - the `SNES` context
5174: - prefix - the prefix to prepend to all option names

5176:   Level: advanced

5178:   Note:
5179:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5180:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5182: .seealso: [](ch_snes), `SNES`, `SNESSetFromOptions()`, `SNESAppendOptionsPrefix()`
5183: @*/
5184: PetscErrorCode SNESSetOptionsPrefix(SNES snes, const char prefix[])
5185: {
5186:   PetscFunctionBegin;
5188:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes, prefix));
5189:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5190:   if (snes->linesearch) {
5191:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5192:     PetscCall(PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch, prefix));
5193:   }
5194:   PetscCall(KSPSetOptionsPrefix(snes->ksp, prefix));
5195:   PetscFunctionReturn(PETSC_SUCCESS);
5196: }

5198: /*@
5199:   SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
5200:   `SNES` options in the database.

5202:   Logically Collective

5204:   Input Parameters:
5205: + snes   - the `SNES` context
5206: - prefix - the prefix to prepend to all option names

5208:   Level: advanced

5210:   Note:
5211:   A hyphen (-) must NOT be given at the beginning of the prefix name.
5212:   The first character of all runtime options is AUTOMATICALLY the hyphen.

5214: .seealso: [](ch_snes), `SNESGetOptionsPrefix()`, `SNESSetOptionsPrefix()`
5215: @*/
5216: PetscErrorCode SNESAppendOptionsPrefix(SNES snes, const char prefix[])
5217: {
5218:   PetscFunctionBegin;
5220:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes, prefix));
5221:   if (!snes->ksp) PetscCall(SNESGetKSP(snes, &snes->ksp));
5222:   if (snes->linesearch) {
5223:     PetscCall(SNESGetLineSearch(snes, &snes->linesearch));
5224:     PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch, prefix));
5225:   }
5226:   PetscCall(KSPAppendOptionsPrefix(snes->ksp, prefix));
5227:   PetscFunctionReturn(PETSC_SUCCESS);
5228: }

5230: /*@
5231:   SNESGetOptionsPrefix - Gets the prefix used for searching for all
5232:   `SNES` options in the database.

5234:   Not Collective

5236:   Input Parameter:
5237: . snes - the `SNES` context

5239:   Output Parameter:
5240: . prefix - pointer to the prefix string used

5242:   Level: advanced

5244: .seealso: [](ch_snes), `SNES`, `SNESSetOptionsPrefix()`, `SNESAppendOptionsPrefix()`
5245: @*/
5246: PetscErrorCode SNESGetOptionsPrefix(SNES snes, const char *prefix[])
5247: {
5248:   PetscFunctionBegin;
5250:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)snes, prefix));
5251:   PetscFunctionReturn(PETSC_SUCCESS);
5252: }

5254: /*@C
5255:   SNESRegister - Adds a method to the nonlinear solver package.

5257:   Not Collective

5259:   Input Parameters:
5260: + sname    - name of a new user-defined solver
5261: - function - routine to create method context

5263:   Level: advanced

5265:   Note:
5266:   `SNESRegister()` may be called multiple times to add several user-defined solvers.

5268:   Example Usage:
5269: .vb
5270:    SNESRegister("my_solver", MySolverCreate);
5271: .ve

5273:   Then, your solver can be chosen with the procedural interface via
5274: .vb
5275:   SNESSetType(snes, "my_solver")
5276: .ve
5277:   or at runtime via the option
5278: .vb
5279:   -snes_type my_solver
5280: .ve

5282: .seealso: [](ch_snes), `SNESRegisterAll()`, `SNESRegisterDestroy()`
5283: @*/
5284: PetscErrorCode SNESRegister(const char sname[], PetscErrorCode (*function)(SNES))
5285: {
5286:   PetscFunctionBegin;
5287:   PetscCall(SNESInitializePackage());
5288:   PetscCall(PetscFunctionListAdd(&SNESList, sname, function));
5289:   PetscFunctionReturn(PETSC_SUCCESS);
5290: }

5292: PetscErrorCode SNESTestLocalMin(SNES snes)
5293: {
5294:   PetscInt    N, i, j;
5295:   Vec         u, uh, fh;
5296:   PetscScalar value;
5297:   PetscReal   norm;

5299:   PetscFunctionBegin;
5300:   PetscCall(SNESGetSolution(snes, &u));
5301:   PetscCall(VecDuplicate(u, &uh));
5302:   PetscCall(VecDuplicate(u, &fh));

5304:   /* currently only works for sequential */
5305:   PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "Testing FormFunction() for local min\n"));
5306:   PetscCall(VecGetSize(u, &N));
5307:   for (i = 0; i < N; i++) {
5308:     PetscCall(VecCopy(u, uh));
5309:     PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "i = %" PetscInt_FMT "\n", i));
5310:     for (j = -10; j < 11; j++) {
5311:       value = PetscSign(j) * PetscExpReal(PetscAbs(j) - 10.0);
5312:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5313:       PetscCall(SNESComputeFunction(snes, uh, fh));
5314:       PetscCall(VecNorm(fh, NORM_2, &norm));
5315:       PetscCall(PetscPrintf(PetscObjectComm((PetscObject)snes), "       j norm %" PetscInt_FMT " %18.16e\n", j, (double)norm));
5316:       value = -value;
5317:       PetscCall(VecSetValue(uh, i, value, ADD_VALUES));
5318:     }
5319:   }
5320:   PetscCall(VecDestroy(&uh));
5321:   PetscCall(VecDestroy(&fh));
5322:   PetscFunctionReturn(PETSC_SUCCESS);
5323: }

5325: /*@
5326:   SNESKSPSetUseEW - Sets `SNES` to the use Eisenstat-Walker method for
5327:   computing relative tolerance for linear solvers within an inexact
5328:   Newton method.

5330:   Logically Collective

5332:   Input Parameters:
5333: + snes - `SNES` context
5334: - flag - `PETSC_TRUE` or `PETSC_FALSE`

5336:   Options Database Keys:
5337: + -snes_ksp_ew                       - use Eisenstat-Walker method for determining linear system convergence
5338: . -snes_ksp_ew_version ver           - version of  Eisenstat-Walker method
5339: . -snes_ksp_ew_rtol0 <rtol0>         - Sets rtol0
5340: . -snes_ksp_ew_rtolmax <rtolmax>     - Sets rtolmax
5341: . -snes_ksp_ew_gamma <gamma>         - Sets gamma
5342: . -snes_ksp_ew_alpha <alpha>         - Sets alpha
5343: . -snes_ksp_ew_alpha2 <alpha2>       - Sets alpha2
5344: - -snes_ksp_ew_threshold <threshold> - Sets threshold

5346:   Level: advanced

5348:   Note:
5349:   The default is to use a constant relative tolerance for
5350:   the inner linear solvers.  Alternatively, one can use the
5351:   Eisenstat-Walker method {cite}`ew96`, where the relative convergence tolerance
5352:   is reset at each Newton iteration according progress of the nonlinear
5353:   solver.

5355: .seealso: [](ch_snes), `KSP`, `SNES`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5356: @*/
5357: PetscErrorCode SNESKSPSetUseEW(SNES snes, PetscBool flag)
5358: {
5359:   PetscFunctionBegin;
5362:   snes->ksp_ewconv = flag;
5363:   PetscFunctionReturn(PETSC_SUCCESS);
5364: }

5366: /*@
5367:   SNESKSPGetUseEW - Gets if `SNES` is using Eisenstat-Walker method
5368:   for computing relative tolerance for linear solvers within an
5369:   inexact Newton method.

5371:   Not Collective

5373:   Input Parameter:
5374: . snes - `SNES` context

5376:   Output Parameter:
5377: . flag - `PETSC_TRUE` or `PETSC_FALSE`

5379:   Level: advanced

5381: .seealso: [](ch_snes), `SNESKSPSetUseEW()`, `SNESKSPGetParametersEW()`, `SNESKSPSetParametersEW()`
5382: @*/
5383: PetscErrorCode SNESKSPGetUseEW(SNES snes, PetscBool *flag)
5384: {
5385:   PetscFunctionBegin;
5387:   PetscAssertPointer(flag, 2);
5388:   *flag = snes->ksp_ewconv;
5389:   PetscFunctionReturn(PETSC_SUCCESS);
5390: }

5392: /*@
5393:   SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
5394:   convergence criteria for the linear solvers within an inexact
5395:   Newton method.

5397:   Logically Collective

5399:   Input Parameters:
5400: + snes      - `SNES` context
5401: . version   - version 1, 2 (default is 2), 3 or 4
5402: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5403: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5404: . gamma     - multiplicative factor for version 2 rtol computation
5405:              (0 <= gamma2 <= 1)
5406: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5407: . alpha2    - power for safeguard
5408: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5410:   Level: advanced

5412:   Notes:
5413:   Version 3 was contributed by Luis Chacon, June 2006.

5415:   Use `PETSC_CURRENT` to retain the default for any of the parameters.

5417: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPGetParametersEW()`
5418: @*/
5419: PetscErrorCode SNESKSPSetParametersEW(SNES snes, PetscInt version, PetscReal rtol_0, PetscReal rtol_max, PetscReal gamma, PetscReal alpha, PetscReal alpha2, PetscReal threshold)
5420: {
5421:   SNESKSPEW *kctx;

5423:   PetscFunctionBegin;
5425:   kctx = (SNESKSPEW *)snes->kspconvctx;
5426:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");

5435:   if (version != PETSC_CURRENT) kctx->version = version;
5436:   if (rtol_0 != (PetscReal)PETSC_CURRENT) kctx->rtol_0 = rtol_0;
5437:   if (rtol_max != (PetscReal)PETSC_CURRENT) kctx->rtol_max = rtol_max;
5438:   if (gamma != (PetscReal)PETSC_CURRENT) kctx->gamma = gamma;
5439:   if (alpha != (PetscReal)PETSC_CURRENT) kctx->alpha = alpha;
5440:   if (alpha2 != (PetscReal)PETSC_CURRENT) kctx->alpha2 = alpha2;
5441:   if (threshold != (PetscReal)PETSC_CURRENT) kctx->threshold = threshold;

5443:   PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1 to 4 are supported: %" PetscInt_FMT, kctx->version);
5444:   PetscCheck(kctx->rtol_0 >= 0.0 && kctx->rtol_0 < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_0 < 1.0: %g", (double)kctx->rtol_0);
5445:   PetscCheck(kctx->rtol_max >= 0.0 && kctx->rtol_max < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= rtol_max (%g) < 1.0", (double)kctx->rtol_max);
5446:   PetscCheck(kctx->gamma >= 0.0 && kctx->gamma <= 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 <= gamma (%g) <= 1.0", (double)kctx->gamma);
5447:   PetscCheck(kctx->alpha > 1.0 && kctx->alpha <= 2.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "1.0 < alpha (%g) <= 2.0", (double)kctx->alpha);
5448:   PetscCheck(kctx->threshold > 0.0 && kctx->threshold < 1.0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "0.0 < threshold (%g) < 1.0", (double)kctx->threshold);
5449:   PetscFunctionReturn(PETSC_SUCCESS);
5450: }

5452: /*@
5453:   SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
5454:   convergence criteria for the linear solvers within an inexact
5455:   Newton method.

5457:   Not Collective

5459:   Input Parameter:
5460: . snes - `SNES` context

5462:   Output Parameters:
5463: + version   - version 1, 2 (default is 2), 3 or 4
5464: . rtol_0    - initial relative tolerance (0 <= rtol_0 < 1)
5465: . rtol_max  - maximum relative tolerance (0 <= rtol_max < 1)
5466: . gamma     - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
5467: . alpha     - power for version 2 rtol computation (1 < alpha <= 2)
5468: . alpha2    - power for safeguard
5469: - threshold - threshold for imposing safeguard (0 < threshold < 1)

5471:   Level: advanced

5473: .seealso: [](ch_snes), `SNES`, `SNESKSPSetUseEW()`, `SNESKSPGetUseEW()`, `SNESKSPSetParametersEW()`
5474: @*/
5475: PetscErrorCode SNESKSPGetParametersEW(SNES snes, PetscInt *version, PetscReal *rtol_0, PetscReal *rtol_max, PetscReal *gamma, PetscReal *alpha, PetscReal *alpha2, PetscReal *threshold)
5476: {
5477:   SNESKSPEW *kctx;

5479:   PetscFunctionBegin;
5481:   kctx = (SNESKSPEW *)snes->kspconvctx;
5482:   PetscCheck(kctx, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "No Eisenstat-Walker context existing");
5483:   if (version) *version = kctx->version;
5484:   if (rtol_0) *rtol_0 = kctx->rtol_0;
5485:   if (rtol_max) *rtol_max = kctx->rtol_max;
5486:   if (gamma) *gamma = kctx->gamma;
5487:   if (alpha) *alpha = kctx->alpha;
5488:   if (alpha2) *alpha2 = kctx->alpha2;
5489:   if (threshold) *threshold = kctx->threshold;
5490:   PetscFunctionReturn(PETSC_SUCCESS);
5491: }

5493: PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5494: {
5495:   SNES       snes = (SNES)ctx;
5496:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5497:   PetscReal  rtol = PETSC_CURRENT, stol;

5499:   PetscFunctionBegin;
5500:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5501:   if (!snes->iter) {
5502:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
5503:     PetscCall(VecNorm(snes->vec_func, NORM_2, &kctx->norm_first));
5504:   } else {
5505:     PetscCheck(kctx->version >= 1 && kctx->version <= 4, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only versions 1-4 are supported: %" PetscInt_FMT, kctx->version);
5506:     if (kctx->version == 1) {
5507:       rtol = PetscAbsReal(snes->norm - kctx->lresid_last) / kctx->norm_last;
5508:       stol = PetscPowReal(kctx->rtol_last, kctx->alpha2);
5509:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5510:     } else if (kctx->version == 2) {
5511:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5512:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5513:       if (stol > kctx->threshold) rtol = PetscMax(rtol, stol);
5514:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
5515:       rtol = kctx->gamma * PetscPowReal(snes->norm / kctx->norm_last, kctx->alpha);
5516:       /* safeguard: avoid sharp decrease of rtol */
5517:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last, kctx->alpha);
5518:       stol = PetscMax(rtol, stol);
5519:       rtol = PetscMin(kctx->rtol_0, stol);
5520:       /* safeguard: avoid oversolving */
5521:       stol = kctx->gamma * (kctx->norm_first * snes->rtol) / snes->norm;
5522:       stol = PetscMax(rtol, stol);
5523:       rtol = PetscMin(kctx->rtol_0, stol);
5524:     } else /* if (kctx->version == 4) */ {
5525:       /* H.-B. An et al. Journal of Computational and Applied Mathematics 200 (2007) 47-60 */
5526:       PetscReal ared = PetscAbsReal(kctx->norm_last - snes->norm);
5527:       PetscReal pred = PetscAbsReal(kctx->norm_last - kctx->lresid_last);
5528:       PetscReal rk   = ared / pred;
5529:       if (rk < kctx->v4_p1) rtol = 1. - 2. * kctx->v4_p1;
5530:       else if (rk < kctx->v4_p2) rtol = kctx->rtol_last;
5531:       else if (rk < kctx->v4_p3) rtol = kctx->v4_m1 * kctx->rtol_last;
5532:       else rtol = kctx->v4_m2 * kctx->rtol_last;

5534:       if (kctx->rtol_last_2 > kctx->v4_m3 && kctx->rtol_last > kctx->v4_m3 && kctx->rk_last_2 < kctx->v4_p1 && kctx->rk_last < kctx->v4_p1) rtol = kctx->v4_m4 * kctx->rtol_last;
5535:       kctx->rtol_last_2 = kctx->rtol_last;
5536:       kctx->rk_last_2   = kctx->rk_last;
5537:       kctx->rk_last     = rk;
5538:     }
5539:   }
5540:   /* safeguard: avoid rtol greater than rtol_max */
5541:   rtol = PetscMin(rtol, kctx->rtol_max);
5542:   PetscCall(KSPSetTolerances(ksp, rtol, PETSC_CURRENT, PETSC_CURRENT, PETSC_CURRENT));
5543:   PetscCall(PetscInfo(snes, "iter %" PetscInt_FMT ", Eisenstat-Walker (version %" PetscInt_FMT ") KSP rtol=%g\n", snes->iter, kctx->version, (double)rtol));
5544:   PetscFunctionReturn(PETSC_SUCCESS);
5545: }

5547: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, void *ctx)
5548: {
5549:   SNES       snes = (SNES)ctx;
5550:   SNESKSPEW *kctx = (SNESKSPEW *)snes->kspconvctx;
5551:   PCSide     pcside;
5552:   Vec        lres;

5554:   PetscFunctionBegin;
5555:   if (!snes->ksp_ewconv) PetscFunctionReturn(PETSC_SUCCESS);
5556:   PetscCall(KSPGetTolerances(ksp, &kctx->rtol_last, NULL, NULL, NULL));
5557:   kctx->norm_last = snes->norm;
5558:   if (kctx->version == 1 || kctx->version == 4) {
5559:     PC        pc;
5560:     PetscBool getRes;

5562:     PetscCall(KSPGetPC(ksp, &pc));
5563:     PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCNONE, &getRes));
5564:     if (!getRes) {
5565:       KSPNormType normtype;

5567:       PetscCall(KSPGetNormType(ksp, &normtype));
5568:       getRes = (PetscBool)(normtype == KSP_NORM_UNPRECONDITIONED);
5569:     }
5570:     PetscCall(KSPGetPCSide(ksp, &pcside));
5571:     if (pcside == PC_RIGHT || getRes) { /* KSP residual is true linear residual */
5572:       PetscCall(KSPGetResidualNorm(ksp, &kctx->lresid_last));
5573:     } else {
5574:       /* KSP residual is preconditioned residual */
5575:       /* compute true linear residual norm */
5576:       Mat J;
5577:       PetscCall(KSPGetOperators(ksp, &J, NULL));
5578:       PetscCall(VecDuplicate(b, &lres));
5579:       PetscCall(MatMult(J, x, lres));
5580:       PetscCall(VecAYPX(lres, -1.0, b));
5581:       PetscCall(VecNorm(lres, NORM_2, &kctx->lresid_last));
5582:       PetscCall(VecDestroy(&lres));
5583:     }
5584:   }
5585:   PetscFunctionReturn(PETSC_SUCCESS);
5586: }

5588: /*@
5589:   SNESGetKSP - Returns the `KSP` context for a `SNES` solver.

5591:   Not Collective, but if `snes` is parallel, then `ksp` is parallel

5593:   Input Parameter:
5594: . snes - the `SNES` context

5596:   Output Parameter:
5597: . ksp - the `KSP` context

5599:   Level: beginner

5601:   Notes:
5602:   The user can then directly manipulate the `KSP` context to set various
5603:   options, etc.  Likewise, the user can then extract and manipulate the
5604:   `PC` contexts as well.

5606:   Some `SNESType`s do not use a `KSP` but a `KSP` is still returned by this function, changes to that `KSP` will have no effect.

5608: .seealso: [](ch_snes), `SNES`, `KSP`, `PC`, `KSPGetPC()`, `SNESCreate()`, `KSPCreate()`, `SNESSetKSP()`
5609: @*/
5610: PetscErrorCode SNESGetKSP(SNES snes, KSP *ksp)
5611: {
5612:   PetscFunctionBegin;
5614:   PetscAssertPointer(ksp, 2);

5616:   if (!snes->ksp) {
5617:     PetscCall(KSPCreate(PetscObjectComm((PetscObject)snes), &snes->ksp));
5618:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->ksp, (PetscObject)snes, 1));

5620:     PetscCall(KSPSetPreSolve(snes->ksp, KSPPreSolve_SNESEW, snes));
5621:     PetscCall(KSPSetPostSolve(snes->ksp, KSPPostSolve_SNESEW, snes));

5623:     PetscCall(KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes));
5624:     PetscCall(PetscObjectSetOptions((PetscObject)snes->ksp, ((PetscObject)snes)->options));
5625:   }
5626:   *ksp = snes->ksp;
5627:   PetscFunctionReturn(PETSC_SUCCESS);
5628: }

5630: #include <petsc/private/dmimpl.h>
5631: /*@
5632:   SNESSetDM - Sets the `DM` that may be used by some `SNES` nonlinear solvers or their underlying preconditioners

5634:   Logically Collective

5636:   Input Parameters:
5637: + snes - the nonlinear solver context
5638: - dm   - the `DM`, cannot be `NULL`

5640:   Level: intermediate

5642:   Note:
5643:   A `DM` can only be used for solving one problem at a time because information about the problem is stored on the `DM`,
5644:   even when not using interfaces like `DMSNESSetFunction()`.  Use `DMClone()` to get a distinct `DM` when solving different
5645:   problems using the same function space.

5647: .seealso: [](ch_snes), `DM`, `SNES`, `SNESGetDM()`, `KSPSetDM()`, `KSPGetDM()`
5648: @*/
5649: PetscErrorCode SNESSetDM(SNES snes, DM dm)
5650: {
5651:   KSP    ksp;
5652:   DMSNES sdm;

5654:   PetscFunctionBegin;
5657:   PetscCall(PetscObjectReference((PetscObject)dm));
5658:   if (snes->dm) { /* Move the DMSNES context over to the new DM unless the new DM already has one */
5659:     if (snes->dm->dmsnes && !dm->dmsnes) {
5660:       PetscCall(DMCopyDMSNES(snes->dm, dm));
5661:       PetscCall(DMGetDMSNES(snes->dm, &sdm));
5662:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
5663:     }
5664:     PetscCall(DMCoarsenHookRemove(snes->dm, DMCoarsenHook_SNESVecSol, DMRestrictHook_SNESVecSol, snes));
5665:     PetscCall(DMDestroy(&snes->dm));
5666:   }
5667:   snes->dm     = dm;
5668:   snes->dmAuto = PETSC_FALSE;

5670:   PetscCall(SNESGetKSP(snes, &ksp));
5671:   PetscCall(KSPSetDM(ksp, dm));
5672:   PetscCall(KSPSetDMActive(ksp, PETSC_FALSE));
5673:   if (snes->npc) {
5674:     PetscCall(SNESSetDM(snes->npc, snes->dm));
5675:     PetscCall(SNESSetNPCSide(snes, snes->npcside));
5676:   }
5677:   PetscFunctionReturn(PETSC_SUCCESS);
5678: }

5680: /*@
5681:   SNESGetDM - Gets the `DM` that may be used by some `SNES` nonlinear solvers/preconditioners

5683:   Not Collective but `dm` obtained is parallel on `snes`

5685:   Input Parameter:
5686: . snes - the `SNES` context

5688:   Output Parameter:
5689: . dm - the `DM`

5691:   Level: intermediate

5693: .seealso: [](ch_snes), `DM`, `SNES`, `SNESSetDM()`, `KSPSetDM()`, `KSPGetDM()`
5694: @*/
5695: PetscErrorCode SNESGetDM(SNES snes, DM *dm)
5696: {
5697:   PetscFunctionBegin;
5699:   if (!snes->dm) {
5700:     PetscCall(DMShellCreate(PetscObjectComm((PetscObject)snes), &snes->dm));
5701:     snes->dmAuto = PETSC_TRUE;
5702:   }
5703:   *dm = snes->dm;
5704:   PetscFunctionReturn(PETSC_SUCCESS);
5705: }

5707: /*@
5708:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

5710:   Collective

5712:   Input Parameters:
5713: + snes - iterative context obtained from `SNESCreate()`
5714: - npc  - the `SNES` nonlinear preconditioner object

5716:   Options Database Key:
5717: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5719:   Level: developer

5721:   Notes:
5722:   This is rarely used, rather use `SNESGetNPC()` to retrieve the preconditioner and configure it using the API.

5724:   Only some `SNESType` can use a nonlinear preconditioner

5726: .seealso: [](ch_snes), `SNES`, `SNESNGS`, `SNESFAS`, `SNESGetNPC()`, `SNESHasNPC()`
5727: @*/
5728: PetscErrorCode SNESSetNPC(SNES snes, SNES npc)
5729: {
5730:   PetscFunctionBegin;
5733:   PetscCheckSameComm(snes, 1, npc, 2);
5734:   PetscCall(PetscObjectReference((PetscObject)npc));
5735:   PetscCall(SNESDestroy(&snes->npc));
5736:   snes->npc = npc;
5737:   PetscFunctionReturn(PETSC_SUCCESS);
5738: }

5740: /*@
5741:   SNESGetNPC - Gets a nonlinear preconditioning solver SNES` to be used to precondition the original nonlinear solver.

5743:   Not Collective; but any changes to the obtained the `pc` object must be applied collectively

5745:   Input Parameter:
5746: . snes - iterative context obtained from `SNESCreate()`

5748:   Output Parameter:
5749: . pc - the `SNES` preconditioner context

5751:   Options Database Key:
5752: . -npc_snes_type <type> - set the type of the `SNES` to use as the nonlinear preconditioner

5754:   Level: advanced

5756:   Notes:
5757:   If a `SNES` was previously set with `SNESSetNPC()` then that value is returned, otherwise a new `SNES` object is created that will
5758:   be used as the nonlinear preconditioner for the current `SNES`.

5760:   The (preconditioner) `SNES` returned automatically inherits the same nonlinear function and Jacobian supplied to the original
5761:   `SNES`. These may be overwritten if needed.

5763:   Use the options database prefixes `-npc_snes`, `-npc_ksp`, etc., to control the configuration of the nonlinear preconditioner

5765: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESHasNPC()`, `SNES`, `SNESCreate()`
5766: @*/
5767: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
5768: {
5769:   const char *optionsprefix;

5771:   PetscFunctionBegin;
5773:   PetscAssertPointer(pc, 2);
5774:   if (!snes->npc) {
5775:     void *ctx;

5777:     PetscCall(SNESCreate(PetscObjectComm((PetscObject)snes), &snes->npc));
5778:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->npc, (PetscObject)snes, 1));
5779:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5780:     PetscCall(SNESSetOptionsPrefix(snes->npc, optionsprefix));
5781:     PetscCall(SNESAppendOptionsPrefix(snes->npc, "npc_"));
5782:     if (snes->ops->usercompute) {
5783:       PetscCall(SNESSetComputeApplicationContext(snes, snes->ops->usercompute, snes->ops->ctxdestroy));
5784:     } else {
5785:       PetscCall(SNESGetApplicationContext(snes, &ctx));
5786:       PetscCall(SNESSetApplicationContext(snes->npc, ctx));
5787:     }
5788:     PetscCall(SNESSetCountersReset(snes->npc, PETSC_FALSE));
5789:   }
5790:   *pc = snes->npc;
5791:   PetscFunctionReturn(PETSC_SUCCESS);
5792: }

5794: /*@
5795:   SNESHasNPC - Returns whether a nonlinear preconditioner is associated with the given `SNES`

5797:   Not Collective

5799:   Input Parameter:
5800: . snes - iterative context obtained from `SNESCreate()`

5802:   Output Parameter:
5803: . has_npc - whether the `SNES` has a nonlinear preconditioner or not

5805:   Level: developer

5807: .seealso: [](ch_snes), `SNESSetNPC()`, `SNESGetNPC()`
5808: @*/
5809: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
5810: {
5811:   PetscFunctionBegin;
5813:   PetscAssertPointer(has_npc, 2);
5814:   *has_npc = snes->npc ? PETSC_TRUE : PETSC_FALSE;
5815:   PetscFunctionReturn(PETSC_SUCCESS);
5816: }

5818: /*@
5819:   SNESSetNPCSide - Sets the nonlinear preconditioning side used by the nonlinear preconditioner inside `SNES`.

5821:   Logically Collective

5823:   Input Parameter:
5824: . snes - iterative context obtained from `SNESCreate()`

5826:   Output Parameter:
5827: . side - the preconditioning side, where side is one of
5828: .vb
5829:       PC_LEFT  - left preconditioning
5830:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
5831: .ve

5833:   Options Database Key:
5834: . -snes_npc_side <right,left> - nonlinear preconditioner side

5836:   Level: intermediate

5838:   Note:
5839:   `SNESNRICHARDSON` and `SNESNCG` only support left preconditioning.

5841: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESNRICHARDSON`, `SNESNCG`, `SNESType`, `SNESGetNPCSide()`, `KSPSetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5842: @*/
5843: PetscErrorCode SNESSetNPCSide(SNES snes, PCSide side)
5844: {
5845:   PetscFunctionBegin;
5848:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
5849:   PetscCheck((side == PC_LEFT) || (side == PC_RIGHT), PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONG, "Only PC_LEFT and PC_RIGHT are supported");
5850:   snes->npcside = side;
5851:   PetscFunctionReturn(PETSC_SUCCESS);
5852: }

5854: /*@
5855:   SNESGetNPCSide - Gets the preconditioning side used by the nonlinear preconditioner inside `SNES`.

5857:   Not Collective

5859:   Input Parameter:
5860: . snes - iterative context obtained from `SNESCreate()`

5862:   Output Parameter:
5863: . side - the preconditioning side, where side is one of
5864: .vb
5865:       `PC_LEFT` - left preconditioning
5866:       `PC_RIGHT` - right preconditioning (default for most nonlinear solvers)
5867: .ve

5869:   Level: intermediate

5871: .seealso: [](ch_snes), `SNES`, `SNESGetNPC()`, `SNESSetNPCSide()`, `KSPGetPCSide()`, `PC_LEFT`, `PC_RIGHT`, `PCSide`
5872: @*/
5873: PetscErrorCode SNESGetNPCSide(SNES snes, PCSide *side)
5874: {
5875:   PetscFunctionBegin;
5877:   PetscAssertPointer(side, 2);
5878:   *side = snes->npcside;
5879:   PetscFunctionReturn(PETSC_SUCCESS);
5880: }

5882: /*@
5883:   SNESSetLineSearch - Sets the `SNESLineSearch` to be used for a given `SNES`

5885:   Collective

5887:   Input Parameters:
5888: + snes       - iterative context obtained from `SNESCreate()`
5889: - linesearch - the linesearch object

5891:   Level: developer

5893:   Note:
5894:   This is almost never used, rather one uses `SNESGetLineSearch()` to retrieve the line search and set options on it
5895:   to configure it using the API).

5897: .seealso: [](ch_snes), `SNES`, `SNESLineSearch`, `SNESGetLineSearch()`
5898: @*/
5899: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5900: {
5901:   PetscFunctionBegin;
5904:   PetscCheckSameComm(snes, 1, linesearch, 2);
5905:   PetscCall(PetscObjectReference((PetscObject)linesearch));
5906:   PetscCall(SNESLineSearchDestroy(&snes->linesearch));

5908:   snes->linesearch = linesearch;
5909:   PetscFunctionReturn(PETSC_SUCCESS);
5910: }

5912: /*@
5913:   SNESGetLineSearch - Returns the line search associated with the `SNES`.

5915:   Not Collective

5917:   Input Parameter:
5918: . snes - iterative context obtained from `SNESCreate()`

5920:   Output Parameter:
5921: . linesearch - linesearch context

5923:   Level: beginner

5925:   Notes:
5926:   It creates a default line search instance which can be configured as needed in case it has not been already set with `SNESSetLineSearch()`.

5928:   You can also use the options database keys `-snes_linesearch_*` to configure the line search. See `SNESLineSearchSetFromOptions()` for the possible options.

5930: .seealso: [](ch_snes), `SNESLineSearch`, `SNESSetLineSearch()`, `SNESLineSearchCreate()`, `SNESLineSearchSetFromOptions()`
5931: @*/
5932: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5933: {
5934:   const char *optionsprefix;

5936:   PetscFunctionBegin;
5938:   PetscAssertPointer(linesearch, 2);
5939:   if (!snes->linesearch) {
5940:     PetscCall(SNESGetOptionsPrefix(snes, &optionsprefix));
5941:     PetscCall(SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch));
5942:     PetscCall(SNESLineSearchSetSNES(snes->linesearch, snes));
5943:     PetscCall(SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix));
5944:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)snes->linesearch, (PetscObject)snes, 1));
5945:   }
5946:   *linesearch = snes->linesearch;
5947:   PetscFunctionReturn(PETSC_SUCCESS);
5948: }