Actual source code: ex3.c

  1: static char help[] = "Newton methods to solve u'' + u^{2} = f in parallel.\n\
  2: This example employs a user-defined monitoring routine and optionally a user-defined\n\
  3: routine to check candidate iterates produced by line search routines.\n\
  4: The command line options include:\n\
  5:   -pre_check_iterates : activate checking of iterates\n\
  6:   -post_check_iterates : activate checking of iterates\n\
  7:   -check_tol <tol>: set tolerance for iterate checking\n\
  8:   -user_precond : activate a (trivial) user-defined preconditioner\n\n";

 10: /*
 11:    Include "petscdm.h" so that we can use data management objects (DMs)
 12:    Include "petscdmda.h" so that we can use distributed arrays (DMDAs).
 13:    Include "petscsnes.h" so that we can use SNES solvers.  Note that this
 14:    file automatically includes:
 15:      petscsys.h    - base PETSc routines
 16:      petscvec.h    - vectors
 17:      petscmat.h    - matrices
 18:      petscis.h     - index sets
 19:      petscksp.h    - Krylov subspace methods
 20:      petscviewer.h - viewers
 21:      petscpc.h     - preconditioners
 22:      petscksp.h    - linear solvers
 23: */

 25: #include <petscdm.h>
 26: #include <petscdmda.h>
 27: #include <petscsnes.h>

 29: /*
 30:    User-defined routines.
 31: */
 32: PetscErrorCode FormJacobian(SNES, Vec, Mat, Mat, void *);
 33: PetscErrorCode FormFunction(SNES, Vec, Vec, void *);
 34: PetscErrorCode FormInitialGuess(Vec);
 35: PetscErrorCode Monitor(SNES, PetscInt, PetscReal, void *);
 36: PetscErrorCode PreCheck(SNESLineSearch, Vec, Vec, PetscBool *, void *);
 37: PetscErrorCode PostCheck(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
 38: PetscErrorCode PostSetSubKSP(SNESLineSearch, Vec, Vec, Vec, PetscBool *, PetscBool *, void *);
 39: PetscErrorCode MatrixFreePreconditioner(PC, Vec, Vec);

 41: /*
 42:    User-defined application context
 43: */
 44: typedef struct {
 45:   DM          da;    /* distributed array */
 46:   Vec         F;     /* right-hand-side of PDE */
 47:   PetscMPIInt rank;  /* rank of processor */
 48:   PetscMPIInt size;  /* size of communicator */
 49:   PetscReal   h;     /* mesh spacing */
 50:   PetscBool   sjerr; /* if or not to test jacobian domain error */
 51: } ApplicationCtx;

 53: /*
 54:    User-defined context for monitoring
 55: */
 56: typedef struct {
 57:   PetscViewer viewer;
 58: } MonitorCtx;

 60: /*
 61:    User-defined context for checking candidate iterates that are
 62:    determined by line search methods
 63: */
 64: typedef struct {
 65:   Vec             last_step; /* previous iterate */
 66:   PetscReal       tolerance; /* tolerance for changes between successive iterates */
 67:   ApplicationCtx *user;
 68: } StepCheckCtx;

 70: typedef struct {
 71:   PetscInt its0; /* num of previous outer KSP iterations */
 72: } SetSubKSPCtx;

 74: int main(int argc, char **argv)
 75: {
 76:   SNES           snes;       /* SNES context */
 77:   SNESLineSearch linesearch; /* SNESLineSearch context */
 78:   Mat            J;          /* Jacobian matrix */
 79:   ApplicationCtx ctx;        /* user-defined context */
 80:   Vec            x, r, U, F; /* vectors */
 81:   MonitorCtx     monP;       /* monitoring context */
 82:   StepCheckCtx   checkP;     /* step-checking context */
 83:   SetSubKSPCtx   checkP1;
 84:   PetscBool      pre_check, post_check, post_setsubksp; /* flag indicating whether we're checking candidate iterates */
 85:   PetscScalar    xp, *FF, *UU, none = -1.0;
 86:   PetscInt       its, N = 5, i, maxit, maxf, xs, xm;
 87:   PetscReal      abstol, rtol, stol, norm;
 88:   PetscBool      flg, viewinitial = PETSC_FALSE;

 90:   PetscFunctionBeginUser;
 91:   PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
 92:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &ctx.rank));
 93:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &ctx.size));
 94:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &N, NULL));
 95:   ctx.h     = 1.0 / (N - 1);
 96:   ctx.sjerr = PETSC_FALSE;
 97:   PetscCall(PetscOptionsGetBool(NULL, NULL, "-test_jacobian_domain_error", &ctx.sjerr, NULL));
 98:   PetscCall(PetscOptionsGetBool(NULL, NULL, "-view_initial", &viewinitial, NULL));

100:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
101:      Create nonlinear solver context
102:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

104:   PetscCall(SNESCreate(PETSC_COMM_WORLD, &snes));

106:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
107:      Create vector data structures; set function evaluation routine
108:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

110:   /*
111:      Create distributed array (DMDA) to manage parallel grid and vectors
112:   */
113:   PetscCall(DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, N, 1, 1, NULL, &ctx.da));
114:   PetscCall(DMSetFromOptions(ctx.da));
115:   PetscCall(DMSetUp(ctx.da));

117:   /*
118:      Extract global and local vectors from DMDA; then duplicate for remaining
119:      vectors that are the same types
120:   */
121:   PetscCall(DMCreateGlobalVector(ctx.da, &x));
122:   PetscCall(VecDuplicate(x, &r));
123:   PetscCall(VecDuplicate(x, &F));
124:   ctx.F = F;
125:   PetscCall(VecDuplicate(x, &U));

127:   /*
128:      Set function evaluation routine and vector.  Whenever the nonlinear
129:      solver needs to compute the nonlinear function, it will call this
130:      routine.
131:       - Note that the final routine argument is the user-defined
132:         context that provides application-specific data for the
133:         function evaluation routine.
134:   */
135:   PetscCall(SNESSetFunction(snes, r, FormFunction, &ctx));

137:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
138:      Create matrix data structure; set Jacobian evaluation routine
139:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

141:   PetscCall(MatCreate(PETSC_COMM_WORLD, &J));
142:   PetscCall(MatSetSizes(J, PETSC_DECIDE, PETSC_DECIDE, N, N));
143:   PetscCall(MatSetFromOptions(J));
144:   PetscCall(MatSeqAIJSetPreallocation(J, 3, NULL));
145:   PetscCall(MatMPIAIJSetPreallocation(J, 3, NULL, 3, NULL));

147:   /*
148:      Set Jacobian matrix data structure and default Jacobian evaluation
149:      routine.  Whenever the nonlinear solver needs to compute the
150:      Jacobian matrix, it will call this routine.
151:       - Note that the final routine argument is the user-defined
152:         context that provides application-specific data for the
153:         Jacobian evaluation routine.
154:   */
155:   PetscCall(SNESSetJacobian(snes, J, J, FormJacobian, &ctx));

157:   /*
158:      Optionally allow user-provided preconditioner
159:    */
160:   PetscCall(PetscOptionsHasName(NULL, NULL, "-user_precond", &flg));
161:   if (flg) {
162:     KSP ksp;
163:     PC  pc;
164:     PetscCall(SNESGetKSP(snes, &ksp));
165:     PetscCall(KSPGetPC(ksp, &pc));
166:     PetscCall(PCSetType(pc, PCSHELL));
167:     PetscCall(PCShellSetApply(pc, MatrixFreePreconditioner));
168:   }

170:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
171:      Customize nonlinear solver; set runtime options
172:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

174:   /*
175:      Set an optional user-defined monitoring routine
176:   */
177:   PetscCall(PetscViewerDrawOpen(PETSC_COMM_WORLD, 0, 0, 0, 0, 400, 400, &monP.viewer));
178:   PetscCall(SNESMonitorSet(snes, Monitor, &monP, 0));

180:   /*
181:      Set names for some vectors to facilitate monitoring (optional)
182:   */
183:   PetscCall(PetscObjectSetName((PetscObject)x, "Approximate Solution"));
184:   PetscCall(PetscObjectSetName((PetscObject)U, "Exact Solution"));

186:   /*
187:      Set SNES/KSP/KSP/PC runtime options, e.g.,
188:          -snes_view -snes_monitor -ksp_type <ksp> -pc_type <pc>
189:   */
190:   PetscCall(SNESSetFromOptions(snes));

192:   /*
193:      Set an optional user-defined routine to check the validity of candidate
194:      iterates that are determined by line search methods
195:   */
196:   PetscCall(SNESGetLineSearch(snes, &linesearch));
197:   PetscCall(PetscOptionsHasName(NULL, NULL, "-post_check_iterates", &post_check));

199:   if (post_check) {
200:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Activating post step checking routine\n"));
201:     PetscCall(SNESLineSearchSetPostCheck(linesearch, PostCheck, &checkP));
202:     PetscCall(VecDuplicate(x, &(checkP.last_step)));

204:     checkP.tolerance = 1.0;
205:     checkP.user      = &ctx;

207:     PetscCall(PetscOptionsGetReal(NULL, NULL, "-check_tol", &checkP.tolerance, NULL));
208:   }

210:   PetscCall(PetscOptionsHasName(NULL, NULL, "-post_setsubksp", &post_setsubksp));
211:   if (post_setsubksp) {
212:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Activating post setsubksp\n"));
213:     PetscCall(SNESLineSearchSetPostCheck(linesearch, PostSetSubKSP, &checkP1));
214:   }

216:   PetscCall(PetscOptionsHasName(NULL, NULL, "-pre_check_iterates", &pre_check));
217:   if (pre_check) {
218:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Activating pre step checking routine\n"));
219:     PetscCall(SNESLineSearchSetPreCheck(linesearch, PreCheck, &checkP));
220:   }

222:   /*
223:      Print parameters used for convergence testing (optional) ... just
224:      to demonstrate this routine; this information is also printed with
225:      the option -snes_view
226:   */
227:   PetscCall(SNESGetTolerances(snes, &abstol, &rtol, &stol, &maxit, &maxf));
228:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "atol=%g, rtol=%g, stol=%g, maxit=%" PetscInt_FMT ", maxf=%" PetscInt_FMT "\n", (double)abstol, (double)rtol, (double)stol, maxit, maxf));

230:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
231:      Initialize application:
232:      Store right-hand-side of PDE and exact solution
233:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

235:   /*
236:      Get local grid boundaries (for 1-dimensional DMDA):
237:        xs, xm - starting grid index, width of local grid (no ghost points)
238:   */
239:   PetscCall(DMDAGetCorners(ctx.da, &xs, NULL, NULL, &xm, NULL, NULL));

241:   /*
242:      Get pointers to vector data
243:   */
244:   PetscCall(DMDAVecGetArray(ctx.da, F, &FF));
245:   PetscCall(DMDAVecGetArray(ctx.da, U, &UU));

247:   /*
248:      Compute local vector entries
249:   */
250:   xp = ctx.h * xs;
251:   for (i = xs; i < xs + xm; i++) {
252:     FF[i] = 6.0 * xp + PetscPowScalar(xp + 1.e-12, 6.0); /* +1.e-12 is to prevent 0^6 */
253:     UU[i] = xp * xp * xp;
254:     xp += ctx.h;
255:   }

257:   /*
258:      Restore vectors
259:   */
260:   PetscCall(DMDAVecRestoreArray(ctx.da, F, &FF));
261:   PetscCall(DMDAVecRestoreArray(ctx.da, U, &UU));
262:   if (viewinitial) {
263:     PetscCall(VecView(U, 0));
264:     PetscCall(VecView(F, 0));
265:   }

267:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
268:      Evaluate initial guess; then solve nonlinear system
269:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

271:   /*
272:      Note: The user should initialize the vector, x, with the initial guess
273:      for the nonlinear solver prior to calling SNESSolve().  In particular,
274:      to employ an initial guess of zero, the user should explicitly set
275:      this vector to zero by calling VecSet().
276:   */
277:   PetscCall(FormInitialGuess(x));
278:   PetscCall(SNESSolve(snes, NULL, x));
279:   PetscCall(SNESGetIterationNumber(snes, &its));
280:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Number of SNES iterations = %" PetscInt_FMT "\n", its));

282:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
283:      Check solution and clean up
284:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

286:   /*
287:      Check the error
288:   */
289:   PetscCall(VecAXPY(x, none, U));
290:   PetscCall(VecNorm(x, NORM_2, &norm));
291:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Norm of error %g Iterations %" PetscInt_FMT "\n", (double)norm, its));
292:   if (ctx.sjerr) {
293:     SNESType snestype;
294:     PetscCall(SNESGetType(snes, &snestype));
295:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "SNES Type %s\n", snestype));
296:   }

298:   /*
299:      Free work space.  All PETSc objects should be destroyed when they
300:      are no longer needed.
301:   */
302:   PetscCall(PetscViewerDestroy(&monP.viewer));
303:   if (post_check) PetscCall(VecDestroy(&checkP.last_step));
304:   PetscCall(VecDestroy(&x));
305:   PetscCall(VecDestroy(&r));
306:   PetscCall(VecDestroy(&U));
307:   PetscCall(VecDestroy(&F));
308:   PetscCall(MatDestroy(&J));
309:   PetscCall(SNESDestroy(&snes));
310:   PetscCall(DMDestroy(&ctx.da));
311:   PetscCall(PetscFinalize());
312:   return 0;
313: }

315: /* ------------------------------------------------------------------- */
316: /*
317:    FormInitialGuess - Computes initial guess.

319:    Input/Output Parameter:
320: .  x - the solution vector
321: */
322: PetscErrorCode FormInitialGuess(Vec x)
323: {
324:   PetscScalar pfive = .50;

326:   PetscFunctionBeginUser;
327:   PetscCall(VecSet(x, pfive));
328:   PetscFunctionReturn(PETSC_SUCCESS);
329: }

331: /* ------------------------------------------------------------------- */
332: /*
333:    FormFunction - Evaluates nonlinear function, F(x).

335:    Input Parameters:
336: .  snes - the SNES context
337: .  x - input vector
338: .  ctx - optional user-defined context, as set by SNESSetFunction()

340:    Output Parameter:
341: .  f - function vector

343:    Note:
344:    The user-defined context can contain any application-specific
345:    data needed for the function evaluation.
346: */
347: PetscErrorCode FormFunction(SNES snes, Vec x, Vec f, void *ctx)
348: {
349:   ApplicationCtx    *user = (ApplicationCtx *)ctx;
350:   DM                 da   = user->da;
351:   PetscScalar       *ff, d;
352:   const PetscScalar *xx, *FF;
353:   PetscInt           i, M, xs, xm;
354:   Vec                xlocal;

356:   PetscFunctionBeginUser;
357:   PetscCall(DMGetLocalVector(da, &xlocal));
358:   /*
359:      Scatter ghost points to local vector, using the 2-step process
360:         DMGlobalToLocalBegin(), DMGlobalToLocalEnd().
361:      By placing code between these two statements, computations can
362:      be done while messages are in transition.
363:   */
364:   PetscCall(DMGlobalToLocalBegin(da, x, INSERT_VALUES, xlocal));
365:   PetscCall(DMGlobalToLocalEnd(da, x, INSERT_VALUES, xlocal));

367:   /*
368:      Get pointers to vector data.
369:        - The vector xlocal includes ghost point; the vectors x and f do
370:          NOT include ghost points.
371:        - Using DMDAVecGetArray() allows accessing the values using global ordering
372:   */
373:   PetscCall(DMDAVecGetArrayRead(da, xlocal, (void *)&xx));
374:   PetscCall(DMDAVecGetArray(da, f, &ff));
375:   PetscCall(DMDAVecGetArrayRead(da, user->F, (void *)&FF));

377:   /*
378:      Get local grid boundaries (for 1-dimensional DMDA):
379:        xs, xm  - starting grid index, width of local grid (no ghost points)
380:   */
381:   PetscCall(DMDAGetCorners(da, &xs, NULL, NULL, &xm, NULL, NULL));
382:   PetscCall(DMDAGetInfo(da, NULL, &M, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL));

384:   /*
385:      Set function values for boundary points; define local interior grid point range:
386:         xsi - starting interior grid index
387:         xei - ending interior grid index
388:   */
389:   if (xs == 0) { /* left boundary */
390:     ff[0] = xx[0];
391:     xs++;
392:     xm--;
393:   }
394:   if (xs + xm == M) { /* right boundary */
395:     ff[xs + xm - 1] = xx[xs + xm - 1] - 1.0;
396:     xm--;
397:   }

399:   /*
400:      Compute function over locally owned part of the grid (interior points only)
401:   */
402:   d = 1.0 / (user->h * user->h);
403:   for (i = xs; i < xs + xm; i++) ff[i] = d * (xx[i - 1] - 2.0 * xx[i] + xx[i + 1]) + xx[i] * xx[i] - FF[i];

405:   /*
406:      Restore vectors
407:   */
408:   PetscCall(DMDAVecRestoreArrayRead(da, xlocal, (void *)&xx));
409:   PetscCall(DMDAVecRestoreArray(da, f, &ff));
410:   PetscCall(DMDAVecRestoreArrayRead(da, user->F, (void *)&FF));
411:   PetscCall(DMRestoreLocalVector(da, &xlocal));
412:   PetscFunctionReturn(PETSC_SUCCESS);
413: }

415: /* ------------------------------------------------------------------- */
416: /*
417:    FormJacobian - Evaluates Jacobian matrix.

419:    Input Parameters:
420: .  snes - the SNES context
421: .  x - input vector
422: .  dummy - optional user-defined context (not used here)

424:    Output Parameters:
425: .  jac - Jacobian matrix
426: .  B - optionally different preconditioning matrix
427: .  flag - flag indicating matrix structure
428: */
429: PetscErrorCode FormJacobian(SNES snes, Vec x, Mat jac, Mat B, void *ctx)
430: {
431:   ApplicationCtx *user = (ApplicationCtx *)ctx;
432:   PetscScalar    *xx, d, A[3];
433:   PetscInt        i, j[3], M, xs, xm;
434:   DM              da = user->da;

436:   PetscFunctionBeginUser;
437:   if (user->sjerr) {
438:     PetscCall(SNESSetJacobianDomainError(snes));
439:     PetscFunctionReturn(PETSC_SUCCESS);
440:   }
441:   /*
442:      Get pointer to vector data
443:   */
444:   PetscCall(DMDAVecGetArrayRead(da, x, &xx));
445:   PetscCall(DMDAGetCorners(da, &xs, NULL, NULL, &xm, NULL, NULL));

447:   /*
448:     Get range of locally owned matrix
449:   */
450:   PetscCall(DMDAGetInfo(da, NULL, &M, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL));

452:   /*
453:      Determine starting and ending local indices for interior grid points.
454:      Set Jacobian entries for boundary points.
455:   */

457:   if (xs == 0) { /* left boundary */
458:     i    = 0;
459:     A[0] = 1.0;

461:     PetscCall(MatSetValues(jac, 1, &i, 1, &i, A, INSERT_VALUES));
462:     xs++;
463:     xm--;
464:   }
465:   if (xs + xm == M) { /* right boundary */
466:     i    = M - 1;
467:     A[0] = 1.0;
468:     PetscCall(MatSetValues(jac, 1, &i, 1, &i, A, INSERT_VALUES));
469:     xm--;
470:   }

472:   /*
473:      Interior grid points
474:       - Note that in this case we set all elements for a particular
475:         row at once.
476:   */
477:   d = 1.0 / (user->h * user->h);
478:   for (i = xs; i < xs + xm; i++) {
479:     j[0] = i - 1;
480:     j[1] = i;
481:     j[2] = i + 1;
482:     A[0] = A[2] = d;
483:     A[1]        = -2.0 * d + 2.0 * xx[i];
484:     PetscCall(MatSetValues(jac, 1, &i, 3, j, A, INSERT_VALUES));
485:   }

487:   /*
488:      Assemble matrix, using the 2-step process:
489:        MatAssemblyBegin(), MatAssemblyEnd().
490:      By placing code between these two statements, computations can be
491:      done while messages are in transition.

493:      Also, restore vector.
494:   */

496:   PetscCall(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY));
497:   PetscCall(DMDAVecRestoreArrayRead(da, x, &xx));
498:   PetscCall(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY));

500:   PetscFunctionReturn(PETSC_SUCCESS);
501: }

503: /* ------------------------------------------------------------------- */
504: /*
505:    Monitor - Optional user-defined monitoring routine that views the
506:    current iterate with an x-window plot. Set by SNESMonitorSet().

508:    Input Parameters:
509:    snes - the SNES context
510:    its - iteration number
511:    norm - 2-norm function value (may be estimated)
512:    ctx - optional user-defined context for private data for the
513:          monitor routine, as set by SNESMonitorSet()

515:    Note:
516:    See the manpage for PetscViewerDrawOpen() for useful runtime options,
517:    such as -nox to deactivate all x-window output.
518:  */
519: PetscErrorCode Monitor(SNES snes, PetscInt its, PetscReal fnorm, void *ctx)
520: {
521:   MonitorCtx *monP = (MonitorCtx *)ctx;
522:   Vec         x;

524:   PetscFunctionBeginUser;
525:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "iter = %" PetscInt_FMT ",SNES Function norm %g\n", its, (double)fnorm));
526:   PetscCall(SNESGetSolution(snes, &x));
527:   PetscCall(VecView(x, monP->viewer));
528:   PetscFunctionReturn(PETSC_SUCCESS);
529: }

531: /* ------------------------------------------------------------------- */
532: /*
533:    PreCheck - Optional user-defined routine that checks the validity of
534:    candidate steps of a line search method.  Set by SNESLineSearchSetPreCheck().

536:    Input Parameters:
537:    snes - the SNES context
538:    xcurrent - current solution
539:    y - search direction and length

541:    Output Parameters:
542:    y         - proposed step (search direction and length) (possibly changed)
543:    changed_y - tells if the step has changed or not
544:  */
545: PetscErrorCode PreCheck(SNESLineSearch linesearch, Vec xcurrent, Vec y, PetscBool *changed_y, void *ctx)
546: {
547:   PetscFunctionBeginUser;
548:   *changed_y = PETSC_FALSE;
549:   PetscFunctionReturn(PETSC_SUCCESS);
550: }

552: /* ------------------------------------------------------------------- */
553: /*
554:    PostCheck - Optional user-defined routine that checks the validity of
555:    candidate steps of a line search method.  Set by SNESLineSearchSetPostCheck().

557:    Input Parameters:
558:    snes - the SNES context
559:    ctx  - optional user-defined context for private data for the
560:           monitor routine, as set by SNESLineSearchSetPostCheck()
561:    xcurrent - current solution
562:    y - search direction and length
563:    x    - the new candidate iterate

565:    Output Parameters:
566:    y    - proposed step (search direction and length) (possibly changed)
567:    x    - current iterate (possibly modified)

569:  */
570: PetscErrorCode PostCheck(SNESLineSearch linesearch, Vec xcurrent, Vec y, Vec x, PetscBool *changed_y, PetscBool *changed_x, void *ctx)
571: {
572:   PetscInt        i, iter, xs, xm;
573:   StepCheckCtx   *check;
574:   ApplicationCtx *user;
575:   PetscScalar    *xa, *xa_last, tmp;
576:   PetscReal       rdiff;
577:   DM              da;
578:   SNES            snes;

580:   PetscFunctionBeginUser;
581:   *changed_x = PETSC_FALSE;
582:   *changed_y = PETSC_FALSE;

584:   PetscCall(SNESLineSearchGetSNES(linesearch, &snes));
585:   check = (StepCheckCtx *)ctx;
586:   user  = check->user;
587:   PetscCall(SNESGetIterationNumber(snes, &iter));

589:   /* iteration 1 indicates we are working on the second iteration */
590:   if (iter > 0) {
591:     da = user->da;
592:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Checking candidate step at iteration %" PetscInt_FMT " with tolerance %g\n", iter, (double)check->tolerance));

594:     /* Access local array data */
595:     PetscCall(DMDAVecGetArray(da, check->last_step, &xa_last));
596:     PetscCall(DMDAVecGetArray(da, x, &xa));
597:     PetscCall(DMDAGetCorners(da, &xs, NULL, NULL, &xm, NULL, NULL));

599:     /*
600:        If we fail the user-defined check for validity of the candidate iterate,
601:        then modify the iterate as we like.  (Note that the particular modification
602:        below is intended simply to demonstrate how to manipulate this data, not
603:        as a meaningful or appropriate choice.)
604:     */
605:     for (i = xs; i < xs + xm; i++) {
606:       if (!PetscAbsScalar(xa[i])) rdiff = 2 * check->tolerance;
607:       else rdiff = PetscAbsScalar((xa[i] - xa_last[i]) / xa[i]);
608:       if (rdiff > check->tolerance) {
609:         tmp        = xa[i];
610:         xa[i]      = .5 * (xa[i] + xa_last[i]);
611:         *changed_x = PETSC_TRUE;
612:         PetscCall(PetscPrintf(PETSC_COMM_WORLD, "  Altering entry %" PetscInt_FMT ": x=%g, x_last=%g, diff=%g, x_new=%g\n", i, (double)PetscAbsScalar(tmp), (double)PetscAbsScalar(xa_last[i]), (double)rdiff, (double)PetscAbsScalar(xa[i])));
613:       }
614:     }
615:     PetscCall(DMDAVecRestoreArray(da, check->last_step, &xa_last));
616:     PetscCall(DMDAVecRestoreArray(da, x, &xa));
617:   }
618:   PetscCall(VecCopy(x, check->last_step));
619:   PetscFunctionReturn(PETSC_SUCCESS);
620: }

622: /* ------------------------------------------------------------------- */
623: /*
624:    PostSetSubKSP - Optional user-defined routine that reset SubKSP options when hierarchical bjacobi PC is used
625:    e.g,
626:      mpiexec -n 8 ./ex3 -nox -n 10000 -ksp_type fgmres -pc_type bjacobi -pc_bjacobi_blocks 4 -sub_ksp_type gmres -sub_ksp_max_it 3 -post_setsubksp -sub_ksp_rtol 1.e-16
627:    Set by SNESLineSearchSetPostCheck().

629:    Input Parameters:
630:    linesearch - the LineSearch context
631:    xcurrent - current solution
632:    y - search direction and length
633:    x    - the new candidate iterate

635:    Output Parameters:
636:    y    - proposed step (search direction and length) (possibly changed)
637:    x    - current iterate (possibly modified)

639:  */
640: PetscErrorCode PostSetSubKSP(SNESLineSearch linesearch, Vec xcurrent, Vec y, Vec x, PetscBool *changed_y, PetscBool *changed_x, void *ctx)
641: {
642:   SetSubKSPCtx *check;
643:   PetscInt      iter, its, sub_its, maxit;
644:   KSP           ksp, sub_ksp, *sub_ksps;
645:   PC            pc;
646:   PetscReal     ksp_ratio;
647:   SNES          snes;

649:   PetscFunctionBeginUser;
650:   PetscCall(SNESLineSearchGetSNES(linesearch, &snes));
651:   check = (SetSubKSPCtx *)ctx;
652:   PetscCall(SNESGetIterationNumber(snes, &iter));
653:   PetscCall(SNESGetKSP(snes, &ksp));
654:   PetscCall(KSPGetPC(ksp, &pc));
655:   PetscCall(PCBJacobiGetSubKSP(pc, NULL, NULL, &sub_ksps));
656:   sub_ksp = sub_ksps[0];
657:   PetscCall(KSPGetIterationNumber(ksp, &its));         /* outer KSP iteration number */
658:   PetscCall(KSPGetIterationNumber(sub_ksp, &sub_its)); /* inner KSP iteration number */

660:   if (iter) {
661:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "    ...PostCheck snes iteration %" PetscInt_FMT ", ksp_it %" PetscInt_FMT " %" PetscInt_FMT ", subksp_it %" PetscInt_FMT "\n", iter, check->its0, its, sub_its));
662:     ksp_ratio = ((PetscReal)(its)) / check->its0;
663:     maxit     = (PetscInt)(ksp_ratio * sub_its + 0.5);
664:     if (maxit < 2) maxit = 2;
665:     PetscCall(KSPSetTolerances(sub_ksp, PETSC_DEFAULT, PETSC_DEFAULT, PETSC_DEFAULT, maxit));
666:     PetscCall(PetscPrintf(PETSC_COMM_WORLD, "    ...ksp_ratio %g, new maxit %" PetscInt_FMT "\n\n", (double)ksp_ratio, maxit));
667:   }
668:   check->its0 = its; /* save current outer KSP iteration number */
669:   PetscFunctionReturn(PETSC_SUCCESS);
670: }

672: /* ------------------------------------------------------------------- */
673: /*
674:    MatrixFreePreconditioner - This routine demonstrates the use of a
675:    user-provided preconditioner.  This code implements just the null
676:    preconditioner, which of course is not recommended for general use.

678:    Input Parameters:
679: +  pc - preconditioner
680: -  x - input vector

682:    Output Parameter:
683: .  y - preconditioned vector
684: */
685: PetscErrorCode MatrixFreePreconditioner(PC pc, Vec x, Vec y)
686: {
687:   PetscFunctionBeginUser;
688:   PetscCall(VecCopy(x, y));
689:   PetscFunctionReturn(PETSC_SUCCESS);
690: }

692: /*TEST

694:    test:
695:       args: -nox -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

697:    test:
698:       suffix: 2
699:       nsize: 3
700:       args: -nox -pc_type asm -mat_type mpiaij -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

702:    test:
703:       suffix: 3
704:       nsize: 2
705:       args: -nox -snes_monitor_cancel -snes_monitor_short -ksp_gmres_cgs_refinement_type refine_always

707:    test:
708:       suffix: 4
709:       args: -nox -pre_check_iterates -post_check_iterates

711:    test:
712:       suffix: 5
713:       requires: double !complex !single
714:       nsize: 2
715:       args: -nox -snes_test_jacobian  -snes_test_jacobian_view

717:    test:
718:       suffix: 6
719:       requires: double !complex !single
720:       nsize: 4
721:       args: -test_jacobian_domain_error -snes_converged_reason -snes_check_jacobian_domain_error 1

723:    test:
724:       suffix: 7
725:       requires: double !complex !single
726:       nsize: 4
727:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type newtontr -snes_check_jacobian_domain_error 1

729:    test:
730:       suffix: 8
731:       requires: double !complex !single
732:       nsize: 4
733:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type vinewtonrsls -snes_check_jacobian_domain_error 1

735:    test:
736:       suffix: 9
737:       requires: double !complex !single
738:       nsize: 4
739:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type vinewtonssls -snes_check_jacobian_domain_error 1

741:    test:
742:       suffix: 10
743:       requires: double !complex !single
744:       nsize: 4
745:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type qn -snes_qn_scale_type jacobian -snes_check_jacobian_domain_error 1

747:    test:
748:       suffix: 11
749:       requires: double !complex !single
750:       nsize: 4
751:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type ms -snes_ms_type m62 -snes_ms_damping 0.9 -snes_check_jacobian_domain_error 1

753:    test:
754:       suffix: 12
755:       args: -view_initial
756:       filter: grep -v "type:"

758:    test:
759:       suffix: 13
760:       requires: double !complex !single
761:       nsize: 4
762:       args: -test_jacobian_domain_error -snes_converged_reason -snes_type newtontrdc -snes_check_jacobian_domain_error 1

764: TEST*/