Actual source code: snesgs.c
1: #include <../src/snes/impls/gs/gsimpl.h>
3: /*@
4: SNESNGSSetTolerances - Sets various parameters used in convergence tests.
6: Logically Collective on SNES
8: Input Parameters:
9: + snes - the SNES context
10: . abstol - absolute convergence tolerance
11: . rtol - relative convergence tolerance
12: . stol - convergence tolerance in terms of the norm of the change in the solution between steps, || delta x || < stol*|| x ||
13: - maxit - maximum number of iterations
15: Options Database Keys:
16: + -snes_ngs_atol <abstol> - Sets abstol
17: . -snes_ngs_rtol <rtol> - Sets rtol
18: . -snes_ngs_stol <stol> - Sets stol
19: - -snes_max_it <maxit> - Sets maxit
21: Level: intermediate
23: .seealso: SNESSetTrustRegionTolerance()
24: @*/
25: PetscErrorCode SNESNGSSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit)
26: {
27: SNES_NGS *gs = (SNES_NGS*)snes->data;
32: if (abstol != PETSC_DEFAULT) {
33: if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %g must be non-negative",(double)abstol);
34: gs->abstol = abstol;
35: }
36: if (rtol != PETSC_DEFAULT) {
37: if (rtol < 0.0 || 1.0 <= rtol) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Relative tolerance %g must be non-negative and less than 1.0",(double)rtol);
38: gs->rtol = rtol;
39: }
40: if (stol != PETSC_DEFAULT) {
41: if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %g must be non-negative",(double)stol);
42: gs->stol = stol;
43: }
44: if (maxit != PETSC_DEFAULT) {
45: if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
46: gs->max_its = maxit;
47: }
48: return(0);
49: }
51: /*@
52: SNESNGSGetTolerances - Gets various parameters used in convergence tests.
54: Not Collective
56: Input Parameters:
57: + snes - the SNES context
58: . atol - absolute convergence tolerance
59: . rtol - relative convergence tolerance
60: . stol - convergence tolerance in terms of the norm
61: of the change in the solution between steps
62: - maxit - maximum number of iterations
64: Notes:
65: The user can specify NULL for any parameter that is not needed.
67: Level: intermediate
69: .seealso: SNESSetTolerances()
70: @*/
71: PetscErrorCode SNESNGSGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit)
72: {
73: SNES_NGS *gs = (SNES_NGS*)snes->data;
77: if (atol) *atol = gs->abstol;
78: if (rtol) *rtol = gs->rtol;
79: if (stol) *stol = gs->stol;
80: if (maxit) *maxit = gs->max_its;
81: return(0);
82: }
84: /*@
85: SNESNGSSetSweeps - Sets the number of sweeps of GS to use.
87: Input Parameters:
88: + snes - the SNES context
89: - sweeps - the number of sweeps of GS to perform.
91: Level: intermediate
93: .seealso: SNESSetNGS(), SNESGetNGS(), SNESSetNPC(), SNESNGSGetSweeps()
94: @*/
96: PetscErrorCode SNESNGSSetSweeps(SNES snes, PetscInt sweeps)
97: {
98: SNES_NGS *gs = (SNES_NGS*)snes->data;
102: gs->sweeps = sweeps;
103: return(0);
104: }
106: /*@
107: SNESNGSGetSweeps - Gets the number of sweeps GS will use.
109: Input Parameters:
110: . snes - the SNES context
112: Output Parameters:
113: . sweeps - the number of sweeps of GS to perform.
115: Level: intermediate
117: .seealso: SNESSetNGS(), SNESGetNGS(), SNESSetNPC(), SNESNGSSetSweeps()
118: @*/
119: PetscErrorCode SNESNGSGetSweeps(SNES snes, PetscInt * sweeps)
120: {
121: SNES_NGS *gs = (SNES_NGS*)snes->data;
125: *sweeps = gs->sweeps;
126: return(0);
127: }
129: PetscErrorCode SNESReset_NGS(SNES snes)
130: {
131: SNES_NGS *gs = (SNES_NGS*)snes->data;
135: ISColoringDestroy(&gs->coloring);
136: return(0);
137: }
139: PetscErrorCode SNESDestroy_NGS(SNES snes)
140: {
144: SNESReset_NGS(snes);
145: PetscFree(snes->data);
146: return(0);
147: }
149: PetscErrorCode SNESSetUp_NGS(SNES snes)
150: {
152: PetscErrorCode (*f)(SNES,Vec,Vec,void*);
155: SNESGetNGS(snes,&f,NULL);
156: if (!f) {
157: SNESSetNGS(snes,SNESComputeNGSDefaultSecant,NULL);
158: }
159: return(0);
160: }
162: PetscErrorCode SNESSetFromOptions_NGS(PetscOptionItems *PetscOptionsObject,SNES snes)
163: {
164: SNES_NGS *gs = (SNES_NGS*)snes->data;
166: PetscInt sweeps,max_its=PETSC_DEFAULT;
167: PetscReal rtol=PETSC_DEFAULT,atol=PETSC_DEFAULT,stol=PETSC_DEFAULT;
168: PetscBool flg,flg1,flg2,flg3;
171: PetscOptionsHead(PetscOptionsObject,"SNES GS options");
172: /* GS Options */
173: PetscOptionsInt("-snes_ngs_sweeps","Number of sweeps of GS to apply","SNESComputeGS",gs->sweeps,&sweeps,&flg);
174: if (flg) {
175: SNESNGSSetSweeps(snes,sweeps);
176: }
177: PetscOptionsReal("-snes_ngs_atol","Absolute residual tolerance for GS iteration","SNESComputeGS",gs->abstol,&atol,&flg);
178: PetscOptionsReal("-snes_ngs_rtol","Relative residual tolerance for GS iteration","SNESComputeGS",gs->rtol,&rtol,&flg1);
179: PetscOptionsReal("-snes_ngs_stol","Absolute update tolerance for GS iteration","SNESComputeGS",gs->stol,&stol,&flg2);
180: PetscOptionsInt("-snes_ngs_max_it","Maximum number of sweeps of GS to apply","SNESComputeGS",gs->max_its,&max_its,&flg3);
181: if (flg || flg1 || flg2 || flg3) {
182: SNESNGSSetTolerances(snes,atol,rtol,stol,max_its);
183: }
184: flg = PETSC_FALSE;
185: PetscOptionsBool("-snes_ngs_secant","Use finite difference secant approximation with coloring","",flg,&flg,NULL);
186: if (flg) {
187: SNESSetNGS(snes,SNESComputeNGSDefaultSecant,NULL);
188: PetscInfo(snes,"Setting default finite difference secant approximation with coloring\n");
189: }
190: PetscOptionsReal("-snes_ngs_secant_h","Differencing parameter for secant search","",gs->h,&gs->h,NULL);
191: PetscOptionsBool("-snes_ngs_secant_mat_coloring","Use the graph coloring of the Jacobian for the secant GS","",gs->secant_mat,&gs->secant_mat,&flg);
193: PetscOptionsTail();
194: return(0);
195: }
197: PetscErrorCode SNESView_NGS(SNES snes, PetscViewer viewer)
198: {
200: PetscErrorCode (*f)(SNES,Vec,Vec,void*);
201: SNES_NGS *gs = (SNES_NGS*)snes->data;
202: PetscBool iascii;
205: PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
206: if (iascii) {
207: DMSNESGetNGS(snes->dm,&f,NULL);
208: if (f == SNESComputeNGSDefaultSecant) {
209: PetscViewerASCIIPrintf(viewer," Use finite difference secant approximation with coloring with h = %g \n",(double)gs->h);
210: }
211: }
212: return(0);
213: }
215: PetscErrorCode SNESSolve_NGS(SNES snes)
216: {
217: Vec F;
218: Vec X;
219: Vec B;
220: PetscInt i;
221: PetscReal fnorm;
222: PetscErrorCode ierr;
223: SNESNormSchedule normschedule;
227: if (snes->xl || snes->xu || snes->ops->computevariablebounds) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);
229: PetscCitationsRegister(SNESCitation,&SNEScite);
230: X = snes->vec_sol;
231: F = snes->vec_func;
232: B = snes->vec_rhs;
234: PetscObjectSAWsTakeAccess((PetscObject)snes);
235: snes->iter = 0;
236: snes->norm = 0.;
237: PetscObjectSAWsGrantAccess((PetscObject)snes);
238: snes->reason = SNES_CONVERGED_ITERATING;
240: SNESGetNormSchedule(snes, &normschedule);
241: if (normschedule == SNES_NORM_ALWAYS || normschedule == SNES_NORM_INITIAL_ONLY || normschedule == SNES_NORM_INITIAL_FINAL_ONLY) {
242: /* compute the initial function and preconditioned update delX */
243: if (!snes->vec_func_init_set) {
244: SNESComputeFunction(snes,X,F);
245: } else snes->vec_func_init_set = PETSC_FALSE;
247: VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F|| */
248: SNESCheckFunctionNorm(snes,fnorm);
249: PetscObjectSAWsTakeAccess((PetscObject)snes);
250: snes->iter = 0;
251: snes->norm = fnorm;
252: PetscObjectSAWsGrantAccess((PetscObject)snes);
253: SNESLogConvergenceHistory(snes,snes->norm,0);
254: SNESMonitor(snes,0,snes->norm);
256: /* test convergence */
257: (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
258: if (snes->reason) return(0);
259: } else {
260: PetscObjectSAWsGrantAccess((PetscObject)snes);
261: SNESLogConvergenceHistory(snes,snes->norm,0);
262: }
264: /* Call general purpose update function */
265: if (snes->ops->update) {
266: (*snes->ops->update)(snes, snes->iter);
267: }
269: for (i = 0; i < snes->max_its; i++) {
270: SNESComputeNGS(snes, B, X);
271: /* only compute norms if requested or about to exit due to maximum iterations */
272: if (normschedule == SNES_NORM_ALWAYS || ((i == snes->max_its - 1) && (normschedule == SNES_NORM_INITIAL_FINAL_ONLY || normschedule == SNES_NORM_FINAL_ONLY))) {
273: SNESComputeFunction(snes,X,F);
274: VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F|| */
275: SNESCheckFunctionNorm(snes,fnorm);
276: /* Monitor convergence */
277: PetscObjectSAWsTakeAccess((PetscObject)snes);
278: snes->iter = i+1;
279: snes->norm = fnorm;
280: PetscObjectSAWsGrantAccess((PetscObject)snes);
281: SNESLogConvergenceHistory(snes,snes->norm,0);
282: SNESMonitor(snes,snes->iter,snes->norm);
283: }
284: /* Test for convergence */
285: if (normschedule == SNES_NORM_ALWAYS) {(*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);}
286: if (snes->reason) return(0);
287: /* Call general purpose update function */
288: if (snes->ops->update) {
289: (*snes->ops->update)(snes, snes->iter);
290: }
291: }
292: if (normschedule == SNES_NORM_ALWAYS) {
293: if (i == snes->max_its) {
294: PetscInfo1(snes,"Maximum number of iterations has been reached: %D\n",snes->max_its);
295: if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
296: }
297: } else if (!snes->reason) snes->reason = SNES_CONVERGED_ITS; /* GS is meant to be used as a preconditioner */
298: return(0);
299: }
301: /*MC
302: SNESNGS - Either calls the user-provided solution routine provided with SNESSetNGS() or does a finite difference secant approximation
303: using coloring.
305: Level: advanced
307: Options Database:
308: + -snes_ngs_sweeps <n> - Number of sweeps of GS to apply
309: . -snes_ngs_atol <atol> - Absolute residual tolerance for GS iteration
310: . -snes_ngs_rtol <rtol> - Relative residual tolerance for GS iteration
311: . -snes_ngs_stol <stol> - Absolute update tolerance for GS iteration
312: . -snes_ngs_max_it <maxit> - Maximum number of sweeps of GS to apply
313: . -snes_ngs_secant - Use pointwise secant local Jacobian approximation with coloring instead of user provided Gauss-Seidel routine, this is
314: used by default if no user provided Gauss-Seidel routine is available. Requires either that a DM that can compute a coloring
315: is available or a Jacobian sparse matrix is provided (from which to get the coloring).
316: . -snes_ngs_secant_h <h> - Differencing parameter for secant approximation
317: . -snes_ngs_secant_mat_coloring - Use the graph coloring of the Jacobian for the secant GS even if a DM is available.
318: - -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - how often the residual norms are computed
320: Notes:
321: the Gauss-Seidel smoother is inherited through composition. If a solver has been created with SNESGetNPC(), it will have
322: its parent's Gauss-Seidel routine associated with it.
324: By default this routine computes the solution norm at each iteration, this can be time consuming, you can turn this off with SNESSetNormSchedule() or -snes_norm_schedule
325: References:
326: . 1. - Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers",
327: SIAM Review, 57(4), 2015
329: .seealso: SNESCreate(), SNES, SNESSetType(), SNESSetNGS(), SNESType (for list of available types), SNESNGSSetSweeps(), SNESNGSSetTolerances(),
330: SNESSetNormSchedule()
331: M*/
333: PETSC_EXTERN PetscErrorCode SNESCreate_NGS(SNES snes)
334: {
335: SNES_NGS *gs;
339: snes->ops->destroy = SNESDestroy_NGS;
340: snes->ops->setup = SNESSetUp_NGS;
341: snes->ops->setfromoptions = SNESSetFromOptions_NGS;
342: snes->ops->view = SNESView_NGS;
343: snes->ops->solve = SNESSolve_NGS;
344: snes->ops->reset = SNESReset_NGS;
346: snes->usesksp = PETSC_FALSE;
347: snes->usesnpc = PETSC_FALSE;
349: snes->alwayscomputesfinalresidual = PETSC_FALSE;
351: if (!snes->tolerancesset) {
352: snes->max_its = 10000;
353: snes->max_funcs = 10000;
354: }
356: PetscNewLog(snes,&gs);
358: gs->sweeps = 1;
359: gs->rtol = 1e-5;
360: gs->abstol = PETSC_MACHINE_EPSILON;
361: gs->stol = 1000*PETSC_MACHINE_EPSILON;
362: gs->max_its = 50;
363: gs->h = PETSC_SQRT_MACHINE_EPSILON;
365: snes->data = (void*) gs;
366: return(0);
367: }