Actual source code: snesrichardson.c
1: #include <../src/snes/impls/richardson/snesrichardsonimpl.h>
3: static PetscErrorCode SNESReset_NRichardson(SNES snes)
4: {
5: PetscFunctionBegin;
6: PetscFunctionReturn(PETSC_SUCCESS);
7: }
9: static PetscErrorCode SNESDestroy_NRichardson(SNES snes)
10: {
11: PetscFunctionBegin;
12: PetscCall(SNESReset_NRichardson(snes));
13: PetscCall(PetscFree(snes->data));
14: PetscFunctionReturn(PETSC_SUCCESS);
15: }
17: static PetscErrorCode SNESSetUp_NRichardson(SNES snes)
18: {
19: PetscFunctionBegin;
20: PetscCheck(snes->npcside != PC_RIGHT, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "NRichardson only supports left preconditioning");
21: if (snes->functype == SNES_FUNCTION_DEFAULT) snes->functype = SNES_FUNCTION_UNPRECONDITIONED;
22: PetscFunctionReturn(PETSC_SUCCESS);
23: }
25: static PetscErrorCode SNESSetFromOptions_NRichardson(SNES snes, PetscOptionItems *PetscOptionsObject)
26: {
27: PetscFunctionBegin;
28: PetscOptionsHeadBegin(PetscOptionsObject, "SNES Richardson options");
29: PetscOptionsHeadEnd();
30: PetscFunctionReturn(PETSC_SUCCESS);
31: }
33: static PetscErrorCode SNESView_NRichardson(SNES snes, PetscViewer viewer)
34: {
35: PetscBool iascii;
37: PetscFunctionBegin;
38: PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
39: if (iascii) { }
40: PetscFunctionReturn(PETSC_SUCCESS);
41: }
43: static PetscErrorCode SNESSolve_NRichardson(SNES snes)
44: {
45: Vec X, Y, F;
46: PetscReal xnorm, fnorm, ynorm;
47: PetscInt maxits, i;
48: SNESLineSearchReason lsresult;
49: SNESConvergedReason reason;
51: PetscFunctionBegin;
52: PetscCheck(!snes->xl && !snes->xu && !snes->ops->computevariablebounds, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);
54: snes->reason = SNES_CONVERGED_ITERATING;
56: maxits = snes->max_its; /* maximum number of iterations */
57: X = snes->vec_sol; /* X^n */
58: Y = snes->vec_sol_update; /* \tilde X */
59: F = snes->vec_func; /* residual vector */
61: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
62: snes->iter = 0;
63: snes->norm = 0.;
64: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
66: if (snes->npc && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
67: PetscCall(SNESApplyNPC(snes, X, NULL, F));
68: PetscCall(SNESGetConvergedReason(snes->npc, &reason));
69: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
70: snes->reason = SNES_DIVERGED_INNER;
71: PetscFunctionReturn(PETSC_SUCCESS);
72: }
73: PetscCall(VecNorm(F, NORM_2, &fnorm));
74: } else {
75: if (!snes->vec_func_init_set) {
76: PetscCall(SNESComputeFunction(snes, X, F));
77: } else snes->vec_func_init_set = PETSC_FALSE;
79: PetscCall(VecNorm(F, NORM_2, &fnorm));
80: SNESCheckFunctionNorm(snes, fnorm);
81: }
82: if (snes->npc && snes->functype == SNES_FUNCTION_UNPRECONDITIONED) {
83: PetscCall(SNESApplyNPC(snes, X, F, Y));
84: PetscCall(SNESGetConvergedReason(snes->npc, &reason));
85: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
86: snes->reason = SNES_DIVERGED_INNER;
87: PetscFunctionReturn(PETSC_SUCCESS);
88: }
89: } else {
90: PetscCall(VecCopy(F, Y));
91: }
93: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
94: snes->norm = fnorm;
95: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
96: PetscCall(SNESLogConvergenceHistory(snes, fnorm, 0));
98: /* test convergence */
99: PetscCall(SNESConverged(snes, 0, 0.0, 0.0, fnorm));
100: PetscCall(SNESMonitor(snes, 0, fnorm));
101: if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS);
103: /* Call general purpose update function */
104: PetscTryTypeMethod(snes, update, snes->iter);
106: for (i = 1; i < maxits + 1; i++) {
107: PetscCall(SNESLineSearchApply(snes->linesearch, X, F, &fnorm, Y));
108: PetscCall(SNESLineSearchGetReason(snes->linesearch, &lsresult));
109: PetscCall(SNESLineSearchGetNorms(snes->linesearch, &xnorm, &fnorm, &ynorm));
110: if (lsresult) {
111: if (++snes->numFailures >= snes->maxFailures) {
112: snes->reason = SNES_DIVERGED_LINE_SEARCH;
113: break;
114: }
115: }
116: if (snes->nfuncs >= snes->max_funcs && snes->max_funcs >= 0) {
117: snes->reason = SNES_DIVERGED_FUNCTION_COUNT;
118: break;
119: }
121: /* Monitor convergence */
122: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
123: snes->iter = i;
124: snes->norm = fnorm;
125: snes->xnorm = xnorm;
126: snes->ynorm = ynorm;
127: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
128: PetscCall(SNESLogConvergenceHistory(snes, snes->norm, 0));
129: /* Test for convergence */
130: PetscCall(SNESConverged(snes, snes->iter, xnorm, ynorm, fnorm));
131: PetscCall(SNESMonitor(snes, snes->iter, snes->norm));
132: if (snes->reason) break;
134: /* Call general purpose update function */
135: PetscTryTypeMethod(snes, update, snes->iter);
137: if (snes->npc) {
138: if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
139: PetscCall(SNESApplyNPC(snes, X, NULL, Y));
140: PetscCall(VecNorm(F, NORM_2, &fnorm));
141: PetscCall(VecCopy(Y, F));
142: } else {
143: PetscCall(SNESApplyNPC(snes, X, F, Y));
144: }
145: PetscCall(SNESGetConvergedReason(snes->npc, &reason));
146: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
147: snes->reason = SNES_DIVERGED_INNER;
148: PetscFunctionReturn(PETSC_SUCCESS);
149: }
150: } else {
151: PetscCall(VecCopy(F, Y));
152: }
153: }
154: if (i == maxits + 1) {
155: PetscCall(PetscInfo(snes, "Maximum number of iterations has been reached: %" PetscInt_FMT "\n", maxits));
156: if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
157: }
158: PetscFunctionReturn(PETSC_SUCCESS);
159: }
161: /*MC
162: SNESNRICHARDSON - Richardson nonlinear solver that uses successive substitutions, also sometimes known as Picard iteration.
164: Options Database Keys:
165: + -snes_linesearch_type <l2,cp,basic> - Line search type.
166: - -snes_linesearch_damping<1.0> - Damping for the line search.
168: Level: beginner
170: Notes:
171: If no inner nonlinear preconditioner is provided then solves F(x) - b = 0 using x^{n+1} = x^{n} - lambda
172: (F(x^n) - b) where lambda is obtained either `SNESLineSearchSetDamping()`, -snes_damping or a line search. If
173: an inner nonlinear preconditioner is provided (either with -npc_snes_type or `SNESSetNPC()`) then the inner
174: solver is called an initial solution x^n and the nonlinear Richardson uses x^{n+1} = x^{n} + lambda d^{n}
175: where d^{n} = \hat{x}^{n} - x^{n} where \hat{x}^{n} is the solution returned from the inner solver.
177: The update, especially without inner nonlinear preconditioner, may be ill-scaled. If using the basic
178: linesearch, one may have to scale the update with -snes_linesearch_damping
180: This uses no derivative information thus will be much slower then Newton's method obtained with -snes_type ls
182: Only supports left non-linear preconditioning.
184: .seealso: [](ch_snes), `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESNEWTONLS`, `SNESNEWTONTR`, `SNESNGMRES`, `SNESQN`, `SNESNCG`,
185: `SNESLineSearchSetDamping()`
186: M*/
187: PETSC_EXTERN PetscErrorCode SNESCreate_NRichardson(SNES snes)
188: {
189: SNES_NRichardson *neP;
190: SNESLineSearch linesearch;
192: PetscFunctionBegin;
193: snes->ops->destroy = SNESDestroy_NRichardson;
194: snes->ops->setup = SNESSetUp_NRichardson;
195: snes->ops->setfromoptions = SNESSetFromOptions_NRichardson;
196: snes->ops->view = SNESView_NRichardson;
197: snes->ops->solve = SNESSolve_NRichardson;
198: snes->ops->reset = SNESReset_NRichardson;
200: snes->usesksp = PETSC_FALSE;
201: snes->usesnpc = PETSC_TRUE;
203: snes->npcside = PC_LEFT;
205: PetscCall(SNESGetLineSearch(snes, &linesearch));
206: if (!((PetscObject)linesearch)->type_name) PetscCall(SNESLineSearchSetType(linesearch, SNESLINESEARCHL2));
208: snes->alwayscomputesfinalresidual = PETSC_TRUE;
210: PetscCall(SNESParametersInitialize(snes));
211: PetscObjectParameterSetDefault(snes, max_funcs, 30000);
212: PetscObjectParameterSetDefault(snes, max_its, 10000);
213: PetscObjectParameterSetDefault(snes, stol, 1e-20);
215: PetscCall(PetscNew(&neP));
216: snes->data = (void *)neP;
217: PetscFunctionReturn(PETSC_SUCCESS);
218: }