Actual source code: snesrichardson.c
1: #include <../src/snes/impls/richardson/snesrichardsonimpl.h>
4: PetscErrorCode SNESReset_NRichardson(SNES snes)
5: {
7: return(0);
8: }
10: /*
11: SNESDestroy_NRichardson - Destroys the private SNES_NRichardson context that was created with SNESCreate_NRichardson().
13: Input Parameter:
14: . snes - the SNES context
16: Application Interface Routine: SNESDestroy()
17: */
18: PetscErrorCode SNESDestroy_NRichardson(SNES snes)
19: {
23: SNESReset_NRichardson(snes);
24: PetscFree(snes->data);
25: return(0);
26: }
28: /*
29: SNESSetUp_NRichardson - Sets up the internal data structures for the later use
30: of the SNESNRICHARDSON nonlinear solver.
32: Input Parameters:
33: + snes - the SNES context
34: - x - the solution vector
36: Application Interface Routine: SNESSetUp()
37: */
38: PetscErrorCode SNESSetUp_NRichardson(SNES snes)
39: {
41: if (snes->npcside== PC_RIGHT) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"NRichardson only supports left preconditioning");
42: if (snes->functype == SNES_FUNCTION_DEFAULT) snes->functype = SNES_FUNCTION_UNPRECONDITIONED;
43: return(0);
44: }
46: /*
47: SNESSetFromOptions_NRichardson - Sets various parameters for the SNESNEWTONLS method.
49: Input Parameter:
50: . snes - the SNES context
52: Application Interface Routine: SNESSetFromOptions()
53: */
54: static PetscErrorCode SNESSetFromOptions_NRichardson(PetscOptionItems *PetscOptionsObject,SNES snes)
55: {
59: PetscOptionsHead(PetscOptionsObject,"SNES Richardson options");
60: PetscOptionsTail();
61: return(0);
62: }
64: /*
65: SNESView_NRichardson - Prints info from the SNESRichardson data structure.
67: Input Parameters:
68: + SNES - the SNES context
69: - viewer - visualization context
71: Application Interface Routine: SNESView()
72: */
73: static PetscErrorCode SNESView_NRichardson(SNES snes, PetscViewer viewer)
74: {
75: PetscBool iascii;
79: PetscObjectTypeCompare((PetscObject) viewer, PETSCVIEWERASCII, &iascii);
80: if (iascii) {
81: }
82: return(0);
83: }
85: /*
86: SNESSolve_NRichardson - Solves a nonlinear system with the Richardson method.
88: Input Parameters:
89: . snes - the SNES context
91: Output Parameter:
92: . outits - number of iterations until termination
94: Application Interface Routine: SNESSolve()
95: */
96: PetscErrorCode SNESSolve_NRichardson(SNES snes)
97: {
98: Vec X, Y, F;
99: PetscReal xnorm, fnorm, ynorm;
100: PetscInt maxits, i;
101: PetscErrorCode ierr;
102: SNESLineSearchReason lsresult;
103: SNESConvergedReason reason;
106: 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);
108: snes->reason = SNES_CONVERGED_ITERATING;
110: maxits = snes->max_its; /* maximum number of iterations */
111: X = snes->vec_sol; /* X^n */
112: Y = snes->vec_sol_update; /* \tilde X */
113: F = snes->vec_func; /* residual vector */
115: PetscObjectSAWsTakeAccess((PetscObject)snes);
116: snes->iter = 0;
117: snes->norm = 0.;
118: PetscObjectSAWsGrantAccess((PetscObject)snes);
120: if (snes->npc && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
121: SNESApplyNPC(snes,X,NULL,F);
122: SNESGetConvergedReason(snes->npc,&reason);
123: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
124: snes->reason = SNES_DIVERGED_INNER;
125: return(0);
126: }
127: VecNorm(F,NORM_2,&fnorm);
128: } else {
129: if (!snes->vec_func_init_set) {
130: SNESComputeFunction(snes,X,F);
131: } else snes->vec_func_init_set = PETSC_FALSE;
133: VecNorm(F,NORM_2,&fnorm);
134: SNESCheckFunctionNorm(snes,fnorm);
135: }
136: if (snes->npc && snes->functype == SNES_FUNCTION_UNPRECONDITIONED) {
137: SNESApplyNPC(snes,X,F,Y);
138: SNESGetConvergedReason(snes->npc,&reason);
139: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
140: snes->reason = SNES_DIVERGED_INNER;
141: return(0);
142: }
143: } else {
144: VecCopy(F,Y);
145: }
147: PetscObjectSAWsTakeAccess((PetscObject)snes);
148: snes->norm = fnorm;
149: PetscObjectSAWsGrantAccess((PetscObject)snes);
150: SNESLogConvergenceHistory(snes,fnorm,0);
151: SNESMonitor(snes,0,fnorm);
153: /* test convergence */
154: (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
155: if (snes->reason) return(0);
157: /* Call general purpose update function */
158: if (snes->ops->update) {
159: (*snes->ops->update)(snes, snes->iter);
160: }
162: /* set parameter for default relative tolerance convergence test */
163: snes->ttol = fnorm*snes->rtol;
164: /* test convergence */
165: (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
166: if (snes->reason) return(0);
168: for (i = 1; i < maxits+1; i++) {
169: SNESLineSearchApply(snes->linesearch, X, F, &fnorm, Y);
170: SNESLineSearchGetReason(snes->linesearch, &lsresult);
171: SNESLineSearchGetNorms(snes->linesearch, &xnorm, &fnorm, &ynorm);
172: if (lsresult) {
173: if (++snes->numFailures >= snes->maxFailures) {
174: snes->reason = SNES_DIVERGED_LINE_SEARCH;
175: break;
176: }
177: }
178: if (snes->nfuncs >= snes->max_funcs && snes->max_funcs >= 0) {
179: snes->reason = SNES_DIVERGED_FUNCTION_COUNT;
180: break;
181: }
183: /* Monitor convergence */
184: PetscObjectSAWsTakeAccess((PetscObject)snes);
185: snes->iter = i;
186: snes->norm = fnorm;
187: snes->xnorm = xnorm;
188: snes->ynorm = ynorm;
189: PetscObjectSAWsGrantAccess((PetscObject)snes);
190: SNESLogConvergenceHistory(snes,snes->norm,0);
191: SNESMonitor(snes,snes->iter,snes->norm);
192: /* Test for convergence */
193: (*snes->ops->converged)(snes,snes->iter,xnorm,ynorm,fnorm,&snes->reason,snes->cnvP);
194: if (snes->reason) break;
196: /* Call general purpose update function */
197: if (snes->ops->update) {
198: (*snes->ops->update)(snes, snes->iter);
199: }
201: if (snes->npc) {
202: if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
203: SNESApplyNPC(snes,X,NULL,Y);
204: VecNorm(F,NORM_2,&fnorm);
205: VecCopy(Y,F);
206: } else {
207: SNESApplyNPC(snes,X,F,Y);
208: }
209: SNESGetConvergedReason(snes->npc,&reason);
210: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
211: snes->reason = SNES_DIVERGED_INNER;
212: return(0);
213: }
214: } else {
215: VecCopy(F,Y);
216: }
217: }
218: if (i == maxits+1) {
219: PetscInfo1(snes, "Maximum number of iterations has been reached: %D\n", maxits);
220: if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
221: }
222: return(0);
223: }
225: /*MC
226: SNESNRICHARDSON - Richardson nonlinear solver that uses successive substitutions, also sometimes known as Picard iteration.
228: Level: beginner
230: Options Database:
231: + -snes_linesearch_type <l2,cp,basic> Line search type.
232: - -snes_linesearch_damping<1.0> Damping for the line search.
234: Notes:
235: If no inner nonlinear preconditioner is provided then solves F(x) - b = 0 using x^{n+1} = x^{n} - lambda
236: (F(x^n) - b) where lambda is obtained either SNESLineSearchSetDamping(), -snes_damping or a line search. If
237: an inner nonlinear preconditioner is provided (either with -npc_snes_type or SNESSetNPC()) then the inner
238: solver is called an initial solution x^n and the nonlinear Richardson uses x^{n+1} = x^{n} + lambda d^{n}
239: where d^{n} = \hat{x}^{n} - x^{n} where \hat{x}^{n} is the solution returned from the inner solver.
241: The update, especially without inner nonlinear preconditioner, may be ill-scaled. If using the basic
242: linesearch, one may have to scale the update with -snes_linesearch_damping
244: This uses no derivative information thus will be much slower then Newton's method obtained with -snes_type ls
246: Only supports left non-linear preconditioning.
248: .seealso: SNESCreate(), SNES, SNESSetType(), SNESNEWTONLS, SNESNEWTONTR, SNESNGMRES, SNESQN, SNESNCG
249: M*/
250: PETSC_EXTERN PetscErrorCode SNESCreate_NRichardson(SNES snes)
251: {
252: PetscErrorCode ierr;
253: SNES_NRichardson *neP;
254: SNESLineSearch linesearch;
257: snes->ops->destroy = SNESDestroy_NRichardson;
258: snes->ops->setup = SNESSetUp_NRichardson;
259: snes->ops->setfromoptions = SNESSetFromOptions_NRichardson;
260: snes->ops->view = SNESView_NRichardson;
261: snes->ops->solve = SNESSolve_NRichardson;
262: snes->ops->reset = SNESReset_NRichardson;
264: snes->usesksp = PETSC_FALSE;
265: snes->usesnpc = PETSC_TRUE;
267: snes->npcside= PC_LEFT;
269: SNESGetLineSearch(snes, &linesearch);
270: if (!((PetscObject)linesearch)->type_name) {
271: SNESLineSearchSetType(linesearch, SNESLINESEARCHL2);
272: }
274: snes->alwayscomputesfinalresidual = PETSC_TRUE;
276: PetscNewLog(snes,&neP);
277: snes->data = (void*) neP;
279: if (!snes->tolerancesset) {
280: snes->max_funcs = 30000;
281: snes->max_its = 10000;
282: snes->stol = 1e-20;
283: }
284: return(0);
285: }