Actual source code: anderson.c
petsc-3.4.5 2014-06-29
1: #include <../src/snes/impls/ngmres/snesngmres.h> /*I "petscsnes.h" I*/
3: extern PetscErrorCode SNESDestroy_NGMRES(SNES);
4: extern PetscErrorCode SNESReset_NGMRES(SNES);
5: extern PetscErrorCode SNESSetUp_NGMRES(SNES);
6: extern PetscErrorCode SNESView_NGMRES(SNES,PetscViewer);
8: PETSC_EXTERN const char *const SNESNGMRESRestartTypes[];
12: PetscErrorCode SNESSetFromOptions_Anderson(SNES snes)
13: {
14: SNES_NGMRES *ngmres = (SNES_NGMRES*) snes->data;
16: PetscBool debug;
17: SNESLineSearch linesearch;
20: PetscOptionsHead("SNES NGMRES options");
21: PetscOptionsInt("-snes_anderson_m", "Number of directions","SNES",ngmres->msize,&ngmres->msize,NULL);
22: PetscOptionsReal("-snes_anderson_beta", "Mixing parameter","SNES",ngmres->andersonBeta,&ngmres->andersonBeta,NULL);
23: PetscOptionsBool("-snes_anderson_monitor", "Monitor steps of Anderson Mixing","SNES",ngmres->monitor ? PETSC_TRUE : PETSC_FALSE,&debug,NULL);
24: PetscOptionsInt("-snes_anderson_restart", "Iterations before forced restart", "SNES",ngmres->restart_periodic,&ngmres->restart_periodic,NULL);
25: PetscOptionsInt("-snes_anderson_restart_it", "Tolerance iterations before restart","SNES",ngmres->restart_it,&ngmres->restart_it,NULL);
26: PetscOptionsEnum("-snes_anderson_restart_type","Restart type","SNESNGMRESSetRestartType",SNESNGMRESRestartTypes,
27: (PetscEnum)ngmres->restart_type,(PetscEnum*)&ngmres->restart_type,NULL);
28: if (debug) {
29: ngmres->monitor = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
30: }
31: PetscOptionsTail();
32: /* set the default type of the line search if the user hasn't already. */
33: if (!snes->linesearch) {
34: SNESGetLineSearch(snes,&linesearch);
35: SNESLineSearchSetType(linesearch,SNESLINESEARCHBASIC);
36: }
37: return(0);
38: }
42: PetscErrorCode SNESSolve_Anderson(SNES snes)
43: {
44: SNES_NGMRES *ngmres = (SNES_NGMRES*) snes->data;
45: /* present solution, residual, and preconditioned residual */
46: Vec X,F,B,D;
48: /* candidate linear combination answers */
49: Vec XA,FA,XM,FM,FPC;
51: /* coefficients and RHS to the minimization problem */
52: PetscReal fnorm,fMnorm;
53: PetscReal dnorm,dminnorm=0.0,fminnorm;
54: PetscInt restart_count=0;
55: PetscInt k,k_restart,l,ivec;
57: PetscBool selectRestart;
59: SNESConvergedReason reason;
60: PetscErrorCode ierr;
63: /* variable initialization */
64: snes->reason = SNES_CONVERGED_ITERATING;
65: X = snes->vec_sol;
66: F = snes->vec_func;
67: B = snes->vec_rhs;
68: XA = snes->vec_sol_update;
69: FA = snes->work[0];
70: D = snes->work[1];
72: /* work for the line search */
73: XM = snes->work[3];
74: FM = snes->work[4];
76: PetscObjectAMSTakeAccess((PetscObject)snes);
77: snes->iter = 0;
78: snes->norm = 0.;
79: PetscObjectAMSGrantAccess((PetscObject)snes);
81: /* initialization */
83: /* r = F(x) */
84: if (!snes->vec_func_init_set) {
85: SNESComputeFunction(snes,X,F);
86: if (snes->domainerror) {
87: snes->reason = SNES_DIVERGED_FUNCTION_DOMAIN;
88: return(0);
89: }
90: } else snes->vec_func_init_set = PETSC_FALSE;
92: if (!snes->norm_init_set) {
93: VecNorm(F,NORM_2,&fnorm);
94: if (PetscIsInfOrNanReal(fnorm)) {
95: snes->reason = SNES_DIVERGED_FNORM_NAN;
96: return(0);
97: }
98: } else {
99: fnorm = snes->norm_init;
100: snes->norm_init_set = PETSC_FALSE;
101: }
102: fminnorm = fnorm;
104: PetscObjectAMSTakeAccess((PetscObject)snes);
105: snes->norm = fnorm;
106: PetscObjectAMSGrantAccess((PetscObject)snes);
107: SNESLogConvergenceHistory(snes,fnorm,0);
108: SNESMonitor(snes,0,fnorm);
109: (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
110: if (snes->reason) return(0);
112: k_restart = 0;
113: l = 0;
114: for (k=1; k < snes->max_its+1; k++) {
115: /* select which vector of the stored subspace will be updated */
116: ivec = k_restart % ngmres->msize;
117: if (snes->pc && snes->pcside == PC_RIGHT) {
118: VecCopy(X,XM);
119: SNESSetInitialFunction(snes->pc,F);
120: SNESSetInitialFunctionNorm(snes->pc,fnorm);
122: PetscLogEventBegin(SNES_NPCSolve,snes->pc,XM,B,0);
123: SNESSolve(snes->pc,B,XM);
124: PetscLogEventEnd(SNES_NPCSolve,snes->pc,XM,B,0);
126: SNESGetConvergedReason(snes->pc,&reason);
127: if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
128: snes->reason = SNES_DIVERGED_INNER;
129: return(0);
130: }
131: SNESGetFunction(snes->pc,&FPC,NULL,NULL);
132: VecCopy(FPC,FM);
133: SNESGetFunctionNorm(snes->pc,&fMnorm);
134: if (ngmres->andersonBeta != 1.0) {
135: VecAXPBY(XM,(1.0 - ngmres->andersonBeta),ngmres->andersonBeta,X);
136: }
137: } else {
138: VecCopy(F,FM);
139: VecCopy(X,XM);
140: VecAXPY(XM,-ngmres->andersonBeta,FM);
141: fMnorm = fnorm;
142: }
144: SNESNGMRESFormCombinedSolution_Private(snes,l,XM,FM,fMnorm,X,XA,FA);
145: if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE) {
146: SNESNGMRESCalculateDifferences_Private(snes,l,X,F,XM,FM,XA,FA,D,&dnorm,&dminnorm,NULL);
147: SNESNGMRESSelectRestart_Private(snes,l,fnorm,dnorm,fminnorm,dminnorm,&selectRestart);
148: /* if the restart conditions persist for more than restart_it iterations, restart. */
149: if (selectRestart) restart_count++;
150: else restart_count = 0;
151: } else if (ngmres->restart_type == SNES_NGMRES_RESTART_PERIODIC) {
152: if (k_restart > ngmres->restart_periodic) {
153: if (ngmres->monitor) PetscViewerASCIIPrintf(ngmres->monitor,"periodic restart after %D iterations\n",k_restart);
154: restart_count = ngmres->restart_it;
155: }
156: }
157: /* restart after restart conditions have persisted for a fixed number of iterations */
158: if (restart_count >= ngmres->restart_it) {
159: if (ngmres->monitor) {
160: PetscViewerASCIIPrintf(ngmres->monitor,"Restarted at iteration %d\n",k_restart);
161: }
162: restart_count = 0;
163: k_restart = 0;
164: l = 0;
165: } else {
166: if (l < ngmres->msize) l++;
167: k_restart++;
168: SNESNGMRESUpdateSubspace_Private(snes,ivec,l,FM,fnorm,XM);
169: }
171: VecNorm(FA,NORM_2,&fnorm);
172: if (fminnorm > fnorm) fminnorm = fnorm;
174: VecCopy(XA,X);
175: VecCopy(FA,F);
177: PetscObjectAMSTakeAccess((PetscObject)snes);
178: snes->iter = k;
179: snes->norm = fnorm;
180: PetscObjectAMSGrantAccess((PetscObject)snes);
181: SNESLogConvergenceHistory(snes,snes->norm,snes->iter);
182: SNESMonitor(snes,snes->iter,snes->norm);
183: (*snes->ops->converged)(snes,snes->iter,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
184: if (snes->reason) return(0);
185: }
186: snes->reason = SNES_DIVERGED_MAX_IT;
187: return(0);
188: }
190: /*MC
191: SNESAnderson - Anderson Mixing method.
193: Level: beginner