1 #include <../src/snes/impls/ngmres/snesngmres.h> /*I "petscsnes.h" I*/ 2 3 static PetscErrorCode SNESSetFromOptions_Anderson(SNES snes, PetscOptionItems *PetscOptionsObject) 4 { 5 SNES_NGMRES *ngmres = (SNES_NGMRES *)snes->data; 6 PetscBool monitor = PETSC_FALSE; 7 8 PetscFunctionBegin; 9 PetscOptionsHeadBegin(PetscOptionsObject, "SNES NGMRES options"); 10 PetscCall(PetscOptionsInt("-snes_anderson_m", "Number of directions", "SNES", ngmres->msize, &ngmres->msize, NULL)); 11 PetscCall(PetscOptionsReal("-snes_anderson_beta", "Mixing parameter", "SNES", ngmres->andersonBeta, &ngmres->andersonBeta, NULL)); 12 PetscCall(PetscOptionsInt("-snes_anderson_restart", "Iterations before forced restart", "SNES", ngmres->restart_periodic, &ngmres->restart_periodic, NULL)); 13 PetscCall(PetscOptionsInt("-snes_anderson_restart_it", "Tolerance iterations before restart", "SNES", ngmres->restart_it, &ngmres->restart_it, NULL)); 14 PetscCall(PetscOptionsEnum("-snes_anderson_restart_type", "Restart type", "SNESNGMRESSetRestartType", SNESNGMRESRestartTypes, (PetscEnum)ngmres->restart_type, (PetscEnum *)&ngmres->restart_type, NULL)); 15 PetscCall(PetscOptionsBool("-snes_anderson_monitor", "Monitor steps of Anderson Mixing", "SNES", ngmres->monitor ? PETSC_TRUE : PETSC_FALSE, &monitor, NULL)); 16 if (monitor) ngmres->monitor = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)); 17 PetscOptionsHeadEnd(); 18 PetscFunctionReturn(PETSC_SUCCESS); 19 } 20 21 static PetscErrorCode SNESSolve_Anderson(SNES snes) 22 { 23 SNES_NGMRES *ngmres = (SNES_NGMRES *)snes->data; 24 /* present solution, residual, and preconditioned residual */ 25 Vec X, F, B, D; 26 /* candidate linear combination answers */ 27 Vec XA, FA, XM, FM; 28 29 /* coefficients and RHS to the minimization problem */ 30 PetscReal fnorm, fMnorm, fAnorm; 31 PetscReal xnorm, ynorm; 32 PetscReal dnorm, dminnorm = 0.0, fminnorm; 33 PetscInt restart_count = 0; 34 PetscInt k, k_restart, l, ivec; 35 PetscBool selectRestart; 36 SNESConvergedReason reason; 37 38 PetscFunctionBegin; 39 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); 40 41 PetscCall(PetscCitationsRegister(SNESCitation, &SNEScite)); 42 /* variable initialization */ 43 snes->reason = SNES_CONVERGED_ITERATING; 44 X = snes->vec_sol; 45 F = snes->vec_func; 46 B = snes->vec_rhs; 47 XA = snes->work[2]; 48 FA = snes->work[0]; 49 D = snes->work[1]; 50 51 /* work for the line search */ 52 XM = snes->work[3]; 53 FM = snes->work[4]; 54 55 PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes)); 56 snes->iter = 0; 57 snes->norm = 0.; 58 PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes)); 59 60 /* initialization */ 61 62 /* r = F(x) */ 63 64 if (snes->npc && snes->npcside == PC_LEFT) { 65 PetscCall(SNESApplyNPC(snes, X, NULL, F)); 66 PetscCall(SNESGetConvergedReason(snes->npc, &reason)); 67 if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) { 68 snes->reason = SNES_DIVERGED_INNER; 69 PetscFunctionReturn(PETSC_SUCCESS); 70 } 71 PetscCall(VecNorm(F, NORM_2, &fnorm)); 72 } else { 73 if (!snes->vec_func_init_set) { 74 PetscCall(SNESComputeFunction(snes, X, F)); 75 } else snes->vec_func_init_set = PETSC_FALSE; 76 77 PetscCall(VecNorm(F, NORM_2, &fnorm)); 78 SNESCheckFunctionNorm(snes, fnorm); 79 } 80 fminnorm = fnorm; 81 82 PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes)); 83 snes->norm = fnorm; 84 PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes)); 85 PetscCall(SNESLogConvergenceHistory(snes, fnorm, 0)); 86 PetscCall(SNESConverged(snes, 0, 0.0, 0.0, fnorm)); 87 PetscCall(SNESMonitor(snes, 0, fnorm)); 88 if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS); 89 PetscCall(SNESNGMRESUpdateSubspace_Private(snes, 0, 0, F, fnorm, X)); 90 91 k_restart = 0; 92 l = 0; 93 ivec = 0; 94 for (k = 1; k < snes->max_its + 1; k++) { 95 /* Call general purpose update function */ 96 PetscTryTypeMethod(snes, update, snes->iter); 97 98 /* select which vector of the stored subspace will be updated */ 99 if (snes->npc && snes->npcside == PC_RIGHT) { 100 PetscCall(VecCopy(X, XM)); 101 PetscCall(SNESSetInitialFunction(snes->npc, F)); 102 103 PetscCall(PetscLogEventBegin(SNES_NPCSolve, snes->npc, XM, B, 0)); 104 PetscCall(SNESSolve(snes->npc, B, XM)); 105 PetscCall(PetscLogEventEnd(SNES_NPCSolve, snes->npc, XM, B, 0)); 106 107 PetscCall(SNESGetConvergedReason(snes->npc, &reason)); 108 if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) { 109 snes->reason = SNES_DIVERGED_INNER; 110 PetscFunctionReturn(PETSC_SUCCESS); 111 } 112 PetscCall(SNESGetNPCFunction(snes, FM, &fMnorm)); 113 PetscCall(VecAXPBY(XM, 1.0 - ngmres->andersonBeta, ngmres->andersonBeta, X)); 114 } else { 115 PetscCall(VecCopy(F, FM)); 116 PetscCall(VecWAXPY(XM, -ngmres->andersonBeta, FM, X)); 117 fMnorm = fnorm; 118 } 119 120 PetscCall(SNESNGMRESFormCombinedSolution_Private(snes, ivec, l, XM, FM, fMnorm, X, XA, FA)); 121 ivec = k_restart % ngmres->msize; 122 if (ngmres->restart_type == SNES_NGMRES_RESTART_DIFFERENCE) { 123 PetscCall(SNESNGMRESNorms_Private(snes, l, X, F, XM, FM, XA, FA, D, &dnorm, &dminnorm, NULL, NULL, NULL, &xnorm, &fAnorm, &ynorm)); 124 PetscCall(SNESNGMRESSelectRestart_Private(snes, l, snes->norm, fMnorm, fnorm, dnorm, fminnorm, dminnorm, &selectRestart)); 125 /* if the restart conditions persist for more than restart_it iterations, restart. */ 126 if (selectRestart) restart_count++; 127 else restart_count = 0; 128 } else if (ngmres->restart_type == SNES_NGMRES_RESTART_PERIODIC) { 129 PetscCall(SNESNGMRESNorms_Private(snes, l, X, F, XM, FM, XA, FA, D, NULL, NULL, NULL, NULL, NULL, &xnorm, &fAnorm, &ynorm)); 130 if (k_restart > ngmres->restart_periodic) { 131 if (ngmres->monitor) PetscCall(PetscViewerASCIIPrintf(ngmres->monitor, "periodic restart after %" PetscInt_FMT " iterations\n", k_restart)); 132 restart_count = ngmres->restart_it; 133 } 134 } else { 135 PetscCall(SNESNGMRESNorms_Private(snes, l, X, F, XM, FM, XA, FA, D, NULL, NULL, NULL, NULL, NULL, &xnorm, &fAnorm, &ynorm)); 136 } 137 /* restart after restart conditions have persisted for a fixed number of iterations */ 138 if (restart_count >= ngmres->restart_it) { 139 if (ngmres->monitor) PetscCall(PetscViewerASCIIPrintf(ngmres->monitor, "Restarted at iteration %" PetscInt_FMT "\n", k_restart)); 140 restart_count = 0; 141 k_restart = 0; 142 l = 0; 143 ivec = 0; 144 } else { 145 if (l < ngmres->msize) l++; 146 k_restart++; 147 PetscCall(SNESNGMRESUpdateSubspace_Private(snes, ivec, l, FM, fnorm, XM)); 148 } 149 150 fnorm = fAnorm; 151 if (fminnorm > fnorm) fminnorm = fnorm; 152 153 PetscCall(VecCopy(XA, X)); 154 PetscCall(VecCopy(FA, F)); 155 156 PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes)); 157 snes->iter = k; 158 snes->norm = fnorm; 159 snes->xnorm = xnorm; 160 snes->ynorm = ynorm; 161 PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes)); 162 PetscCall(SNESLogConvergenceHistory(snes, snes->norm, snes->iter)); 163 PetscCall(SNESConverged(snes, snes->iter, xnorm, ynorm, fnorm)); 164 PetscCall(SNESMonitor(snes, snes->iter, snes->norm)); 165 if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS); 166 } 167 snes->reason = SNES_DIVERGED_MAX_IT; 168 PetscFunctionReturn(PETSC_SUCCESS); 169 } 170 171 /*MC 172 SNESANDERSON - Implements the Anderson Mixing nonlinear solver {cite}`anderson1965`, {cite}`bruneknepleysmithtu15` 173 174 Level: beginner 175 176 Options Database Keys: 177 + -snes_anderson_m - Number of stored previous solutions and residuals 178 . -snes_anderson_beta - Anderson mixing parameter 179 . -snes_anderson_restart_type - Type of restart (see `SNESNGMRES`) 180 . -snes_anderson_restart_it - Number of iterations of restart conditions before restart 181 . -snes_anderson_restart - Number of iterations before periodic restart 182 - -snes_anderson_monitor - Prints relevant information about the Anderson mixing iteration 183 184 Notes: 185 The Anderson Mixing method combines m previous solutions into a minimum-residual solution by solving a small linearized 186 optimization problem at each iteration. 187 188 Very similar to the `SNESNGMRES` algorithm. 189 190 This algorithm ignores any Jacobian provided with `SNESSetJacobian()` 191 192 .seealso: [](ch_snes), `SNESNGMRES`, `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESType` 193 M*/ 194 195 PETSC_EXTERN PetscErrorCode SNESCreate_Anderson(SNES snes) 196 { 197 SNES_NGMRES *ngmres; 198 SNESLineSearch linesearch; 199 200 PetscFunctionBegin; 201 snes->ops->destroy = SNESDestroy_NGMRES; 202 snes->ops->setup = SNESSetUp_NGMRES; 203 snes->ops->setfromoptions = SNESSetFromOptions_Anderson; 204 snes->ops->view = SNESView_NGMRES; 205 snes->ops->solve = SNESSolve_Anderson; 206 snes->ops->reset = SNESReset_NGMRES; 207 208 snes->usesnpc = PETSC_TRUE; 209 snes->usesksp = PETSC_FALSE; 210 snes->npcside = PC_RIGHT; 211 212 snes->alwayscomputesfinalresidual = PETSC_TRUE; 213 214 PetscCall(PetscNew(&ngmres)); 215 snes->data = (void *)ngmres; 216 ngmres->msize = 30; 217 218 PetscCall(SNESParametersInitialize(snes)); 219 PetscObjectParameterSetDefault(snes, max_funcs, 30000); 220 PetscObjectParameterSetDefault(snes, max_its, 10000); 221 222 PetscCall(SNESGetLineSearch(snes, &linesearch)); 223 if (!((PetscObject)linesearch)->type_name) PetscCall(SNESLineSearchSetType(linesearch, SNESLINESEARCHBASIC)); 224 225 ngmres->additive_linesearch = NULL; 226 ngmres->approxfunc = PETSC_FALSE; 227 ngmres->restart_type = SNES_NGMRES_RESTART_NONE; 228 ngmres->restart_it = 2; 229 ngmres->restart_periodic = 30; 230 ngmres->gammaA = 2.0; 231 ngmres->gammaC = 2.0; 232 ngmres->deltaB = 0.9; 233 ngmres->epsilonB = 0.1; 234 235 ngmres->andersonBeta = 1.0; 236 PetscFunctionReturn(PETSC_SUCCESS); 237 } 238