Date: 2025-03-28T21:11:07+00:00

Actual source code: gssecant.c

      1: #include <../src/snes/impls/gs/gsimpl.h>

      3: PETSC_EXTERN PetscErrorCode SNESComputeNGSDefaultSecant(SNES snes, Vec X, Vec B, void *ctx)
      4: {
      5:   SNES_NGS          *gs = (SNES_NGS *)snes->data;
      6:   PetscInt           i, j, k, ncolors;
      7:   DM                 dm;
      8:   PetscBool          flg;
      9:   ISColoring         coloring = gs->coloring;
     10:   MatColoring        mc;
     11:   Vec                W, G, F;
     12:   PetscScalar        h = gs->h;
     13:   IS                *coloris;
     14:   PetscScalar        f, g, x, w, d;
     15:   PetscReal          dxt, xt, ft, ft1 = 0;
     16:   const PetscInt    *idx;
     17:   PetscInt           size, s;
     18:   PetscReal          atol, rtol, stol;
     19:   PetscInt           its;
     20:   SNESFunctionFn    *func;
     21:   void              *fctx;
     22:   PetscBool          mat = gs->secant_mat, equal, isdone, alldone;
     23:   PetscScalar       *xa, *wa;
     24:   const PetscScalar *fa, *ga;

     26:   PetscFunctionBegin;
     27:   if (snes->nwork < 3) PetscCall(SNESSetWorkVecs(snes, 3));
     28:   W = snes->work[0];
     29:   G = snes->work[1];
     30:   F = snes->work[2];
     31:   PetscCall(VecGetOwnershipRange(X, &s, NULL));
     32:   PetscCall(SNESNGSGetTolerances(snes, &atol, &rtol, &stol, &its));
     33:   PetscCall(SNESGetDM(snes, &dm));
     34:   PetscCall(SNESGetFunction(snes, NULL, &func, &fctx));
     35:   if (!coloring) {
     36:     /* create the coloring */
     37:     PetscCall(DMHasColoring(dm, &flg));
     38:     if (flg && !mat) {
     39:       PetscCall(DMCreateColoring(dm, IS_COLORING_GLOBAL, &coloring));
     40:     } else {
     41:       if (!snes->jacobian) PetscCall(SNESSetUpMatrices(snes));
     42:       PetscCall(MatColoringCreate(snes->jacobian, &mc));
     43:       PetscCall(MatColoringSetDistance(mc, 1));
     44:       PetscCall(MatColoringSetFromOptions(mc));
     45:       PetscCall(MatColoringApply(mc, &coloring));
     46:       PetscCall(MatColoringDestroy(&mc));
     47:     }
     48:     gs->coloring = coloring;
     49:   }
     50:   PetscCall(ISColoringGetIS(coloring, PETSC_USE_POINTER, &ncolors, &coloris));
     51:   PetscCall(VecEqual(X, snes->vec_sol, &equal));
     52:   if (equal && snes->normschedule == SNES_NORM_ALWAYS) {
     53:     /* assume that the function is already computed */
     54:     PetscCall(VecCopy(snes->vec_func, F));
     55:   } else {
     56:     PetscCall(PetscLogEventBegin(SNES_NGSFuncEval, snes, X, B, 0));
     57:     PetscCall((*func)(snes, X, F, fctx));
     58:     PetscCall(PetscLogEventEnd(SNES_NGSFuncEval, snes, X, B, 0));
     59:     if (B) PetscCall(VecAXPY(F, -1.0, B));
     60:   }
     61:   for (i = 0; i < ncolors; i++) {
     62:     PetscCall(ISGetIndices(coloris[i], &idx));
     63:     PetscCall(ISGetLocalSize(coloris[i], &size));
     64:     PetscCall(VecCopy(X, W));
     65:     PetscCall(VecGetArray(W, &wa));
     66:     for (j = 0; j < size; j++) wa[idx[j] - s] += h;
     67:     PetscCall(VecRestoreArray(W, &wa));
     68:     PetscCall(PetscLogEventBegin(SNES_NGSFuncEval, snes, X, B, 0));
     69:     PetscCall((*func)(snes, W, G, fctx));
     70:     PetscCall(PetscLogEventEnd(SNES_NGSFuncEval, snes, X, B, 0));
     71:     if (B) PetscCall(VecAXPY(G, -1.0, B));
     72:     for (k = 0; k < its; k++) {
     73:       dxt = 0.;
     74:       xt  = 0.;
     75:       ft  = 0.;
     76:       PetscCall(VecGetArray(W, &wa));
     77:       PetscCall(VecGetArray(X, &xa));
     78:       PetscCall(VecGetArrayRead(F, &fa));
     79:       PetscCall(VecGetArrayRead(G, &ga));
     80:       for (j = 0; j < size; j++) {
     81:         f = fa[idx[j] - s];
     82:         x = xa[idx[j] - s];
     83:         g = ga[idx[j] - s];
     84:         w = wa[idx[j] - s];
     85:         if (PetscAbsScalar(g - f) > atol) {
     86:           /* This is equivalent to d = x - (h*f) / PetscRealPart(g-f) */
     87:           d = (x * g - w * f) / PetscRealPart(g - f);
     88:         } else {
     89:           d = x;
     90:         }
     91:         dxt += PetscRealPart(PetscSqr(d - x));
     92:         xt += PetscRealPart(PetscSqr(x));
     93:         ft += PetscRealPart(PetscSqr(f));
     94:         xa[idx[j] - s] = d;
     95:       }
     96:       PetscCall(VecRestoreArray(X, &xa));
     97:       PetscCall(VecRestoreArrayRead(F, &fa));
     98:       PetscCall(VecRestoreArrayRead(G, &ga));
     99:       PetscCall(VecRestoreArray(W, &wa));

    101:       if (k == 0) ft1 = PetscSqrtReal(ft);
    102:       if (k < its - 1) {
    103:         isdone = PETSC_FALSE;
    104:         if (stol * PetscSqrtReal(xt) > PetscSqrtReal(dxt)) isdone = PETSC_TRUE;
    105:         if (PetscSqrtReal(ft) < atol) isdone = PETSC_TRUE;
    106:         if (rtol * ft1 > PetscSqrtReal(ft)) isdone = PETSC_TRUE;
    107:         PetscCallMPI(MPIU_Allreduce(&isdone, &alldone, 1, MPIU_BOOL, MPI_BAND, PetscObjectComm((PetscObject)snes)));
    108:         if (alldone) break;
    109:       }
    110:       if (i < ncolors - 1 || k < its - 1) {
    111:         PetscCall(PetscLogEventBegin(SNES_NGSFuncEval, snes, X, B, 0));
    112:         PetscCall((*func)(snes, X, F, fctx));
    113:         PetscCall(PetscLogEventEnd(SNES_NGSFuncEval, snes, X, B, 0));
    114:         if (B) PetscCall(VecAXPY(F, -1.0, B));
    115:       }
    116:       if (k < its - 1) {
    117:         PetscCall(VecSwap(X, W));
    118:         PetscCall(VecSwap(F, G));
    119:       }
    120:     }
    121:   }
    122:   PetscCall(ISColoringRestoreIS(coloring, PETSC_USE_POINTER, &coloris));
    123:   PetscFunctionReturn(PETSC_SUCCESS);
    124: }