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

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

 28:   if (snes->nwork < 3) {
 29:     SNESSetWorkVecs(snes,3);
 30:   }
 31:   W = snes->work[0];
 32:   G = snes->work[1];
 33:   F = snes->work[2];
 34:   VecGetOwnershipRange(X,&s,NULL);
 35:   SNESNGSGetTolerances(snes,&atol,&rtol,&stol,&its);
 36:   SNESGetDM(snes,&dm);
 37:   SNESGetFunction(snes,NULL,&func,&fctx);
 38:   if (!coloring) {
 39:     /* create the coloring */
 40:     DMHasColoring(dm,&flg);
 41:     if (flg && !mat) {
 42:       DMCreateColoring(dm,IS_COLORING_GLOBAL,&coloring);
 43:     } else {
 44:       if (!snes->jacobian) {SNESSetUpMatrices(snes);}
 45:       MatColoringCreate(snes->jacobian,&mc);
 46:       MatColoringSetDistance(mc,1);
 47:       MatColoringSetFromOptions(mc);
 48:       MatColoringApply(mc,&coloring);
 49:       MatColoringDestroy(&mc);
 50:     }
 51:     gs->coloring = coloring;
 52:   }
 53:   ISColoringGetIS(coloring,PETSC_USE_POINTER,&ncolors,&coloris);
 54:   VecEqual(X,snes->vec_sol,&equal);
 55:   if (equal && snes->normschedule == SNES_NORM_ALWAYS) {
 56:     /* assume that the function is already computed */
 57:     VecCopy(snes->vec_func,F);
 58:   } else {
 59:     PetscLogEventBegin(SNES_NGSFuncEval,snes,X,B,0);
 60:     (*func)(snes,X,F,fctx);
 61:     PetscLogEventEnd(SNES_NGSFuncEval,snes,X,B,0);
 62:     if (B) {VecAXPY(F,-1.0,B);}
 63:   }
 64:   for (i=0;i<ncolors;i++) {
 65:     ISGetIndices(coloris[i],&idx);
 66:     ISGetLocalSize(coloris[i],&size);
 67:     VecCopy(X,W);
 68:     VecGetArray(W,&wa);
 69:     for (j=0;j<size;j++) {
 70:       wa[idx[j]-s] += h;
 71:     }
 72:     VecRestoreArray(W,&wa);
 73:     PetscLogEventBegin(SNES_NGSFuncEval,snes,X,B,0);
 74:     (*func)(snes,W,G,fctx);
 75:     PetscLogEventEnd(SNES_NGSFuncEval,snes,X,B,0);
 76:     if (B) {VecAXPY(G,-1.0,B);}
 77:     for (k=0;k<its;k++) {
 78:       dxt = 0.;
 79:       xt = 0.;
 80:       ft = 0.;
 81:       VecGetArray(W,&wa);
 82:       VecGetArray(X,&xa);
 83:       VecGetArrayRead(F,&fa);
 84:       VecGetArrayRead(G,&ga);
 85:       for (j=0;j<size;j++) {
 86:         f = fa[idx[j]-s];
 87:         x = xa[idx[j]-s];
 88:         g = ga[idx[j]-s];
 89:         w = wa[idx[j]-s];
 90:         if (PetscAbsScalar(g-f) > atol) {
 91:           /* This is equivalent to d = x - (h*f) / PetscRealPart(g-f) */
 92:           d = (x*g-w*f) / PetscRealPart(g-f);
 93:         } else {
 94:           d = x;
 95:         }
 96:         dxt += PetscRealPart(PetscSqr(d-x));
 97:         xt += PetscRealPart(PetscSqr(x));
 98:         ft += PetscRealPart(PetscSqr(f));
 99:         xa[idx[j]-s] = d;
100:       }
101:       VecRestoreArray(X,&xa);
102:       VecRestoreArrayRead(F,&fa);
103:       VecRestoreArrayRead(G,&ga);
104:       VecRestoreArray(W,&wa);

106:       if (k == 0) ft1 = PetscSqrtReal(ft);
107:       if (k<its-1) {
108:         isdone = PETSC_FALSE;
109:         if (stol*PetscSqrtReal(xt) > PetscSqrtReal(dxt)) isdone = PETSC_TRUE;
110:         if (PetscSqrtReal(ft) < atol) isdone = PETSC_TRUE;
111:         if (rtol*ft1 > PetscSqrtReal(ft)) isdone = PETSC_TRUE;
112:         MPIU_Allreduce(&isdone,&alldone,1,MPIU_BOOL,MPI_BAND,PetscObjectComm((PetscObject)snes));
113:         if (alldone) break;
114:       }
115:       if (i < ncolors-1 || k < its-1) {
116:         PetscLogEventBegin(SNES_NGSFuncEval,snes,X,B,0);
117:         (*func)(snes,X,F,fctx);
118:         PetscLogEventEnd(SNES_NGSFuncEval,snes,X,B,0);
119:         if (B) {VecAXPY(F,-1.0,B);}
120:       }
121:       if (k<its-1) {
122:         VecSwap(X,W);
123:         VecSwap(F,G);
124:       }
125:     }
126:   }
127:   ISColoringRestoreIS(coloring,PETSC_USE_POINTER,&coloris);
128:   return(0);
129: }