Actual source code: snesj2.c
petsc-3.7.1 2016-05-15
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      2: #include <petsc/private/snesimpl.h>    /*I  "petscsnes.h"  I*/
      3: #include <petscdm.h>                   /*I  "petscdm.h"    I*/

      5: /*
      6:    MatFDColoringSetFunction() takes a function with four arguments, we want to use SNESComputeFunction()
      7:    since it logs function computation information.
      8: */
      9: static PetscErrorCode SNESComputeFunctionCtx(SNES snes,Vec x,Vec f,void *ctx)
     10: {
     11:   return SNESComputeFunction(snes,x,f);
     12: }

     16: /*@C
     17:     SNESComputeJacobianDefaultColor - Computes the Jacobian using
     18:     finite differences and coloring to exploit matrix sparsity.

     20:     Collective on SNES

     22:     Input Parameters:
     23: +   snes - nonlinear solver object
     24: .   x1 - location at which to evaluate Jacobian
     25: -   ctx - MatFDColoring context or NULL

     27:     Output Parameters:
     28: +   J - Jacobian matrix (not altered in this routine)
     29: -   B - newly computed Jacobian matrix to use with preconditioner (generally the same as J)

     31:     Level: intermediate

     33:    Options Database Key:
     34: +  -snes_fd_color_use_mat - use a matrix coloring from the explicit matrix nonzero pattern instead of from the DM providing the matrix
     35: .  -snes_fd_color - Activates SNESComputeJacobianDefaultColor() in SNESSetFromOptions()
     36: .  -mat_fd_coloring_err <err> - Sets <err> (square root of relative error in the function)
     37: .  -mat_fd_coloring_umin <umin> - Sets umin, the minimum allowable u-value magnitude
     38: -  -mat_fd_type - Either wp or ds (see MATMFFD_WP or MATMFFD_DS)

     40:     Notes: If the coloring is not provided through the context, this will first try to get the
     41:         coloring from the DM.  If the DM type has no coloring routine, then it will try to
     42:         get the coloring from the matrix.  This requires that the matrix have nonzero entries
     43:         precomputed.  This is discouraged, as MatColoringApply() is not parallel by default.

     45: .keywords: SNES, finite differences, Jacobian, coloring, sparse

     47: .seealso: SNESSetJacobian(), SNESTestJacobian(), SNESComputeJacobianDefault()
     48:           MatFDColoringCreate(), MatFDColoringSetFunction()

     50: @*/

     52: PetscErrorCode  SNESComputeJacobianDefaultColor(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
     53: {
     54:   MatFDColoring  color = (MatFDColoring)ctx;
     56:   DM             dm;
     57:   MatColoring    mc;
     58:   ISColoring     iscoloring;
     59:   PetscBool      hascolor;
     60:   PetscBool      solvec,matcolor = PETSC_FALSE;

     64:   else {PetscObjectQuery((PetscObject)B,"SNESMatFDColoring",(PetscObject*)&color);}

     66:   if (!color) {
     67:     SNESGetDM(snes,&dm);
     68:     DMHasColoring(dm,&hascolor);
     69:     matcolor = PETSC_FALSE;
     70:     PetscOptionsGetBool(((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_fd_color_use_mat",&matcolor,NULL);
     71:     if (hascolor && !matcolor) {
     72:       DMCreateColoring(dm,IS_COLORING_GLOBAL,&iscoloring);
     73:       MatFDColoringCreate(B,iscoloring,&color);
     74:       MatFDColoringSetFunction(color,(PetscErrorCode (*)(void))SNESComputeFunctionCtx,NULL);
     75:       MatFDColoringSetFromOptions(color);
     76:       MatFDColoringSetUp(B,iscoloring,color);
     77:       ISColoringDestroy(&iscoloring);
     78:     } else {
     79:       MatColoringCreate(B,&mc);
     80:       MatColoringSetDistance(mc,2);
     81:       MatColoringSetType(mc,MATCOLORINGSL);
     82:       MatColoringSetFromOptions(mc);
     83:       MatColoringApply(mc,&iscoloring);
     84:       MatColoringDestroy(&mc);
     85:       MatFDColoringCreate(B,iscoloring,&color);
     86:       MatFDColoringSetFunction(color,(PetscErrorCode (*)(void))SNESComputeFunctionCtx,NULL);
     87:       MatFDColoringSetFromOptions(color);
     88:       MatFDColoringSetUp(B,iscoloring,color);
     89:       ISColoringDestroy(&iscoloring);
     90:     }
     91:     PetscObjectCompose((PetscObject)B,"SNESMatFDColoring",(PetscObject)color);
     92:     PetscObjectDereference((PetscObject)color);
     93:   }

     95:   /* F is only usable if there is no RHS on the SNES and the full solution corresponds to x1 */
     96:   VecEqual(x1,snes->vec_sol,&solvec);
     97:   if (!snes->vec_rhs && solvec) {
     98:     Vec F;
     99:     SNESGetFunction(snes,&F,NULL,NULL);
    100:     MatFDColoringSetF(color,F);
    101:   }
    102:   MatFDColoringApply(B,color,x1,snes);
    103:   if (J != B) {
    104:     MatAssemblyBegin(J,MAT_FINAL_ASSEMBLY);
    105:     MatAssemblyEnd(J,MAT_FINAL_ASSEMBLY);
    106:   }
    107:   return(0);
    108: }