Actual source code: snesj2.c
petsc-3.10.5 2019-03-28
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      2:  #include <petsc/private/snesimpl.h>
      3:  #include <petscdm.h>

      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: }

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

     18:     Collective on SNES

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

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

     29:     Level: intermediate

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

     38:     Notes:
     39:     If the coloring is not provided through the context, this will first try to get the
     40:         coloring from the DM.  If the DM type has no coloring routine, then it will try to
     41:         get the coloring from the matrix.  This requires that the matrix have nonzero entries
     42:         precomputed.

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

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

     49: @*/

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

     63:   if (!color) {PetscObjectQuery((PetscObject)B,"SNESMatFDColoring",(PetscObject*)&color);}

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

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