2: #include <petsc/private/snesimpl.h>    /*I  "petscsnes.h"  I*/
  3: #include <petscdm.h>                   /*I  "petscdm.h"    I*/

  7: /*@C
  8:     SNESComputeJacobianDefaultColor - Computes the Jacobian using
  9:     finite differences and coloring to exploit matrix sparsity.

 11:     Collective on SNES

 13:     Input Parameters:
 14: +   snes - nonlinear solver object
 15: .   x1 - location at which to evaluate Jacobian
 16: -   ctx - MatFDColoring context or NULL

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

 22:     Level: intermediate

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

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

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

 38: .seealso: SNESSetJacobian(), SNESTestJacobian(), SNESComputeJacobianDefault()
 39:           MatFDColoringCreate(), MatFDColoringSetFunction()

 41: @*/

 43: PetscErrorCode  SNESComputeJacobianDefaultColor(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
 44: {
 45:   MatFDColoring  color = (MatFDColoring)ctx;
 47:   DM             dm;
 48:   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
 49:   Vec            F;
 50:   void           *funcctx;
 51:   MatColoring    mc;
 52:   ISColoring     iscoloring;
 53:   PetscBool      hascolor;
 54:   PetscBool      solvec,matcolor = PETSC_FALSE;

 58:   else {PetscObjectQuery((PetscObject)B,"SNESMatFDColoring",(PetscObject*)&color);}
 59:   SNESGetFunction(snes,&F,&func,&funcctx);
 60:   if (!color) {
 61:     SNESGetDM(snes,&dm);
 62:     DMHasColoring(dm,&hascolor);
 63:     matcolor = PETSC_FALSE;
 64:     PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_fd_color_use_mat",&matcolor,NULL);
 65:     if (hascolor && !matcolor) {
 66:       DMCreateColoring(dm,IS_COLORING_GLOBAL,&iscoloring);
 67:       MatFDColoringCreate(B,iscoloring,&color);
 68:       MatFDColoringSetFunction(color,(PetscErrorCode (*)(void))func,funcctx);
 69:       MatFDColoringSetFromOptions(color);
 70:       MatFDColoringSetUp(B,iscoloring,color);
 71:       ISColoringDestroy(&iscoloring);
 72:     } else {
 73:       MatColoringCreate(B,&mc);
 74:       MatColoringSetDistance(mc,2);
 75:       MatColoringSetType(mc,MATCOLORINGSL);
 76:       MatColoringSetFromOptions(mc);
 77:       MatColoringApply(mc,&iscoloring);
 78:       MatColoringDestroy(&mc);
 79:       MatFDColoringCreate(B,iscoloring,&color);
 80:       MatFDColoringSetFunction(color,(PetscErrorCode (*)(void))func,(void*)funcctx);
 81:       MatFDColoringSetFromOptions(color);
 82:       MatFDColoringSetUp(B,iscoloring,color);
 83:       ISColoringDestroy(&iscoloring);
 84:     }
 85:     PetscObjectCompose((PetscObject)B,"SNESMatFDColoring",(PetscObject)color);
 86:     PetscObjectDereference((PetscObject)color);
 87:   }

 89:   /* F is only usable if there is no RHS on the SNES and the full solution corresponds to x1 */
 90:   VecEqual(x1,snes->vec_sol,&solvec);
 91:   if (!snes->vec_rhs && solvec) {
 92:     MatFDColoringSetF(color,F);
 93:   }
 94:   MatFDColoringApply(B,color,x1,snes);
 95:   if (J != B) {
 96:     MatAssemblyBegin(J,MAT_FINAL_ASSEMBLY);
 97:     MatAssemblyEnd(J,MAT_FINAL_ASSEMBLY);
 98:   }
 99:   return(0);
100: }