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

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

 31: .seealso: SNESSetJacobian(), SNESTestJacobian(), SNESComputeJacobianDefault()
 32:           MatFDColoringCreate(), MatFDColoringSetFunction()

 34: @*/

 36: PetscErrorCode  SNESComputeJacobianDefaultColor(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
 37: {
 38:   MatFDColoring  color = (MatFDColoring)ctx;
 40:   DM             dm;
 41:   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
 42:   Vec            F;
 43:   void           *funcctx;
 44:   MatColoring    mc;
 45:   ISColoring     iscoloring;
 46:   PetscBool      hascolor;
 47:   PetscBool      solvec,matcolor = PETSC_FALSE;

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

 82:   /* F is only usable if there is no RHS on the SNES and the full solution corresponds to x1 */
 83:   VecEqual(x1,snes->vec_sol,&solvec);
 84:   if (!snes->vec_rhs && solvec) {
 85:     MatFDColoringSetF(color,F);
 86:   }
 87:   MatFDColoringApply(B,color,x1,snes);
 88:   if (J != B) {
 89:     MatAssemblyBegin(J,MAT_FINAL_ASSEMBLY);
 90:     MatAssemblyEnd(J,MAT_FINAL_ASSEMBLY);
 91:   }
 92:   return(0);
 93: }