xref: /petsc/src/snes/interface/snesj2.c (revision 97eb6af2371cd04b71d75d3ff32186e92fb81114)

#include <private/snesimpl.h>    /*I  "petscsnes.h"  I*/

#undef __FUNCT__
#define __FUNCT__ "SNESDefaultComputeJacobianColor"
/*@C
    SNESDefaultComputeJacobianColor - Computes the Jacobian using
    finite differences and coloring to exploit matrix sparsity.

    Collective on SNES

    Input Parameters:
+   snes - nonlinear solver object
.   x1 - location at which to evaluate Jacobian
-   ctx - coloring context, where ctx must have type MatFDColoring,
          as created via MatFDColoringCreate()

    Output Parameters:
+   J - Jacobian matrix (not altered in this routine)
.   B - newly computed Jacobian matrix to use with preconditioner (generally the same as J)
-   flag - flag indicating whether the matrix sparsity structure has changed

    Level: intermediate

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

.seealso: SNESSetJacobian(), SNESTestJacobian(), SNESDefaultComputeJacobian()
          MatFDColoringCreate(), MatFDColoringSetFunction()

@*/

PetscErrorCode  SNESDefaultComputeJacobianColor(SNES snes,Vec x1,Mat *J,Mat *B,MatStructure *flag,void *ctx)
{
  MatFDColoring  color = (MatFDColoring) ctx;
  PetscErrorCode ierr;
  Vec            f;
  PetscErrorCode (*ff)(void),(*fd)(void);

  PetscFunctionBegin;
  PetscValidHeaderSpecific(color,MAT_FDCOLORING_CLASSID,6);
  *flag = SAME_NONZERO_PATTERN;
  ierr  = SNESGetFunction(snes,&f,(PetscErrorCode (**)(SNES,Vec,Vec,void*))&ff,0);CHKERRQ(ierr);
  ierr  = MatFDColoringGetFunction(color,&fd,PETSC_NULL);CHKERRQ(ierr);
  if (fd == ff && !snes->vec_rhs) { /* reuse function value computed in SNES */
    ierr  = MatFDColoringSetF(color,f);CHKERRQ(ierr);
  }
  ierr  = MatFDColoringApply(*B,color,x1,flag,snes);CHKERRQ(ierr);
  if (*J != *B) {
    ierr = MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
    ierr = MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}