Actual source code: snesj2.c
1: #define PETSCSNES_DLL
3: #include src/mat/matimpl.h
4: #include src/snes/snesimpl.h
8: /*@C
9: SNESDefaultComputeJacobianColor - Computes the Jacobian using
10: finite differences and coloring to exploit matrix sparsity.
11:
12: Collective on SNES
14: Input Parameters:
15: + snes - nonlinear solver object
16: . x1 - location at which to evaluate Jacobian
17: - ctx - coloring context, where ctx must have type MatFDColoring,
18: as created via MatFDColoringCreate()
20: Output Parameters:
21: + J - Jacobian matrix (not altered in this routine)
22: . B - newly computed Jacobian matrix to use with preconditioner (generally the same as J)
23: - flag - flag indicating whether the matrix sparsity structure has changed
25: Options Database Keys:
26: . -mat_fd_coloring_freq <freq> - Activates SNESDefaultComputeJacobianColor()
28: Level: intermediate
30: .keywords: SNES, finite differences, Jacobian, coloring, sparse
32: .seealso: SNESSetJacobian(), SNESTestJacobian(), SNESDefaultComputeJacobian()
33: TSDefaultComputeJacobianColor(), MatFDColoringCreate(),
34: MatFDColoringSetFunction()
36: @*/
37: PetscErrorCode PETSCSNES_DLLEXPORT SNESDefaultComputeJacobianColor(SNES snes,Vec x1,Mat *J,Mat *B,MatStructure *flag,void *ctx)
38: {
39: MatFDColoring color = (MatFDColoring) ctx;
41: PetscInt freq,it;
42: Vec f;
43: PetscErrorCode (*ff)(void),(*fd)(void);
46: MatFDColoringGetFrequency(color,&freq);
47: SNESGetIterationNumber(snes,&it);
49: if ((freq > 1) && ((it % freq))) {
50: PetscInfo2(color,"Skipping Jacobian recomputation, it %D, freq %D\n",it,freq);
51: *flag = SAME_PRECONDITIONER;
52: } else {
53: PetscInfo2(color,"Computing Jacobian, it %D, freq %D\n",it,freq);
54: *flag = SAME_NONZERO_PATTERN;
55: SNESGetFunction(snes,&f,(PetscErrorCode (**)(SNES,Vec,Vec,void*))&ff,0);
56: MatFDColoringGetFunction(color,&fd,PETSC_NULL);
57: if (fd == ff) { /* reuse function value computed in SNES */
58: MatFDColoringSetF(color,f);
59: }
60: MatFDColoringApply(*B,color,x1,flag,snes);
61: }
62: if (*J != *B) {
63: MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);
64: MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);
65: }
66: return(0);
67: }