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;

     45:   MatFDColoringGetFrequency(color,&freq);
     46:   SNESGetIterationNumber(snes,&it);

     48:   if ((freq > 1) && ((it % freq))) {
     49:     PetscLogInfo((color,"SNESDefaultComputeJacobianColor:Skipping Jacobian recomputation, it %D, freq %D\n",it,freq));
     50:     *flag = SAME_PRECONDITIONER;
     51:   } else {
     52:     PetscLogInfo((color,"SNESDefaultComputeJacobianColor:Computing Jacobian, it %D, freq %D\n",it,freq));
     53:     *flag = SAME_NONZERO_PATTERN;
     54:     SNESGetFunction(snes,&f,0,0);
     55:     MatFDColoringSetF(color,f);
     56:     MatFDColoringApply(*B,color,x1,flag,snes);
     57:   }
     58:   if (*J != *B) {
     59:     MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);
     60:     MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);
     61:   }
     62:   return(0);
     63: }