1: /*$Id: snesj2.c,v 1.31 2001/06/21 21:18:37 bsmith Exp $*/

 3:  #include src/mat/matimpl.h
 4:  #include src/snes/snesimpl.h

  6: #undef __FUNCT__  
  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: int SNESDefaultComputeJacobianColor(SNES snes,Vec x1,Mat *J,Mat *B,MatStructure *flag,void *ctx)
 38: {
 39:   MatFDColoring color = (MatFDColoring) ctx;
 40:   int           ierr,freq,it;
 41:   Vec           f;

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

 47:   if ((freq > 1) && ((it % freq))) {
 48:     PetscLogInfo(color,"SNESDefaultComputeJacobianColor:Skipping Jacobian recomputation, it %d, freq %dn",it,freq);
 49:     *flag = SAME_PRECONDITIONER;
 50:   } else {
 51:     PetscLogInfo(color,"SNESDefaultComputeJacobianColor:Computing Jacobian, it %d, freq %dn",it,freq);
 52:     *flag = SAME_NONZERO_PATTERN;
 53:     ierr  = SNESGetFunction(snes,&f,0,0);
 54:     ierr  = MatFDColoringSetF(color,f);
 55:     ierr  = PetscLogEventBegin(SNES_FunctionEval,snes,x1,0,0);
 56:     PetscStackPush("SNES user function");
 57:     ierr  = MatFDColoringApply(*B,color,x1,flag,snes);
 58:     PetscStackPop;
 59:     snes->nfuncs++;
 60:     PetscLogEventEnd(SNES_FunctionEval,snes,x1,0,0);
 61:   }
 62:   if (J != B) {
 63:     MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);
 64:     MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);
 65:   }
 66:   return(0);
 67: }