Actual source code: snesj2.c

  1: #define PETSCSNES_DLL

 3:  #include private/snesimpl.h

  7: /*@C
  8:     SNESDefaultComputeJacobianColor - Computes the Jacobian using
  9:     finite differences and coloring to exploit matrix sparsity. 
 10:   
 11:     Collective on SNES

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

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

 24:     Level: intermediate

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

 28: .seealso: SNESSetJacobian(), SNESTestJacobian(), SNESDefaultComputeJacobian()
 29:           TSDefaultComputeJacobianColor(), MatFDColoringCreate(),
 30:           MatFDColoringSetFunction()

 32: @*/

 34: PetscErrorCode  SNESDefaultComputeJacobianColor(SNES snes,Vec x1,Mat *J,Mat *B,MatStructure *flag,void *ctx)
 35: {
 36:   MatFDColoring  color = (MatFDColoring) ctx;
 38:   Vec            f;
 39:   PetscErrorCode (*ff)(void),(*fd)(void);

 42:   *flag = SAME_NONZERO_PATTERN;
 43:   SNESGetFunction(snes,&f,(PetscErrorCode (**)(SNES,Vec,Vec,void*))&ff,0);
 44:   MatFDColoringGetFunction(color,&fd,PETSC_NULL);
 45:   if (fd == ff) { /* reuse function value computed in SNES */
 46:     MatFDColoringSetF(color,f);
 47:   }
 48:   MatFDColoringApply(*B,color,x1,flag,snes);
 49:   if (*J != *B) {
 50:     MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);
 51:     MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);
 52:   }
 53:   return(0);
 54: }