Actual source code: snesj2.c

  1: #define PETSCSNES_DLL

 3:  #include private/matimpl.h
 4:  #include private/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:     Level: intermediate

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

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

 33: @*/

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

 43:   *flag = SAME_NONZERO_PATTERN;
 44:   SNESGetFunction(snes,&f,(PetscErrorCode (**)(SNES,Vec,Vec,void*))&ff,0);
 45:   MatFDColoringGetFunction(color,&fd,PETSC_NULL);
 46:   if (fd == ff) { /* reuse function value computed in SNES */
 47:     MatFDColoringSetF(color,f);
 48:   }
 49:   MatFDColoringApply(*B,color,x1,flag,snes);
 50:   if (*J != *B) {
 51:     MatAssemblyBegin(*J,MAT_FINAL_ASSEMBLY);
 52:     MatAssemblyEnd(*J,MAT_FINAL_ASSEMBLY);
 53:   }
 54:   return(0);
 55: }