xref: /petsc/src/ksp/pc/impls/mg/fmg.c (revision 6849ba73f22fecb8f92ef896a42e4e8bd4cd6965)

/*
     Full multigrid using either additive or multiplicative V or W cycle
*/
#include "src/ksp/pc/impls/mg/mgimpl.h"

EXTERN PetscErrorCode MGMCycle_Private(MG *,PetscTruth*);

/*
       MGFCycle_Private - Given an MG structure created with MGCreate() runs
               full multigrid.

    Iput Parameters:
.   mg - structure created with MGCreate().

    Note: This may not be what others call full multigrid. What we
          do is restrict the rhs to all levels, then starting
          on the coarsest level work our way up generating
          initial guess for the next level. This provides an
          improved preconditioner but not a great improvement.
*/
#undef __FUNCT__
#define __FUNCT__ "MGFCycle_Private"
PetscErrorCode MGFCycle_Private(MG *mg)
{
  PetscErrorCode ierr;
  int    i,l = mg[0]->levels;
  PetscScalar zero = 0.0;

  PetscFunctionBegin;
  /* restrict the RHS through all levels to coarsest. */
  for (i=l-1; i>0; i--){
    ierr = MatRestrict(mg[i]->restrct,mg[i]->b,mg[i-1]->b);CHKERRQ(ierr);
  }

  /* work our way up through the levels */
  ierr = VecSet(&zero,mg[0]->x);CHKERRQ(ierr);
  for (i=0; i<l-1; i++) {
    ierr = MGMCycle_Private(&mg[i],PETSC_NULL);CHKERRQ(ierr);
    ierr = MatInterpolate(mg[i+1]->interpolate,mg[i]->x,mg[i+1]->x);CHKERRQ(ierr);
  }
  ierr = MGMCycle_Private(&mg[l-1],PETSC_NULL);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*
       MGKCycle_Private - Given an MG structure created with MGCreate() runs
               full Kascade MG solve.

    Iput Parameters:
.   mg - structure created with MGCreate().

    Note: This may not be what others call Kascadic MG.
*/
#undef __FUNCT__
#define __FUNCT__ "MGKCycle_Private"
PetscErrorCode MGKCycle_Private(MG *mg)
{
  PetscErrorCode ierr;
  int    i,l = mg[0]->levels;
  PetscScalar zero = 0.0;

  PetscFunctionBegin;
  /* restrict the RHS through all levels to coarsest. */
  for (i=l-1; i>0; i--){
    ierr = MatRestrict(mg[i]->restrct,mg[i]->b,mg[i-1]->b);CHKERRQ(ierr);
  }

  /* work our way up through the levels */
  ierr = VecSet(&zero,mg[0]->x);CHKERRQ(ierr);
  for (i=0; i<l-1; i++) {
    if (mg[i]->eventsolve) {ierr = PetscLogEventBegin(mg[i]->eventsolve,0,0,0,0);CHKERRQ(ierr);}
    ierr = KSPSolve(mg[i]->smoothd,mg[i]->b,mg[i]->x);CHKERRQ(ierr);
    if (mg[i]->eventsolve) {ierr = PetscLogEventEnd(mg[i]->eventsolve,0,0,0,0);CHKERRQ(ierr);}
    ierr = MatInterpolate(mg[i+1]->interpolate,mg[i]->x,mg[i+1]->x);CHKERRQ(ierr);
  }
  if (mg[l-1]->eventsolve) {ierr = PetscLogEventBegin(mg[l-1]->eventsolve,0,0,0,0);CHKERRQ(ierr);}
  ierr = KSPSolve(mg[l-1]->smoothd,mg[l-1]->b,mg[l-1]->x);CHKERRQ(ierr);
  if (mg[l-1]->eventsolve) {ierr = PetscLogEventEnd(mg[l-1]->eventsolve,0,0,0,0);CHKERRQ(ierr);}

  PetscFunctionReturn(0);
}