#include <petsc/private/pcimpl.h> /*I "petscpc.h" I*/

static PetscErrorCode PCApply_Mat(PC pc, Vec x, Vec y) {
  PetscFunctionBegin;
  PetscCall(MatMult(pc->pmat, x, y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCMatApply_Mat(PC pc, Mat X, Mat Y) {
  PetscFunctionBegin;
  PetscCall(MatMatMult(pc->pmat, X, MAT_REUSE_MATRIX, PETSC_DEFAULT, &Y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplyTranspose_Mat(PC pc, Vec x, Vec y) {
  PetscFunctionBegin;
  PetscCall(MatMultTranspose(pc->pmat, x, y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCDestroy_Mat(PC pc) {
  PetscFunctionBegin;
  PetscFunctionReturn(0);
}

/*MC
     PCMAT - A preconditioner obtained by multiplying by the preconditioner matrix supplied
             in PCSetOperators() or KSPSetOperators()

   Notes:
    This one is a little strange. One rarely has an explicit matrix that approximates the
         inverse of the matrix they wish to solve for.

   Level: intermediate

.seealso: `PCCreate()`, `PCSetType()`, `PCType`, `PC`,
          `PCSHELL`

M*/

PETSC_EXTERN PetscErrorCode PCCreate_Mat(PC pc) {
  PetscFunctionBegin;
  pc->ops->apply               = PCApply_Mat;
  pc->ops->matapply            = PCMatApply_Mat;
  pc->ops->applytranspose      = PCApplyTranspose_Mat;
  pc->ops->setup               = NULL;
  pc->ops->destroy             = PCDestroy_Mat;
  pc->ops->setfromoptions      = NULL;
  pc->ops->view                = NULL;
  pc->ops->applyrichardson     = NULL;
  pc->ops->applysymmetricleft  = NULL;
  pc->ops->applysymmetricright = NULL;
  PetscFunctionReturn(0);
}