xref: /petsc/src/mat/utils/convert.c (revision b9147fbb7375951b83d4ce6f264c883d157e3a5b)

#define PETSCMAT_DLL

#include "include/private/matimpl.h"

#undef __FUNCT__
#define __FUNCT__ "MatConvert_Basic"
/*
  MatConvert_Basic - Converts from any input format to another format. For
  parallel formats, the new matrix distribution is determined by PETSc.

  Does not do preallocation so in general will be slow
 */
PetscErrorCode MatConvert_Basic(Mat mat, MatType newtype,MatReuse reuse,Mat *newmat)
{
  Mat                M;
  const PetscScalar  *vwork;
  PetscErrorCode     ierr;
  PetscInt           i,nz,m,n,rstart,rend,lm,ln;
  const PetscInt     *cwork;

  PetscFunctionBegin;
  ierr = MatGetSize(mat,&m,&n);CHKERRQ(ierr);
  ierr = MatGetLocalSize(mat,&lm,&ln);CHKERRQ(ierr);

  if (ln == n) ln = PETSC_DECIDE; /* try to preserve column ownership */

  ierr = MatCreate(mat->comm,&M);CHKERRQ(ierr);
  ierr = MatSetSizes(M,lm,ln,m,n);CHKERRQ(ierr);
  ierr = MatSetType(M,newtype);CHKERRQ(ierr);

  ierr = MatGetOwnershipRange(mat,&rstart,&rend);CHKERRQ(ierr);
  for (i=rstart; i<rend; i++) {
    ierr = MatGetRow(mat,i,&nz,&cwork,&vwork);CHKERRQ(ierr);
    ierr = MatSetValues(M,1,&i,nz,cwork,vwork,INSERT_VALUES);CHKERRQ(ierr);
    ierr = MatRestoreRow(mat,i,&nz,&cwork,&vwork);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  if (reuse == MAT_REUSE_MATRIX) {
    ierr = MatHeaderReplace(mat,M);CHKERRQ(ierr);
  } else {
    *newmat = M;
  }
  PetscFunctionReturn(0);
}