/*@
MatShift - Computes Y = Y + a I, where a is a PetscScalar and I is the identity matrix.
Neighbor-wise Collective on Mat
Input Parameters:
+ Y - the matrices
- a - the PetscScalar
Level: intermediate
.keywords: matrix, add, shift
.seealso: MatDiagonalSet()
@*/
PetscErrorCode MatShift(Mat Y,PetscScalar a)
{
PetscErrorCode ierr;
PetscInt i,start,end;
PetscFunctionBegin;
PetscValidHeaderSpecific(Y,MAT_CLASSID,1);
if (!Y->assembled) SETERRQ(PetscObjectComm((PetscObject)Y),PETSC_ERR_ARG_WRONGSTATE,"Not for unassembled matrix");
if (Y->factortype) SETERRQ(PetscObjectComm((PetscObject)Y),PETSC_ERR_ARG_WRONGSTATE,"Not for factored matrix");
MatCheckPreallocated(Y,1);
if (Y->ops->shift) {
ierr = (*Y->ops->shift)(Y,a);CHKERRQ(ierr);
} else {
PetscScalar alpha = a;
ierr = MatGetOwnershipRange(Y,&start,&end);CHKERRQ(ierr);
for (i=start; i<end; i++) {
ierr = MatSetValues(Y,1,&i,1,&i,&alpha,ADD_VALUES);CHKERRQ(ierr);
}
ierr = MatAssemblyBegin(Y,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
ierr = MatAssemblyEnd(Y,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
}
#if defined(PETSC_HAVE_CUSP)
if (Y->valid_GPU_matrix != PETSC_CUSP_UNALLOCATED) {
Y->valid_GPU_matrix = PETSC_CUSP_CPU;
}
#endif
PetscFunctionReturn(0);
}
/*@
MatShift - Computes Y = Y + a I, where a is a PetscScalar and I is the identity matrix.
Neighbor-wise Collective on Mat
Input Parameters:
+ Y - the matrices
- a - the PetscScalar
Level: intermediate
Notes: If the matrix Y is missing some diagonal entries this routine can be very slow. To make it fast one should initially
fill the matrix so that all diagonal entries have a value (with a value of zero for those locations that would not have an
entry).
Developers Note: If the local "diagonal part" of the matrix Y has no entries then the local diagonal part is
preallocated with 1 nonzero per row for the to be added values. This allows for fast shifting of an empty matrix.
.keywords: matrix, add, shift
.seealso: MatDiagonalSet()
@*/
PetscErrorCode MatShift(Mat Y,PetscScalar a)
{
PetscErrorCode ierr;
PetscFunctionBegin;
PetscValidHeaderSpecific(Y,MAT_CLASSID,1);
if (!Y->assembled) SETERRQ(PetscObjectComm((PetscObject)Y),PETSC_ERR_ARG_WRONGSTATE,"Not for unassembled matrix");
if (Y->factortype) SETERRQ(PetscObjectComm((PetscObject)Y),PETSC_ERR_ARG_WRONGSTATE,"Not for factored matrix");
MatCheckPreallocated(Y,1);
ierr = (*Y->ops->shift)(Y,a);CHKERRQ(ierr);
#if defined(PETSC_HAVE_CUSP)
if (Y->valid_GPU_matrix != PETSC_CUSP_UNALLOCATED) {
Y->valid_GPU_matrix = PETSC_CUSP_CPU;
}
#elif defined(PETSC_HAVE_VIENNACL)
if (Y->valid_GPU_matrix != PETSC_VIENNACL_UNALLOCATED) {
Y->valid_GPU_matrix = PETSC_VIENNACL_CPU;
}
#elif defined(PETSC_HAVE_VECCUDA)
if (Y->valid_GPU_matrix != PETSC_CUDA_UNALLOCATED) {
Y->valid_GPU_matrix = PETSC_CUDA_CPU;
}
#endif
PetscFunctionReturn(0);
}
