# DMDACreatePatchIS#

Creates an index set corresponding to a patch of the DMDA.

## Synopsis#

#include "petscdmda.h"
PetscErrorCode DMDACreatePatchIS(DM da, MatStencil *lower, MatStencil *upper, IS *is, PetscBool offproc)


Collective

## Input Parameters#

• da - the DMDA

• lower - a matstencil with i, j and k corresponding to the lower corner of the patch

• upper - a matstencil with i, j and k corresponding to the upper corner of the patch

• offproc - indicate whether the returned IS will contain off process indices

## Output Parameters#

• is - the IS corresponding to the patch

## Notes#

This routine always returns an IS on the DMDA comm, if offproc is set to PETSC_TRUE, the routine returns an IS with all the indices requested regardless of whether these indices are present on the requesting rank or not. Thus, it is upon the caller to ensure that the indices returned in this mode are appropriate. If offproc is set to PETSC_FALSE, the IS only returns the subset of indices that are present on the requesting rank and there is no duplication of indices.

DM, DMDA, DMCreateDomainDecomposition(), DMCreateDomainDecompositionScatters()

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