:orphan:
# PCFieldSplitRestrictIS
Restricts the fieldsplit `IS`s to be within a given `IS`.
## Synopsis
```
#include "petscpc.h"
PetscErrorCode PCFieldSplitRestrictIS(PC pc, IS isy)
```
## Input Parameters
- ***pc -*** the preconditioner context
- ***is -*** the index set that defines the indices to which the fieldsplit is to be restricted
## Developer Note
It seems the resulting `IS`s will not cover the entire space, so
how can they define a convergent preconditioner? Needs explaining.
## See Also
[](sec_block_matrices), `PCFIELDSPLIT`, `PCFieldSplitSetFields()`, `PCFieldSplitSetIS()`
## Level
advanced
## Location
src/ksp/pc/impls/fieldsplit/fieldsplit.c
## Implementations
PCFieldSplitRestrictIS_FieldSplit in src/ksp/pc/impls/fieldsplit/fieldsplit.c
---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/pc/impls/fieldsplit/fieldsplit.c)
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