# PCFieldSplitSetBlockSize
Sets the block size for defining where fields start in the fieldsplit preconditioner when calling `PCFieldSplitSetIS()`. If not set the matrix block size is used. 
## Synopsis
```
#include "petscpc.h" 
PetscErrorCode PCFieldSplitSetBlockSize(PC pc, PetscInt bs)
```
Logically Collective on pc


## Input Parameters

- ***pc  -*** the preconditioner context
- ***bs -*** the block size





## See Also
 `PCFieldSplitGetSubKSP()`, `PCFIELDSPLIT`, `PCFieldSplitSetFields()`, `PCFieldSplitSetIS()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/fieldsplit/fieldsplit.c.html#PCFieldSplitSetBlockSize">src/ksp/pc/impls/fieldsplit/fieldsplit.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex42.c.html">src/ksp/ksp/tutorials/ex42.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex43.c.html">src/ksp/ksp/tutorials/ex43.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex70.c.html">src/ksp/ksp/tutorials/ex70.c.html</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/fieldsplit/fieldsplit.c.html#PCFieldSplitSetBlockSize_FieldSplit">PCFieldSplitSetBlockSize_FieldSplit in src/ksp/pc/impls/fieldsplit/fieldsplit.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/pc/impls/fieldsplit/fieldsplit.c)


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[Index of all manual pages](/docs/manualpages/singleindex.md)  
