:orphan:
# 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
## Input Parameters
- ***pc -*** the preconditioner context
- ***bs -*** the block size
## See Also
[](sec_block_matrices), `PC`, `PCFieldSplitGetSubKSP()`, `PCFIELDSPLIT`, `PCFieldSplitSetFields()`, `PCFieldSplitSetIS()`
## Level
intermediate
## Location
src/ksp/pc/impls/fieldsplit/fieldsplit.c
## Examples
src/ksp/ksp/tutorials/ex42.c
src/ksp/ksp/tutorials/ex43.c
src/ksp/ksp/tutorials/ex70.c
## Implementations
PCFieldSplitSetBlockSize_FieldSplit in src/ksp/pc/impls/fieldsplit/fieldsplit.c
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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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