# PCFieldSplitSetDiagUseAmat
set flag indicating whether to extract diagonal blocks from Amat (rather than Pmat) to build the sub-matrices associated with each split. Where `KSPSetOperators`(ksp,Amat,Pmat)) was used to supply the operators. 
## Synopsis
```
#include "petscpc.h" 
PetscErrorCode PCFieldSplitSetDiagUseAmat(PC pc, PetscBool flg)
```
Logically Collective


## Input Parameters

- ***pc  -*** the preconditioner object
- ***flg -*** boolean flag indicating whether or not to use Amat to extract the diagonal blocks from



## Options Database Keys

- ***-pc_fieldsplit_diag_use_amat -*** use the Amat to provide the diagonal blocks





## See Also
 [](sec_block_matrices), `PC`, `PCSetOperators()`, `KSPSetOperators()`, `PCFieldSplitGetDiagUseAmat()`, `PCFieldSplitSetOffDiagUseAmat()`, `PCFIELDSPLIT`

## Level
intermediate

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


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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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