# PCSetUseAmat
Sets a flag to indicate that when the preconditioner needs to apply (part of) the operator during the preconditioning process it applies the Amat provided to `TSSetRHSJacobian()`, `TSSetIJacobian()`, `SNESSetJacobian()`, `KSPSetOperators()` or `PCSetOperators()` not the Pmat. 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode PCSetUseAmat(PC pc, PetscBool flg)
```
Logically Collective


## Input Parameters

- ***pc -*** the preconditioner context
- ***flg -*** `PETSC_TRUE` to use the Amat, `PETSC_FALSE` to use the Pmat (default is false)



## Options Database Key

- ***-pc_use_amat <true,false> -*** use the amat to apply the operator



## Note
For the common case in which the linear system matrix and the matrix used to construct the
preconditioner are identical, this routine is does nothing.




## See Also
 `PC`, `PCGetUseAmat()`, `PCBJACOBI`, `PGMG`, `PCFIELDSPLIT`, `PCCOMPOSITE`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/interface/precon.c.html#PCSetUseAmat">src/ksp/pc/interface/precon.c</A>


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


[Index of all PC routines](index.md)  
[Table of Contents for all manual pages](/docs/manualpages/index.md)  
[Index of all manual pages](/docs/manualpages/singleindex.md)  
