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# PCShellSetApplyBA
Sets routine to use as preconditioner times operator.
## Synopsis
```
#include "petscpc.h"
PetscErrorCode PCShellSetApplyBA(PC pc, PetscErrorCode (*applyBA)(PC, PCSide, Vec, Vec, Vec))
```
Logically Collective
## Input Parameters
- ***pc -*** the preconditioner context
- ***applyBA -*** the application-provided BA routine
## Calling sequence of `applyBA`
```none
PetscErrorCode applyBA(PC pc, Vec xin, Vec xout)
```
- ***pc -*** the preconditioner, get the application context with `PCShellGetContext()`
- ***xin -*** input vector
- ***xout -*** output vector
## See Also
`PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetContext()`, `PCShellSetApply()`
## Level
intermediate
## Location
src/ksp/pc/impls/shell/shellpc.c
## Implementations
PCShellSetApplyBA_Shell(PC pc, PetscErrorCode (*applyBA) in src/ksp/pc/impls/shell/shellpc.c
---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/pc/impls/shell/shellpc.c)
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