:orphan:
# KSPSetComputeRHS
set routine to compute the right hand side of the linear system 
## Synopsis
```
#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetComputeRHS(KSP ksp, PetscErrorCode (*func)(KSP, Vec, void *), void *ctx)
```
Logically Collective


## Input Parameters

- ***ksp -*** the `KSP` context
- ***func -*** function to compute the right hand side
- ***ctx -*** optional context



## Calling sequence of `func`
```none
PetscErrorCode func(KSP ksp, Vec b, void *ctx)
```

- ***ksp -*** the `KSP` context
- ***b -*** right hand side of linear system
- ***ctx -*** optional user-provided context





## Notes
The routine you provide will be called EACH you call `KSPSolve()` to prepare the new right hand side for that solve


## See Also
 [](ch_ksp), `KSP`, `KSPSolve()`, `DMKSPSetComputeRHS()`, `KSPSetComputeOperators()`, `KSPSetOperators()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/interface/itfunc.c.html#KSPSetComputeRHS">src/ksp/ksp/interface/itfunc.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex22f.F90.html">src/ksp/ksp/tutorials/ex22f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex25.c.html">src/ksp/ksp/tutorials/ex25.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex28.c.html">src/ksp/ksp/tutorials/ex28.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex29.c.html">src/ksp/ksp/tutorials/ex29.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex32.c.html">src/ksp/ksp/tutorials/ex32.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex34.c.html">src/ksp/ksp/tutorials/ex34.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex35.cxx.html">src/ksp/ksp/tutorials/ex35.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex36.cxx.html">src/ksp/ksp/tutorials/ex36.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex45.c.html">src/ksp/ksp/tutorials/ex45.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex45f.F90.html">src/ksp/ksp/tutorials/ex45f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex50.c.html">src/ksp/ksp/tutorials/ex50.c</A><BR>


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


[Index of all KSP routines](index.md)  
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[Index of all manual pages](/manualpages/singleindex.md)