# PCMGSetR
Sets the vector to be used to store the residual on a particular level. 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode PCMGSetR(PC pc, PetscInt l, Vec c)
```
Logically Collective


## Input Parameters

- ***pc -*** the multigrid context
- ***l -*** the level (0 is coarsest) this is to be used for
- ***c -*** the Vec





## Note
If this is not provided PETSc will automatically generate one. You do not need to keep a reference to this vector if you do not need it. `PCDestroy()` will properly free it.


## See Also
 `PCMG`, `PCMGSetRhs()`, `PCMGSetX()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/mg/mgfunc.c.html#PCMGSetR">src/ksp/pc/impls/mg/mgfunc.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/pc/impls/mg/mgfunc.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)  
