# SNESVISetRedundancyCheck
Provide a function to check for any redundancy in the VI active set 
## Synopsis
```
#include "petscsnes.h" 
PetscErrorCode SNESVISetRedundancyCheck(SNES snes, PetscErrorCode (*func)(SNES, IS, IS *, void *), void *ctx)
```
Logically Collective on snes


## Input Parameters

- ***snes -*** the `SNESVINEWTONRSLS` context
- ***func -*** the function to check of redundancies
- ***ctx -*** optional context used by the function





## Note
Sometimes the inactive set will result in a non-singular sub-Jacobian problem that needs to be solved, this allows the user,
when they know more about their specific problem to provide a function that removes the redundancy that results in the singular linear system


## See Also
 `SNESVINEWTONRSLS`, `SNESVIGetInactiveSet()`, `DMSetVI()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/impls/vi/rs/virs.c.html#SNESVISetRedundancyCheck">src/snes/impls/vi/rs/virs.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/snes/impls/vi/rs/virs.c)


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