# ISSetPermutation
Informs the index set that it is a permutation. 
## Synopsis
```
#include "petscis.h" 
PetscErrorCode ISSetPermutation(IS is)
```
Logically Collective


## Input Parameter

- ***is -*** the index set




The debug version of the libraries (./configure --with-debugging=1) checks if the
index set is actually a permutation. The optimized version just believes you.

Note: The IS will be considered a permutation permanently, even if indices have been changes (for example, with
ISGeneralSetIndices()).  It's a good idea to only set this property if the IS will not change in the future.
To clear this property, use ISClearInfoCache().


## See Also
 `ISPermutation()`, `ISSetInfo()`, `ISClearInfoCache().`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/is/is/interface/index.c.html#ISSetPermutation">src/vec/is/is/interface/index.c</A>


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


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