:orphan:
# ISSetIdentity
Informs the index set that it is an identity. 
## Synopsis
```
#include "petscis.h" 
PetscErrorCode ISSetIdentity(IS is)
```
Logically Collective


## Input Parameter

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





## Notes
`is` will be considered the identity permanently, even if indices have been changes (for example, with
`ISGeneralSetIndices()`).  It's a good idea to only set this property if `is` will not change in the future.

To clear this property, use `ISClearInfoCache()`.


## Developer Note
Some of these info routines have statements about values changing in the `IS`, this seems to contradict the fact that `IS` cannot be changed?


## See Also
 `IS`, `ISIdentity()`, `ISSetInfo()`, `ISClearInfoCache()`

## Level
intermediate

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


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