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# AOApplicationToPetscIS
Maps an index set in the application-defined ordering to the PETSc ordering. 
## Synopsis
```
#include "petscao.h" 
PetscErrorCode AOApplicationToPetscIS(AO ao, IS is)
```
Collective


## Input Parameters

- ***ao -*** the application ordering context
- ***is -*** the index set; this is replaced with its mapped values



## Output Parameter

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





## Notes
The index set cannot be of type stride or block

Any integers in is that are negative are left unchanged. This
allows one to convert, for example, neighbor lists that use negative
entries to indicate nonexistent neighbors due to boundary conditions, etc.


## See Also
 [](sec_ao), `AO`, `AOCreateBasic()`, `AOView()`, `AOPetscToApplication()`,
`AOPetscToApplicationIS()`, `AOApplicationToPetsc()`

## Level
beginner

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


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


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