# AOCreateMappingIS
Creates an application mapping using two index sets. 
## Synopsis
```
#include "petscao.h" 
PetscErrorCode AOCreateMappingIS(IS isapp, IS ispetsc, AO *aoout)
```

## Input Parameters

- ***comm    -*** MPI communicator that is to share `AO`
- ***isapp   -*** index set that defines an ordering
- ***ispetsc -*** index set that defines another ordering, maybe NULL for identity `IS`



## Output Parameter

- ***aoout   -*** the new application ordering



## Options Database Key

- ***-ao_view -*** call `AOView()` at the conclusion of `AOCreateMappingIS()`





## Note
The index sets isapp and ispetsc need NOT contain the all the integers 0 to N-1, that is there CAN be "holes"  in the indices.
Use `AOCreateBasic()` or `AOCreateBasicIS()` if they do not have holes for better performance.


## See Also
 [](sec_ao), [](sec_scatter), `AOCreateBasic()`, `AOCreateMapping()`, `AODestroy()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/is/ao/impls/mapping/aomapping.c.html#AOCreateMappingIS">src/vec/is/ao/impls/mapping/aomapping.c</A>


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


[Index of all AO routines](index.md)  
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