# DMCreateDomainDecomposition
Returns lists of `IS` objects defining a decomposition of a problem into subproblems corresponding to restrictions to pairs of nested subdomains: each `IS` contains the global indices of the dofs of the corresponding subdomains with in the dofs of the original `DM`. The inner subdomains conceptually define a nonoverlapping covering, while outer subdomains can overlap. The optional list of `DM`s define a `DM` for each subproblem. 
## Synopsis
```
#include "petscdm.h"          
#include "petscdmlabel.h"     
#include "petscds.h"     
PetscErrorCode DMCreateDomainDecomposition(DM dm, PetscInt *n, char ***namelist, IS **innerislist, IS **outerislist, DM **dmlist)
```
Not collective


## Input Parameter

- ***dm -*** the `DM` object



## Output Parameters

- ***n            -*** The number of subproblems in the domain decomposition (or NULL if not requested)
- ***namelist    -*** The name for each subdomain (or NULL if not requested)
- ***innerislist -*** The global indices for each inner subdomain (or NULL, if not requested)
- ***outerislist -*** The global indices for each outer subdomain (or NULL, if not requested)
- ***dmlist      -*** The `DM`s for each subdomain subproblem (or NULL, if not requested; if NULL is returned, no `DM`s are defined)





## Note
The user is responsible for freeing all requested arrays. In particular, every entry of names should be freed with
`PetscFree()`, every entry of is should be destroyed with `ISDestroy()`, every entry of dm should be destroyed with `DMDestroy()`,
and all of the arrays should be freed with `PetscFree()`.


## Questions
The dmlist is for the inner subdomains or the outer subdomains or all subdomains?


## See Also
 `DMCreateFieldDecomposition()`, `DMDestroy()`, `DMCreateDomainDecompositionScatters()`, `DMView()`, `DMCreateInterpolation()`, `DMCreateColoring()`, `DMCreateMatrix()`, `DMCreateMassMatrix()`, `DMCreateFieldDecomposition()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/interface/dm.c.html#DMCreateDomainDecomposition">src/dm/interface/dm.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/tutorials/ex14.c.html">src/dm/tutorials/ex14.c.html</A><BR>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/da/dadd.c.html#DMCreateDomainDecomposition_DA">DMCreateDomainDecomposition_DA in src/dm/impls/da/dadd.c</A><BR>


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


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