:orphan:
# 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
[](ch_dmbase), `DM`, `DMCreateFieldDecomposition()`, `DMDestroy()`, `DMCreateDomainDecompositionScatters()`, `DMView()`, `DMCreateInterpolation()`, `DMCreateColoring()`, `DMCreateMatrix()`, `DMCreateMassMatrix()`, `DMCreateFieldDecomposition()`
## Level
intermediate
## Location
src/dm/interface/dm.c
## Examples
src/dm/tutorials/ex14.c
## Implementations
DMCreateDomainDecomposition_DA in src/dm/impls/da/dadd.c
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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](/manualpages/index.md)
[Index of all manual pages](/manualpages/singleindex.md)