# DMForestSetBaseDM
During the pre-setup phase, set the DM that defines the base mesh of a DMForest forest.  The forest will be hierarchically refined from the base, and all refinements/coarsenings of the forest will share its base.  In general, two forest must share a base to be comparable, to do things like construct interpolators. 
## Synopsis
```
#include "petscdmforest.h" 
#include "petscdm.h" 
#include "petscdmlabel.h" 
PetscErrorCode DMForestSetBaseDM(DM dm, DM base)
```
Logically collective on dm


## Input Parameters

- ***dm -*** the forest
- ***base -*** the base DM of the forest



## Notes
Currently the base DM must be a DMPLEX




## See Also
 `DMForestGetBaseDM()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/forest/forest.c.html#DMForestSetBaseDM">src/dm/impls/forest/forest.c</A>


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


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