:orphan:
# DMGetNullSpaceConstructor
Return the callback function which constructs the nullspace for a given field, defined with `DMAddField()` 
## Synopsis
```
#include "petscdm.h"          
#include "petscdmlabel.h"     
#include "petscds.h"     
PetscErrorCode DMGetNullSpaceConstructor(DM dm, PetscInt field, PetscErrorCode (**nullsp)(DM, PetscInt, PetscInt, MatNullSpace *))
```
Not Collective; No Fortran Support


## Input Parameters

- ***dm     -*** The `DM`
- ***field  -*** The field number for the nullspace



## Output Parameter

- ***nullsp -*** A callback to create the nullspace



## Calling sequence of `nullsp`
```none
    PetscErrorCode nullsp(DM dm, PetscInt origField, PetscInt field, MatNullSpace *nullSpace)
```


- ***dm        -*** The present DM
- ***origField -*** The field number given above, in the original DM
- ***field     -*** The field number in dm
- ***nullSpace -*** The nullspace for the given field





## See Also
 [](ch_dmbase), `DM`, `DMAddField()`, `DMGetField()`, `DMSetNullSpaceConstructor()`, `DMSetNearNullSpaceConstructor()`, `DMGetNearNullSpaceConstructor()`, `DMCreateSubDM()`, `DMCreateSuperDM()`

## Level
intermediate

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


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