# PetscDualSpaceGetPointSubspace
Get the subset of the dual space basis that is supported on a particular mesh point. 
## Synopsis
```
#include "petscfe.h" 
PetscErrorCode PetscDualSpaceGetPointSubspace(PetscDualSpace sp, PetscInt point, PetscDualSpace *bdsp)
```
Not collective


## Input Parameters

- ***sp -*** the `PetscDualSpace` object
- ***point -*** the point (in the dual space's DM) for which the subspace is desired



## Output Parameters
bdsp - the subspace. The functionals in the subspace are with respect to the intrinsic geometry of the
point, which will be of lesser dimension if height > 0.




## Notes
If the dual space is not defined on the mesh point (e.g. if the space is discontinuous and pointwise values are not
defined on the element boundaries), or if the implementation of `PetscDualSpace` does not support extracting
subspaces, then NULL is returned.

This does not increment the reference count on the returned dual space, and the user should not destroy it.


## See Also
 `PetscDualSpace`, `PetscDualSpaceGetHeightSubspace()`

## Level
advanced

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


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


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