:orphan:
# PCExoticSetType
Sets the type of coarse grid interpolation to use 
## Synopsis
```
#include "petscdmda.h" 
#include "petscksp.h" 
PetscErrorCode PCExoticSetType(PC pc, PCExoticType type)
```
Logically Collective


## Input Parameters

- ***pc -*** the preconditioner context
- ***type -*** either PC_EXOTIC_FACE or PC_EXOTIC_WIREBASKET (defaults to face)



## Notes
The face based interpolation has 1 degree of freedom per face and ignores the
edge and vertex values completely in the coarse problem. For any seven point
stencil the interpolation of a constant on all faces into the interior is that constant.

The wirebasket interpolation has 1 degree of freedom per vertex, per edge and
per face. A constant on the subdomain boundary is interpolated as that constant
in the interior of the domain.

The coarse grid matrix is obtained via the Galerkin computation A_c = R A R^T, hence
if A is nonsingular A_c is also nonsingular.

Both interpolations are suitable for only scalar problems.




## See Also
 `PCEXOTIC`, `PCExoticType()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/wb/wb.c.html#PCExoticSetType">src/ksp/pc/impls/wb/wb.c</A>

## Implementations

<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/wb/wb.c.html#PCExoticSetType_Exotic">PCExoticSetType_Exotic in src/ksp/pc/impls/wb/wb.c</A><BR>


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


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