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# PCMGSetInterpolation
Sets the function to be used to calculate the interpolation from l-1 to the lth level 
## Synopsis
```
#include "petscksp.h" 
PetscErrorCode PCMGSetInterpolation(PC pc, PetscInt l, Mat mat)
```
Logically Collective


## Input Parameters

- ***pc  -*** the multigrid context
- ***mat -*** the interpolation operator
- ***l   -*** the level (0 is coarsest) to supply [do not supply 0]





## Notes
Usually this is the same matrix used also to set the restriction
for the same level.

One can pass in the interpolation matrix or its transpose; PETSc figures
out from the matrix size which one it is.


## See Also
 `PCMG`, `PCMGSetRestriction()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/pc/impls/mg/mgfunc.c.html#PCMGSetInterpolation">src/ksp/pc/impls/mg/mgfunc.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/dm/impls/stag/tutorials/ex4.c.html">src/dm/impls/stag/tutorials/ex4.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex35.cxx.html">src/ksp/ksp/tutorials/ex35.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex36.cxx.html">src/ksp/ksp/tutorials/ex36.cxx</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex42.c.html">src/ksp/ksp/tutorials/ex42.c</A><BR>


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