# MatMatInterpolate
Y = A*X or A'*X 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatMatInterpolate(Mat A, Mat x, Mat *y)
```
Neighbor-wise Collective on Mat


## Input Parameters

- ***mat   -*** the matrix
- ***x -*** the input dense matrix



## Output Parameters

- ***y -*** the output dense matrix





## Note
This allows one to use either the restriction or interpolation (its transpose)
matrix to do the interpolation. y matrix can be reused if already created with the proper sizes,
otherwise it will be recreated. y must be initialized to `NULL` if not supplied.


## See Also
 `Mat`, `MatInterpolate()`, `MatRestrict()`, `MatMatRestrict()`, `PCMG`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/interface/matrix.c.html#MatMatInterpolate">src/mat/interface/matrix.c</A>


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


[Index of all Mat routines](index.md)  
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