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# MatKAIJSetAIJ
Set the `MATAIJ` matrix describing the blockwise action of the `MATKAIJ` matrix 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatKAIJSetAIJ(Mat A, Mat B)
```
Logically Collective; if the `MATAIJ` matrix is parallel, the `MATKAIJ` matrix is also parallel


## Input Parameters

- ***A -*** the `MATKAIJ` matrix
- ***B -*** the `MATAIJ` matrix





## Notes
This function increases the reference count on the `MATAIJ` matrix, so the user is free to destroy the matrix if it is not needed.

Changes to the entries of the `MATAIJ` matrix will immediately affect the `MATKAIJ` matrix.


## See Also
 [](ch_matrices), `Mat`, `MATKAIJ`, `MatKAIJGetAIJ()`, `MatKAIJSetS()`, `MatKAIJSetT()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/kaij/kaij.c.html#MatKAIJSetAIJ">src/mat/impls/kaij/kaij.c</A>


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


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