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# MatCreateIS
Creates a "process" unassembled matrix, `MATIS`, assembled on each process but not across processes. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatCreateIS(MPI_Comm comm, PetscInt bs, PetscInt m, PetscInt n, PetscInt M, PetscInt N, ISLocalToGlobalMapping rmap, ISLocalToGlobalMapping cmap, Mat *A)
```

## Input Parameters

- ***comm    -*** MPI communicator that will share the matrix
- ***bs      -*** block size of the matrix
- ***m,n,M,N -*** local and/or global sizes of the left and right vector used in matrix vector products
- ***rmap    -*** local to global map for rows
- ***cmap    -*** local to global map for cols



## Output Parameter

- ***A -*** the resulting matrix





## Notes
`m` and `n` are NOT related to the size of the map; they represent the size of the local parts of the distributed vectors
used in `MatMult()` operations. The sizes of rmap and cmap define the size of the local matrices.

If `rmap` (`cmap`) is `NULL`, then the local row (column) spaces matches the global space.


## See Also
 [](ch_matrices), `Mat`, `MATIS`, `MatSetLocalToGlobalMapping()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/is/matis.c.html#MatCreateIS">src/mat/impls/is/matis.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex59.c.html">src/ksp/ksp/tutorials/ex59.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/tutorials/ex3.c.html">src/mat/tutorials/ex3.c</A><BR>


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


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