:orphan:
# MatReuse
Indicates if matrices obtained from a previous call to `MatCreateSubMatrices()`, `MatCreateSubMatrix()`, `MatConvert()` or several other functions are to be reused to store the new matrix values. 
## Synopsis
```
typedef enum {
  MAT_INITIAL_MATRIX,
  MAT_REUSE_MATRIX,
  MAT_IGNORE_MATRIX,
  MAT_INPLACE_MATRIX
} MatReuse;
```

## Values

- ***`MAT_INITIAL_MATRIX` -*** create a new matrix
- ***`MAT_REUSE_MATRIX` -*** reuse the matrix created with a previous call that used `MAT_INITIAL_MATRIX`
- ***`MAT_INPLACE_MATRIX` -*** replace the first input matrix with the new matrix (not applicable to all functions)
- ***`MAT_IGNORE_MATRIX` -*** do not create a new matrix or reuse a give matrix, just ignore that matrix argument (not applicable to all functions)





## See Also
 [](ch_matrices), `Mat`, `MatCreateSubMatrices()`, `MatCreateSubMatrix()`, `MatDestroyMatrices()`, `MatConvert()`

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/include/petscmat.h.html#MatReuse">include/petscmat.h</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex27.c.html">src/ksp/ksp/tutorials/ex27.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex29.c.html">src/ksp/ksp/tutorials/ex29.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex34.c.html">src/ksp/ksp/tutorials/ex34.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex43.c.html">src/ksp/ksp/tutorials/ex43.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex49.c.html">src/ksp/ksp/tutorials/ex49.c</A><BR>
<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/ksp/ksp/tutorials/ex64.c.html">src/ksp/ksp/tutorials/ex64.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex65.c.html">src/ksp/ksp/tutorials/ex65.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex6f.F90.html">src/ksp/ksp/tutorials/ex6f.F90</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex71.c.html">src/ksp/ksp/tutorials/ex71.c</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex72.c.html">src/ksp/ksp/tutorials/ex72.c</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/include/petscmat.h)


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