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# MatGetValuesLocal
retrieves values from certain locations in a matrix using the local numbering of the indices defined previously by `MatSetLocalToGlobalMapping()` 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatGetValuesLocal(Mat mat, PetscInt nrow, const PetscInt irow[], PetscInt ncol, const PetscInt icol[], PetscScalar y[])
```
Not Collective


## Input Parameters

- ***mat -*** the matrix
- ***nrow -*** number of rows
- ***irow -*** the row local indices
- ***ncol -*** number of columns
- ***icol -*** the column local indices



## Output Parameter

- ***y -*** a logically two-dimensional array of values





## Notes
If you create the matrix yourself (that is not with a call to `DMCreateMatrix()`) then you MUST call `MatSetLocalToGlobalMapping()` before using this routine.

This routine can only return values that are owned by the requesting MPI rank. That is, for standard matrix formats, rows that, in the global numbering,
are greater than or equal to rstart and less than rend where rstart and rend are obtainable from `MatGetOwnershipRange`(mat,&rstart,&rend). One can
determine if the resulting global row associated with the local row r is owned by the requesting MPI rank by applying the `ISLocalToGlobalMapping` set
with `MatSetLocalToGlobalMapping()`.


## Developer Note
This is labelled with C so does not automatically generate Fortran stubs and interfaces
because it requires multiple Fortran interfaces depending on which arguments are scalar or arrays.


## See Also
 [](ch_matrices), `Mat`, `MatAssemblyBegin()`, `MatAssemblyEnd()`, `MatSetValues()`, `MatSetLocalToGlobalMapping()`,
`MatSetValuesLocal()`, `MatGetValues()`

## Level
advanced

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


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