:orphan:
# MatCreateMPIAIJWithSplitArrays
creates a `MATMPIAIJ` matrix using arrays that contain the "diagonal" and "off-diagonal" part of the matrix in CSR format. 
## Synopsis
```
#include "petscmat.h" 
PetscErrorCode MatCreateMPIAIJWithSplitArrays(MPI_Comm comm, PetscInt m, PetscInt n, PetscInt M, PetscInt N, PetscInt i[], PetscInt j[], PetscScalar a[], PetscInt oi[], PetscInt oj[], PetscScalar oa[], Mat *mat)
```
Collective


## Input Parameters

- ***comm -*** MPI communicator
- ***m -*** number of local rows (Cannot be `PETSC_DECIDE`)
- ***n -*** This value should be the same as the local size used in creating the
x vector for the matrix-vector product y = Ax. (or `PETSC_DECIDE` to have
calculated if `N` is given) For square matrices `n` is almost always `m`.
- ***M -*** number of global rows (or `PETSC_DETERMINE` to have calculated if `m` is given)
- ***N -*** number of global columns (or `PETSC_DETERMINE` to have calculated if `n` is given)
- ***i -*** row indices for "diagonal" portion of matrix; that is i[0] = 0, i[row] = i[row-1] + number of elements in that row of the matrix
- ***j -*** column indices, which must be local, i.e., based off the start column of the diagonal portion
- ***a -*** matrix values
- ***oi -*** row indices for "off-diagonal" portion of matrix; that is oi[0] = 0, oi[row] = oi[row-1] + number of elements in that row of the matrix
- ***oj -*** column indices, which must be global, representing global columns in the `MATMPIAIJ` matrix
- ***oa -*** matrix values



## Output Parameter

- ***mat -*** the matrix





## Notes
The `i`, `j`, and `a` arrays ARE NOT copied by this routine into the internal format used by PETSc. The user
must free the arrays once the matrix has been destroyed and not before.

The `i` and `j` indices are 0 based

See `MatCreateAIJ()` for the definition of "diagonal" and "off-diagonal" portion of the matrix

This sets local rows and cannot be used to set off-processor values.

Use of this routine is discouraged because it is inflexible and cumbersome to use. It is extremely rare that a
legacy application natively assembles into exactly this split format. The code to do so is nontrivial and does
not easily support in-place reassembly. It is recommended to use MatSetValues() (or a variant thereof) because
the resulting assembly is easier to implement, will work with any matrix format, and the user does not have to
keep track of the underlying array. Use `MatSetOption`(A,`MAT_NO_OFF_PROC_ENTRIES`,`PETSC_TRUE`) to disable all
communication if it is known that only local entries will be set.


## See Also
 [](ch_matrices), `Mat`, `MatCreate()`, `MatCreateSeqAIJ()`, `MatSetValues()`, `MatMPIAIJSetPreallocation()`, `MatMPIAIJSetPreallocationCSR()`,
`MATMPIAIJ`, `MatCreateAIJ()`, `MatCreateMPIAIJWithArrays()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/mat/impls/aij/mpi/mpiaij.c.html#MatCreateMPIAIJWithSplitArrays">src/mat/impls/aij/mpi/mpiaij.c</A>


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


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