PETSc version 3.17.4
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# MatCreateMPIAIJWithSplitArrays

creates a MPI AIJ 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 MPIAIJ 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

MatCreate(), MatCreateSeqAIJ(), MatSetValues(), MatMPIAIJSetPreallocation(), MatMPIAIJSetPreallocationCSR(),
MATMPIAIJ, MatCreateAIJ(), MatCreateMPIAIJWithArrays()

### Level

advanced

### Location

src/mat/impls/aij/mpi/mpiaij.c
Index of all Mat routines
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