# MatCreateMPIAdj

Creates a sparse matrix representing an adjacency list. The matrix does not have numerical values associated with it, but is intended for ordering (to reduce bandwidth etc) and partitioning.

### Synopsis

    PetscErrorCode PETSCMAT_DLLEXPORT MatCreateMPIAdj(MPI_Comm comm,PetscInt m,PetscInt n,PetscInt *i,PetscInt *j,PetscInt *values,Mat *A)

Collective on MPI_Comm

### Input Parameters

| comm | - MPI communicator
| m | - number of local rows
| n | - number of columns
| i | - the indices into j for the start of each row
| j | - the column indices for each row (sorted for each row). The indices in i and j start with zero (NOT with one).
| values | - [optional] edge weights

### Output Parameter

A -the matrix

Notes: This matrix object does not support most matrix operations, include MatSetValues(). You must NOT free the ii, values and jj arrays yourself. PETSc will free them when the matrix is destroyed; you must allocate them with PetscMalloc(). If you call from Fortran you need not create the arrays with PetscMalloc(). Should not include the matrix diagonals.

If you already have a matrix, you can create its adjacency matrix by a call to MatConvert, specifying a type of MATMPIADJ.

Possible values for MatSetOption() - MAT_STRUCTURALLY_SYMMETRIC

### See Also

MatCreate(), MatConvert(), MatGetOrdering()

Level:intermediate
Location:src/mat/impls/adj/mpi/mpiadj.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages

### Examples

src/dm/ao/examples/tutorials/ex2.c.html