MatCreateMPIAIJWithArrays#

creates a MATMPIAIJ matrix using arrays that contain in standard CSR format for the local rows.

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatCreateMPIAIJWithArrays(MPI_Comm comm, PetscInt m, PetscInt n, PetscInt M, PetscInt N, const PetscInt i[], const PetscInt j[], const PetscScalar a[], 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; that is i[0] = 0, i[row] = i[row-1] + number of elements in that row of the matrix

  • j - column indices

  • a - optional matrix values

Output Parameter#

  • mat - the matrix

Notes#

The i, j, and a arrays ARE copied by this routine into the internal format used by PETSc; thus you CANNOT change the matrix entries by changing the values of a[] after you have called this routine. Use MatCreateMPIAIJWithSplitArrays() to avoid needing to copy the arrays.

The i and j indices are 0 based, and i indices are indices corresponding to the local j array.

The format which is used for the sparse matrix input, is equivalent to a row-major ordering.. i.e for the following matrix, the input data expected is as shown

Once you have created the matrix you can update it with new numerical values using MatUpdateMPIAIJWithArrays

        1 0 0
        2 0 3     P0
       -------
        4 5 6     P1

     Process0 [P0] rows_owned=[0,1]
        i =  {0,1,3}  [size = nrow+1  = 2+1]
        j =  {0,0,2}  [size = 3]
        v =  {1,2,3}  [size = 3]

     Process1 [P1] rows_owned=[2]
        i =  {0,3}    [size = nrow+1  = 1+1]
        j =  {0,1,2}  [size = 3]
        v =  {4,5,6}  [size = 3]

See Also#

Matrices, Mat, MATMPIAIK, MatCreate(), MatCreateSeqAIJ(), MatSetValues(), MatMPIAIJSetPreallocation(), MatMPIAIJSetPreallocationCSR(), MATMPIAIJ, MatCreateAIJ(), MatCreateMPIAIJWithSplitArrays(), MatUpdateMPIAIJWithArrays()

Level#

intermediate

Location#

src/mat/impls/aij/mpi/mpiaij.c

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