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_DECIDEto have calculated if- Nis given) For square matrices n is almost always- m.
- M - number of global rows (or - PETSC_DETERMINEto have calculated if- mis given)
- N - number of global columns (or - PETSC_DETERMINEto have calculated if- nis given)
- i - row indices (of length m+1); that is i[0] = 0, i[row] = i[row-1] + number of elements in that row of the matrix 
- j - global 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.
Once you have created the matrix you can update it with new numerical values using MatUpdateMPIAIJWithArray()
If you do not use MatUpdateMPIAIJWithArray(), the column indices in j do not need to be sorted. If you will use
MatUpdateMPIAIJWithArrays(), the column indices must be sorted.
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
        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, MatCreate(), MatCreateSeqAIJ(), MatSetValues(), MatMPIAIJSetPreallocation(), MatMPIAIJSetPreallocationCSR(),
MATMPIAIJ, MatCreateAIJ(), MatCreateMPIAIJWithSplitArrays(), MatUpdateMPIAIJWithArray(), MatSetPreallocationCOO(), MatSetValuesCOO()
Level#
intermediate
Location#
src/mat/impls/aij/mpi/mpiaij.c
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