#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
| 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 | - matrix values |
| mat | - the matrix |
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]