int MatCreateMPIAIJ(MPI_Comm comm,int m,int n,int M,int N,int d_nz,int *d_nnz,int o_nz,int *o_nnz,Mat *A)Collective on MPI_Comm
comm | - MPI communicator |
m | - number of local rows (or PETSC_DECIDE to have calculated if M is given) This value should be the same as the local size used in creating the y vector for the matrix-vector product y = Ax. |
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_DECIDE to have calculated if m is given) |
N | - number of global columns (or PETSC_DECIDE to have calculated if n is given) |
d_nz | - number of nonzeros per row in diagonal portion of local submatrix (same for all local rows) |
d_nzz | - array containing the number of nonzeros in the various rows of the diagonal portion of the local submatrix (possibly different for each row) or PETSC_NULL. You must leave room for the diagonal entry even if it is zero. |
o_nz | - number of nonzeros per row in the off-diagonal portion of local submatrix (same for all local rows). |
o_nzz | - array containing the number of nonzeros in the various rows of the off-diagonal portion of the local submatrix (possibly different for each row) or PETSC_NULL. |
The user MUST specify either the local or global matrix dimensions(possibly both).
By default, this format uses inodes (identical nodes) when possible. We search for consecutive rows with the same nonzero structure, therebyreusing matrix information to achieve increased efficiency.
-mat_aij_no_inode | - Do not use inodes |
-mat_aij_inode_limit <limit> | - Sets inode limit (max limit=5) |
-mat_aij_oneindex | - Internally use indexing starting at 1 rather than 0. Note that when calling MatSetValues(), the user still MUST index entries starting at 0! |
The user can specify preallocated storage for the diagonal part ofthe local submatrix with either d_nz or d_nnz (not both). Setd_nz=PETSC_DEFAULT and d_nnz=PETSC_NULL for PETSc to control dynamicmemory allocation. Likewise, specify preallocated storage for theoff-diagonal part of the local submatrix with o_nz or o_nnz (not both).
Consider a processor that owns rows 3, 4 and 5 of a parallel matrix. Inthe figure below we depict these three local rows and all columns (0-11).
0 1 2 3 4 5 6 7 8 9 10 11 ------------------- row 3 | o o o d d d o o o o o o row 4 | o o o d d d o o o o o o row 5 | o o o d d d o o o o o o -------------------Thus, any entries in the d locations are stored in the d (diagonal) submatrix, and any entries in the o locations are stored in theo (off-diagonal) submatrix. Note that the d and the o submatrices arestored simply in the MATSEQAIJ format for compressed row storage.
Now d_nz should indicate the number of nonzeros per row in the d matrix, and o_nz should indicate the number of nonzeros per row in the o matrix. In general, for PDE problems in which most nonzeros are near the diagonal, one expects d_nz >> o_nz. For large problems you MUST preallocate memoryor you will get TERRIBLE performance; see the users' manual chapter onmatrices.
Location: src/mat/impls/aij/mpi/mpiaij.c
Matrix Index
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