MatCreateSeqAIJ#

Creates a sparse matrix in MATSEQAIJ (compressed row) format (the default parallel PETSc format). For good matrix assembly performance the user should preallocate the matrix storage by setting the parameter nz (or the array nnz).

Synopsis#

#include "petscmat.h" 
PetscErrorCode MatCreateSeqAIJ(MPI_Comm comm, PetscInt m, PetscInt n, PetscInt nz, const PetscInt nnz[], Mat *A)

Collective

Input Parameters#

comm - MPI communicator, set to PETSC_COMM_SELF
m - number of rows
n - number of columns
nz - number of nonzeros per row (same for all rows)
nnz - array containing the number of nonzeros in the various rows (possibly different for each row) or NULL

Output Parameter#

A - the matrix

Options Database Keys#

-mat_no_inode - Do not use inodes
-mat_inode_limit - Sets inode limit (max limit=5)

Notes#

If nnz is given then nz is ignored

The MATSEQAIJ format, also called compressed row storage, is fully compatible with standard Fortran storage. That is, the stored row and column indices can begin at either one (as in Fortran) or zero.

Specify the preallocated storage with either nz or nnz (not both). Set nz = PETSC_DEFAULT and nnz = NULL for PETSc to control dynamic memory allocation.

By default, this format uses inodes (identical nodes) when possible, to improve numerical efficiency of matrix-vector products and solves. We search for consecutive rows with the same nonzero structure, thereby reusing matrix information to achieve increased efficiency.