petsc-3.3-p7 2013-05-11

MatCreateSeqBAIJ

Creates a sparse matrix in block AIJ (block compressed row) format. For good matrix assembly performance the user should preallocate the matrix storage by setting the parameter nz (or the array nnz). By setting these parameters accurately, performance during matrix assembly can be increased by more than a factor of 50.

Synopsis

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

Collective on MPI_Comm

Input Parameters

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

Output Parameter

A -the matrix

It is recommended that one use the MatCreate(), MatSetType() and/or MatSetFromOptions(), MatXXXXSetPreallocation() paradgm instead of this routine directly. [MatXXXXSetPreallocation() is, for example, MatSeqAIJSetPreallocation]

Options Database Keys

-mat_no_unroll -uses code that does not unroll the loops in the block calculations (much slower)

-mat_block_size -size of the blocks to use

Notes

The number of rows and columns must be divisible by blocksize.

If the nnz parameter is given then the nz parameter is ignored

A nonzero block is any block that as 1 or more nonzeros in it

The block AIJ format is fully compatible with standard Fortran 77 storage. That is, the stored row and column indices can begin at either one (as in Fortran) or zero. See the users' manual for details.