BAIJ and AIJ formats

[Hong Zhang]

On Sun, 28 Sep 2008, Manav Bhatia wrote:

> Hi,
>
>  I have a few questions about the block format matrix.
>
>   In the function: MatCreateSeqBAIJ, the arguments are
>
> 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
>
> If I specify the nnz vector, then what is the dimension of this vector? Is 
> that equal to the block size? If so, then is it assumed that all blocks have 
> the same number of non-zeros per row?

Treating each block of BAIJ matrix as a single entry in AIJ format,
nnz is an array of size N/bs.

>
> If my blocks have different non-zero patterns, then should I use an AIJ 
> format instead of a BAIJ format?

You should use AIJ format.
See 
http://www-unix.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#blocks.

Hong
>
> Thanks,
> Manav