[petsc-dev] Can MATAIJ support block size?

[Matthew Knepley]

On Thu, Sep 20, 2018 at 1:26 PM Fande Kong <fdkong.jd at gmail.com> wrote:

> Hi Developers,
>
> MATBAIJ actually assumes that the point-block is dense. It is fine if the
> block size is small for example less than 50, but we may suffer from a
> memory issue if the block is large such as 1000. The block is not necessary
> dense. In my application, neutron transport equations, the block is
> actually sparse (coming from direction and energy grids).  Now I am using
> MATAIJ, but I want to take into consideration there are many variables on
> each spatial grid when doing some ILU(0).  ILU(0) is used as a subdomain
> solver for ASM and BJACOBI.
>
> I would like to support point-block ILU(0) in MATAIJ (not MATBAIJ) because
> the block is sparse. Any comments? It is worthwhile to do that? I think we
> might reduce the symbolic factor time when considering the block.
>

What optimization do you hope to take advantage of? The main optimization
in sparse LU is finding dense blocks,
and it should do a good job of that. I do not see what defining huge,
sparse blocks does for you.

  Thanks,

     Matt


> Thanks,
>
> Fande,
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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