[petsc-dev] Can MATAIJ support block size?

[Fande Kong]

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.

Thanks,

Fande,
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