[petsc-users] AO versus DM for 3D CG solve

[Ronald M. Caplan]

Hi,

I am trying to implement petsc into an existing (very large) FORTRAN code
which splits a 3D grid in each dimension (so for a 100x100x100 problem on 4
cores, each core gets a 25x25x25 part of the grid).

The default partitioning for petsc just assigns contiguous rows of the
coefficient matrix to each core which is hampering performance.

>From looking around I have found that there are AO routines and DM routines
in petsc.

What is the difference between using either of them for my problem?
Should I be using DM to partition the petsc matrices/vectors so that they
match the grid points on each node, or do I use AO routines to do that?
Or do AO routines just map the default petsc partitioning indices to my
problem's indices in which case I want to use DM?

Thanks

Ron Caplan
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