[petsc-dev] Natural numbering for unstructured meshes

Matthew Knepley knepley at gmail.com
Mon Feb 17 18:08:16 CST 2014

On Mon, Feb 17, 2014 at 5:14 PM, Jed Brown <jed at jedbrown.org> wrote:

> Andrés Alessandro León Baldelli <a.leon.baldelli at gmail.com> writes:
> > Hi all,
> > I am working with Blaise Bourdin on implementing a concept of "natural
> numbering" for unstructured meshes using DMplex.
> > Such natural numbering can be, e.g., that of the mesh prior to parallel
> distribution.
> > I have a working example in which I compute a field on the distributed
> DM and I scatter it back to the serial DM on rank0 but I would like to
> create a more general interface. To this regard I ask your advice:
> > 1) Is it reasonable to add an SF within the DM typedef for this "natural
> to global" scatter?
> Surely you don't want the (necessarily non-scalable) serial DM to be a
> necessary part of this interface?  What do you want to do with this
> natural numbering?  Just write output files?

Jed, No, no, no. This is not an SF for a serial DM.

Imagine we start with a distributed mesh. The GlobalToNatural would scatter
from the
PETSc ordering, determined by partitioning, to the original parallel
ordering. Then that
"natural" vector can be output like normal. If you know something about
that original
ordering I guess this helps (although I do not advocate that workflow).

If we start with a serial mesh, we still calculate the SF, but it maps to a
naive partition of
this initial mesh. This will require more code, since we need to actually
do this partition,
but its not too bad.


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
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