[petsc-dev] Natural numbering for unstructured meshes

Jed Brown jed at jedbrown.org
Mon Feb 17 18:21:41 CST 2014

Matthew Knepley <knepley at gmail.com> writes:

> 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.

I was responding to the question above.  Yes, we need a genuine parallel
reader (naive partition) and a way to write back in that ordering.  But
my question remains: do you want to do something other than IO with that
"natural" ordering?

Note that in the natural ordering, you likely have elements for which
you own zero of the vertices, and vice-versa, so it would be _really_
bad to compute on it.
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