[petsc-users] DMPlex ghost cells

Matthew Knepley knepley at gmail.com
Thu Aug 3 22:11:31 CDT 2017

On Thu, Aug 3, 2017 at 10:07 PM, Adrian Croucher <a.croucher at auckland.ac.nz>

> I am adding cells onto a DMPlex (for dual porosity). I notice that
> normally the ghost cells in a DMPlex are at the end of the cell list.
> Does it matter if the cells I add come after those ghost cells, or should
> the ghosts always come last?
> It seems to me it probably shoudn't matter if the partition ghosts
> (created by DMPlexDistribute()) are not at the end. In my cell loops I just
> check the value of the ghost DMLabel and skip them if necessary.
> But perhaps the boundary ghosts (created by DMPlexConstructGhostCells())
> need to come last? Otherwise the output from DMPlexGetHybridBounds() (to
> get the bounds on 'interior' cells, i.e. non-boundary-ghosts) probably
> wouldn't make much sense?

Yes, the only reason to have them last is to have GetHybridBounds() work
for that case.



> - Adrian
> --
> Dr Adrian Croucher
> Senior Research Fellow
> Department of Engineering Science
> University of Auckland, New Zealand
> email: a.croucher at auckland.ac.nz
> tel: +64 (0)9 923 4611

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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