[petsc-dev] DMPLEX cannot support two different edges for the same two vertices, hence DMPLEX cannot?

[Matthew Knepley]

On Wed, Dec 1, 2021 at 6:55 PM Jed Brown <jed at jedbrown.org> wrote:

> Matthew Knepley <knepley at gmail.com> writes:
>
> > On Wed, Dec 1, 2021 at 5:17 PM Abhyankar, Shrirang G <
> > shrirang.abhyankar at pnnl.gov> wrote:
> >
> >> “You can certainly have many fields on a given edge, but I don't know
> >> what it would mean to have two edges since no topological query could
> tell
> >> the difference.”
> >>
> >>
> >>
> >> The two edges in a power grid represent two parallel power lines that
> are
> >> connected between two locations (vertices). There are line ids (stored
> in
> >> the component data) to distinguish the two lines.
> >>
> >
> > Yes, so you can tell the difference in the function space (since
> difference
> > current passes down each one), but _topologically_ you cannot. If you put
> > duplicate cells in, then
> > some topological queries will give unexpected results, like the join of
> the
> > two vertices.
>
> This could be modeled with some ghost vertices. So instead of
>
>   a ------ b
>    \_____/
>
> you would set up
>
>   a ---o---- b
>    \___o___/
>
> Those ghost vertices don't have to "do" anything, but they make the edges
> topologically distinct.
>
> Shri, what problems might this cause?
>

Yes, this would work, but it looks like the multiple cells are not causing
them problems right now with the questions they are asking the mesh.

   Matt

-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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