[petsc-users] removing cells from existing DMPLEX

[Matthew Knepley]

On Fri, Jun 8, 2018 at 5:10 AM, Matteo Semplice <matteo.semplice at unito.it>
wrote:

> Hi.
>
> We are developing a ghost-fluid type scheme, so we start creating a
> (cartesian) grid and then "mark" some cells in which the evolution actually
> takes place and solve a PDE only there.
>
> We currently handle the grid via a DMPLEX, we through a Label that marks
> the fluid cells we define a trivial operator for the non-fluid part of the
> grid, but of course the dofs attached to those cells and faces are still
> there in the Vec's and in the output.
>
> We know that (sometimes large) portions of the original grid will never be
> touched during the evolution, so we would like to remove those from the
> DMPLEX before partitioning it. Is there a simple way to do it? Ideally
> automagically via a Label or an IndexSet...
>

Can this do what you want?


http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/DMPLEX/DMPlexFilter.html

If so, I would caution you that no one uses this right now, so it might
forget to do something (say edit out all those
things from existing labels). I will fix anything that gives you a problem.

  Thanks,

    Matt


> The second best option would be to give less weight to the non-fluid
> portion of the DM when partitioning the DMPLEX: is there an example showing
> the use of weights in a Plex partitioner?
>
> Thanks in advance for your time.
>
> Best,
>
>    Matteo
>
>


-- 
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.caam.rice.edu/~mk51/>
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