[petsc-users] removing cells from existing DMPLEX

[Matteo Semplice]

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...

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