Hello,
We have a partitioned mesh that we want to create a DMPlex from that has
the same distribution of elements (i.e., assignment of elements to
processes) and vertices 'interior' to a process (i.e., vertices not on
the inter-process boundary).
We were trying to use DMPlexCreateFromCellListParallelPetsc() or
DMPlexBuildFromCellListParallel() and found that the vertex ownership
(roots in the returned Vertex SF) appears to be sequentially assigned to
processes based on global vertex id. In general, this will not match
our mesh distribution. As we understand, to subsequently set vertex
coordinates (or other vertex data) we would have to utilize a star
forest (SF) communication API to send data to the correct process. Is
that correct?
Alternatively, if we create a dmplex object from the elements that exist
on each process using DMCreateFromCellList(), and then create a SF from
mesh vertices on inter-process boundaries (using the mapping from local
to global vertex ids provided by our mesh library), could we then
associate the dmplex objects with the SF? Is it as simple as calling
DMSetPointSF()?
If manually defining the PointSF is a way forward, we would like some
help understanding its definition; i.e., which entities become roots and
which become leaves. In DMPlexBuildFromCellListParallel()
https://gitlab.com/petsc/petsc/-/blob/753428fdb0644bc4cb7be6429ce8776c05405d40/src/dm/impls/plex/plexcreate.c#L2875-2899
the PointSF appears to contain roots for elements and vertices and
leaves for owned vertices on the inter-process boundary. Is that correct?
Thank-you,
Cameron
