[petsc-dev] Will DMPlexDistribute only ever distribute Cells?

[Matthew Knepley]

On Thu, Apr 16, 2020 at 9:04 PM Jacob Faibussowitsch <jacob.fai at gmail.com>
wrote:

> Hello All,
>
> TL;DR: Is it possible now, or is it a planned feature, for plex to
> distribute over anything but points with height = 0?
>
> If I understand this correctly when plex currently partitions a graph,
> points with height 0 are only owned by a single process, but all other
> points can be co-owned by multiple procs.  For example for a 2D plex with 8
> vertices, 12 edges, and 6 cells over 2 procs these are the global-local
> IS’s for all points on processes (negative values indicate ownership by
> another proc) the final IS corresponding to cells will always have positive
> values as each proc is the sole owner of its cells.
>

What do you want to do? The system should be flexible enough to distribute
whatever you want, but the current guarantee
is that the cone of any points is always available. So if you decide to
distribute something else, like faces, then it ends up
looking just like an overlapping mesh with some custom overlap. Moreover,
the dual mesh only really makes sense for cells.
For faces/edges you would need a hypergraph partitioner.

  Thanks,

     Matt


> *VERTICES*
> IS Object: 2 MPI processes
>   type: general
> [0] Number of indices in set 7
> [0] 0 -2
> [0] 1 0
> [0] 2 -3
> [0] 3 -4
> [0] 4 -5
> [0] 5 -6
> [0] 6 -8
> [1] Number of indices in set 7
> [1] 0 1
> [1] 1 2
> [1] 2 3
> [1] 3 4
> [1] 4 5
> [1] 5 6
> [1] 6 7
>
> *EDGES*
> IS Object: 2 MPI processes
>   type: general
> [0] Number of indices in set 9
> [0] 0 0
> [0] 1 1
> [0] 2 -4
> [0] 3 -5
> [0] 4 -6
> [0] 5 2
> [0] 6 -7
> [0] 7 -9
> [0] 8 -11
> [1] Number of indices in set 9
> [1] 0 3
> [1] 1 4
> [1] 2 5
> [1] 3 6
> [1] 4 7
> [1] 5 8
> [1] 6 9
> [1] 7 10
> [1] 8 11
>
> *CELLS*
> IS Object: 2 MPI processes
>   type: general
> [0] Number of indices in set 3
> [0] 0 0
> [0] 1 1
> [0] 2 2
> [1] Number of indices in set 3
> [1] 0 3
> [1] 1 4
> [1] 2 5
>
> Best regards,
>
> Jacob Faibussowitsch
> (Jacob Fai - booss - oh - vitch)
> Cell: (312) 694-3391
>
>

-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20200416/8d8023e3/attachment.html>