[petsc-dev] Vertex assignment in DMPlexDistribute

[Matthew Knepley]

On Sat, Nov 16, 2013 at 7:22 AM, Michael Lange <michael.lange at imperial.ac.uk
> wrote:

> Hi,
>
> I notice that, when creating the point SF for the parallel partition in
> DMPlexDistribute, cells are assigned to procs according to the original
> partition but vertices aren't. Was this done by design or is this a bug?
>

If this were true, there would be no communication for the P1 test of SNES
ex12. Here is running it with
-interpolate 1 and -dm_view ::ascii_info_detail

PetscSF Object: 2 MPI processes
  type: basic
    sort=rank-order
  [0] Number of roots=19, leaves=5, remote ranks=1
  [0] 4 <- (1,6)
  [0] 5 <- (1,8)
  [0] 7 <- (1,9)
  [0] 10 <- (1,13)
  [0] 11 <- (1,17)
  [1] Number of roots=19, leaves=0, remote ranks=0
  [0] Roots referenced by my leaves, by rank
  [0] 1: 5 edges
  [0]    4 <- 6
  [0]    5 <- 8
  [0]    7 <- 9
  [0]    10 <- 13
  [0]    11 <- 17
  [1] Roots referenced by my leaves, by rank

So there are 3 vertices and 2 edges in the point SF.

   Matt


> In case it is a bug, I have attached a patch that fixes this by using the
> closure of the original partition instead.
>
> Thanks and kind regards
> Michael
>



-- 
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
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