On Thu, Mar 17, 2016 at 12:41 PM, Matthew Knepley <[email protected]> wrote:
> On Wed, Mar 16, 2016 at 9:19 PM, Adrian Croucher < > [email protected]> wrote: > >> hi >> >> I'm seeing some slightly puzzling behaviour when I set up a DMLabel on a >> DMPlex, then distribute the DMPlex using DMPlexDistribute(). >> >> Specifically, if I make the label values unique to start with (i.e. each >> mesh cell has a unique value), this is no longer always the case after >> distribution. In some cases two cells (not ghost cells) end up with the >> same label value, and one of the original values goes missing. >> >> I'm running the 'next' branch. >> >> The attached minimal example shows it. In this example the label values >> are just the cell indices before distribution, so they're unique. There >> are 900 mesh cells, so if running on 2 processors, each rank gets 450 of >> them. >> >> If I run it using >> >> mpiexec -np 2 testlabel > out >> >> and then go >> >> grep '(45)' out >> >> I get: >> >> [0]: 0 (45) >> [1]: 409 (45) >> [1]: 450 (45) >> >> So there are 3 cells ending up with the label value 45. The first one is >> the one I expect to get this label value. >> >> The third one has cell index > 449, so I figure it's a ghost cell on rank >> 1 (actually the same cell as above on rank 0). So that's probably OK too. >> >> But I don't know where the second one has come from. Its index indicates >> it isn't a ghost cell. >> >> Based on how the other cells are labelled, I would expect this cell 409 >> on rank 1 to have label value 814. But it turns out there is no cell in the >> distributed mesh with that label value- even though there was before >> distribution (I checked). >> > > Yep, that looks wrong. I can reproduce what you show. > > I setup a small test with 8 cells and everything works as expected, so > this is not simple. Will track it down. > I believe I have fixed your bug: https://bitbucket.org/petsc/petsc/branch/knepley/fix-plex-distribute-label I merged to next, and it will get to master before the release. Thanks, Matt > Thanks, > > Matt > > >> >> Am I misunderstanding something or is this unexpected behaviour? >> >> Cheers, Adrian >> >> -- >> Dr Adrian Croucher >> Senior Research Fellow >> Department of Engineering Science >> University of Auckland, New Zealand >> email: [email protected] >> tel: +64 (0)9 923 84611 >> >> > > > -- > 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 > -- 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
