[petsc-dev] DMPlexCreateSection crash in a no-boundary corner case

[Geoffrey Irving]

DMPlexCreateSection expects that the boundary index sets its given are
non-null.  However, if these are retrieved via DMPlexGetStratumIS from
a label generated by DMPlexMarkBoundaryFaces, the index sets will come
out null, causing the following error.

In my case this was caused by a bug: my DMPlex creation routine is
broken.  However, it could also arise from a mesh without boundary,
such as a Klein bottle.  Do we care about this kind of corner case?
If so, what's the right fix?  Two example possibilities are

1. Make DMPlexCreateSection treat null index sets as no boundary.
2. Make DMPlexMarkBoundaryFaces ensure that the stratum for value 1 is
"there" even though it is empty.  I'm not sure if this makes sense in
the desired semantics.

Thanks,
Geoffrey

---------------------------------------------------------------------

[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Null argument, when expecting valid pointer!
[0]PETSC ERROR: Null Object: Parameter # 1!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Development GIT revision:
352a19e720c6e388b1693cf6502c5f90a094459e  GIT Date: 2013-11-20
19:18:56 -0800
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Unknown Name on a debug named cayley by irving Wed Nov
20 20:29:20 2013
[0]PETSC ERROR: Libraries linked from /home/irving/petsc/debug/lib
[0]PETSC ERROR: Configure run at Wed Nov 20 19:39:25 2013
[0]PETSC ERROR: Configure options --download-ctetgen
--download-exodusii --download-generator --with-debugging=1
--with-fortran=1 --with-hdf5-dir=/usr --with-netcdf-dir=/usr
--with-triangle-dir=/usr PETSC_ARCH=debug
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: ISGetLocalSize() line 322 in src/vec/is/is/interface/index.c
[0]PETSC ERROR: DMPlexCreateSectionBCDof() line 4504 in src/dm/impls/plex/plex.c
[0]PETSC ERROR: DMPlexCreateSection() line 4716 in src/dm/impls/plex/plex.c
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Null argument, when expecting valid pointer!
[0]PETSC ERROR:  !
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Development GIT revision:
352a19e720c6e388b1693cf6502c5f90a094459e  GIT Date: 2013-11-20
19:18:56 -0800
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Unknown Name on a debug named cayley by irving Wed Nov
20 20:29:20 2013
[0]PETSC ERROR: Libraries linked from /home/irving/petsc/debug/lib
[0]PETSC ERROR: Configure run at Wed Nov 20 19:39:25 2013
[0]PETSC ERROR: Configure options --download-ctetgen
--download-exodusii --download-generator --with-debugging=1
--with-fortran=1 --with-hdf5-dir=/usr --with-netcdf-dir=/usr
--with-triangle-dir=/usr PETSC_ARCH=debug
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: create_default_section() line 174 in hollow/dm.cpp