[Paraview] Fwd: Segfault reading polyhedral cells xdmf3 file

[Armin Wehrfritz]

> In attach you can find the output of the saving of the polyhedron.vtu
> (saved.xmf and saved.h5) from the Windows machine.
OK, I tested the "saved.xmf" file and I can open it on my Linux machine
without issues. Also, I compared the files generated on windows and
linux machines, and the topology data is the same for both of them. The
datatype in the h5 file is different (H5T_STD_I32LE for the file from
the Windows machine vs. H5T_STD_I64LE for the file from the Linux
machine). The end of line in the xmf file is different, but I don't
think either one of them should cause an issue.

> I've tried also to repeat the procedure (reading of your xmf file) on a
> Linux workstation and the behaviour is different: it seems that
> randomically the crash happens again (once on about ten tries) and
> sometimes it seems that the topology has a connectivity error (see the
> image in attachment), while for the most of the times it seems to do the
> right job.
As said, on my Linux machine it works consistently.

> I've tried also another case, a little bit heavier: a polyhedral mesh
> read from the vtu in attach (cube.vtu) and saved with the Xdmf3 writer.
> Trying to re-read the xmf version of this geometry always  produces a
> crash also on the Linux machine.
I can confirm that the xmf file produce from the cube.vtu (using the
Xdmf3 writer in ParaView 5.2) leads consistently to seg fault.
However, even though the .vtu file works correctly, I'm not entirely
sure if this is xmf specific problem. To be more precise, the
implementation of polyhedral cells requires the face polygons to be
planar (see http://www.vtk.org/Wiki/VTK/Polyhedron_Support). The example
file you send has a whole lot of faces that are not planar.

I extracted a single cell with several non-planar faces from your
example and saved it as .xmf file (attached). I can read this particular
file without issues on my Linux machine, whereas the original data file
leads to a seg fault. One reason why the cube.vtu file works and the
respective .xmf doesn't, could be related to the different approaches
polyhedral cells are stored in vtu and xdmf files, but debugging this
would require quite a bit of work...

Maybe somebody else has an idea here.

-Armin
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