[dune-pdelab] Reg: terminal freezes at vtk output

[Steffen Müthing]

Hi Shubhangi,

> Am 09.10.2018 um 16:32 schrieb Shubhangi Gupta <sgupta at geomar.de>:
> 
> Dear all,
> 
> I am currently experiencing a really strange problem during the execution of my dune program... When I run the problem in parallel, the program execution freezes in the terminal just before writing the vtk output file... the freeze occurs randomly, sometimes right before the first output, but sometimes after 5, 20, or even 500 outputs, even though I don't change anything about my problem setting! I am really puzzled, and I'll be very thankful for suggestions for solving/debugging this!

that really sounds strange. The one explanation I can think of is a race condition. Are you running this on a cluster with a network file system?
In that case, there might be an issue where one rank tries to write to a per-timestep subdirectory before the creation of that subdirectory has
been flushed from rank 0 to the file server and the other compute nodes, but that’s just guessing right now (but that might explain the freeze if
the program crash is not properly propagated by your MPI / batch system).

Steffen

> 
> Thanks in advance, and best wishes, Shubhangi
> 
> PS: So far, this problem occurs only in parallel. I write vtk output as follows:
>         int subsampling = 0;
>         typedef Dune::SubsamplingVTKWriter<GV> VTKWRITER;
>         VTKWRITER vtkwriter(gv,subsampling,(int)0);
>         typedef Dune::VTKSequenceWriter<GV> VTKSEQUENCEWRITER;
>         VTKSEQUENCEWRITER vtkSequenceWriter(    std::make_shared< 
> 	VTKWRITER (vtkwriter), fileName, pathName,""    );
>         .....
>         .....
>         vtkSequenceWriter.write(time,Dune::VTK::appendedraw);
> 
> 
> -- 
> Dr. Shubhangi Gupta
> Marine Geosystems
> GEOMAR Helmholtz Center for Ocean Research
> Wischhofstraße 1-3,
> D-24148 Kiel
> 
> Room: 12-206
> Phone: +49 431 600-1402
> Email: 
> sgupta at geomar.de
> 
> 
> 
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