[Paraview-developers] ParaView plugins with MPI only on client

[Biddiscombe, John A.]

Michael,

I had  the same problem with a plugin of mine, so I added some code to call mpi init in the client,
Have a look at this patch. I can't remember why I put in an #ifdef win32 now, (maybe because I usually run the gui on windows and the servers on the cray and probably it needed a tweak on linux...)
https://github.com/biddisco/ParaView/commit/10e4affe2d7a4736d05d1d14cfaffc996c227649

note also I needed thread multiple, so you might be able to simplify it slightly.

This patch might be obsolete, because I think I found a way of doing it inside the plugin...[pause] ... no in the plugin I swap the global communicator from a dummycontroller to a true mpi controller. Try this patch and if it doesn't work I'll point you to my plugin tweaks.

JB

From: paraview-developers-bounces at paraview.org [mailto:paraview-developers-bounces at paraview.org] On Behalf Of burlen
Sent: 01 June 2013 19:19
To: Michael Schlottke
Cc: ParaView Developers
Subject: Re: [Paraview-developers] ParaView plugins with MPI only on client

Hi Micheal,

I think you better let ParaView start MPI. There is a method that every reader should implement called CanReadFile. If you're reader cannot run with out MPI then in CanReadFile you should check if MPI is initialized and if not then you should return false. Then ParaView will not attempt to use your reader. This will avoid crashes when you are not running in client server mode. Something like this...

276 //-----------------------------------------------------------------------------
277 int vtkSQBOVReaderBase::CanReadFile(const char *file)
278 {
279   #if defined SQTK_DEBUG
280   pCerr() << "=====vtkSQBOVReaderBase::CanReadFile" << endl;
281   pCerr() << "Check " << safeio(file) << "." << endl;
282   #endif
283
284   int status=0;
285
286   #ifdef SQTK_WITHOUT_MPI
287   (void)file;
288   #else
289   // first check that MPI is initialized. in builtin mode MPI will
290   // never be initialized and this reader will be unable to read files
291   // so we always return false in this case
292   int mpiOk=0;
293   MPI_Initialized(&mpiOk);
294   if (!mpiOk)
295     {
296     return 0;
297     }
298
299   // only rank 0 opens the file, this results in metadata
300   // being parsed. If the parsing of md is successful then
301   // the file is ours.
302   this->Reader->SetCommunicator(MPI_COMM_SELF);
303   status=this->Reader->Open(file);
304   this->Reader->Close();
305   #endif
306
307   return status;
308 }

Of course if ParaView is built without MPI then you should always return false. An even better solution is to structure your reader to work both with and without mpi. I know it's doable if you're using unidata netcdf ver 4, not so sure about pnetcdf...

Burlen

On 06/01/2013 08:15 AM, Michael Schlottke wrote:
Hi,

for one of our own ParaView reader plugins we rely on Parallel NetCDF (pnetcdf) to do read in data in parallel, which in turn uses MPI to do the parallel I/O. Principally our reading algorithm works with any number of processes, including one.

At the moment, we always have to start a pvserver instance with MPI (i.e. mpiexec -n NN pvserver), start a normal client, and connect to the pvserver instance if we want to use the plugin - this also works for NN=1. However, when I start the ParaView client, the plugin crashes because MPI was not loaded/started. Thus we always have to go through the extra steps of starting a pvserver if we want to use the plugin.

Thus my question is whether there is a way to either start/load MPI manually from the plugin, or if it is possible to configure the client to automatically load and start the MPI library? Just enabling the Multi-Core option in the ParaView settings does not seem to do the trick.

Regards,

Michael

--
Michael Schlottke

SimLab Highly Scalable Fluids & Solids Engineering
Jülich Aachen Research Alliance (JARA-HPC)
RWTH Aachen University
Wüllnerstraße 5a
52062 Aachen
Germany

Phone: +49 (241) 80 95188
Fax: +49 (241) 80 92257
Mail: m.schlottke at aia.rwth-aachen.de<mailto:m.schlottke at aia.rwth-aachen.de>
Web: http://www.jara.org/jara-hpc





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