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

Sun Jun 2 14:09:52 EDT 2013

@John: Indeed, portability is an issue, so there's no way I can compile ParaView for all users with a custom source code patch :-/ Thanks for your idea, though, if it was just for me, I'd probably go this way and be done with it.

@Burlen: Starting paraview with mpiexec doesn't work either (I think the client is inherently a serial application, so mpiexec -n 2 will just start the client twice). And I double checked: "Use Multi-Core" is enabled and the number of cores is set to 2, but doing an MPI_Initialized(isInit); in my plugin still yields the result that MPI was in fact NOT initialized yet.

I tried starting MPI in the constructor of the plugin, but that is not a good idea since the constructor is called multiple times. Also, if ParaView should (legitimately) try to start MPI afterwards, it will crash since MPI was already started. Argh, it seems like I will have to implement both I/O libraries to get around this…

Michael

On Jun 2, 2013, at 09:30 , burlen wrote:

> that could be a fine solution if you're not overly concerned about portability. if you did that then you might have to use mpiexec(or whatever launcher) to start the paraview client. (but mpich and openmpi seem to be fine without mpiexec for 1 process runs...ymmv) you'd also be prevented from running the client on login nodes at certain hpc sites.
> 
> but wait a second...
>> Just enabling the Multi-Core option in the ParaView settings does not seem to do the trick.
> I think that this should work. at least my reader which can't run without mpi works with it. Is this a recent version of ParaVIew? Are you sure you tried on an mpi endowed build? Once you check the multicore setting you need to restart paraview.
> 
> 
> On 06/01/2013 03:20 PM, Biddiscombe, John A. wrote:
>> 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
>> Web: http://www.jara.org/jara-hpc
>> 
>> 
>> 
>> 
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>>  
> 

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