[Paraview] questions about writing a parallel reader

[Takuya OSHIMA]

Hi John,

Thanks for the excellent explanations, now all is clear to me. I
really appreciate them!!

Takuya OSHIMA, Ph.D.
Faculty of Engineering, Niigata University
8050 Ikarashi-Ninocho, Nishi-ku, Niigata, 950-2181, JAPAN


From: John Biddiscombe <biddisco at cscs.ch>
Subject: Re: [Paraview] questions about writing a parallel reader
Date: Tue, 19 Aug 2008 17:14:56 +0200

> 
> > 1. What is the differences between
> >   outInfo->Get(vtkStreamingDemandDrivenPipeline::UPDATE_NUMBER_OF_PIECES())
> > and
> >   vtkMultiProcessController::GetNumberOfProcesses()?
> >   
> GetNumberOfProcesses gives you the true number of MPI spawned processes. This is usually the same as UPDATE_NUMBER_OF_PIECES, but not necessarily. The UPDATE_NUMBER_OF_PIECES culd be less, due to the way data is split (the reader can say, max num pices is N - you may have some data that cannot be easily split). The UPDATE_NUMBER_OF_PIECES is passed in during processRequest, and set by the downstream pipeline, the GetNumberOf... is always present.
> > Similarly, what is the difference between
> >   outInfo->Get(vtkStreamingDemandDrivenPipeline::UPDATE_PIECE_NUMBER())
> > and
> >   vtkMultiProcessController::GetLocalPricessId()?
> > Is it safe to assume that they return the same values respectively?
> >   
> they nearly always do. Same discussion as above.
> > 2. How do property changes on GUI propagate to each reader thread?
> > Are they supposed to propagate to all threads, or only one thread,
> > e. g. the thread where UPDATE_PIECE_NUMBER is 0?
> >   
> All processes get the information, passed up/down the pipeline. Thread (process) 0 is special in that stuff that you set gets copied from here to the gui, but generally, all processes will be generating the same stuff, apart form extent/piece information
> > 3. How can I update the progress bar at the bottom of the GUI?
> > Sometimes UpdateProgress() works but sometimes not. What is the
> > supposed way of doing it? Again, can I assume that the standard way is
> > to update it from the thread where UPDATE_PIECE_NUMBER is 0?
> >   
> Inside ProcessRequest, you use the standard  UpdateProgress calls and the gui will do the rest. If it's not working, have a look at other reader which you know do work.
> 
> JB
> 
> > Thanks,
> > Takuya
> >
> > Takuya OSHIMA, Ph.D.
> > Faculty of Engineering, Niigata University
> > 8050 Ikarashi-Ninocho, Nishi-ku, Niigata, 950-2181, JAPAN
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> > ParaView at paraview.org
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> >   
> 
> 
> -- John Biddiscombe,                            email:biddisco @ cscs.ch
> http://www.cscs.ch/
> CSCS, Swiss National Supercomputing Centre  | Tel:  +41 (91) 610.82.07
> Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82
> 
>