[Paraview] questions about writing a parallel reader

[John Biddiscombe]

> 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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>   


-- 
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