[Numpy-discussion] multiprocessing shared arrays and numpy

[Nadav Horesh]

I can not give a reliable answer yet, since I have some more improvement to make.
The application is an analysis of a stereoscopic-movie raw-data recording (both channels are recorded in the same file). I treat the data as a huge memory mapped file. The idea was to process each channel (left and right) on a different core. Right now the application is IO bounded since I do classical numpy operation, so each channel (which is handled as one array) is scanned several time. The improvement now over a single process is 10%, but I hope to achieve 10% ore after trivial optimizations.

 I used this application as an excuse to dive into multi-processing. I hope that the code I posted here would help someone.

  Nadav.


-----Original Message-----
From: numpy-discussion-bounces at scipy.org on behalf of Francesc Alted
Sent: Thu 04-Mar-10 15:12
To: Discussion of Numerical Python
Subject: Re: [Numpy-discussion] multiprocessing shared arrays and numpy
 
What kind of calculations are you doing with this module?  Can you please send 
some examples and the speed-ups you are getting?

Thanks,
Francesc

A Thursday 04 March 2010 14:06:34 Nadav Horesh escrigué:
> Extended module that I used for some useful work.
> Comments:
>   1. Sturla's module is better designed, but did not work with very large
>  (although sub GB) arrays 2. Tested on 64 bit linux (amd64) + python-2.6.4
>  + numpy-1.4.0
> 
>   Nadav.
> 
> 
> -----Original Message-----
> From: numpy-discussion-bounces at scipy.org on behalf of Nadav Horesh
> Sent: Thu 04-Mar-10 11:55
> To: Discussion of Numerical Python
> Subject: RE: [Numpy-discussion] multiprocessing shared arrays and numpy
> 
> Maybe the attached file can help. Adpted and tested on amd64 linux
> 
>   Nadav
> 
> 
> -----Original Message-----
> From: numpy-discussion-bounces at scipy.org on behalf of Nadav Horesh
> Sent: Thu 04-Mar-10 10:54
> To: Discussion of Numerical Python
> Subject: Re: [Numpy-discussion] multiprocessing shared arrays and numpy
> 
> There is a work by Sturla Molden: look for multiprocessing-tutorial.pdf
> and sharedmem-feb13-2009.zip. The tutorial includes what is dropped in
> the cookbook page. I am into the same issue and going to test it today.
> 
>   Nadav
> 
> On Wed, 2010-03-03 at 15:31 +0100, Jesper Larsen wrote:
> > Hi people,
> >
> > I was wondering about the status of using the standard library
> > multiprocessing module with numpy. I found a cookbook example last
> > updated one year ago which states that:
> >
> > "This page was obsolete as multiprocessing's internals have changed.
> > More information will come shortly; a link to this page will then be
> > added back to the Cookbook."
> >
> > http://www.scipy.org/Cookbook/multiprocessing
> >
> > I also found the code that used to be on this page in the cookbook but
> > it does not work any more. So my question is:
> >
> > Is it possible to use numpy arrays as shared arrays in an application
> > using multiprocessing and how do you do it?
> >
> > Best regards,
> > Jesper
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
> 
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-- 
Francesc Alted
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