[Insight-users] parallelization

[Badri Roysam]

While on this topic, does anyone have an opinion of Apple's new Grand Central 
Dispatch parallelization method? It is claimed to be much more lightweight
compared to multi-threaded code, but I don;t yet understand why that should be
the case.


Badri Roysam
Professor, Department of Electrical, Computer and Systems Engineering
Associate Director, NSF Center for Subsurface Sensing & Imaging Systems (CenSSIS ERC)
Co-Director, Rensselaer Center for Open Source Software
Rensselaer Polytechnic Institute
110 8th Street, Troy, New York 12180-3590, USA.
Office(JEC 7010): 518-276-8067, Assistant: 518-276-8525, Lab(JEC 6308): 518-276-8207, Fax: 518-276-8715
Email: roysam at ecse.rpi.edu, Web: http://www.ecse.rpi.edu/~roysam



----- Original Message -----
From: Mauro Maiorca [mailto:mauromaiorca at gmail.com]
To: Dan Mueller [mailto:dan.muel at gmail.com]
Cc: itk [mailto:insight-users at itk.org]
Subject: Re: [Insight-users] parallelization


> Hi Dan & list,
> 
> I'm using
> MattesMutualInformationImageToImageMetric
> LinearInterpolateImageFunction
> 
> thanks for mentioning the IJ, it's an excellent source of info indeed!
> However, according to the article "Optimizing ITK’s Registration
> Methods for Multi-processor, Shared-Memory Systems" my code should be
> optimized.
> I would be really pleased to see any improvement on a multicore
> architecture (even because I'm planning to register quite big volumes
> using MMI).
> 
> Do you have any other clue/test/whatever to solve the problem?
> 
> 
> cheers,
> Mauro
> 
> 
> On Fri, Sep 4, 2009 at 8:59 PM, Dan Mueller<dan.muel at gmail.com> wrote:
> > Hi Mauro,
> >
> > Please report to the list what registration components you are using.
> >
> > ie. Linear Interpolator, Mattes Mutual Information Metric, Regular
> > Step Gradient Descent.
> >
> > Only _some_ components have been optimized for parallelization. For
> > which, please refer to the IJ article or the Code/Review folder (look
> > for itkOpt*).
> >
> > Hope this helps.
> >
> > Cheers, Dan
> >
> > 2009/9/4 Mauro Maiorca <mauromaiorca at gmail.com>:
> >> Thankyou very much Dan, John, and  Michael,
> >>
> >> I compiled again ITK with:
> >> ITK_USE_OPTIMIZED_REGISTRATION_METHODS = ON
> >> And still the same excecution time!
> >>
> >> I sent the task to only one processor (exec time 56'14") , four
> >> processors (56'57"), and 8 processors (56'16"). Pretty much the same
> >> time, no matter the number of processors involved in the computation.
> >>
> >> I also tried to add this to the ccmake of my application
> >> CMAKE_CXX_FLAGS   -lpthread
> >> It doesn't make any (significant) difference at all!
> >>
> >> any other clue?
> >> cheers,
> >> Mauro
> >>
> >>
> >>
> >> On Fri, Sep 4, 2009 at 1:10 AM, Dan Mueller<dan.muel at gmail.com> wrote:
> >>> Hi Mauro,
> >>>
> >>> To make use of multiple cores for registration, please set the CMake
> variable
> >>>    ITK_USE_OPTIMIZED_REGISTRATION_METHODS = ON
> >>>
> >>> This allows some interpolators/metrics to utilize multiple cores. For
> >>> full details, please see:
> >>>    http://www.insight-journal.org/browse/publication/172
> >>>
> >>> Hope this helps.
> >>>
> >>> Regards, Dan
> >>>
> >>> 2009/9/3 Mauro Maiorca <mauromaiorca at gmail.com>:
> >>>> Hello list,
> >>>>
> >>>> I'm wondering whether the ITK code is optimized for running on a
> >>>> multiprocessor machine?
> >>>> I wrote a program to register 2 images but it is quite slow because of
> >>>> many resamplings, so I'm running it on a 8 processor architecture ...
> >>>> but no significant improvements.
> >>>>
> >>>> I'm using Itk 3.14 compiled (linux) with the following flags:
> >>>>
> >>>>  CMAKE_THREAD_LIBS                -lpthread
> >>>>  CMAKE_USE_PTHREADS               ON
> >>>>
> >>>> any suggestion?
> >>>>
> >>>> cheers,
> >>>> Mauro
> >>>
> >>
> >
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