[Insight-users] Noise simulation

[Gaëtan Lehmann]

Le 25 mars 10 à 23:27, Gaëtan Lehmann a écrit :

>
> Hi Alex,
>
> I think there is a problem with multithreading and the random  
> generator - more specifically, the seeds are the same in all the  
> threads.
> I didn't noticed this on my macbook with only 2 cores, even when  
> increasing the number of threads to a higher number than the number  
> of cores, but I see the same behavior on my workstation with 16  
> threads.
>
> How many threads are running in parallel on your system? The number  
> is displayed while running one of the noise generator
>
>  [glehmann at gbook build]$ ./shot ../images/cthead1.tif toto.png |  
> grep "  Number Of Threads:"
>    Number Of Threads: 2
>    Number Of Threads: 2
>
> You can limit the number of threads to a small number, or even to 1,  
> with
>
>  export ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS=1
>
> to workaround the problem.
>
> I will restore the (non thread safe) seeding behavior in  
> ThreadSafeMersenneTwisterRandomVariateGenerator and make it thread  
> safe with a lock so that 2 threads can't get the same seed.
>

This is fixed in the main repository:

   http://mima2.jouy.inra.fr/darcs/contrib-itk/noise/

As well as the problem you have reported in median.cxx.
Please let me know if there is something else wrong!

Gaëtan


> Thanks for the report!
>
> Gaëtan
>
>
> Le 25 mars 10 à 22:47, Oleksandr Dzyubak a écrit :
>
>> Dear ITK users,
>>
>> Did anybody tested the noise simulation codes from the submission
>> "Noise simulation" http://hdl.handle.net/10380/3158 ?
>> The most needed (for me at least) noise generators
>> (Gauss and salt and pepper)
>> produce corrupted images with periodic line patterns
>> (see attached images). To generate those images, I followed
>> the parameter recommendations taken from the submission.
>>
>> ./gauss cthead1.tif cthead1_gauss_s22_8_m0.png 22.8 0
>> ./sp cthead1.tif cthead1_sp_0016.png 0.016
>>
>> Did anybody get similar results?
>>
>> Alex
>>
>>
>>
>> Oleksandr Dzyubak wrote:
>>> Hi Gaëtan,
>>>
>>> Nice and long awaited work.
>>> I found a tiny typo in your code that prevents the submitted codes  
>>> from
>>> being compiled.
>>> At least on my Linux box. The typo is sitting in your median.cxx  
>>> and the
>>> fix is below.
>>>
>>> // Part that gives the errors.
>>> /*
>>> FilterType::RadiusType r;
>>> r.Fill(2);
>>> //  filter->SetRadius(r);
>>> */
>>>
>>> //  this fix solves the problem.
>>> IType::SizeType r;
>>> r[0] = 1;
>>> r[1] = 1;
>>> filter->SetRadius(r);
>>>
>>> Could you please add the fix and upload the code?
>>>
>>> Thanks,
>>> Alex
>>>
>>
>> <cthead1_gauss_s22_8_m0.png><cthead1_sp_0016.png>
>
> -- 
> Gaëtan Lehmann
> Biologie du Développement et de la Reproduction
> INRA de Jouy-en-Josas (France)
> tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
> http://voxel.jouy.inra.fr  http://www.itk.org
> http://www.mandriva.org  http://www.bepo.fr
>
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-- 
Gaëtan Lehmann
Biologie du Développement et de la Reproduction
INRA de Jouy-en-Josas (France)
tel: +33 1 34 65 29 66    fax: 01 34 65 29 09
http://voxel.jouy.inra.fr  http://www.itk.org
http://www.mandriva.org  http://www.bepo.fr

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