[Insight-users] Noise simulation

[Oleksandr Dzyubak]

Thanks Gaëtan.
I'll give it a try.

Alex


Gaëtan Lehmann wrote:
>
> 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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>