[Insight-developers] Possible bugs in ImageToImage metric with threads

[Johnson, Hans J]

Dan,Brian, and Luis,

Thanks for your responses!  It sounds like this will be worked on for
ITKv4, and that several of you have found this already.

I will focus on an ITKv3 work around and leave the ITKv4 refactoring to
those of you who are already working on it.

Thanks,
Hans


On 3/7/11 12:40 AM, "Dan Mueller" <dan.muel at gmail.com> wrote:

>Hi Hans, (others),
>
>You might be interested in the following IJ article, which implements
>exactly what you suggest:
>    An image sampling framework for the ITK
>    http://www.insight-journal.org/browse/publication/743
>
>I'm not sure if the ITKv4 registration refactor includes this
>particular enhancement or not...
>
>HTH
>
>Cheers, Dan
>
>On 7 March 2011 01:27, Johnson, Hans J <hans-johnson at uiowa.edu> wrote:
>> Hello all,
>> I can not make heads nor tails of the ImageToImageMetric samples
>>selection
>> methods.  It looks like this is a class that has experienced extreme
>>scope
>> creep over the years in an attempt to be uber flexible with respect to
>> samples selections.
>> How do all the following options interact with each other?
>> SetUseFixedImageSamplesIntensityThreshold
>> SetFixedImageRegion
>> SetUseAllPixels
>> SetUseSequentialSampling
>> SetFixedImageSamplesIntensityThreshold
>> SetUseFixedImageIndexes
>> SetFixedImageIndexes
>> SetNumberOfFixedImageSamples
>> SetFixedImageMask
>> SetMovingImageMask
>>
>> In my particular case, what is the correct behavior when requesting 1e6
>> samples from when the FixedImageMask is set and the MovingImageMask is
>>set,
>> but the intersection of the fixed and moving masks only contains 1e5
>> samples?  Since the threading work distribution is based on the
>> "m_NumberOfFixedImageSamples" and that has several related variables
>> (this->m_NumberOfPixelsCounted +=
>> m_ThreaderNumberOfMovingImageSamples[threadID];)  , and based on the
>>mask
>> overlapping the numberOfSamples seems to dynamically update, it could
>>be the
>> cause of the failing test cases.  I've spent several hours trying to
>>trace
>> through this mess trying to determine if there really is a problem, but
>>I
>> can not narrow it down.
>> Ultimately, all permutations of this result in some sort of iteration
>>over
>> some subset of the fixed image indexes.  If we decoupled the various
>>"fixed
>> image iterator generation schemes" from the ImageToImageMetric, we could
>> greatly simplify the interrelationships AND allow for other sample
>> selections schemes to be added through that consistent interface.
>> I'd like to get some feedback on this proposal before I spend more time
>> trying to identify ways to simplify this.
>> Hans
>>
>>
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