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

[Dan Mueller]

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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