[Insight-developers] Very suspicious behavior.

[Johnson, Hans J]

Dan,

I found a tangentially related bug in ITKv3 & ITKv4 that was complicating my understanding of the BRAINSFit threading issues that you are so kindly looking into.

Rather than make the entire program single threaded, I wanted to isolate and force just itk::MattesMutualInformationImageToImageMetric  into single threaded mode:

BRAINSCommonLib/BRAINSFitHelper.cxx :  Inserted line 115:
106   if(this->m_CostMetric == "MMI")
107     {
108     typedef itk::MattesMutualInformationImageToImageMetric<FixedVolumeType,MovingVolumeType> MetricType;
109     this->SetupRegistration<MetricType>();
110
111     MetricType::Pointer localCostMetric = this->GetCostMetric<MetricType>();
112     localCostMetric->SetNumberOfHistogramBins(this->m_NumberOfHistogramBins);
113     const bool UseCachingOfBSplineWeights = ( m_UseCachingOfBSplineWeightsMode == "ON" ) ? true : false;
114     localCostMetric->SetUseCachingOfBSplineWeights(UseCachingOfBSplineWeights);
115     localCostMetric->SetNumberOfThreads(1);
116     this->RunRegistration<MetricType>();
117     }

The problem was the that ImageRegistrationMethod was modifying the state of my localCostMetric and resetting the number of threads to a larger value.

I've posted patches to both ITKv3 and ITKv4 to avoid changing the prescribed localCostMetric number of threads:
http://review.source.kitware.com/#change,1088
http://review.source.kitware.com/#change,1087

=============================================

Once the ITKv[3,4] bugs are fixed, then I can sacrifice time to get a consistent result in BRAINSFit ( by forcing localCostMetric for MMI to  only use 1 thread).

=============================================

I hope you can find a way to give consistent threaded results from "MMI" because that greatly increases the processing time when it is single threaded.

Thanks,
Hans



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