WIP: PERF: Accumulate joint histograms in ThreadedComputePDFs#1451
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Inspired by a suggestion from Bradley Lowekamp, June 2, 2026, at https://discourse.itk.org/t/8x-slower-registration-with-itk-elastix-python-api-vs-elastix-cli-minimal-reproducible-example/7736/37
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N-Dekker
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Jun 5, 2026
| m_JointPDF = JointPDFType::New(); | ||
| m_JointPDF->SetRegions(JointPDFSizeType{ m_NumberOfMovingHistogramBins, m_NumberOfFixedHistogramBins }); | ||
| m_JointPDF->Allocate(); | ||
| m_JointPDF->AllocateInitialized(); |
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Note to myself: It might not be sufficient to zero-initialize the values here in InitializeHistograms(). Maybe ComputePDFs should (also) do m_JointPDF->FillBuffer(0.0) before calling m_Threader->SetSingleMethodAndExecute.
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Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Inspired by a suggestion from Bradley Lowekamp (@blowekamp), June 2, 2026, at https://discourse.itk.org/t/8x-slower-registration-with-itk-elastix-python-api-vs-elastix-cli-minimal-reproducible-example/7736/37
A major performance improvement (10% to 40%) of elastix.exe was observed on the benchmark data set from https://discourse.itk.org/t/8x-slower-registration-with-itk-elastix-python-api-vs-elastix-cli-minimal-reproducible-example (by @NicoKiaru). However, this PR might cause slightly different results, because it may change the order of additions of floating point numbers, during accumulation.