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Profiling mrregister on macOS showed that the hottest symbol was `MR::Interp::LinearInterp<...>::row(unsigned long)` called from `Registration::Warp::DisplacementThreadKernel::invert_displacement()`. That generic interpolation path builds a dynamic Eigen matrix for each sample, which is often unnecessary for vector fields using 3 component vectors. This change the implementation of `LinearInterp::row()` to avoid constructing an 3x8 matrix and instead does the weighted summation inside the for loop. Additionally, a new vec3() wrapper is added to avoid dynamic allocation for the common case of interpolating 3-volume vector fields. This helps reducing temporary allocations while preserving the existing interpolation behavior.
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clang-tidy review says "All clean, LGTM! 👍" |
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clang-tidy review says "All clean, LGTM! 👍" |
Lestropie
reviewed
Mar 16, 2026
Lestropie
reviewed
Mar 16, 2026
Member
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Left a couple of comments. I wonder if there might be other places in the code base where |
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clang-tidy review says "All clean, LGTM! 👍" |
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Profiling mrregister on macOS showed that the hottest symbol was
MR::Interp::LinearInterp<...>::row(unsigned long)called fromRegistration::Warp::DisplacementThreadKernel::invert_displacement(). That generic interpolation path builds a dynamic Eigen matrix for each sample, which is often unnecessary for vector fields using 3 component vectors.This change the implementation of
LinearInterp::row()to avoid constructing an 3x8 matrix and instead does the weighted summation inside the for loop. Additionally, a newvec3()wrapper is added to avoid dynamic allocation for the common case of interpolating 3-volume vector fields. This helps reducing temporary allocations while preserving the existing interpolation behavior.In my tests, this doesn't yield any noticeable performance gains on Linux, but on macOS there seems to be a consistent 15-20% performance improvement when running scalar registration of 3D volumes.