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Compare polygon contours byte-wise - #2513
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nikosavola wants to merge 2 commits into
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nikosavola wants to merge 2 commits into
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- Uncompressed contours store the logical points 1:1, so for integer coordinates equal bytes mean equal points and memcmp gives the same verdict at SIMD speed - Compressed contours, which reconstruct every second point on access, keep the point-by-point comparison, and so do floating point coordinates (NaN, negative zero) - The rectilinear and hole tag bits live in the pointer, so they do not leak into the bytes
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polygon_contour::operator==compared the points one by one through the tagged-pointer iterator, which never vectorizes. Shape repository insertion and deduplication pay for it on every contour they compare.Uncompressed contours store the logical points one to one, so for integer coordinates equal bytes mean equal points and
memcmpgives the same verdict at SIMD speed. Compressed contours, which reconstruct every second point on access, and floating point coordinates (NaN, negative zero) keep the point-by-point comparison. The rectilinear and hole tag bits live in the pointer, not in the array, and astatic_assertpins the point size, so they cannot leak into the compared bytes.Measured with this change alone, g++ -O2 on a Xeon Gold 6248, repository deduplication:
The benchmark is not part of this PR.