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Dispatch SpacedExpandRightward for 4 and 8 byte trivially copyable types to a 128-bit SIMD implementation (NEON, SSE4.2), keeping the run based implementation as the scalar fallback and for other widths. The bitmap is walked one 64-bit word at a time: words with few nulls or a single valid/null transition go through a run path (memmove/memset, runs kept open across words), sparse words are scattered, and the rest are expanded 8 values at a time with an xsimd byte swizzle driven by an Arrow-owned lookup table. Every table index stays in [0, 16) and null slots are cleared with a keep mask, so only defined swizzle semantics are used and the bundled xsimd 14.2 is enough. Behavior change: the SIMD path zeroes every null slot, the scalar path only the trailing null_count slots. Co-Authored-By: Claude <noreply@anthropic.com>
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This is just a POC by ai, I want to verify performance of SIMD SpaceShift. Don't review it for now |
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@ursabot please benchmark lang=C++ |
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Benchmark runs are scheduled for commit 1bc728e. Watch https://buildkite.com/apache-arrow and https://conbench.arrow-dev.org for updates. A comment will be posted here when the runs are complete. |
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