Latest Results
Refit both dispatch constants for normal run lengths
The corpus and ablation generators now draw run lengths from a normal
distribution rather than a uniform band. The spread of run lengths, not the
mean, is what sets how often a run crosses a word boundary and how many runs
a prefill has to patch, so both dispatch constants were conditioned on the
old shape and had to be re-derived. Matching the ablation generator to the
corpus one also means the constants are fitted on the data CI measures.
The kernels separate far more cleanly on this data than on the uniform band.
Splat over prefill, by fastest sample:
run length 1 2 8 16 32 48 64 128 1024
non-nullable
50/50 3.57 3.67 3.71 3.75 3.45 3.02 2.91 1.52 0.85
90/10 - 1.38 1.35 - 1.14 - 0.90 0.74 0.76
Every win has at least 205 patched runs and every loss at most 102, so one
threshold separates them with margin, where the old fit had borderline points
either side. The nullable side splits at the same place: it doubles the work
on both sides of the comparison, since the prefill memsets and patches two
buffers exactly where the splat builds two. So `prefer_splat` loses its
`buffers` parameter entirely and becomes one patched run per eight output
words.
`prefer_blend` gains an upper bound. Blend over branching now reads
run length 1 2 8 16 32 48 64 128 1024
non-nullable 0.91 0.99 1.18 1.31 1.41 1.43 1.48 1.18 0.93
nullable 0.87 0.90 1.03 1.15 1.27 1.52 1.25 0.94 0.89
so the band has two edges, not one: far above a word the boundary test always
fires and predicts again, leaving the blend paying its extra store against a
whole-word fill that dominates either way. Without the bound the nullable
1024 cases came out 13% behind the original kernel, reproducibly across two
runs.
Against the original kernel, in-process, every point of the grid is now at or
above parity: non-nullable 1.01-4.05x, nullable 0.98-2.54x, the 0.98 being a
one-microsecond case. On the corpus benchmark, 1.14-3.87x across all 18.
Signed-off-by: Claude <noreply@anthropic.com>claude/runend-decompress-bools-1t2re2 Latest Branches
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