perf: swap writer's spread-with-deltaTime for Object.assign - #81
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perf: swap writer's spread-with-deltaTime for Object.assign#81elicwhite wants to merge 1 commit into
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tsup transpiles `{...ev, deltaTime: 0}` to __spreadProps(__spreadValues(...))
which iterates property descriptors — ~7% of total writer profile time was
spent inside __spreadProps. Object.assign({}, ev, { deltaTime: 0 }) is a
native builtin on V8 and 2-3× faster for small objects.
Applied at the three writer sites that clone-with-delta-reset a source
event: buildUnrecognizedTrack (top-level unrecognized MIDI tracks) and
the per-track unrecognizedMidiEvents passes in buildDrumTrack and
buildFretTrack.
Measured on writer autoresearch bench (2000 charts, 8 workers):
previous: 5.710 ms mean, 4.883 ms p50, 15.040 ms p95, 5.132s wall
now: 4.566 ms mean, 4.129 ms p50, 10.424 ms p95, 4.926s wall
delta: -20.0% mean, -30.7% p95
Second run (variance check): 4.609 ms mean — stable.
0 hash mismatches, 442/442 tests still green.
Cumulative: baseline 92 ms -> 4.57 ms, 20× faster.
This was referenced Apr 20, 2026
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This was referenced Apr 20, 2026
elicwhite
marked this pull request as ready for review
April 20, 2026 16:09
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tsup transpiles
{...ev, deltaTime: 0}to __spreadProps(__spreadValues(...))which iterates property descriptors — ~7% of total writer profile time was
spent inside __spreadProps. Object.assign({}, ev, { deltaTime: 0 }) is a
native builtin on V8 and 2-3× faster for small objects.
Applied at the three writer sites that clone-with-delta-reset a source
event: buildUnrecognizedTrack (top-level unrecognized MIDI tracks) and
the per-track unrecognizedMidiEvents passes in buildDrumTrack and
buildFretTrack.
Measured on writer autoresearch bench (2000 charts, 8 workers):
previous: 5.710 ms mean, 4.883 ms p50, 15.040 ms p95, 5.132s wall
now: 4.566 ms mean, 4.129 ms p50, 10.424 ms p95, 4.926s wall
delta: -20.0% mean, -30.7% p95
Second run (variance check): 4.609 ms mean — stable.
0 hash mismatches, 442/442 tests still green.
Cumulative: baseline 92 ms -> 4.57 ms, 20× faster.