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perf: compute latLngToVec3 with math.Sincos in x/h3go - #156
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latLngToVec3 took the sine and cosine of both the latitude and the longitude
through four separate math.Sin / math.Cos calls, range-reducing each angle
twice. math.Sincos returns sine and cosine from a single reduction, so the
forward projection now makes two calls instead of four.
The projected output is unchanged: the pinned known-value tests, the cgo parity
suite and the conformance suite all still pass, and the path stays
allocation-free. latLngToVec3 is unexported, so unlike the other benchmarks it
cannot be reached from paritytest; BenchmarkLatLngToVec3 is added in-package to
guard it.
benchstat, fifteen interleaved rounds of each side on an Apple M3 Max:
│ old │ new │
│ sec/op │ sec/op vs base │
LatLngToVec3-16 13.750n ± 1% 8.614n ± 4% -37.35% (p=0.000 n=15)
End to end the win is small, around 1% off LatLngToCell, since the projection is
well under a tenth of that call, which is dominated by the face-IJK descent.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Coverage Report for CI Build 37078028382Coverage remained the same at 100.0%Details
Uncovered ChangesNo uncovered changes found. Coverage RegressionsNo coverage regressions found. Coverage Stats
💛 - Coveralls |
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What
latLngToVec3took the sine and cosine of both the latitude and the longitude through four separatemath.Sin/math.Coscalls, range-reducing each angle twice.math.Sincosreturns sine and cosine from a single reduction, so the forward projection now makes two calls instead of four.Discovered by #137
Why it's safe
x/h3go/paritytest), and the conformance suite all still pass.Results
latLngToVec3is unexported, so unlike the other benchmarks it can't be reached fromparitytest;BenchmarkLatLngToVec3is added in-package to guard it.benchstat, fifteen interleaved rounds of each side on an Apple M3 Max:
End to end the win is small — around 1% off
LatLngToCell— since the projection is well under a tenth of that call, which is dominated by the face-IJK descent.🤖 Generated with Claude Code