removes offset > 0 branches from WeightedShuffle implementation #4128
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behzadnouri
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Changing the offset definition to:
let offset = (index - 1) & BIT_MASK
will avoid all the
if offset > 0 { /* ... */ }
branches and massively simplifies the implementation.
It also improves performance in the benchmarks:
On master:
test bench_weighted_shuffle_collect ... bench: 150,789.57 ns/iter (+/- 2,123.07)
test bench_weighted_shuffle_new ... bench: 33,039.23 ns/iter (+/- 1,696.02)
test bench_weighted_shuffle_shuffle ... bench: 140,193.88 ns/iter (+/- 2,739.95)
On the branch:
test bench_weighted_shuffle_collect ... bench: 145,451.45 ns/iter (+/- 1,307.71)
test bench_weighted_shuffle_new ... bench: 30,309.99 ns/iter (+/- 3,577.51)
test bench_weighted_shuffle_shuffle ... bench: 136,634.04 ns/iter (+/- 3,124.60)
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Problem
Changing the offset definition to:
will avoid all the
branches and massively simplifies the implementation.
It also improves performance in the benchmarks:
On master:
On the branch:
Summary of Changes
removed
offset > 0branches fromWeightedShuffleimplementation