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Optimize unnecessary check in VecDeque::retain by Xuanwo · Pull Request #88075 ·...

 2 years ago
source link: https://github.com/rust-lang/rust/pull/88075
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Xuanwo commented 12 days ago

This pr is highly inspired by #88060 which shared the same idea: we can split the for loop into stages so that we can remove unnecessary checks like del > 0.

Benchmarks

Before

test collections::vec_deque::tests::bench_retain_half_10000  ... bench:     290,125 ns/iter (+/- 8,717)
test collections::vec_deque::tests::bench_retain_odd_10000   ... bench:     291,588 ns/iter (+/- 9,621)
test collections::vec_deque::tests::bench_retain_whole_10000 ... bench:     287,426 ns/iter (+/- 9,009)

After

test collections::vec_deque::tests::bench_retain_half_10000  ... bench:     243,940 ns/iter (+/- 8,563)
test collections::vec_deque::tests::bench_retain_odd_10000   ... bench:     242,768 ns/iter (+/- 3,903)
test collections::vec_deque::tests::bench_retain_whole_10000 ... bench:     202,926 ns/iter (+/- 6,332)

Based on the current benchmark, this PR will improve the perf of VecDeque::retain by around 16%. For special cases, the improvement will be up to 30%.

Signed-off-by: Xuanwo [email protected]


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