From a12edb8db6f3fa93a1ccd96a0f84b647d08429ef Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Fri, 17 Feb 2017 14:20:11 -0800 Subject: math/bits: faster OnesCount, added respective benchmarks MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Also: Changed Reverse/ReverseBytes implementations to use the same (smaller) masks as OnesCount. BenchmarkOnesCount-8 37.0 6.26 -83.08% BenchmarkOnesCount8-8 7.24 1.99 -72.51% BenchmarkOnesCount16-8 11.3 2.47 -78.14% BenchmarkOnesCount32-8 18.4 3.02 -83.59% BenchmarkOnesCount64-8 40.0 3.78 -90.55% BenchmarkReverse-8 6.69 6.22 -7.03% BenchmarkReverse8-8 1.64 1.64 +0.00% BenchmarkReverse16-8 2.26 2.18 -3.54% BenchmarkReverse32-8 2.88 2.87 -0.35% BenchmarkReverse64-8 5.64 4.34 -23.05% BenchmarkReverseBytes-8 2.48 2.17 -12.50% BenchmarkReverseBytes16-8 0.63 0.95 +50.79% BenchmarkReverseBytes32-8 1.13 1.24 +9.73% BenchmarkReverseBytes64-8 2.50 2.16 -13.60% OnesCount-8 37.0ns ± 0% 6.3ns ± 0% ~ (p=1.000 n=1+1) OnesCount8-8 7.24ns ± 0% 1.99ns ± 0% ~ (p=1.000 n=1+1) OnesCount16-8 11.3ns ± 0% 2.5ns ± 0% ~ (p=1.000 n=1+1) OnesCount32-8 18.4ns ± 0% 3.0ns ± 0% ~ (p=1.000 n=1+1) OnesCount64-8 40.0ns ± 0% 3.8ns ± 0% ~ (p=1.000 n=1+1) Reverse-8 6.69ns ± 0% 6.22ns ± 0% ~ (p=1.000 n=1+1) Reverse8-8 1.64ns ± 0% 1.64ns ± 0% ~ (all samples are equal) Reverse16-8 2.26ns ± 0% 2.18ns ± 0% ~ (p=1.000 n=1+1) Reverse32-8 2.88ns ± 0% 2.87ns ± 0% ~ (p=1.000 n=1+1) Reverse64-8 5.64ns ± 0% 4.34ns ± 0% ~ (p=1.000 n=1+1) ReverseBytes-8 2.48ns ± 0% 2.17ns ± 0% ~ (p=1.000 n=1+1) ReverseBytes16-8 0.63ns ± 0% 0.95ns ± 0% ~ (p=1.000 n=1+1) ReverseBytes32-8 1.13ns ± 0% 1.24ns ± 0% ~ (p=1.000 n=1+1) ReverseBytes64-8 2.50ns ± 0% 2.16ns ± 0% ~ (p=1.000 n=1+1) Change-Id: I591b0ffc83fc3a42828256b6e5030f32c64f9497 Reviewed-on: https://go-review.googlesource.com/37218 Reviewed-by: Matthew Dempsky --- src/math/bits/bits_impl.go | 8 -------- 1 file changed, 8 deletions(-) (limited to 'src/math/bits/bits_impl.go') diff --git a/src/math/bits/bits_impl.go b/src/math/bits/bits_impl.go index 3a425e3b83..c7834106c8 100644 --- a/src/math/bits/bits_impl.go +++ b/src/math/bits/bits_impl.go @@ -74,14 +74,6 @@ func ntz64(x uint64) int { return int(deBruijn64tab[(x&-x)*deBruijn64>>(64-6)]) } -func pop(x uint64) (n int) { - for x != 0 { - n++ - x &= x - 1 - } - return -} - func pos(k int) uint { if k < 0 { panic("negative rotation count") -- cgit v1.3