Overview

Reddit にて、以下のスレッドを発見。

Go is 2-3 times slower than JS in a similar code. What makes Go slow in this specific code?

IntelのCPUだと、% を使った計算がとても遅くなるとの話。

内容を見ると、int と uint32 (int32) では、速度が全然異なる状態であると判明している。

どうも、intの状態だと実行時にint64で解釈されてしまうため、遅くなるとのこと。

以下に、AMDとIntelで試してみた結果を記載する。

CPU: AMD EPYC 7B13

$ task -d examples/singleapp/mod_operator_performance/
task: [run] go test . -bench . -benchtime 10s -cpu 8
goos: linux
goarch: amd64
pkg: github.com/devlights/try-golang/examples/singleapp/mod_operator_performance
cpu: AMD EPYC 7B13
BenchmarkModOperatorInt-8            261          45508221 ns/op
BenchmarkModOperatorUInt32-8         306          39010884 ns/op
PASS
ok      github.com/devlights/try-golang/examples/singleapp/mod_operator_performance     32.406s

CPU: Intel(R) Core(TM) i7-10510U

Windows

$ task -d .\examples\singleapp\mod_operator_performance\
task: [run] go test . -bench . -benchtime 10s -cpu 8
goos: windows
goarch: amd64
pkg: github.com/devlights/try-golang/examples/singleapp/mod_operator_performance
cpu: Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
BenchmarkModOperatorInt-8             76         147983075 ns/op
BenchmarkModOperatorUInt32-8         274          44632203 ns/op
PASS
ok      github.com/devlights/try-golang/examples/singleapp/mod_operator_performance     28.765s

WSL

$ task -d examples/singleapp/mod_operator_performance/
task: [run] go test . -bench . -benchtime 10s -cpu 8
goos: linux
goarch: amd64
pkg: github.com/devlights/try-golang/examples/singleapp/mod_operator_performance
cpu: Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
BenchmarkModOperatorInt-8             78         144214159 ns/op
BenchmarkModOperatorUInt32-8         283          42288278 ns/op
PASS
ok      github.com/devlights/try-golang/examples/singleapp/mod_operator_performance     27.647s

たしかに、Intelの場合、差がとても大きい。