KDOC 508: 除算の実行速度を計測する

go install golang.org/x/perf/cmd/benchstat@latest

tmpdir=$(mktemp -d)
cd $tmpdir

cat > $tmpdir/bench_test.go <<EOF
  package main

  import "testing"

  func BenchmarkAdd(b *testing.B) {
  	for i := 0; i < b.N; i++ {
  		_ = add(42)
  	}
  }

  func BenchmarkDiv(b *testing.B) {
  	for i := 0; i < b.N; i++ {
  		_ = div(42)
  	}
  }

  //go:noinline
  func add(a int) int {
  	return a + a
  }

  //go:noinline
  func div(a int) int {
  	return a / a
  }
EOF

go mod init bench
go mod tidy
go test -bench=. -benchmem -count=10 > exec.log

benchstat exec.log 2>&1

rm -rf $tmpdir

goos: linux
goarch: amd64
pkg: bench
cpu: AMD Ryzen 9 9900X 12-Core Processor
        │   exec.log   │
        │    sec/op    │
Add-24    0.9069n ± 1% 👈
Div-24     1.262n ± 4% 👈
geomean    1.070n

        │   exec.log   │
        │     B/op     │
Add-24    0.000 ± 0%
Div-24    0.000 ± 0%
geomean              ¹
¹ summaries must be >0 to compute geomean

        │   exec.log   │
        │  allocs/op   │
Add-24    0.000 ± 0%
Div-24    0.000 ± 0%
geomean              ¹
¹ summaries must be >0 to compute geomean