Goでベンチマークを取る

Goでのベンチマークの取り方。
https://golang.org/pkg/testing/

package main

import (
    "fmt"
    "testing"
)

func makeSlice1(n int) []string {
    var r []string
    for i := 0; i < n; i++ {
        r = append(r, fmt.Sprintf("%03d hello", i))
    }
    return r
}

func makeSlice2(n int) []string {
    r := make([]string, n)
    for i := 0; i < n; i++ {
        r[i] = fmt.Sprintf("%03d hello", i)
    }
    return r
}

func BenchmarkMakeSlice1(b *testing.B) {
    b.ResetTimer()
    makeSlice1(b.N)
}

func BenchmarkMakeSlice2(b *testing.B) {
    b.ResetTimer()
    makeSlice2(b.N)
}

$ go test -bench .
goos: darwin
goarch: amd64
BenchmarkMakeSlice1-4        5000000           285 ns/op
BenchmarkMakeSlice2-4       10000000           144 ns/op
PASS
ok      _/go/to/path    3.383s