strconv.AppendIntはやい

bench_test.go

package main

import (
	"fmt"
	"strconv"
	"testing"
)

func F1(n int) string {
	res := ""
	for i := 0; i < n; i++ {
		res += fmt.Sprintf("%d yen\n", i)
	}
	return res
}

func F2(n int) string {
	res := make([]byte, 0, n*3+5*n)
	for i := 0; i < n; i++ {
		res = append(res, fmt.Sprintf("%d yen\n", i)...)
	}
	return string(res)
}

func F3(n int) string {
	res := make([]byte, 0, n*3+5*n)
	for i := 0; i < n; i++ {
		res = append(res, strconv.Itoa(i)...)
		res = append(res, " yen\n"...)
	}
	return string(res)
}
func F4(n int) string {
	res := make([]byte, 0, n*3+5*n)
	for i := 0; i < n; i++ {
		res = strconv.AppendInt(res, int64(i), 10)
		res = append(res, " yen\n"...)
	}
	return string(res)
}

func TestEq(t *testing.T) {
	n := 100
	res := F1(n)
	if !(res == F2(n) && res == F3(n) && res == F4(n)) {
		t.Error("fail")
	}
}

func BenchmarkF1(b *testing.B) {
	for i := 0; i < b.N; i++ {
		F1(100)
	}
}
func BenchmarkF2(b *testing.B) {
	for i := 0; i < b.N; i++ {
		F2(100)
	}
}
func BenchmarkF3(b *testing.B) {
	for i := 0; i < b.N; i++ {
		F3(100)
	}
}
func BenchmarkF4(b *testing.B) {
	for i := 0; i < b.N; i++ {
		F4(100)
	}
}

$ go version
go version go1.4.2 linux/amd64