stringbuild_test.go

package stringbuild_test

import (
	"bytes"
	"testing"
)

func StringBuild_bad() string {
	str := ""
	for i := 0; i < 1000; i++ {
		str += "a"
	}
	return str
}

func StringBuild_good() string {
	var buffer bytes.Buffer
	for i := 0; i < 1000; i++ {
		buffer.WriteString("a")
	}
	return buffer.String()
}

func StringBuild_good2() string {
	buffer := bytes.NewBufferString("")
	for i := 0; i < 1000; i++ {
		buffer.WriteString("a")
	}
	return buffer.String()
}

func BenchmarkStringBuild_bad(b *testing.B) {
	for i := 0; i < b.N; i++ {
		StringBuild_bad()
	}
}

func BenchmarkStringBuild_good(b *testing.B) {
	for i := 0; i < b.N; i++ {
		StringBuild_good()
	}
}

func BenchmarkStringBuild_good2(b *testing.B) {
	for i := 0; i < b.N; i++ {
		StringBuild_good2()
	}
}

/* result
$ go version
go version devel +2a50b4f1d9f9 Sat Apr 13 23:09:08 2013 -0700 darwin/amd64

$ go test -test.bench Bench -test.benchmem
testing: warning: no tests to run
PASS
BenchmarkStringBuild_bad           10000            284844 ns/op          545081 B/op       1000 allocs/op
BenchmarkStringBuild_good          50000             34119 ns/op            3341 B/op          6 allocs/op
ok      github.com/atotto/tmp    4.965s
*/

Blog : http://atotto.hatenadiary.jp/entry/2013/04/26/202701