Golang string join benchmark

run.sh

#!/bin/bash

go version
go test -benchmem -bench .

string_join.go

package main

func main() {}

string_join_test.go

package main

import (
	"bytes"
	"strings"
	"testing"
)

var m = [...]string{
	"AAAAAAAAA",
	"AAAAAAAAA",
	"AAAAAAAAA",
	"AAAAAAAAA",
	"AAAAAAAAA",
	"AAAAAAAAA",
	"AAAAAAAAA",
}

func BenchmarkStringsJoin____(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = strings.Join(m[:], ",") + ","
	}
}

func BenchmarkAppendOperator_(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 string
		for _, v := range m {
			m2 += m2 + "," + v
		}
		m2 += ","
	}
}

func BenchmarkAppendOperatorF(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 string
		for _, v := range m {
			m2 += v + ","
		}
		m2 += ","
	}
}

func BenchmarkHardCoding_____(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = m[0] + "," + m[1] + "," + m[2] + "," + m[3] + "," + m[4] + "," + m[5] + "," + m[6]
	}
}

func BenchmarkByteArray______(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 []byte
		for _, v := range m {
			m2 = append(m2, v...)
			m2 = append(m2, ',')
		}
		_ = string(m2)
	}
}

func BenchmarkCapByteArray___(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 = make([]byte, 0, 100)
		for _, v := range m {
			m2 = append(m2, v...)
			m2 = append(m2, ',')
		}
		_ = string(m2)
	}
}

func BenchmarkBytesBuffer____(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 bytes.Buffer
		for _, v := range m {
			m2.Write([]byte(v))
			m2.Write([]byte{','})
		}
		_ = m2.String()
	}
}

func BenchmarkCapBytesBuffer_(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 = bytes.NewBuffer(make([]byte, 0, 100))
		for _, v := range m {
			m2.Write([]byte(v))
			m2.Write([]byte{','})
		}
		_ = m2.String()
	}
}

func BenchmarkCapBytesBuffer2(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var m2 = bytes.NewBuffer(make([]byte, 0, 100))
		for _, v := range m {
			m2.WriteString(v)
			m2.WriteString(",")
		}
		_ = m2.String()
	}
}

./run.sh

go version go1.4.2 linux/amd64
testing: warning: no tests to run
PASS
BenchmarkStringsJoin____     2000000           766 ns/op         240 B/op          3 allocs/op
BenchmarkAppendOperator_      200000          7919 ns/op        3808 B/op          8 allocs/op
BenchmarkAppendOperatorF     1000000          1472 ns/op         416 B/op          8 allocs/op
BenchmarkHardCoding_____     5000000           421 ns/op          80 B/op          1 allocs/op
BenchmarkByteArray______     1000000          1344 ns/op         320 B/op          5 allocs/op
BenchmarkCapByteArray___     3000000           359 ns/op          80 B/op          1 allocs/op
BenchmarkBytesBuffer____      500000          2715 ns/op         448 B/op         10 allocs/op
BenchmarkCapBytesBuffer_      500000          2520 ns/op         416 B/op         10 allocs/op
BenchmarkCapBytesBuffer2     1000000          1432 ns/op         304 B/op          3 allocs/op

go1.5beta3

./run.sh

go version devel +d3ffc97 Wed Jul 29 23:50:20 2015 +0000 linux/amd64
testing: warning: no tests to run
PASS
BenchmarkStringsJoin____-4   5000000           357 ns/op         240 B/op          3 allocs/op
BenchmarkAppendOperator_-4   1000000          1985 ns/op        3808 B/op          8 allocs/op
BenchmarkAppendOperatorF-4   2000000           837 ns/op         416 B/op          8 allocs/op
BenchmarkHardCoding_____-4   5000000           276 ns/op          80 B/op          1 allocs/op
BenchmarkByteArray______-4   3000000           518 ns/op         320 B/op          5 allocs/op
BenchmarkCapByteArray___-4  10000000           148 ns/op          80 B/op          1 allocs/op
BenchmarkBytesBuffer____-4   2000000           716 ns/op         336 B/op          3 allocs/op
BenchmarkCapBytesBuffer_-4   3000000           563 ns/op         304 B/op          3 allocs/op
BenchmarkCapBytesBuffer2-4   3000000           486 ns/op         304 B/op          3 allocs/op

./run.sh

go version go1.6.1 darwin/amd64
testing: warning: no tests to run
PASS
BenchmarkStringsJoin____-4   5000000           347 ns/op         240 B/op          3 allocs/op
BenchmarkAppendOperator_-4   1000000          1805 ns/op        3808 B/op          8 allocs/op
BenchmarkAppendOperatorF-4   2000000           760 ns/op         416 B/op          8 allocs/op
BenchmarkHardCoding_____-4   5000000           265 ns/op          80 B/op          1 allocs/op
BenchmarkByteArray______-4   3000000           455 ns/op         320 B/op          5 allocs/op
BenchmarkCapByteArray___-4  10000000           134 ns/op          80 B/op          1 allocs/op
BenchmarkBytesBuffer____-4   2000000           666 ns/op         336 B/op          3 allocs/op
BenchmarkCapBytesBuffer_-4   3000000           519 ns/op         304 B/op          3 allocs/op
BenchmarkCapBytesBuffer2-4   3000000           441 ns/op         304 B/op          3 allocs/op