Go: Benchmark of repeat and concatenation of characters

a_test.go

package s

import (
	"bytes"
	"testing"
)

func A1() (s string) {
	for i := 0; i < 1000; i++ {
		s += "a"
	}
	return
}
func A2() string {
	var b bytes.Buffer
	for i := 0; i < 1000; i++ {
		b.WriteString("a")
	}
	return b.String()
}
func A3() string {
	b := make([]byte, 1000)
	bp := copy(b, "a")
	for bp < len(b) {
		copy(b[bp:], b[:bp])
		bp *= 2
	}
	return string(b)
}
func BenchmarkA1(b *testing.B) {
	for i := 0; i < b.N; i++ {
		A1()
	}
}
func BenchmarkA2(b *testing.B) {
	for i := 0; i < b.N; i++ {
		A2()
	}
}
func BenchmarkA3(b *testing.B) {
	for i := 0; i < b.N; i++ {
		A3()
	}
}

// BenchmarkA1-4	   10000	    244578 ns/op
// BenchmarkA2-4	  100000	     18698 ns/op
// BenchmarkA3-4	 3000000	       464 ns/op
// A3() == strings.Repeat()