benchmark for writing to buffer

benchmark_buffer.go

package buffer_benchmark

import (
	"bufio"
	"bytes"
	"testing"
)

const hoge = "hogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehogehoge"

func TestBuffer(t *testing.T) {
	n := 10

	buf := []byte{}
	for i := 0; i < n; i++ {
		buf = append(buf, []byte(hoge)...)
	}

	var buffer bytes.Buffer
	for i := 0; i < n; i++ {
		buffer.Write([]byte(hoge))
	}

	var buffer2 bytes.Buffer
	bio := bufio.NewWriter(&buffer2)
	for i := 0; i < n; i++ {
		bio.Write([]byte(hoge))
	}
	bio.Flush()

	l1 := len(buf)
	l2 := len(buffer.Bytes())
	l3 := len(buffer2.Bytes())
	if l1 != l2 || l1 != l3 {
		t.Fatal(l1, l2, l3)
	}

	s1 := string(buf)
	s2 := string(buffer.Bytes())
	s3 := string(buffer2.Bytes())
	if s1 != s2 || s1 != s3 {
		t.Fatal(s1, s2, s3)
	}
}

func BenchmarkBufIO(b *testing.B) {
	var buf bytes.Buffer
	bio := bufio.NewWriter(&buf)
	for i := 0; i < b.N; i++ {
		bio.Write([]byte(hoge))
	}
	bio.Flush()
}

func BenchmarkBytes_(b *testing.B) {
	var buf bytes.Buffer
	for i := 0; i < b.N; i++ {
		buf.Write([]byte(hoge))
	}
}

func BenchmarkBuffer(b *testing.B) {
	buf := []byte{}
	for i := 0; i < b.N; i++ {
		buf = append(buf, []byte(hoge)...)
	}
}

result.txt

dictav$ go test -benchmem -bench .                                         hello
PASS
BenchmarkBuffer	 1000000	      1098 ns/op	    2437 B/op	       1 allocs/op
BenchmarkBytes_	 5000000	      2150 ns/op	    1758 B/op	       1 allocs/op
BenchmarkBufIO	 2000000	      1512 ns/op	    1489 B/op	       1 allocs/op
ok  	buffer_benchmark	16.296s

---
dictav$ go test -benchmem -bench .                                         hello
PASS
BenchmarkBytes_	 5000000	      2050 ns/op	    1758 B/op	       1 allocs/op
BenchmarkBufIO	 5000000	      3106 ns/op	    1274 B/op	       1 allocs/op
BenchmarkBuffer	 2000000	      2958 ns/op	    2883 B/op	       1 allocs/op
ok  	buffer_benchmark	34.761s

---
dictav$ go test -benchmem -bench .                                         hello
PASS
BenchmarkBufIO	 2000000	       602 ns/op	    1489 B/op	       1 allocs/op
BenchmarkBytes_	 5000000	      2688 ns/op	    1758 B/op	       1 allocs/op
BenchmarkBuffer	  500000	      3261 ns/op	    2485 B/op	       1 allocs/op
ok  	buffer_benchmark	18.077s

---
dictav$ go test -benchmem -bench .                                         hello
PASS
BenchmarkBytes_	 5000000	      2591 ns/op	    1758 B/op	       1 allocs/op
BenchmarkBufIO	 2000000	      1894 ns/op	    1489 B/op	       1 allocs/op
BenchmarkBuffer	  500000	      2049 ns/op	    2485 B/op	       1 allocs/op
ok  	buffer_benchmark	19.551s

書き込むサイズ変えると差が出る。
実行する順番で結果が変わる