Go: bytes.Equal vs. reflect.DeepEqual (vs. self-implemented equal) (https://wang.yuxuan.org/blog/item/2017/02/comparing-byte-s-in-go)

equal_test.go

package main_test

import (
	"bytes"
	"fmt"
	"math/rand"
	"os"
	"reflect"
	"testing"
	"time"
)

var sizes = []int{
	1024,
	1024 * 1024,
	64 * 1024 * 1024,
}

func TestMain(m *testing.M) {
	rand.Seed(time.Now().Unix())
	os.Exit(m.Run())
}

func BenchmarkEqual(b *testing.B) {
	for _, size := range sizes {
		b1 := make([]byte, size)
		rand.Read(b1)
		b2 := make([]byte, size)
		copy(b2, b1)

		b.Run(
			fmt.Sprintf("reflect.DeepEqual-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					reflect.DeepEqual(b1, b2)
				}
			},
		)

		b.Run(
			fmt.Sprintf("equal-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					equal(b1, b2)
				}
			},
		)

		b.Run(
			fmt.Sprintf("bytes.Equal-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					bytes.Equal(b1, b2)
				}
			},
		)
	}
}

func BenchmarkNonEqual(b *testing.B) {
	for _, size := range sizes {
		b1 := make([]byte, size)
		rand.Read(b1)
		b2 := make([]byte, size)
		rand.Read(b2)

		b.Run(
			fmt.Sprintf("reflect.DeepEqual-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					reflect.DeepEqual(b1, b2)
				}
			},
		)

		b.Run(
			fmt.Sprintf("equal-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					equal(b1, b2)
				}
			},
		)

		b.Run(
			fmt.Sprintf("bytes.Equal-%d", size),
			func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					bytes.Equal(b1, b2)
				}
			},
		)
	}
}

func TestEqual(t *testing.T) {
	for _, size := range sizes {
		b1 := make([]byte, size)
		rand.Read(b1)
		b2 := make([]byte, size)
		rand.Read(b2)
		b3 := make([]byte, size)
		copy(b3, b1)

		t.Run(
			fmt.Sprintf("reflect.DeepEqual-%d", size),
			func(t *testing.T) {
				if reflect.DeepEqual(b1, b2) {
					t.Error("reflect.DeepEqual(b1, b2) should return false")
				}
				if !reflect.DeepEqual(b1, b3) {
					t.Error("reflect.DeepEqual(b1, b2) should return true")
				}
			},
		)

		t.Run(
			fmt.Sprintf("equal-%d", size),
			func(t *testing.T) {
				if equal(b1, b2) {
					t.Error("equal(b1, b2) should return false")
				}
				if !equal(b1, b3) {
					t.Error("equal(b1, b2) should return true")
				}
			},
		)

		t.Run(
			fmt.Sprintf("bytes.Equal-%d", size),
			func(t *testing.T) {
				if bytes.Equal(b1, b2) {
					t.Error("bytes.Equal(b1, b2) should return false")
				}
				if !bytes.Equal(b1, b3) {
					t.Error("bytes.Equal(b1, b2) should return true")
				}
			},
		)
	}
}

func equal(b1, b2 []byte) bool {
	if len(b1) != len(b2) {
		return false
	}
	for i, b := range b1 {
		if b != b2[i] {
			return false
		}
	}
	return true
}

test-result.txt

$ go test -bench=.
BenchmarkEqual/reflect.DeepEqual-1024-4         	   20000	     91193 ns/op
BenchmarkEqual/equal-1024-4                     	 3000000	       544 ns/op
BenchmarkEqual/bytes.Equal-1024-4               	50000000	        22.6 ns/op
BenchmarkEqual/reflect.DeepEqual-1048576-4      	      20	  89556304 ns/op
BenchmarkEqual/equal-1048576-4                  	    3000	    536891 ns/op
BenchmarkEqual/bytes.Equal-1048576-4            	   30000	     44613 ns/op
BenchmarkEqual/reflect.DeepEqual-67108864-4     	       1	5801186044 ns/op
BenchmarkEqual/equal-67108864-4                 	      30	  37011544 ns/op
BenchmarkEqual/bytes.Equal-67108864-4           	     200	   8574768 ns/op
BenchmarkNonEqual/reflect.DeepEqual-1024-4      	 5000000	       280 ns/op
BenchmarkNonEqual/equal-1024-4                  	500000000	         3.46 ns/op
BenchmarkNonEqual/bytes.Equal-1024-4            	300000000	         4.56 ns/op
BenchmarkNonEqual/reflect.DeepEqual-1048576-4   	 5000000	       272 ns/op
BenchmarkNonEqual/equal-1048576-4               	500000000	         3.44 ns/op
BenchmarkNonEqual/bytes.Equal-1048576-4         	300000000	         4.52 ns/op
BenchmarkNonEqual/reflect.DeepEqual-67108864-4  	 5000000	       269 ns/op
BenchmarkNonEqual/equal-67108864-4              	500000000	         3.42 ns/op
BenchmarkNonEqual/bytes.Equal-67108864-4        	300000000	         4.50 ns/op
PASS
ok  	_/Users/fishy/work/test	44.270s