golang map vs slice sort speed

sort.go

package main

import (
	"fmt"
	"math/rand"
	"sort"
	"time"
)

type S []int

func (s S) Len() int {
	return len(s)
}
func (s S) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

func (s S) Less(i, j int) bool {
	return s[i] < s[j]
}

type M map[int]int

func (m M) Len() int {
	return len(m)
}
func (m M) Swap(i, j int) {
	m[i], m[j] = m[j], m[i]
}

func (m M) Less(i, j int) bool {
	return m[i] < m[j]
}

func main() {
	m := M{}
	b := []int{}
	s := S{}
	for i := 0; i < 1000000; i++ {
		n := rand.Intn(1000000)
		m[i] = n
		s = append(s, n)
		b = append(b, n)
	}
	start := time.Now()
	sort.Sort(s)
	fmt.Println("slice\t", time.Since(start).Seconds())
	start = time.Now()
	sort.Sort(m)
	fmt.Println("map\t", time.Since(start).Seconds())
	start = time.Now()
	sort.Ints(b)
	fmt.Println("int\t", time.Since(start).Seconds())
}


/*
result:
slice	 0.29914495900000004
map	 3.14801621
int	 0.330597454
*/