rangeVsIndex.go

package main

import (
	"fmt"
	"math"
	"time"
)

func sum(a []int) int {
	s := 0
	for i := 0; i < len(a); i++ {
		s += a[i]
	}
	return s
}

func sum2(a []int) int {
	s := 0
	for _, x := range a {
		s += x
	}
	return s
}

func timeit(f func([]int) int) {
	num := uint64(math.Pow(2, 16))
	xs := make([]int, num)
	now := time.Now()
	for i := 0; i < 10000; i++ {
		f(xs)
	}
	fmt.Println(time.Now().Sub(now))
}

func main() {
	timeit(sum)  // 528ms
	timeit(sum2) // 385m
}