go：多核并行化问题

package main

import (
	"fmt"
	//"runtime"//执行并行段时需要引入该包
	"time"
)
const (
	NUM = 100000000
)
type vint struct {
	n []int
}
func (v vint) Doadd(p, i, n int, u []int, c chan int) {
	tempv=v.n[p]
	for j := 0; j < 1000; j++ {
		for ti := i; ti < n; ti++ {
			v.n[p] += u[ti]
		}
		v.n[p]=tempv//重置v.n[p]
	}
	c <- 1
	return
}
func (v vint) Doall(ncpu int, u []int) (sum int) {
	c := make(chan int, ncpu)
	segment := NUM / ncpu
	for i := 0; i < ncpu; i++ {
		go v.Doadd(i, i*segment, (i+1)*segment, u, c)
	}
	for i := 0; i < ncpu; i++ {
		<-c
	}
	for i := 0; i < ncpu; i++ {
		sum += v.n[i]
	}
	return
}
func main() {
	/*并行段
	ncpu := runtime.NumCPU()
	runtime.GOMAXPROCS(ncpu)
	u := make([]int, NUM)
	for i := 0; i < NUM; i++ {
		u[i] = 1
	}
	v := new(vint)
	v.n = make([]int, ncpu)

	ts := time.Now().UnixNano()
	sum := v.Doall(ncpu, u)
	te := time.Now().UnixNano()
	fmt.Println((te - ts), sum)*/
	
	//串行段
	u := make([]int, NUM)
	for i := 0; i < NUM; i++ {
		u[i] = 1
	}
	ts := time.Now().UnixNano()
	for j := 0; j < 1000; j++ {
		sum := 0
		for i := 0; i < NUM; i++ {
			sum += u[i]
		}
	}
	te := time.Now().UnixNano()
	fmt.Println((te - ts))

	return
}