barrier

gistfile1.txt

package main

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

type Barrier struct {
	para  chan int
	br    chan int
	items *[]int
	f     func(int)
}

func NewBarrier(parallelism int, items []int, f func(int)) Barrier {
	return Barrier{
		make(chan int, parallelism),
		make(chan int, 1),
		&items,
		f,
	}
}

func (b Barrier) Wait() {
	c := len(*b.items)
	for _, i := range *b.items {
		func(captured_i int) {
			b.Enter()
			go func() {
				b.f(captured_i)
				b.Leave()
			}()
		}(i)
	}

	for {
		<-b.br
		c -= 1
		if c <= 0 {
			break
		}
	}

}

func (b Barrier) Enter() {
	b.para <- 1
}
func (b Barrier) Leave() {
	n := <-b.para
	b.br <- n
}

func main() {
	items := []int{1, 2, 3, 4, 5, 6, 7, 8 }
	b := NewBarrier(4, items, func(i int) {
		get(i)
	})
	b.Wait()

	fmt.Printf("quitting pc %d\n", pc)
	//	<- barrier
}
var pc int = 0
func get(i int) int {
	time.Sleep(time.Duration(rand.Intn(800)) * time.Millisecond)
	fmt.Printf("%d\n", i)
	pc += 1
	return 100
}