ring.go

package main

import (
	"fmt"
	"sync"
	"time"
)

var wg sync.WaitGroup

func main() {
	start := time.Now()
	ring(5, 100000)
	elapsed := time.Since(start)
	fmt.Printf("Time taken: %v\n", elapsed)
}

func ring(N int, M int) {
	wg.Add(N)
	chanarr := make([](chan int), N)

	for i, _ := range chanarr {
		chanarr[i] = make(chan int)
	}

	for i := 0; i < (N - 1); i++ {
		go node(chanarr[i], chanarr[i+1])
	}
	go decnode(chanarr[N-1], chanarr[0])

	chanarr[0] <- M

	wg.Wait()
}

func node(this chan int, next chan int) {
	for {
		msg := <-this
		next <- msg
		if msg == 0 {
			close(next)
			wg.Done()
			break
		}
	}
}

func decnode(this chan int, next chan int) {
	for {
		msg := <-this
		if msg == 0 {
			close(next)
			wg.Done()
			break
		}
		next <- (msg - 1)
	}
}

// $ go build
// $ ./ring 
// Time taken: 131.612955ms