test/bench/shootout/threadring.go

/*
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    * Redistributions of source code must retain the above copyright
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    * Redistributions in binary form must reproduce the above copyright
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    documentation and/or other materials provided with the distribution.

    * Neither the name of "The Computer Language Benchmarks Game" nor the
    name of "The Computer Language Shootout Benchmarks" nor the names of
    its contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.

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*/

/* The Computer Language Benchmarks Game
 * http://shootout.alioth.debian.org/
 *
 * contributed by The Go Authors.
 */

package main

import (
	"flag"
	"fmt"
	"os"
)

var n = flag.Int("n", 1000, "how many passes")

const Nthread = 503

func f(i int, in <-chan int, out chan<- int) {
	for {
		n := <-in
		if n == 0 {
			fmt.Printf("%d\n", i)
			os.Exit(0)
		}
		out <- n - 1
	}
}

func main() {
	flag.Parse()

	one := make(chan int) // will be input to thread 1
	var in, out chan int = nil, one
	for i := 1; i <= Nthread-1; i++ {
		in, out = out, make(chan int)
		go f(i, in, out)
	}
	go f(Nthread, out, one)
	one <- *n
	<-make(chan int) // hang until ring completes
}