benchmark/bench/threadring.groovy

/**
 * The Computer Language Benchmarks Game
 * http://shootout.alioth.debian.org/
 * contributed by Klaus Friedel
 * converted to Groovy by Danno Ferrin
 */

import java.util.concurrent.locks.LockSupport;

public static class MessageThread extends Thread {
  MessageThread nextThread;
  volatile Integer message;

  public MessageThread(MessageThread nextThread, int name) {
    super(""+name);
    this.nextThread = nextThread;
  }

  public void run() {
    while(true) nextThread.enqueue(dequeue());
  }

  public void enqueue(Integer hopsRemaining) {
    if(hopsRemaining == 0){
      System.out.println(getName());
      System.exit(0);
    }
    // as only one message populates the ring, it's impossible
    // that queue is not empty
    message = hopsRemaining - 1;
    LockSupport.unpark(this); // work waiting...
  }

  private Integer dequeue(){
    while(message == null){
      LockSupport.park();
    }
    Integer msg = message;
    message = null;
    return msg;
  }
}

int THREAD_COUNT = 503;
int hopCount = Integer.parseInt(args[0]);

MessageThread first = null;
MessageThread last = null;
for (int i = THREAD_COUNT; i >= 1 ; i--) {
  first = new MessageThread(first, i);
  if(i == THREAD_COUNT) last = first;
}
// close the ring:
last.nextThread = first;

// start all Threads
MessageThread t = first;
t.start();
t = t.nextThread;
while(t != first) {
  t.start();
  t = t.nextThread;
}
// inject message
first.enqueue(hopCount);
first.join(); // wait for System.exit