sclass FastCollab is ICollab, AutoCloseable {

  settable bool useMainThread = true;

  volatile settable bool isDone;

  gettable int coresToUse;

  FastCollabWorker[] workers;

  AtomicReferenceArray<Runnable> workArray;

  // 0 = spin-wait, otherwise time to sleep in milliseconds

  settable int sleepTime = 0;

  settable PingSource interruptor = new;

  static final Runnable DONE = r { fail("Collab done") };

  *(int coresToUse) {

    this.coresToUse = max(1, coresToUse);

    workArray = new AtomicReferenceArray(this.coresToUse);

  }

  public void addWork(Runnable work) {

    if (work == null) ret;

    for (int i = 0; i < workArray.length(); i++)

      if (workArray.compareAndSet(i, null, work))

        ret;

    // Everyone is busy - do the work ourselves

    work.run();

  }

  // returns null => sleep

  // returns DONE => all work done

  public Runnable grabWork(int workerIndex) {

    if (isDone) ret DONE;

    Runnable work = workArray.get(workerIndex);

    if (work != null)

      workArray.set(workerIndex, null);

    ret work;

  }

  public void done { isDone(true); }

  toString { ret "FastCollab*" + n2(coresToUse); }

  run {

    workers = new FastCollabWorker[coresToUse];

    for i to coresToUse: 

      workers[i] = new FastCollabWorker(this, i).interruptor(interruptor);

    int iFirst = useMainThread ? 1 : 0; 

    for (int i = iFirst; i < coresToUse; i++)

      startThread(workers[i]);

    if (useMainThread)

      workers[0].run();

    for (int i = iFirst; i < coresToUse; i++)

      workers[i].join();

  }

  close {

    interruptor().cancel();

  }

}