public final class CancelledFutureLoops {
static final ExecutorService pool = Executors.newCachedThreadPool();
static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
static boolean print = false;
static final int ITERS = 1000000;
static final long TIMEOUT = 100;
public static void main(String[] args) throws Exception {
int maxThreads = 5;
if (args.length > 0) maxThreads = Integer.parseInt(args[0]);
print = true;
for (int i = 2; i <= maxThreads; i += (i + 1) >>> 1) {
System.out.print("Threads: " + i);
try {
new FutureLoop(i).test();
} catch (BrokenBarrierException bb) {
// OK; ignore
} catch (ExecutionException ee) {
// OK; ignore
}
Thread.sleep(TIMEOUT);
}
pool.shutdown();
if (!pool.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS)) throw new Error();
}
static final class FutureLoop implements Callable {
private int v = rng.next();
private final ReentrantLock lock = new ReentrantLock();
private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
private final CyclicBarrier barrier;
private final int nthreads;
FutureLoop(int nthreads) {
this.nthreads = nthreads;
barrier = new CyclicBarrier(nthreads + 1, timer);
}
final void test() throws Exception {
Future[] futures = new Future[nthreads];
for (int i = 0; i < nthreads; ++i) futures[i] = pool.submit(this);
barrier.await();
Thread.sleep(TIMEOUT);
boolean tooLate = false;
for (int i = 1; i < nthreads; ++i) {
if (!futures[i].cancel(true)) tooLate = true;
// Unbunch some of the cancels
if ((i & 3) == 0) Thread.sleep(1 + rng.next() % 10);
}
Object f0 = futures[0].get();
if (!tooLate) {
for (int i = 1; i < nthreads; ++i) {
if (!futures[i].isDone() || !futures[i].isCancelled())
throw new Error("Only one thread should complete");
}
} else System.out.print("(cancelled too late) ");
long endTime = System.nanoTime();
long time = endTime - timer.startTime;
if (print) {
double secs = (double) (time) / 1000000000.0;
System.out.println("\t " + secs + "s run time");
}
}
public final Object call() throws Exception {
barrier.await();
int sum = v;
int x = 0;
int n = ITERS;
while (n-- > 0) {
lock.lockInterruptibly();
try {
v = x = LoopHelpers.compute1(v);
} finally {
lock.unlock();
}
sum += LoopHelpers.compute2(LoopHelpers.compute2(x));
}
return new Integer(sum);
}
}
}
