/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Doug Lea with assistance from members of JCP JSR-166

 * Expert Group and released to the public domain, as explained at

 * http://creativecommons.org/licenses/publicdomain

 */

/*

 * @test

 * @bug 4486658

 * @compile CancelledFutureLoops.java

 * @run main/timeout=2000 CancelledFutureLoops

 * @summary Checks for responsiveness of futures to cancellation.

 * Runs under the assumption that ITERS computations require more than

 * TIMEOUT msecs to complete.

 */

import java.util.concurrent.*;

import java.util.concurrent.locks.*;

import java.util.*;

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);

        }

    }

}