| /* |
| * 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. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * 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. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * 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/publicdomain/zero/1.0/ |
| */ |
| |
| |
| package java.util.concurrent; |
| |
| |
| /** |
| * A synchronization aid that allows a set of threads to all wait for |
| * each other to reach a common barrier point. CyclicBarriers are |
| * useful in programs involving a fixed sized party of threads that |
| * must occasionally wait for each other. The barrier is called |
| * <em>cyclic</em> because it can be re-used after the waiting threads |
| * are released. |
| * |
| * <p>A {@code CyclicBarrier} supports an optional {@link java.lang.Runnable Runnable} command |
| * that is run once per barrier point, after the last thread in the party |
| * arrives, but before any threads are released. |
| * This <em>barrier action</em> is useful |
| * for updating shared-state before any of the parties continue. |
| * |
| * <p><b>Sample usage:</b> Here is an example of using a barrier in a |
| * parallel decomposition design: |
| * |
| * <pre> {@code |
| * class Solver { |
| * final int N; |
| * final float[][] data; |
| * final CyclicBarrier barrier; |
| * |
| * class Worker implements Runnable { |
| * int myRow; |
| * Worker(int row) { myRow = row; } |
| * public void run() { |
| * while (!done()) { |
| * processRow(myRow); |
| * |
| * try { |
| * barrier.await(); |
| * } catch (InterruptedException ex) { |
| * return; |
| * } catch (BrokenBarrierException ex) { |
| * return; |
| * } |
| * } |
| * } |
| * } |
| * |
| * public Solver(float[][] matrix) { |
| * data = matrix; |
| * N = matrix.length; |
| * Runnable barrierAction = |
| * new Runnable() { public void run() { mergeRows(...); }}; |
| * barrier = new CyclicBarrier(N, barrierAction); |
| * |
| * List<Thread> threads = new ArrayList<>(N); |
| * for (int i = 0; i < N; i++) { |
| * Thread thread = new Thread(new Worker(i)); |
| * threads.add(thread); |
| * thread.start(); |
| * } |
| * |
| * // wait until done |
| * for (Thread thread : threads) |
| * thread.join(); |
| * } |
| * }}</pre> |
| * |
| * Here, each worker thread processes a row of the matrix then waits at the |
| * barrier until all rows have been processed. When all rows are processed |
| * the supplied {@link java.lang.Runnable Runnable} barrier action is executed and merges the |
| * rows. If the merger |
| * determines that a solution has been found then {@code done()} will return |
| * {@code true} and each worker will terminate. |
| * |
| * <p>If the barrier action does not rely on the parties being suspended when |
| * it is executed, then any of the threads in the party could execute that |
| * action when it is released. To facilitate this, each invocation of |
| * {@link #await} returns the arrival index of that thread at the barrier. |
| * You can then choose which thread should execute the barrier action, for |
| * example: |
| * <pre> {@code |
| * if (barrier.await() == 0) { |
| * // log the completion of this iteration |
| * }}</pre> |
| * |
| * <p>The {@code CyclicBarrier} uses an all-or-none breakage model |
| * for failed synchronization attempts: If a thread leaves a barrier |
| * point prematurely because of interruption, failure, or timeout, all |
| * other threads waiting at that barrier point will also leave |
| * abnormally via {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException} (or |
| * {@link java.lang.InterruptedException InterruptedException} if they too were interrupted at about |
| * the same time). |
| * |
| * <p>Memory consistency effects: Actions in a thread prior to calling |
| * {@code await()} |
| * <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a> |
| * actions that are part of the barrier action, which in turn |
| * <i>happen-before</i> actions following a successful return from the |
| * corresponding {@code await()} in other threads. |
| * |
| * @since 1.5 |
| * @see java.util.concurrent.CountDownLatch |
| * |
| * @author Doug Lea |
| */ |
| |
| @SuppressWarnings({"unchecked", "deprecation", "all"}) |
| public class CyclicBarrier { |
| |
| /** |
| * Creates a new {@code CyclicBarrier} that will trip when the |
| * given number of parties (threads) are waiting upon it, and which |
| * will execute the given barrier action when the barrier is tripped, |
| * performed by the last thread entering the barrier. |
| * |
| * @param parties the number of threads that must invoke {@link #await} |
| * before the barrier is tripped |
| * @param barrierAction the command to execute when the barrier is |
| * tripped, or {@code null} if there is no action |
| * @throws java.lang.IllegalArgumentException if {@code parties} is less than 1 |
| */ |
| |
| public CyclicBarrier(int parties, java.lang.Runnable barrierAction) { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Creates a new {@code CyclicBarrier} that will trip when the |
| * given number of parties (threads) are waiting upon it, and |
| * does not perform a predefined action when the barrier is tripped. |
| * |
| * @param parties the number of threads that must invoke {@link #await} |
| * before the barrier is tripped |
| * @throws java.lang.IllegalArgumentException if {@code parties} is less than 1 |
| */ |
| |
| public CyclicBarrier(int parties) { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Returns the number of parties required to trip this barrier. |
| * |
| * @return the number of parties required to trip this barrier |
| */ |
| |
| public int getParties() { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Waits until all {@linkplain #getParties parties} have invoked |
| * {@code await} on this barrier. |
| * |
| * <p>If the current thread is not the last to arrive then it is |
| * disabled for thread scheduling purposes and lies dormant until |
| * one of the following things happens: |
| * <ul> |
| * <li>The last thread arrives; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * the current thread; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * one of the other waiting threads; or |
| * <li>Some other thread times out while waiting for barrier; or |
| * <li>Some other thread invokes {@link #reset} on this barrier. |
| * </ul> |
| * |
| * <p>If the current thread: |
| * <ul> |
| * <li>has its interrupted status set on entry to this method; or |
| * <li>is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while waiting |
| * </ul> |
| * then {@link java.lang.InterruptedException InterruptedException} is thrown and the current thread's |
| * interrupted status is cleared. |
| * |
| * <p>If the barrier is {@link #reset} while any thread is waiting, |
| * or if the barrier {@linkplain #isBroken is broken} when |
| * {@code await} is invoked, or while any thread is waiting, then |
| * {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException} is thrown. |
| * |
| * <p>If any thread is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while waiting, |
| * then all other waiting threads will throw |
| * {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException} and the barrier is placed in the broken |
| * state. |
| * |
| * <p>If the current thread is the last thread to arrive, and a |
| * non-null barrier action was supplied in the constructor, then the |
| * current thread runs the action before allowing the other threads to |
| * continue. |
| * If an exception occurs during the barrier action then that exception |
| * will be propagated in the current thread and the barrier is placed in |
| * the broken state. |
| * |
| * @return the arrival index of the current thread, where index |
| * {@code getParties() - 1} indicates the first |
| * to arrive and zero indicates the last to arrive |
| * @throws java.lang.InterruptedException if the current thread was interrupted |
| * while waiting |
| * @throws java.util.concurrent.BrokenBarrierException if <em>another</em> thread was |
| * interrupted or timed out while the current thread was |
| * waiting, or the barrier was reset, or the barrier was |
| * broken when {@code await} was called, or the barrier |
| * action (if present) failed due to an exception |
| */ |
| |
| public int await() throws java.util.concurrent.BrokenBarrierException, java.lang.InterruptedException { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Waits until all {@linkplain #getParties parties} have invoked |
| * {@code await} on this barrier, or the specified waiting time elapses. |
| * |
| * <p>If the current thread is not the last to arrive then it is |
| * disabled for thread scheduling purposes and lies dormant until |
| * one of the following things happens: |
| * <ul> |
| * <li>The last thread arrives; or |
| * <li>The specified timeout elapses; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * the current thread; or |
| * <li>Some other thread {@linkplain java.lang.Thread#interrupt Thread#interrupt} |
| * one of the other waiting threads; or |
| * <li>Some other thread times out while waiting for barrier; or |
| * <li>Some other thread invokes {@link #reset} on this barrier. |
| * </ul> |
| * |
| * <p>If the current thread: |
| * <ul> |
| * <li>has its interrupted status set on entry to this method; or |
| * <li>is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while waiting |
| * </ul> |
| * then {@link java.lang.InterruptedException InterruptedException} is thrown and the current thread's |
| * interrupted status is cleared. |
| * |
| * <p>If the specified waiting time elapses then {@link java.util.concurrent.TimeoutException TimeoutException} |
| * is thrown. If the time is less than or equal to zero, the |
| * method will not wait at all. |
| * |
| * <p>If the barrier is {@link #reset} while any thread is waiting, |
| * or if the barrier {@linkplain #isBroken is broken} when |
| * {@code await} is invoked, or while any thread is waiting, then |
| * {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException} is thrown. |
| * |
| * <p>If any thread is {@linkplain java.lang.Thread#interrupt Thread#interrupt} while |
| * waiting, then all other waiting threads will throw {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException} and the barrier is placed in the broken |
| * state. |
| * |
| * <p>If the current thread is the last thread to arrive, and a |
| * non-null barrier action was supplied in the constructor, then the |
| * current thread runs the action before allowing the other threads to |
| * continue. |
| * If an exception occurs during the barrier action then that exception |
| * will be propagated in the current thread and the barrier is placed in |
| * the broken state. |
| * |
| * @param timeout the time to wait for the barrier |
| * @param unit the time unit of the timeout parameter |
| * @return the arrival index of the current thread, where index |
| * {@code getParties() - 1} indicates the first |
| * to arrive and zero indicates the last to arrive |
| * @throws java.lang.InterruptedException if the current thread was interrupted |
| * while waiting |
| * @throws java.util.concurrent.TimeoutException if the specified timeout elapses. |
| * In this case the barrier will be broken. |
| * @throws java.util.concurrent.BrokenBarrierException if <em>another</em> thread was |
| * interrupted or timed out while the current thread was |
| * waiting, or the barrier was reset, or the barrier was broken |
| * when {@code await} was called, or the barrier action (if |
| * present) failed due to an exception |
| */ |
| |
| public int await(long timeout, java.util.concurrent.TimeUnit unit) throws java.util.concurrent.BrokenBarrierException, java.lang.InterruptedException, java.util.concurrent.TimeoutException { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Queries if this barrier is in a broken state. |
| * |
| * @return {@code true} if one or more parties broke out of this |
| * barrier due to interruption or timeout since |
| * construction or the last reset, or a barrier action |
| * failed due to an exception; {@code false} otherwise. |
| */ |
| |
| public boolean isBroken() { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Resets the barrier to its initial state. If any parties are |
| * currently waiting at the barrier, they will return with a |
| * {@link java.util.concurrent.BrokenBarrierException BrokenBarrierException}. Note that resets <em>after</em> |
| * a breakage has occurred for other reasons can be complicated to |
| * carry out; threads need to re-synchronize in some other way, |
| * and choose one to perform the reset. It may be preferable to |
| * instead create a new barrier for subsequent use. |
| */ |
| |
| public void reset() { throw new RuntimeException("Stub!"); } |
| |
| /** |
| * Returns the number of parties currently waiting at the barrier. |
| * This method is primarily useful for debugging and assertions. |
| * |
| * @return the number of parties currently blocked in {@link #await} |
| */ |
| |
| public int getNumberWaiting() { throw new RuntimeException("Stub!"); } |
| } |
| |
