001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.util.parallel;
031
032import java.util.concurrent.Executors;
033import java.util.concurrent.ThreadFactory;
034import java.util.concurrent.ThreadPoolExecutor;
035
036/**
037 * A globally available (static) fixed-size {@link ThreadPoolExecutor}. The number of
038 * threads is equal to the number of available hardware threads as reported by
039 * {@link Runtime#availableProcessors()}. 
040 * 
041 * To avoid the need to shutdown the threadpool, the threads are all daemons.
042 * 
043 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
044 *
045 */
046public class GlobalExecutorPool {
047        /**
048         * A {@link ThreadFactory} that produces daemon threads.
049         * 
050         * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
051         */
052        public static class DaemonThreadFactory implements ThreadFactory {
053                @Override
054                public Thread newThread(Runnable paramRunnable) {
055                        Thread t = new Thread(paramRunnable);
056                        t.setDaemon(true);
057                        return t;
058                }
059        }
060        
061        private static ThreadPoolExecutor pool = (ThreadPoolExecutor) Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors(), new DaemonThreadFactory());
062        
063        /**
064         * Get the pool.
065         * @return the pool.
066         */
067        public static ThreadPoolExecutor getPool() {
068                return pool;
069        }
070}