org.grouplens.lenskit.util.parallel.ParallelTaskGraphExecutor.java Source code

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Here is the source code for org.grouplens.lenskit.util.parallel.ParallelTaskGraphExecutor.java

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/*
 * LensKit, an open source recommender systems toolkit.
 * Copyright 2010-2014 LensKit Contributors.  See CONTRIBUTORS.md.
 * Work on LensKit has been funded by the National Science Foundation under
 * grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of the
 * License, or (at your option) any later version.
 *
 * This program 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 for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
package org.grouplens.lenskit.util.parallel;

import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import org.grouplens.grapht.graph.DAGNode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;

/**
 * Multithreaded task graph executor.
 * @author <a href="http://www.grouplens.org">GroupLens Research</a>
 */
class ParallelTaskGraphExecutor extends TaskGraphExecutor {
    private static final Logger logger = LoggerFactory.getLogger(ParallelTaskGraphExecutor.class);
    private final int threadCount;
    private final String name;

    ParallelTaskGraphExecutor(int nthreads, String n) {
        Preconditions.checkArgument(nthreads > 0, "thread count is not positive");
        threadCount = nthreads;
        name = n;
    }

    @Override
    public <T extends Callable<?>, E> void execute(DAGNode<T, E> graph)
            throws ExecutionException, InterruptedException {
        logger.info("{}: executing {} tasks on {} threads", name, graph.getReachableNodes().size(), threadCount);
        TaskGraphManager<T, E> manager = new TaskGraphManager<T, E>(name, graph);
        List<Thread> threads = Lists.newArrayListWithCapacity(threadCount);
        for (int i = 1; i <= threadCount; i++) {
            Thread thread = new TaskGraphThread<T, E>(manager, String.format("%s-%d", name, i));
            threads.add(thread);
            manager.addThread(thread);
            thread.start();
        }
        try {
            manager.waitForFinished();
        } catch (Exception ex) {
            for (Thread th : threads) {
                th.interrupt();
            }
            Throwables.propagateIfPossible(ex, ExecutionException.class, InterruptedException.class);
            throw new RuntimeException(ex);
        }
    }
}