SynchronizedWorker.java

/* -*- tab-width: 4 -*-
 *
 * Electric(tm) VLSI Design System
 *
 * File: SimpleWorker.java
 *
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 *
 * Electric(tm) is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Electric(tm) 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 Electric(tm); see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, Mass 02111-1307, USA.
 */
package com.sun.electric.tool.util.concurrent.runtime.taskParallel;

import java.util.concurrent.Semaphore;

import com.sun.electric.tool.util.concurrent.datastructures.IStructure;
import com.sun.electric.tool.util.concurrent.patterns.PTask;
import com.sun.electric.tool.util.concurrent.runtime.ThreadID;

/**
 * 
 * Synchronized thread pool worker
 * 
 * Some algorithms requires that the calculation of different steps should run
 * step-by-step in parallel. This worker implements the PRAM aspect that in one
 * time unit one instruction could be executed in parallel. This worker uses a
 * bigger grain size. N (#threads) tasks could be implemented in parallel. After
 * the parallel execution is a barrier which could be release by a timer or the
 * client application (ThreadPool.getThreadPool().trigger()).
 * 
 * @author Felix Schmidt
 * 
 */
public class SynchronizedWorker extends PoolWorkerStrategy {

    protected IStructure<PTask> taskPool = null;
    protected Semaphore sem;

    public SynchronizedWorker(IStructure<PTask> taskPool, Semaphore sem) {
        super();
        this.taskPool = taskPool;
        this.abort = false;
        this.sem = sem;
    }

    public void trigger() {
        sem.release();
    }

    /**
     * This function iterates while the flag abort is false. <br>
     * <b>Algorithm:</b>
     * <ul>
     * <li>wait for trigger</li>
     * <li>pick one task from thread pool's task queue</li>
     * <li>if task not equal to null, then set threadId and do some
     * initialization work on the task object</li>
     * <li>execute the task</li>
     * <li>finalize work on the task object</li>
     * <li>do it again ...</li>
     * </ul>
     */
    @Override
    public void execute() {
        this.threadId = ThreadID.get();
        this.executed = 0;
        while (!abort) {
            this.checkForWait();

            sem.acquireUninterruptibly();

            // retrieve a new task
            PTask task = taskPool.remove();
            if (task != null) {
                try {
                    // set the current thread id
                    task.setThreadID(ThreadID.get());
                    // do something before execution
                    task.before();
                    // execute the task
                    task.execute();
                    this.executed++;
                } finally {
                    // do some clean up work etc. after execution of the task
                    task.after();

                    // Debug

                }
            } else {
                Thread.yield();
            }
        }
    }

}