fork.java

一个用于排队系统仿真的开源软件,有非常形象的图象仿真过程!

/**
 * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

 * This program 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 2 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 St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package jmt.engine.NodeSections;

import jmt.common.exception.NetException;
import jmt.engine.QueueNet.*;

import java.util.Iterator;

/**
 * <p>Title: Fork</p>
 * <p>Description: This class is a fork output section, used to split a job on every
 * output link. Splitted job can be assembled back in a join input section.
 * A maximum number of jobs inside a fork-join section can be specified: when reached
 * this component will block until at least one job is joined.</p>
 *
 * @author Bertoli Marco
 *         Date: 13-mar-2006
 *         Time: 15.23.22
 */
public class Fork extends OutputSection{
    /** Maximum number of jobs allowed in a fork-join region (-1 or 0 is infinity) */
    private int block;

    /** Counts received ACK by following nodes */
    private int ackCount;

    /** Number of jobs to be routed on each link */
    private int jobsPerLink;

    /** Number of output nodes */
    private int numOut;

    /** Current number of jobs inside a fork-join region */
    private int jobNum;

// --- Constructors -----------------------------------------------------------------------------
    /**
     * Constructs a new Fork without blocking and with 1 job per link
     */
    public Fork() {
        this(1, -1);
    }

    /**
     * Construst a new Fork node
     * @param jobsPerLink number of jobs to be routed on each link
     * @param block maximum number of jobs allowed in a fork-join
     * region (-1 or 0 is infinity)
     */
    public Fork(Integer jobsPerLink, Integer block) {
        this(jobsPerLink.intValue(), block.intValue());
    }

    /**
     * Construst a new Fork node
     * @param jobsPerLink number of jobs to be routed on each link
     * @param block maximum number of jobs allowed in a fork-join
     * region (-1 or 0 is infinity)
     */
    public Fork(int jobsPerLink, int block) {
        // Disables automatic handling of jobinfolists
        super(false);
        jobNum = 0;
        this.block = block;
        this.jobsPerLink = jobsPerLink;
    }
// ----------------------------------------------------------------------------------------------

    /**
     * Splits input job on every output link and waits if 'block' job number are
     * not joined if and only if block is enabled.
     *
     * @param message message to be processed.
     * @throws NetException if something goes wrong
     * @return message processing result.
     */
    protected int process(NetMessage message) throws NetException {
        Job job;
        job = message.getJob();
        // Finds event type
        switch (message.getEvent()) {
            case NetEvent.EVENT_JOB:
                NodeList output = getOwnerNode().getOutputNodes();
                // Finds number of output jobs
                numOut = output.size() * jobsPerLink;
                // Resets ack count
                ackCount = 0;

                // Removes job from global node list
                JobInfoList info = getOwnerNode().getJobInfoList();
                JobInfo jobData = info.lookFor(job);
                if (jobData != null)
                    info.remove(jobData);

                // Gets global jobInfoList
                GlobalJobInfoList global = getOwnerNode().getQueueNet().getJobInfoList();

                // Sends "jobsPerLink" jobs on each output link
                Iterator i = output.listIterator();
                while (i.hasNext()) {
                    NetNode outNode = (NetNode) i.next();
                    for (int n=0; n<jobsPerLink; n++) {
                        ForkJob newJob = new ForkJob(numOut, job, this);
                        // Sends new job to all following stations
                        send(newJob, 0.0, outNode);
                        // Adds job to system jobinfolist
                        global.addForkedJob(newJob);
                    }
                }
                // Increment job counter
                jobNum++;

                // Removes original job, otherwise we will have one extra job in the network
                global.removeForkedJob(job);
                break;

            case NetEvent.EVENT_ACK:
                 ackCount++;
                // If this fork doesn't block, sends ACK back when all messages are delivered
                // to unlock this fork
                if ((jobNum < block || block <= 0) && ackCount == numOut)
                    sendBackward(NetEvent.EVENT_ACK, job, 0.0);
                break;
            case NetEvent.EVENT_JOIN:
                // If this fork blocks, finally sends ACK back and unlocks this
                if (jobNum == block)
                    sendBackward(NetEvent.EVENT_ACK, job, 0.0);

                // Decrement job counter
                jobNum--;
                break;
        }
        // Everything was okay
        return MSG_PROCESSED;
    }
}