randomstrategy.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.NetStrategies.RoutingStrategies;

import jmt.engine.NetStrategies.RoutingStrategy;
import jmt.engine.QueueNet.JobClass;
import jmt.engine.QueueNet.NetNode;
import jmt.engine.QueueNet.NodeList;
import jmt.engine.random.engine.RandomEngine;

/**
 * This class implements a random strategy: the output node
 * is chosen with a random number
 * @author  Stefano Omini, Bertoli Marco
 * @version 13/11/2005
 * Reimplemented by Bertoli Marco to correct behaviour with closed classes and sinks
 */
public class RandomStrategy extends RoutingStrategy {
    private RandomEngine randomEngine;
    private int CLOSED_CLASS = JobClass.CLOSED_CLASS;
    
	public RandomStrategy() {
        randomEngine = RandomEngine.makeDefault();
	}

	/**
     * Gets the output node, into which the job must be routed, using a random
     * strategy.
     * @param Nodes the list of output nodes
     * @param jobClass class ofcurrent job to be routed
     * @return The selected node.
     */
    public NetNode getOutNode(NodeList Nodes, JobClass jobClass) {
		int outNodes = Nodes.size();
        // Find output node
        NetNode output;
        if (outNodes > 1)
            output = Nodes.get((int)Math.floor(randomEngine.raw() * outNodes));
        else
            output = Nodes.getFirst();

        // Check to avoid discarding closed classes into a sink
        if (jobClass.getType() == CLOSED_CLASS && output.isSink()) {
            NetNode[] validOutputs = new NetNode[outNodes];
            outNodes = 0; // Here outNodes is used as a counter to valid elements into valisOutputs array
            for (int i=0; i<Nodes.size(); i++)
                if (!Nodes.get(i).isSink())
                    validOutputs[outNodes++] = Nodes.get(i);

            if (outNodes == 0)
                output = null;
            else if (outNodes == 1)
                output = validOutputs[0];
            else // Do a random routing between non-
                output = validOutputs[(int)Math.floor(randomEngine.raw() * outNodes)];
        }
        return output;
	}
}