directedmutation.java

著名的开源仿真软件yale

/*
 *  YALE - Yet Another Learning Environment
 *  Copyright (C) 2002, 2003
 *      Simon Fischer, Ralf Klinkenberg, Ingo Mierswa, 
 *          Katharina Morik, Oliver Ritthoff
 *      Artificial Intelligence Unit
 *      Computer Science Department
 *      University of Dortmund
 *      44221 Dortmund,  Germany
 *  email: [e-mail]
 *  web:   http://yale.cs.uni-dortmund.de/
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 *  USA.
 */
package edu.udo.cs.yale.operator.features.ga;

import edu.udo.cs.yale.example.AttributeSelectionExampleSet;
import edu.udo.cs.yale.example.AttributeWeightedExampleSet;
import edu.udo.cs.yale.operator.features.*;
import edu.udo.cs.yale.operator.AttributeInformationGain;
import edu.udo.cs.yale.tools.RandomGenerator;

import java.util.LinkedList;
import java.util.List;
import java.util.Random;

/** Switches on attributes with higher information gain with higher probability. Therefore, 
 *  the range of the information gain is scaled acording to the following equation: <br><br>
 *  <tt>new value  = (((old value - smallest value) / (largest value - smallest value)) * (right margin - left margin)) 
 *                   + left margin</tt> <br><br>
 *
 *  The margins are set by parameters.
 *
 *  @author ingo
 *  @version $Id: DirectedMutation.java,v 2.4 2003/08/27 15:28:14 mierswa Exp $
 */
public class DirectedMutation extends IndividualOperator {

    /** Die Wahrscheinlichkeit, da&szlig; Attribut &uuml;berhaupt zu mutieren. */
    private double prob;

    /** Die linke Grenze des neuen Bereichs. */
    double leftBound;

    /** Die rechte Grenze des neuen Bereichs. */
    double rightBound;


    public DirectedMutation(double prob, double leftBound, double rightBound) {
	this.prob = prob;
	this.leftBound  = leftBound;
	this.rightBound = rightBound;
    }

    public List operate(AttributeWeightedExampleSet es) {
	LinkedList l = new LinkedList();
	if (es instanceof AttributeSelectionExampleSet) {
	    AttributeSelectionExampleSet exampleSet = (AttributeSelectionExampleSet)es;
	    AttributeSelectionExampleSet clone = (AttributeSelectionExampleSet)exampleSet.clone();
	    RandomGenerator random = RandomGenerator.getGlobalRandomGenerator();
	    double smallest = 
		((Double)es.getUserData(AttributeInformationGain.SMALLEST_INFORMATION_GAIN_KEY)).doubleValue();
	    double greatest = 1;
	    
	    for (int i = 0; i < exampleSet.getNumberOfAttributes(); i++) {
		if (random.nextDouble() < prob) {
		    double informationGain[] = 
			(double[])exampleSet.getUserData(AttributeInformationGain.INFORMATION_GAIN_KEY);
		    double shouldBeUsed = 
			(((informationGain[i] - smallest) / 
			  (greatest - smallest))
			 * (rightBound - leftBound)) 
			+ leftBound;
		    
		    if (random.nextDouble() < shouldBeUsed) exampleSet.setAttributeUsed(i, true);
		    else exampleSet.setAttributeUsed(i, false);
		}
	    }
	    
	    if (exampleSet.getNumberOfUsedAttributes() > 0) {
		l.add(exampleSet);
	    } else {
		l.add(clone);
	    }
	} else {
	    l.add(es);
	}
	return l;
    }
}