generatingmutation.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.generator.FeatureGenerator;
import edu.udo.cs.yale.generator.GenerationException;
import edu.udo.cs.yale.operator.features.IndividualOperator;
import edu.udo.cs.yale.example.AttributeSelectionExampleSet;
import edu.udo.cs.yale.example.AttributeWeightedExampleSet;
import edu.udo.cs.yale.example.Attribute;
import edu.udo.cs.yale.example.Tools;
import edu.udo.cs.yale.tools.RandomGenerator;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

/** The mutation operator for YAGGA.
 *  @version $Id: GeneratingMutation.java,v 2.6 2003/08/27 15:28:14 mierswa Exp $
 *  @see YAGGA */
public class GeneratingMutation extends IndividualOperator {

    private List generators;
    private List originalAttributes;
    private double p;
    private RandomGenerator random = RandomGenerator.getGlobalRandomGenerator();

    public GeneratingMutation(List originalAttributes, double p, List generators) {
	this.originalAttributes = originalAttributes;
	this.p = p/4;
	this.generators = generators;
    }

    /** Performs one of the following three mutations:
     *  <ul>
     *    <li>add a newly generated attribute</li>
     *    <li>add an original attribute</li>
     *    <li>remove an attribute</li>
     *  </ul> */
    public List operate(AttributeWeightedExampleSet es) throws Exception {
	LinkedList l = new LinkedList();
	if (es instanceof AttributeSelectionExampleSet) {
	    AttributeSelectionExampleSet exampleSet = (AttributeSelectionExampleSet)es;
	    AttributeSelectionExampleSet clone = (AttributeSelectionExampleSet)exampleSet.clone();
	    
	    addOriginalAttribute(exampleSet);
	    boolean generationPossible = addGeneratedAttribute(exampleSet);
	    deselect(exampleSet, generationPossible ? 2 : 1);
	    
	    if (exampleSet.getNumberOfUsedAttributes() > 0) {
		l.add(exampleSet);
	    } else {
		l.add(clone);
	    }
	} else {
	    l.add(es);
	}
	return l;
    }

    private boolean addGeneratedAttribute(AttributeSelectionExampleSet exampleSet) throws Exception {
	int numberOfCombinations = Tools.setArgumentCombinations(exampleSet, generators);

	if (random.nextDouble() < p) {
	    FeatureGenerator generator = FeatureGenerator.selectGenerator(generators).newInstance();
	    Attribute[] args = Tools.getRandomCompatibleAttributes(exampleSet, generator.getInputAttributes());
	    generator.setArguments(args);

	    List generatorList = new LinkedList();
	    generatorList.add(generator);
	    exampleSet.addAllAttributes(FeatureGenerator.generateAll(exampleSet.getExampleTable(), generatorList));
	}

	return numberOfCombinations > 0;
    }

    private void addOriginalAttribute(AttributeSelectionExampleSet exampleSet) {
	if (random.nextDouble() < p) {
	    int i = random.nextInt(originalAttributes.size());
	    Attribute originalAttribute = (Attribute)originalAttributes.get(i);
	    if (exampleSet.getAttribute(originalAttribute.getName()) == null)
		exampleSet.addAttribute(originalAttribute);
	}
    }

    private void deselect(AttributeSelectionExampleSet exampleSet, int m) {
	int n = exampleSet.getNumberOfAttributes();
	for (int i = n-1; i >= 0; i--) {
	    if (random.nextDouble() < m*p/originalAttributes.size()) {
		exampleSet.removeAttribute(i);
	    }
	}
    }
}