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File org.dgpf.search.api.comparators.WeightedMajorityComparator.java

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/*
 * Copyright (c) 2006 Thomas Weise
 *
 * E-Mail           : tweise@gmx.de
 * Creation Date    : 2006-03-31 14:44:33
 * Original Filename: org.dgpf.search.api.comparators.WeightedMajorityComparator.java
 * Version          : 2.0.1
 * Last modification: 2006-05-28
 *                by: Thomas Weise
 *
 * License          : GNU LESSER GENERAL PUBLIC LICENSE
 *                    Version 2.1, February 1999
 *                    You should have received a copy of this license along
 *                    with this library; if not, write to the Free Software
 *                    Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *                    MA 02111-1307, USA or download the license under
 *                    http://www.gnu.org/copyleft/lesser.html.
 *
 * Warranty         : This software is provided "as is" without any
 *                    warranty; without even the implied warranty of
 *                    merchantability or fitness for a particular purpose.
 *                    See the Gnu Lesser General Public License for more
 *                    details.
 */


package org.dgpf.search.api.comparators;

import org.dgpf.search.api.Individual;


/**
 * This comparator works similar to the majority comparator, but you can
 * assign weights to the fitness functions.
 *
 * @author Thomas Weise
 */

public final class WeightedMajorityComparator extends WeightedComparator
  {
/**
 * The serial version uid.
 */

  private static final long serialVersionUID = 1;

/**
 * Create a new instance of the majority comparator.
 * @param p_weights  The weights of the single fitness function's
 *                      dominances. The higher a priority is, the bigger
 *                      the absolute influence of its according fitness
 *                      function's dominance.
 */

  public  WeightedMajorityComparator(final  double[]  p_weights)
    {
    super(p_weights);
    }

/**
 * <p>
 * Compares its two individuals for fitness.  Returns a negative integer,
 * zero, or a positive integer as the first argument is fitter than, equal
 * to, or less fit than the second.
 * </p>
 * @param p_i1 The first individual to be compared.
 * @param p_i2 The second individual to be compared.
 * @return a negative integer, zero, or a positive integer as the
 *         first individual is fitter than, equal to, or less fit than the
 *         second.
 * @throws ClassCastException if the arguments' types prevent them from
 *         being compared by this Comparator.
 */

  @Override
  public  final int compare(final Individual<?>  p_i1,
                            final Individual<?>  p_i2)
    {
    final double   l_res;

    l_res = this.get_scalar_difference(p_i1, p_i2);

    return ((l_res == 0.0d) ? 0 : ((l_res > 0.0d) ? 1 : -1));
    }
  
/**
 * <p>
 * Obtain the scalar difference of two individuals. This method is
 * compatible with <code>compare</code> by fulfilling the contract that
 * <code>sign(compare(a,b)) == sign(get_scalar_difference(a,b))</code>
 * where <code>sign(x)</code> computes the sign of the number
 * <code>x</code>. <code>get_scalar_difference</code> is used by some
 * search techniques that require a numeric resolution of the comparison
 * of two individuals more precise than <code>compare</code> can deliver.
 * However, <code>compare</code> should be the prefered way to compare
 * two individuals. 
 * </p>
 * <p>TODO: Check whether a vector norm would be better here than just the
 * fitness scalar sum.</p>
 * @param p_i1 The first individual to be compared.
 * @param p_i2 The second individual to be compared.
 * @return a negative double, zero, or a positive double as the
 *         first individual is fitter than, equal to, or less fit than the
 *         second denoting the difference of the two individuals.
 * @throws ClassCastException if the arguments' types prevent them from
 *         being compared by this Comparator.
 * @see #compare(Individual, Individual)
 */

  @Override
  public final  double get_scalar_difference(final Individual<?>  p_i1,
                                             final Individual<?>  p_i2)
    {
          int      l_i, l_r;
          double   l_res;
    final double[] l_p;

    l_res = 0.0d;
    l_p   = this.m_weights;

    for(l_i = (p_i1.get_fitness_function_count()-1); l_i >= 0; l_i--)
      {
      l_r = Double.compare(p_i2.get_fitness(l_i), p_i1.get_fitness(l_i));
      if(l_r != 0)
        {
        if(l_r > 0) l_res += l_p[l_i];
        else        l_res -= l_p[l_i];
        }
      }

    return l_res;
    }
  }

File Information:

file name:WeightedMajorityComparator.java
package:org.dgpf.search.api.comparators
qualified name:org.dgpf.search.api.comparators.WeightedMajorityComparator.java
file type:Java Source File
download location:download http://dgpf.sourceforge.net/source/org/dgpf/search/api/comparators/WeightedMajorityComparator.java
size:4.568 KB (4678 B)
uploaded: 2015-07-22 04:11:00 GMT+0000
last update: 2006-05-28 13:51:00 GMT+0000
last access: 2017-11-17 21:20:55 GMT+0000

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