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

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/*
 * Copyright (c) 2006 Thomas Weise
 *
 * E-Mail           : tweise@gmx.de
 * Creation Date    : 2006-04-10 15:08:51
 * Original Filename: org.dgpf.search.api.comparators.SumComparator.java
 * Version          : 2.0.2
 * Last modification: 2006-05-29
 *                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;
import org.dgpf.search.api.IndividualComparator;

/**
 * This comparator transforms the multi-objective genetic algorithm into a
 * single-objective one by simple adding up all the fitness functions and
 * comparing one total fitness.
 *
 * @author Thomas Weise
 */

public class SumComparator  extends IndividualComparator
  {
/**
 * The serial version uid.
 */

  private static final long serialVersionUID = 1;

/**
 * The globally shared instance of this comparator.
 */

  public  static  final IndividualComparator  INSTANCE =
                                        new SumComparator();

/**
 * The internal constructor stops you from instantiating this class.
 * Use <code>INSTANCE</code> to obtain the shared instance.
 * @see #INSTANCE
 */

  private SumComparator()
    {
    super();
    }

/**
 * <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) ? -1 : ((l_res == 0.0d) ? 0 : 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;
    double  l_res;

    l_res = 0.0d;

    for(l_i = (p_i1.get_fitness_function_count()-1); l_i >= 0; l_i--)
      {
      l_res += (p_i2.get_fitness(l_i) - p_i1.get_fitness(l_i));
      }


    return l_res;
    }
  
/**
 * Deserialize to the proper instance.
 * @return  The globally shared instance.
 */

  private  final Object readResolve()
    {
    return INSTANCE;
    }

/**
 * Perform a write replace of this object.
 * @return  The object to store.
 */

  private final Object writeReplace()
    {
    return INSTANCE;
    }


/**
 * Create of copy of this halt parameters instance.
 * @return A copy of this halt parameters instance.
 */

  @Override
  public  final Object  clone ()
    {
    return INSTANCE;
    }
  

  
/**
 * Check whether this comparator equals another object.
 * @param p_object  The object to compare with.
 * @return <code>true</code> if and only if <code>p_object</code> is also
 *         an individual comparator and will always return the same result
 *         for all possible comparisons to be performed.
 */

  @Override
  public  final boolean equals  (final Object p_object)
    {
    return ((p_object == this) ||
            (p_object instanceof SumComparator));
    }
  }

File Information:

file name:SumComparator.java
package:org.dgpf.search.api.comparators
qualified name:org.dgpf.search.api.comparators.SumComparator.java
file type:Java Source File
download location:download http://dgpf.sourceforge.net/source/org/dgpf/search/api/comparators/SumComparator.java
size:5.444 KB (5575 B)
uploaded: 2015-07-22 04:11:00 GMT+0000
last update: 2006-05-29 14:15:01 GMT+0000
last access: 2017-11-18 21:25:38 GMT+0000

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