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File org.dgpf.search.algorithms.ga.selection.TournamentSelection.java

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/*
 * Copyright (c) 2006 Thomas Weise
 *
 * E-Mail           : tweise@gmx.de
 * Creation Date    : 2006-04-10 06:15:46
 * Original Filename: org.dgpf.search.algorithms.ga.selection.TournamentSelection.java
 * Version          : 2.0.2
 * Last modification: 2006-05-31
 *                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.algorithms.ga.selection;

import java.io.Serializable;

import org.dgpf.search.algorithms.ga.SelectionAlgorithm;
import org.dgpf.search.algorithms.ga.SortingAlgorithm;
import org.dgpf.search.api.Individual;
import org.sfc.math.stochastic.Randomizer;

/**
 * <p>
 * The selection algorithm "tournament selection". This is a stylish
 * selection algorithm taking always <code>n</code> individuals out of a
 * population and allow the best one of the <code>n</code> individuals to
 * reproduce.</p>
 * <p>
 * The selection parameter represents (integer) tournament size, the count
 * of individuals competing for reproduction.</p>
 *
 * @author Thomas Weise
 */

public final  class TournamentSelection extends SelectionAlgorithm
  {
/**
 * The serial version uid.
 */

  private   static  final long    serialVersionUID        = 1;

  
/**
 * A default instance of the tournament selection algorithms.
 */

  public  static  final SelectionAlgorithm  DEFAULT_INSTANCE =
                                        new TournamentSelection(7);

/**
 * The size of the tournament to perform for each reproduction.
 */

  private final int m_size  ;

/**
 * Create a new instance of the tournament selection algorithm.
 * @param p_size    The size of the tournament to perform for each
 *                  reproduction.
 */

  public  TournamentSelection  (final int  p_size)
    {
    this(p_size, null);
    }
  
/**
 * Create a new instance of the tournament selection algorithm.
 * @param p_size    The size of the tournament to perform for each
 *                  reproduction.
 * @param p_sorting The underlying sorting algorithm.
 */

  public  TournamentSelection  (final int               p_size,
                                final SortingAlgorithm  p_sorting)
    {
    super(p_sorting);
    this.m_size = ((p_size > 1) ? p_size : 1);
    }
  
/**
 * Select one individual out of the population for reproduction (crossover
 * or mutation). The individuals in the array are ordered by the search's
 * current comparator, with the fittest individual at index <code>0</code>
 * and the worst at index <code>p_count-1</code>.
 * @param p_random        The randomizer to be used for the selection.
 * @param p_individuals   The population of individuals after being
 *                        preprocessed.
 * @param p_count         The count of valid items inside the population
 *                        array.
 * @param <Genotype>      The genotype of the individuals to select.
 * @return  An individual to reproduce.
 */

  @Override
  public  final  <Genotype extends Serializable> Individual<Genotype>
                         select(final Randomizer             p_random,
                                final Individual<Genotype>[] p_individuals,
                                final int                    p_count)
    {
    int l_i, l_j, l_k;

    l_i = p_random.nextInt(p_count);
    for(l_j = (this.m_size-1); l_j > 0; l_j--)
      {
      l_k = p_random.nextInt(p_count);
      if(l_k < l_i) l_i = l_k;
      }

    return p_individuals[l_i];
    }


/**
 * Returns unique, textual identifier of this genetic selection algorithm.
 * @return The unique, textual identifier of this genetic selection
 *         algorithm.
 */

  @Override
  public  final String  toString  ()
    {
    return super.toString() + '(' + this.m_size + ')';
    }
  

/**
 * Check whether this object equals another one. This method is internally
 * invoked by <code>equals()</code>. 
 * @param p_object  The object to compare with.
 * @return <code>true</code> if and only if this object equals to the other
 *         one.
 */

  @Override
  protected final boolean is_equal  (final Object p_object)
    {
    return ((p_object instanceof TournamentSelection) &&
            (((TournamentSelection)p_object).m_size == this.m_size));
    }
  }

File Information:

file name:TournamentSelection.java
package:org.dgpf.search.algorithms.ga.selection
qualified name:org.dgpf.search.algorithms.ga.selection.TournamentSelection.java
file type:Java Source File
download location:download http://dgpf.sourceforge.net/source/org/dgpf/search/algorithms/ga/selection/TournamentSelection.java
size:4.972 KB (5092 B)
uploaded: 2015-07-22 04:10:59 GMT+0000
last update: 2006-05-31 03:14:49 GMT+0000
last access: 2017-11-19 04:55:41 GMT+0000

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