source: trunk/sources/HeuristicLab.Permutation/3.3/AbsolutePositionTopologicalCrossover.cs @ 2865

#region License Information
/* HeuristicLab
 * Copyright (C) 2002-2010 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
 *
 * This file is part of HeuristicLab.
 *
 * HeuristicLab 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 3 of the License, or
 * (at your option) any later version.
 *
 * HeuristicLab 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 HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
 */
#endregion

using System;
using HeuristicLab.Core;
using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;

namespace HeuristicLab.Permutation {
  /// <summary>
  /// Performs a cross over permutation between two permutation arrays by taking
  /// the entries with the same index (starting at position 0) from both parents 
  /// (minding already inserted values).
  /// </summary>
  /// <remarks>It is implemented as described in Moraglio, A. and Poli, R. 2005. Topological crossover for the permutation representation. In Proceedings of the 2005 Workshops on Genetic and Evolutionary Computation.<br />
  /// </remarks>
  /// <example>First take the value at position 0 from parent1 then take the value at position 0
  /// from parent2 if it has not already been inserted, afterwards take the value at position 1 from
  /// parent1 if it has not already been inserted, then from parent2 and so on.</example>
  [Item("AbsolutePositionTopologicalCrossover", @"An operator which performs a cross over permutation between two permutation arrays by taking the 
entries with the same index (starting at position 0) from both parents 
(minding already inserted values).")]
  [EmptyStorableClass]
  [Creatable("Test")]
  public class AbsolutePositionTopologicalCrossover : PermutationCrossover {
    /// <summary>
    /// Performs a cross over permutation of <paramref name="parent1"/> and <paramref name="parent2"/>
    /// by taking the values from both parents one by one with the same index starting at position 0.
    /// </summary>
    /// <example>First take the value at position 0 from parent1 then take the value at position 0
    /// from parent2 if it has not already been inserted, afterwards take the value at position 1 from
    /// parent1 if it has not already been inserted, then from parent2 and so on.</example>
    /// <exception cref="ArgumentException">Thrown when <paramref name="parent1"/> and <paramref name="parent2"/> are not of equal length.</exception>
    /// <param name="random">The random number generator.</param>
    /// <param name="parent1">The parent scope 1 to cross over.</param>
    /// <param name="parent2">The parent scope 2 to cross over.</param>
    /// <returns>The created cross over permutation as int array.</returns>
    public static Permutation Apply(IRandom random, Permutation parent1, Permutation parent2) {
      if (parent1.Length != parent2.Length) throw new ArgumentException("AbsolutePositionTopologicalCrossover: The parent permutations are of unequal length.");
      int length = parent1.Length;
      int[] result = new int[length];
      bool[] numberCopied = new bool[length];
      int index;

      index = 0;
      for (int i = 0; i < length; i++) {  // copy numbers from both parent permutations
        if (!numberCopied[parent1[i]]) {
          result[index] = parent1[i];
          numberCopied[parent1[i]] = true;
          index++;
        }
        if (!numberCopied[parent2[i]]) {
          result[index] = parent2[i];
          numberCopied[parent2[i]] = true;
          index++;
        }
      }
      return new Permutation(result);
    }

    /// <summary>
    /// Performs an absolute position topological crossover operation for two given parent permutations.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown if there are not exactly two parents.</exception>
    /// <param name="random">A random number generator.</param>
    /// <param name="parents">An array containing the two permutations that should be crossed.</param>
    /// <returns>The newly created permutation, resulting from the crossover operation.</returns>
    protected override Permutation Cross(IRandom random, ItemArray<Permutation> parents) {
      if (parents.Length != 2) throw new InvalidOperationException("ERROR in AbsolutePositionTopologicalCrossover: The number of parents is not equal to 2");
      return Apply(random, parents[0], parents[1]);
    }
  }
}