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source: trunk/sources/HeuristicLab.Encodings.PermutationEncoding/3.3/Crossovers/OrderCrossover.cs @ 3160

Last change on this file since 3160 was 3160, checked in by swagner, 14 years ago

Removed Creatable test attribute (#935).

File size: 5.0 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2010 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using HeuristicLab.Core;
24using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
25
26namespace HeuristicLab.Encodings.PermutationEncoding {
27  /// <summary>
28  /// An operator which performs the order crossover on two permutations.
29  /// </summary>
30  /// <remarks>
31  /// It is implemented as described in Eiben, A.E. and Smith, J.E. 2003. Introduction to Evolutionary Computation. Natural Computing Series, Springer-Verlag Berlin Heidelberg.<br />
32  /// Crosses two permutations by copying a randomly chosen interval from the first permutation, preserving
33  /// the positions. Then, starting from the end of the copied interval, copies the missing values from the second permutation
34  /// in the order they occur.
35  /// </remarks>
36  [Item("OrderCrossover", "An operator which performs an order crossover of two permutations. It is implemented as described in Eiben, A.E. and Smith, J.E. 2003. Introduction to Evolutionary Computation. Natural Computing Series, Springer-Verlag Berlin Heidelberg.")]
37  [StorableClass]
38  public class OrderCrossover : PermutationCrossover {
39    /// <summary>
40    /// Performs the order crossover of two permutations.
41    /// </summary>
42    /// <exception cref="ArgumentException">Thrown when <paramref name="parent1"/> and <paramref name="parent2"/> are not of equal length.</exception>
43    /// <exception cref="InvalidOperationException">Thrown if the numbers in the permutation elements are not in the range [0,N) with N = length of the permutation.</exception>
44    /// <remarks>
45    /// Crosses two permutations by copying a randomly chosen interval from the first permutation, preserving
46    /// the positions. Then, starting from the end of the copied interval, copies the missing values from the second permutation
47    /// in the order they occur.
48    /// </remarks>
49    /// <param name="random">A random number generator.</param>
50    /// <param name="parent1">The first parent permutation to cross.</param>
51    /// <param name="parent2">The second parent permutation to cross.</param>
52    /// <returns>The new permutation resulting from the crossover.</returns>
53    public static Permutation Apply(IRandom random, Permutation parent1, Permutation parent2) {
54      if (parent1.Length != parent2.Length) throw new ArgumentException("OrderCrossover: The parent permutations are of unequal length.");
55      int length = parent1.Length;
56      int[] result = new int[length];
57      bool[] copied = new bool[length];
58
59      int breakPoint1 = random.Next(length - 1);
60      int breakPoint2 = random.Next(breakPoint1 + 1, length);
61
62      try {
63        for (int j = breakPoint1; j <= breakPoint2; j++) {  // copy part of first permutation
64          result[j] = parent1[j];
65          copied[parent1[j]] = true;
66        }
67
68        int index = ((breakPoint2 + 1 >= length) ? (0) : (breakPoint2 + 1));
69        int i = index; // for moving in parent2
70        while (index != breakPoint1) {
71          if (!copied[parent2[i]]) {
72            result[index] = parent2[i];
73            index++;
74            if (index >= length) index = 0;
75          }
76          i++;
77          if (i >= length) i = 0;
78        }
79      } catch (IndexOutOfRangeException) {
80        throw new InvalidOperationException("OrderCrossover: The permutation must consist of numbers in the interval [0;N) with N = length of the permutation.");
81      }
82      return new Permutation(result);
83    }
84
85    /// <summary>
86    /// Checks number of parents and calls <see cref="Apply(IRandom, Permutation, Permutation)"/>.
87    /// </summary>
88    /// <exception cref="InvalidOperationException">Thrown if there are not exactly two parents.</exception>
89    /// <param name="random">A random number generator.</param>
90    /// <param name="parents">An array containing the two permutations that should be crossed.</param>
91    /// <returns>The new permutation resulting from the crossover.</returns>
92    protected override Permutation Cross(IRandom random, ItemArray<Permutation> parents) {
93      if (parents.Length != 2) throw new InvalidOperationException("OrderCrossover: Number of parents is not equal to 2.");
94      return Apply(random, parents[0], parents[1]);
95    }
96  }
97}
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