1  #region License Information


2  /* HeuristicLab


3  * Copyright (C) 20022019 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 


22  using System;


23  using HeuristicLab.Common;


24  using HeuristicLab.Core;


25  using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;


26 


27  namespace HeuristicLab.Encodings.PermutationEncoding {


28  /// <summary>


29  /// An operator which performs the order crossover on two permutations.


30  /// </summary>


31  /// <remarks>


32  /// It is implemented as described in Eiben, A.E. and Smith, J.E. 2003. Introduction to Evolutionary Computation. Natural Computing Series, SpringerVerlag Berlin Heidelberg.<br />


33  /// Crosses two permutations by copying a randomly chosen interval from the first permutation, preserving


34  /// the positions. Then, starting from the end of the copied interval, copies the missing values from the second permutation


35  /// in the order they occur.


36  /// </remarks>


37  [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, SpringerVerlag Berlin Heidelberg.")]


38  [StorableClass]


39  public class OrderCrossover : PermutationCrossover {


40  [StorableConstructor]


41  protected OrderCrossover(bool deserializing) : base(deserializing) { }


42  protected OrderCrossover(OrderCrossover original, Cloner cloner) : base(original, cloner) { }


43  public OrderCrossover() : base() { }


44 


45  public override IDeepCloneable Clone(Cloner cloner) {


46  return new OrderCrossover(this, cloner);


47  }


48 


49  /// <summary>


50  /// Performs the order crossover of two permutations.


51  /// </summary>


52  /// <exception cref="ArgumentException">Thrown when <paramref name="parent1"/> and <paramref name="parent2"/> are not of equal length.</exception>


53  /// <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>


54  /// <remarks>


55  /// Crosses two permutations by copying a randomly chosen interval from the first permutation, preserving


56  /// the positions. Then, starting from the end of the copied interval, copies the missing values from the second permutation


57  /// in the order they occur.


58  /// </remarks>


59  /// <param name="random">A random number generator.</param>


60  /// <param name="parent1">The first parent permutation to cross.</param>


61  /// <param name="parent2">The second parent permutation to cross.</param>


62  /// <returns>The new permutation resulting from the crossover.</returns>


63  public static Permutation Apply(IRandom random, Permutation parent1, Permutation parent2) {


64  if (parent1.Length != parent2.Length) throw new ArgumentException("OrderCrossover: The parent permutations are of unequal length.");


65  int length = parent1.Length;


66  int[] result = new int[length];


67  bool[] copied = new bool[length];


68 


69  int breakPoint1 = random.Next(length  1);


70  int breakPoint2 = random.Next(breakPoint1 + 1, length);


71 


72  try {


73  for (int j = breakPoint1; j <= breakPoint2; j++) { // copy part of first permutation


74  result[j] = parent1[j];


75  copied[parent1[j]] = true;


76  }


77 


78  int index = ((breakPoint2 + 1 >= length) ? (0) : (breakPoint2 + 1));


79  int i = index; // for moving in parent2


80  while (index != breakPoint1) {


81  if (!copied[parent2[i]]) {


82  result[index] = parent2[i];


83  index++;


84  if (index >= length) index = 0;


85  }


86  i++;


87  if (i >= length) i = 0;


88  }


89  }


90  catch (IndexOutOfRangeException) {


91  throw new InvalidOperationException("OrderCrossover: The permutation must consist of numbers in the interval [0;N) with N = length of the permutation.");


92  }


93  return new Permutation(parent1.PermutationType, result);


94  }


95 


96  /// <summary>


97  /// Checks number of parents and calls <see cref="Apply(IRandom, Permutation, Permutation)"/>.


98  /// </summary>


99  /// <exception cref="InvalidOperationException">Thrown if there are not exactly two parents.</exception>


100  /// <param name="random">A random number generator.</param>


101  /// <param name="parents">An array containing the two permutations that should be crossed.</param>


102  /// <returns>The new permutation resulting from the crossover.</returns>


103  protected override Permutation Cross(IRandom random, ItemArray<Permutation> parents) {


104  if (parents.Length != 2) throw new InvalidOperationException("OrderCrossover: Number of parents is not equal to 2.");


105  return Apply(random, parents[0], parents[1]);


106  }


107  }


108  }

