1  #region License Information


2  /* HeuristicLab


3  * Copyright (C) 20022013 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  /// Performs a cross over permutation between two permutation arrays by calculating the edges (neighbours)


30  /// of each element. Starts at a randomly chosen position, the next element is a neighbour with the least


31  /// number of neighbours, the next again a neighbour and so on.


32  /// </summary>


33  /// <remarks>


34  /// It is implemented as described in Whitley et.al. 1991, The Traveling Salesman and Sequence Scheduling, in Davis, L. (Ed.), Handbook of Genetic Algorithms, New York, pp. 350372.<br />


35  /// The operator first determines all cycles in the permutation and then composes the offspring by alternating between the cycles of the two parents.


36  /// </remarks>


37  [Item("EdgeRecombinationCrossover", "An operator which performs the edge recombination crossover on two permutations. It is implemented as described in Whitley et.al. 1991, The Traveling Salesman and Sequence Scheduling, in Davis, L. (Ed.), Handbook of Genetic Algorithms, New York, pp. 350372.")]


38  [StorableClass]


39  public class EdgeRecombinationCrossover : PermutationCrossover {


40  [StorableConstructor]


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


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


43  public EdgeRecombinationCrossover() : base() { }


44 


45  public override IDeepCloneable Clone(Cloner cloner) {


46  return new EdgeRecombinationCrossover(this, cloner);


47  }


48 


49  /// <summary>


50  /// Performs a cross over permutation of <paramref name="parent1"/> and <paramref name="2"/>


51  /// by calculating the edges of each element. Starts at a randomly chosen position,


52  /// the next element is a neighbour with the least


53  /// number of neighbours, the next again a neighbour and so on.


54  /// </summary>


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


56  /// <exception cref="InvalidOperationException">Thrown when the permutation lacks a number.


57  /// </exception>


58  /// <param name="random">The random number generator.</param>


59  /// <param name="parent1">The parent scope 1 to cross over.</param>


60  /// <param name="parent2">The parent scope 2 to cross over.</param>


61  /// <returns>The created cross over permutation as int array.</returns>


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


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


64  int length = parent1.Length;


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


66  int[,] edgeList = new int[length, 4];


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


68  int index, currentEdge, currentNumber, nextNumber, currentEdgeCount, minEdgeCount;


69 


70  for (int i = 0; i < length; i++) { // generate edge list for every number


71  remainingNumbers[i] = true;


72 


73  index = 0;


74  while ((index < length) && (parent1[index] != i)) { // search edges in parent1


75  index++;


76  }


77  if (index == length) {


78  throw (new InvalidOperationException("Permutation doesn't contain number " + i + "."));


79  } else {


80  edgeList[i, 0] = parent1[(index  1 + length) % length];


81  edgeList[i, 1] = parent1[(index + 1) % length];


82  }


83  index = 0;


84  while ((index < length) && (parent2[index] != i)) { // search edges in parent2


85  index++;


86  }


87  if (index == length) {


88  throw (new InvalidOperationException("Permutation doesn't contain number " + i + "."));


89  } else {


90  currentEdge = parent2[(index  1 + length) % length];


91  if ((edgeList[i, 0] != currentEdge) && (edgeList[i, 1] != currentEdge)) { // new edge found ?


92  edgeList[i, 2] = currentEdge;


93  } else {


94  edgeList[i, 2] = 1;


95  }


96  currentEdge = parent2[(index + 1) % length];


97  if ((edgeList[i, 0] != currentEdge) && (edgeList[i, 1] != currentEdge)) { // new edge found ?


98  edgeList[i, 3] = currentEdge;


99  } else {


100  edgeList[i, 3] = 1;


101  }


102  }


103  }


104 


105  currentNumber = random.Next(length); // get number to start


106  for (int i = 0; i < length; i++) {


107  result[i] = currentNumber;


108  remainingNumbers[currentNumber] = false;


109 


110  for (int j = 0; j < 4; j++) { // remove all edges to / from currentNumber


111  if (edgeList[currentNumber, j] != 1) {


112  for (int k = 0; k < 4; k++) {


113  if (edgeList[edgeList[currentNumber, j], k] == currentNumber) {


114  edgeList[edgeList[currentNumber, j], k] = 1;


115  }


116  }


117  }


118  }


119 


120  minEdgeCount = 5; // every number hasn't more than 4 edges


121  nextNumber = 1;


122  for (int j = 0; j < 4; j++) { // find next number with least edges


123  if (edgeList[currentNumber, j] != 1) { // next number found


124  currentEdgeCount = 0;


125  for (int k = 0; k < 4; k++) { // count edges of next number


126  if (edgeList[edgeList[currentNumber, j], k] != 1) {


127  currentEdgeCount++;


128  }


129  }


130  if ((currentEdgeCount < minEdgeCount) 


131  ((currentEdgeCount == minEdgeCount) && (random.NextDouble() < 0.5))) {


132  nextNumber = edgeList[currentNumber, j];


133  minEdgeCount = currentEdgeCount;


134  }


135  }


136  }


137  currentNumber = nextNumber;


138  if (currentNumber == 1) { // current number has no more edge


139  index = 0;


140  while ((index < length) && (!remainingNumbers[index])) { // choose next remaining number


141  index++;


142  }


143  if (index < length) {


144  currentNumber = index;


145  }


146  }


147  }


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


149  }


150 


151  /// <summary>


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


153  /// </summary>


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


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


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


157  /// <returns>The newly created permutation, resulting from the crossover operation.</returns>


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


159  if (parents.Length != 2) throw new InvalidOperationException("ERROR in EdgeRecombinationCrossover: The number of parents is not equal to 2");


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


161  }


162  }


163  }

