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source: branches/2845_EnhancedProgress/HeuristicLab.Encodings.PermutationEncoding/3.3/Crossovers/EdgeRecombinationCrossover.cs @ 16308

Last change on this file since 16308 was 16308, checked in by pfleck, 5 years ago

#2845 reverted the last merge (r16307) because some revisions were missing

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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2016 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.Common;
24using HeuristicLab.Core;
25using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
26
27namespace 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. 350-372.<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. 350-372.")]
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}
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