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source: branches/GP-MoveOperators/HeuristicLab.Encodings.PermutationEncoding/3.3/PermutationEqualityComparer.cs @ 8362

Last change on this file since 8362 was 7259, checked in by swagner, 13 years ago

Updated year of copyrights to 2012 (#1716)

File size: 3.7 KB
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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2012 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 System.Collections.Generic;
24using System.Linq;
25using System.Text;
26using HeuristicLab.PluginInfrastructure;
27
28namespace HeuristicLab.Encodings.PermutationEncoding {
29  [NonDiscoverableType]
30  public class PermutationEqualityComparer : EqualityComparer<Permutation> {
31    public override bool Equals(Permutation x, Permutation y) {
32      if (x.PermutationType != y.PermutationType) return false;
33      if (x.Length != y.Length) return false;
34      switch (x.PermutationType) {
35        case PermutationTypes.Absolute:
36          return EqualsAbsolute(x, y);
37        case PermutationTypes.RelativeDirected:
38          return EqualsRelative(x, y, true);
39        case PermutationTypes.RelativeUndirected:
40          return EqualsRelative(x, y, false);
41        default:
42          throw new InvalidOperationException("unknown permutation type");
43      }
44    }
45
46    private bool EqualsAbsolute(Permutation x, Permutation y) {
47      return x.SequenceEqual(y);
48    }
49
50    private bool EqualsRelative(Permutation x, Permutation y, bool directed) {
51      int[] edgesX = CalculateEdgesVector(x);
52      int[] edgesY = CalculateEdgesVector(y);
53      for (int i = 0; i < x.Length; i++)
54        if ((edgesX[i] != edgesY[i]) && (directed || edgesX[edgesY[i]] != i))
55          return false;
56      return true;
57    }
58
59    private int[] CalculateEdgesVector(Permutation permutation) {
60      // transform path representation into adjacency representation
61      int[] edgesVector = new int[permutation.Length];
62      for (int i = 0; i < permutation.Length - 1; i++)
63        edgesVector[permutation[i]] = permutation[i + 1];
64      edgesVector[permutation[permutation.Length - 1]] = permutation[0];
65      return edgesVector;
66    }
67
68    public override int GetHashCode(Permutation obj) {
69      if (obj == null) return 0;
70      return GenerateHashString(obj).GetHashCode();
71    }
72
73    private string GenerateHashString(Permutation p) {
74      StringBuilder sb = new StringBuilder();
75      if (p.PermutationType == PermutationTypes.Absolute) {
76        for (int i = 0; i < p.Length; i++)
77          sb.Append(p[i].ToString() + ";");
78      } else {
79        int i = 0;
80        while (p[i] != 0) i++; // always start at element 0
81        if (p.PermutationType == PermutationTypes.RelativeDirected) {
82          for (int j = 0; j < p.Length; j++)
83            sb.Append(p.GetCircular(i + j).ToString() + ";");
84        } else {
85          bool goLeft = p.GetCircular(i - 1) < p.GetCircular(i + 1); // go in direction of the lowest edge so that the total inversion and its original return the same hash code
86          for (int j = 0; j < p.Length; j++) {
87            if (goLeft) sb.Append(p.GetCircular(i - j).ToString() + ";");
88            else sb.Append(p.GetCircular(i + j).ToString() + ";");
89          }
90        }
91      }
92      return sb.ToString();
93    }
94  }
95}
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