source: branches/2839_HiveProjectManagement/HeuristicLab.Encodings.PermutationEncoding/3.3/PermutationEqualityComparer.cs @ 16057

Last change on this file since 16057 was 16057, checked in by jkarder, 15 months ago

#2839:

File size: 3.9 KB
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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2018 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 (ReferenceEquals(x, y)) return true;
33      if (x == null || y == null) return false;
34      if (x.Length != y.Length) return false;
35      if (x.PermutationType != y.PermutationType) return false;
36      switch (x.PermutationType) {
37        case PermutationTypes.Absolute:
38          return EqualsAbsolute(x, y);
39        case PermutationTypes.RelativeDirected:
40          return EqualsRelative(x, y, true);
41        case PermutationTypes.RelativeUndirected:
42          return EqualsRelative(x, y, false);
43        default:
44          throw new InvalidOperationException("unknown permutation type");
45      }
46    }
47
48    private bool EqualsAbsolute(Permutation x, Permutation y) {
49      return x.SequenceEqual(y);
50    }
51
52    private bool EqualsRelative(Permutation x, Permutation y, bool directed) {
53      int[] edgesX = CalculateEdgesVector(x);
54      int[] edgesY = CalculateEdgesVector(y);
55      for (int i = 0; i < x.Length; i++)
56        if ((edgesX[i] != edgesY[i]) && (directed || edgesX[edgesY[i]] != i))
57          return false;
58      return true;
59    }
60
61    private int[] CalculateEdgesVector(Permutation permutation) {
62      // transform path representation into adjacency representation
63      int[] edgesVector = new int[permutation.Length];
64      for (int i = 0; i < permutation.Length - 1; i++)
65        edgesVector[permutation[i]] = permutation[i + 1];
66      edgesVector[permutation[permutation.Length - 1]] = permutation[0];
67      return edgesVector;
68    }
69
70    public override int GetHashCode(Permutation obj) {
71      if (obj == null) throw new ArgumentNullException("obj", "PermutationEqualityComparer: Cannot compute hash value of null.");
72      return GenerateHashString(obj).GetHashCode();
73    }
74
75    private string GenerateHashString(Permutation p) {
76      StringBuilder sb = new StringBuilder();
77      if (p.PermutationType == PermutationTypes.Absolute) {
78        for (int i = 0; i < p.Length; i++)
79          sb.Append(p[i].ToString() + ";");
80      } else {
81        int i = 0;
82        while (p[i] != 0) i++; // always start at element 0
83        if (p.PermutationType == PermutationTypes.RelativeDirected) {
84          for (int j = 0; j < p.Length; j++)
85            sb.Append(p.GetCircular(i + j).ToString() + ";");
86        } else {
87          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
88          for (int j = 0; j < p.Length; j++) {
89            if (goLeft) sb.Append(p.GetCircular(i - j).ToString() + ";");
90            else sb.Append(p.GetCircular(i + j).ToString() + ";");
91          }
92        }
93      }
94      return sb.ToString();
95    }
96  }
97}
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