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source: trunk/sources/HeuristicLab.Problems.TravelingSalesman/3.3/Improvers/TSPImprovementOperator.cs @ 11171

Last change on this file since 11171 was 11171, checked in by ascheibe, 10 years ago

#2115 merged r11170 (copyright update) into trunk

File size: 6.1 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2014 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.Data;
26using HeuristicLab.Encodings.PermutationEncoding;
27using HeuristicLab.Operators;
28using HeuristicLab.Optimization;
29using HeuristicLab.Parameters;
30using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
31
32namespace HeuristicLab.Problems.TravelingSalesman {
33  /// <summary>
34  /// An operator that improves traveling salesman solutions.
35  /// </summary>
36  /// <remarks>
37  /// The operator tries to improve the traveling salesman solution by swapping two randomly chosen edges for a certain number of times.
38  /// </remarks>
39  [Item("TSPImprovementOperator", "An operator that improves traveling salesman solutions. The operator tries to improve the traveling salesman solution by swapping two randomly chosen edges for a certain number of times.")]
40  [StorableClass]
41  public sealed class TSPImprovementOperator : SingleSuccessorOperator, ISingleObjectiveImprovementOperator {
42    #region Parameter properties
43    public ScopeParameter CurrentScopeParameter {
44      get { return (ScopeParameter)Parameters["CurrentScope"]; }
45    }
46    public ILookupParameter<DistanceMatrix> DistanceMatrixParameter {
47      get { return (ILookupParameter<DistanceMatrix>)Parameters["DistanceMatrix"]; }
48    }
49    public IValueParameter<IntValue> ImprovementAttemptsParameter {
50      get { return (IValueParameter<IntValue>)Parameters["ImprovementAttempts"]; }
51    }
52    public ILookupParameter<IRandom> RandomParameter {
53      get { return (ILookupParameter<IRandom>)Parameters["Random"]; }
54    }
55    public IValueLookupParameter<IItem> SolutionParameter {
56      get { return (IValueLookupParameter<IItem>)Parameters["Solution"]; }
57    }
58    #endregion
59
60    #region Properties
61    public IScope CurrentScope {
62      get { return CurrentScopeParameter.ActualValue; }
63    }
64    public DistanceMatrix DistanceMatrix {
65      get { return DistanceMatrixParameter.ActualValue; }
66      set { DistanceMatrixParameter.ActualValue = value; }
67    }
68    public IntValue ImprovementAttempts {
69      get { return ImprovementAttemptsParameter.Value; }
70      set { ImprovementAttemptsParameter.Value = value; }
71    }
72    public IRandom Random {
73      get { return RandomParameter.ActualValue; }
74      set { RandomParameter.ActualValue = value; }
75    }
76    #endregion
77
78    [StorableConstructor]
79    private TSPImprovementOperator(bool deserializing) : base(deserializing) { }
80    private TSPImprovementOperator(TSPImprovementOperator original, Cloner cloner) : base(original, cloner) { }
81    public TSPImprovementOperator()
82      : base() {
83      #region Create parameters
84      Parameters.Add(new ScopeParameter("CurrentScope", "The current scope that contains the solution to be improved."));
85      Parameters.Add(new LookupParameter<DistanceMatrix>("DistanceMatrix", "The matrix which contains the distances between the cities."));
86      Parameters.Add(new ValueParameter<IntValue>("ImprovementAttempts", "The number of improvement attempts the operator should perform.", new IntValue(100)));
87      Parameters.Add(new LookupParameter<IRandom>("Random", "A pseudo random number generator."));
88      Parameters.Add(new ValueLookupParameter<IItem>("Solution", "The solution to be improved. This parameter is used for name translation only."));
89      #endregion
90    }
91
92    public override IDeepCloneable Clone(Cloner cloner) {
93      return new TSPImprovementOperator(this, cloner);
94    }
95
96    public override IOperation Apply() {
97      Permutation currSol = CurrentScope.Variables[SolutionParameter.ActualName].Value as Permutation;
98      if (currSol == null)
99        throw new ArgumentException("Cannot improve solution because it has the wrong type.");
100      if (currSol.PermutationType != PermutationTypes.RelativeUndirected)
101        throw new ArgumentException("Cannot improve solution because the permutation type is not supported.");
102
103      for (int i = 0; i < ImprovementAttempts.Value; i++) {
104        int a = Random.Next(currSol.Length);
105        int b = Random.Next(currSol.Length);
106        double oldFirstEdgeLength = DistanceMatrix[currSol[a], currSol[(a - 1 + currSol.Length) % currSol.Length]];
107        double oldSecondEdgeLength = DistanceMatrix[currSol[b], currSol[(b + 1) % currSol.Length]];
108        double newFirstEdgeLength = DistanceMatrix[currSol[b], currSol[(a - 1 + currSol.Length) % currSol.Length]];
109        double newSecondEdgeLength = DistanceMatrix[currSol[a], currSol[(b + 1 + currSol.Length) % currSol.Length]];
110        if (newFirstEdgeLength + newSecondEdgeLength < oldFirstEdgeLength + oldSecondEdgeLength)
111          Invert(currSol, a, b);
112      }
113
114      CurrentScope.Variables.Add(new Variable("LocalEvaluatedSolutions", ImprovementAttempts));
115
116      return base.Apply();
117    }
118
119    private void Invert(Permutation sol, int i, int j) {
120      if (i != j)
121        for (int a = 0; a < Math.Abs(i - j) / 2; a++)
122          if (sol[(i + a) % sol.Length] != sol[(j - a + sol.Length) % sol.Length]) {
123            // XOR swap
124            sol[(i + a) % sol.Length] ^= sol[(j - a + sol.Length) % sol.Length];
125            sol[(j - a + sol.Length) % sol.Length] ^= sol[(i + a) % sol.Length];
126            sol[(i + a) % sol.Length] ^= sol[(j - a + sol.Length) % sol.Length];
127          }
128    }
129  }
130}
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