1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2016 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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4 | *
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5 | * This file is part of HeuristicLab.
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6 | *
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7 | * HeuristicLab is free software: you can redistribute it and/or modify
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8 | * it under the terms of the GNU General Public License as published by
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9 | * the Free Software Foundation, either version 3 of the License, or
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10 | * (at your option) any later version.
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11 | *
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12 | * HeuristicLab is distributed in the hope that it will be useful,
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | * GNU General Public License for more details.
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16 | *
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17 | * You should have received a copy of the GNU General Public License
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18 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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19 | */
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20 | #endregion
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21 |
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22 | using HeuristicLab.Common;
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23 | using HeuristicLab.Core;
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24 | using HeuristicLab.Data;
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25 | using HeuristicLab.Encodings.PermutationEncoding;
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26 | using HeuristicLab.Optimization;
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27 | using HeuristicLab.Parameters;
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28 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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29 | using HeuristicLab.Problems.QuadraticAssignment;
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30 | using HeuristicLab.Random;
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31 | using System;
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32 | using System.Collections.Generic;
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33 | using System.Linq;
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34 |
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35 | namespace HeuristicLab.Problems.CharacteristicAnalysis.QAP {
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36 | [Item("Directed Walk (QAP-specific)", "")]
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37 | [StorableClass]
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38 | public class QAPDirectedWalk : CharacteristicCalculator {
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39 |
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40 | public IFixedValueParameter<IntValue> PathsParameter {
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41 | get { return (IFixedValueParameter<IntValue>)Parameters["Paths"]; }
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42 | }
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43 |
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44 | public IFixedValueParameter<BoolValue> BestImprovementParameter {
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45 | get { return (IFixedValueParameter<BoolValue>)Parameters["BestImprovement"]; }
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46 | }
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47 |
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48 | public IValueParameter<IntValue> SeedParameter {
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49 | get { return (IValueParameter<IntValue>)Parameters["Seed"]; }
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50 | }
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51 |
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52 | public int Paths {
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53 | get { return PathsParameter.Value.Value; }
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54 | set { PathsParameter.Value.Value = value; }
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55 | }
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56 |
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57 | public bool BestImprovement {
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58 | get { return BestImprovementParameter.Value.Value; }
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59 | set { BestImprovementParameter.Value.Value = value; }
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60 | }
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61 |
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62 | public int? Seed {
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63 | get { return SeedParameter.Value != null ? SeedParameter.Value.Value : (int?)null; }
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64 | set { SeedParameter.Value = value.HasValue ? new IntValue(value.Value) : null; }
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65 | }
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66 |
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67 | [StorableConstructor]
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68 | private QAPDirectedWalk(bool deserializing) : base(deserializing) { }
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69 | private QAPDirectedWalk(QAPDirectedWalk original, Cloner cloner) : base(original, cloner) { }
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70 | public QAPDirectedWalk() {
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71 | characteristics.AddRange(new[] { "Swap2.Sharpness", "Swap2.Bumpiness", "Swap2.Flatness", "Swap2.Steadiness" }
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72 | .Select(x => new StringValue(x)).ToList());
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73 | Parameters.Add(new FixedValueParameter<IntValue>("Paths", "The number of paths to explore (a path is a set of solutions that connect two randomly chosen solutions).", new IntValue(50)));
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74 | Parameters.Add(new FixedValueParameter<BoolValue>("BestImprovement", "Whether the best of all alternatives should be chosen for each step in the path or just the first improving (least degrading) move should be made.", new BoolValue(true)));
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75 | Parameters.Add(new OptionalValueParameter<IntValue>("Seed", "The seed for the random number generator."));
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76 | }
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77 |
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78 | public override IDeepCloneable Clone(Cloner cloner) {
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79 | return new QAPDirectedWalk(this, cloner);
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80 | }
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81 |
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82 | public override bool CanCalculate() {
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83 | return Problem is QuadraticAssignmentProblem;
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84 | }
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85 |
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86 | public override IEnumerable<IResult> Calculate() {
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87 | var pathCount = Paths;
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88 | var random = Seed.HasValue ? new MersenneTwister((uint)Seed.Value) : new MersenneTwister();
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89 | var bestImprovement = BestImprovement;
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90 | var qap = (QuadraticAssignmentProblem)Problem;
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91 | var N = qap.Weights.Rows;
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92 | var start = new Permutation(PermutationTypes.Absolute, N, random);
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93 | var end = start;
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94 | List<double> ips = new List<double>(), ups = new List<double>(), sd2 = new List<double>();
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95 | var pathsD1 = new List<List<Tuple<double, double>>>();
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96 | for (var i = 0; i < pathCount; i++) {
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97 | var trajD1 = new List<Tuple<double, double>>();
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98 | pathsD1.Add(trajD1);
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99 |
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100 | if ((i + 1) % N == 0) {
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101 | start = new Permutation(PermutationTypes.Absolute, N, random);
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102 | end = start;
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103 | }
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104 | end = (Permutation)end.Clone();
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105 | Rot1(end);
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106 |
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107 | var hist = new Tuple<Permutation, double>[5];
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108 | var walkDist = 0.0;
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109 | var prevVal = double.NaN;
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110 | var sumD2 = 0.0;
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111 | var inflectionPoints = 0;
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112 | var undulationPoints = 0;
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113 | var countPoints = 0;
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114 | var counter = 0;
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115 | var path = bestImprovement ? BestImprovementWalk(qap, start, QAPEvaluator.Apply(start, qap.Weights, qap.Distances), end)
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116 | : FirstImprovementWalk(qap, start, QAPEvaluator.Apply(start, qap.Weights, qap.Distances), end, random);
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117 | foreach (var next in path) {
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118 | if (hist[0] != null) {
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119 | var dist = Dist(next.Item1, hist[0].Item1);
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120 | walkDist += dist;
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121 | }
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122 | // from the past 5 values we can calculate the 2nd derivative
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123 | // first derivative in point 2 as differential between points 1 and 3
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124 | // first derivative in point 4 as differential between points 3 and 5
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125 | // second derivative in point 3 as differential between the first derivatives in points 2 and 4
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126 | hist[4] = hist[3];
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127 | hist[3] = hist[2];
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128 | hist[2] = hist[1];
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129 | hist[1] = hist[0];
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130 | hist[0] = next;
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131 | counter++;
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132 |
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133 | if (counter < 3) continue;
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134 | var grad1 = (hist[0].Item2 - hist[2].Item2) / Dist(hist[0].Item1, hist[2].Item1);
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135 |
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136 | if (!double.IsNaN(grad1) && !double.IsInfinity(grad1))
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137 | trajD1.Add(Tuple.Create(walkDist, grad1));
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138 |
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139 | if (counter < 5) continue;
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140 | countPoints++;
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141 | var grad2 = (hist[2].Item2 - hist[4].Item2) / Dist(hist[2].Item1, hist[4].Item1);
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142 | var dgrad = (grad1 - grad2) / Dist(hist[1].Item1, hist[3].Item1);
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143 |
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144 | if (double.IsNaN(dgrad) || double.IsInfinity(dgrad)) continue;
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145 | if (!double.IsNaN(prevVal)) {
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146 | if (prevVal < 0 && dgrad > 0 || prevVal > 0 && dgrad < 0)
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147 | inflectionPoints++;
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148 | else if (prevVal.IsAlmost(0) && dgrad.IsAlmost(0)
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149 | || prevVal.IsAlmost(0) && !dgrad.IsAlmost(0)
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150 | || !prevVal.IsAlmost(0) && dgrad.IsAlmost(0))
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151 | undulationPoints++;
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152 | }
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153 | sumD2 += Math.Abs(grad1 - grad2);
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154 | prevVal = dgrad;
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155 | }
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156 | start = end;
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157 | ips.Add(inflectionPoints / (double)countPoints);
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158 | ups.Add(undulationPoints / (double)countPoints);
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159 | sd2.Add(sumD2 / walkDist);
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160 | } // end paths
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161 | var avgZero = pathsD1.Select(path => path.SkipWhile(v => v.Item2 < 0).First().Item1 / path.Last().Item1).Median();
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162 |
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163 | foreach (var chara in characteristics.CheckedItems.Select(x => x.Value.Value)) {
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164 | if (chara == "Swap2.Sharpness") yield return new Result("Swap2.Sharpness", new DoubleValue(sd2.Average()));
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165 | if (chara == "Swap2.Bumpiness") yield return new Result("Swap2.Bumpiness", new DoubleValue(ips.Average()));
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166 | if (chara == "Swap2.Flatness") yield return new Result("Swap2.Flatness", new DoubleValue(ups.Average()));
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167 | if (chara == "Swap2.Steadiness") yield return new Result("Swap2.Steadiness", new DoubleValue(avgZero));
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168 | }
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169 | }
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170 |
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171 | public IEnumerable<Tuple<Permutation, double>> BestImprovementWalk(QuadraticAssignmentProblem qap, Permutation start, double fitness, Permutation end) {
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172 | var N = qap.Weights.Rows;
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173 | var sol = start;
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174 | var invSol = GetInverse(sol);
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175 | // we require at most N-1 steps to move from one permutation to another
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176 | for (var step = 0; step < N - 1; step++) {
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177 | var bestFitness = double.MaxValue;
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178 | var bestIndex = -1;
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179 | sol = (Permutation)sol.Clone();
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180 | for (var index = 0; index < N; index++) {
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181 | if (sol[index] == end[index]) continue;
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182 | var fit = QAPSwap2MoveEvaluator.Apply(sol, new Swap2Move(index, invSol[end[index]]), qap.Weights, qap.Distances);
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183 | if (fit < bestFitness) { // QAP is minimization
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184 | bestFitness = fit;
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185 | bestIndex = index;
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186 | }
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187 | }
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188 | if (bestIndex >= 0) {
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189 | var prev = sol[bestIndex];
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190 | Swap2Manipulator.Apply(sol, bestIndex, invSol[end[bestIndex]]);
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191 | fitness += bestFitness;
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192 | yield return Tuple.Create(sol, fitness);
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193 | invSol[prev] = invSol[end[bestIndex]];
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194 | invSol[sol[bestIndex]] = bestIndex;
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195 | } else break;
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196 | }
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197 | }
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198 |
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199 | public IEnumerable<Tuple<Permutation, double>> FirstImprovementWalk(QuadraticAssignmentProblem qap, Permutation start, double fitness, Permutation end, IRandom random) {
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200 | var N = qap.Weights.Rows;
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201 | var sol = start;
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202 | var invSol = GetInverse(sol);
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203 | // randomize the order in which improvements are tried
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204 | var order = Enumerable.Range(0, N).Shuffle(random).ToArray();
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205 | // we require at most N-1 steps to move from one permutation to another
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206 | for (var step = 0; step < N - 1; step++) {
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207 | var bestFitness = double.MaxValue;
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208 | var bestIndex = -1;
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209 | sol = (Permutation)sol.Clone();
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210 | for (var i = 0; i < N; i++) {
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211 | var index = order[i];
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212 | if (sol[index] == end[index]) continue;
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213 | var fit = QAPSwap2MoveEvaluator.Apply(sol, new Swap2Move(index, invSol[end[index]]), qap.Weights, qap.Distances);
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214 | if (fit < bestFitness) { // QAP is minimization
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215 | bestFitness = fit;
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216 | bestIndex = index;
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217 | if (bestFitness < 0) break;
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218 | }
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219 | }
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220 | if (bestIndex >= 0) {
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221 | var prev = sol[bestIndex];
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222 | Swap2Manipulator.Apply(sol, bestIndex, invSol[end[bestIndex]]);
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223 | fitness += bestFitness;
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224 | yield return Tuple.Create(sol, fitness);
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225 | invSol[prev] = invSol[end[bestIndex]];
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226 | invSol[sol[bestIndex]] = bestIndex;
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227 | } else break;
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228 | }
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229 | }
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230 |
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231 | private static double Dist(Permutation a, Permutation b) {
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232 | return a.Where((t, i) => t != b[i]).Count();
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233 | }
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234 |
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235 | private static int[] GetInverse(Permutation p) {
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236 | var inv = new int[p.Length];
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237 | for (var i = 0; i < p.Length; i++) inv[p[i]] = i;
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238 | return inv;
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239 | }
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240 |
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241 | private static void Rot1(Permutation p) {
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242 | var first = p[0];
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243 | for (var i = 0; i < p.Length - 1; i++) p[i] = p[i + 1];
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244 | p[p.Length - 1] = first;
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245 | }
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246 | }
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247 | }
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