1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2011 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 System;
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23 | using System.Collections.Generic;
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24 | using System.Linq;
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25 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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26 | using HeuristicLab.Common;
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27 | using HeuristicLab.Core;
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28 | using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
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29 | using HeuristicLab.Data;
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30 | using HeuristicLab.Parameters;
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31 |
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32 | namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
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33 |
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34 | [Item("DepthConstrainedCrossover", "An operator which performs subtree swapping within a specific depth range.")]
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35 | public sealed class SymbolicDataAnalysisExpressionDepthConstrainedCrossover<T> :
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36 | SymbolicDataAnalysisExpressionCrossover<T> where T : class, IDataAnalysisProblemData {
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37 | private enum Ranges { HighLevel, Standard, Lowlevel };
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38 | private const string DepthRangeParameterName = "DepthRange";
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39 | #region Parameter properties
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40 |
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41 | public ConstrainedValueParameter<StringValue> DepthRangeParameter {
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42 | get { return (ConstrainedValueParameter<StringValue>)Parameters[DepthRangeParameterName]; }
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43 | }
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44 | #endregion
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45 |
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46 | #region Properties
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47 | public StringValue DepthRange {
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48 | get { return (StringValue)DepthRangeParameter.ActualValue; }
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49 | }
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50 | #endregion
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51 |
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52 | [StorableConstructor]
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53 | private SymbolicDataAnalysisExpressionDepthConstrainedCrossover(bool deserializing) : base(deserializing) { }
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54 | private SymbolicDataAnalysisExpressionDepthConstrainedCrossover(SymbolicDataAnalysisExpressionCrossover<T> original, Cloner cloner)
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55 | : base(original, cloner) { }
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56 | public SymbolicDataAnalysisExpressionDepthConstrainedCrossover()
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57 | : base() {
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58 | Parameters.Add(new ConstrainedValueParameter<StringValue>(DepthRangeParameterName, "Depth range specifier"));
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59 | DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.HighLevel)));
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60 | DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.Standard)));
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61 | DepthRangeParameter.ValidValues.Add(new StringValue(Enum.GetName(typeof(Ranges), Ranges.Lowlevel)));
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62 | Name = "DepthConstrainedCrossover";
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63 | }
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64 | public override IDeepCloneable Clone(Cloner cloner) { return new SymbolicDataAnalysisExpressionDepthConstrainedCrossover<T>(this, cloner); }
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65 |
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66 | protected override ISymbolicExpressionTree Cross(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1) {
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67 | return Cross(random, parent0, parent1, MaximumSymbolicExpressionTreeDepth.Value, MaximumSymbolicExpressionTreeLength.Value, DepthRange.Value);
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68 | }
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69 |
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70 | public override ISymbolicExpressionTree Crossover(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1) {
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71 | return Cross(random, parent0, parent1);
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72 | }
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73 |
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74 | /// <summary>
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75 | /// Takes two parent individuals P0 and P1.
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76 | /// Randomly choose nodes that fall within the specified depth range in both parents.
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77 | /// </summary>
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78 | /// <param name="random">Pseudo-random number generator.</param>
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79 | /// <param name="parent0">First parent.</param>
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80 | /// <param name="parent1">Second parent.</param>
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81 | /// <param name="maxDepth">Maximum allowed length depth.</param>
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82 | /// <param name="maxLength">Maximum allowed tree length.</param>
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83 | /// <param name="mode">Controls the crossover behavior:
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84 | /// - HighLevel (upper 25% of the tree),
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85 | /// - Standard (mid 50%)
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86 | /// - LowLevel (low 25%)</param>
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87 | /// <returns></returns>
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88 | public static ISymbolicExpressionTree Cross(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1, int maxDepth, int maxLength, string mode) {
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89 | int depth = parent0.Root.GetDepth();
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90 | var depthRange = new DoubleRange();
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91 | const int depthOffset = 2; // skip the first 2 levels (root + startNode)
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92 | switch ((int)Enum.Parse(typeof(Ranges), mode)) {
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93 | case (int)Ranges.HighLevel:
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94 | depthRange.Start = depthOffset; // skip the first 2 levels (root + startNode)
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95 | depthRange.End = depthRange.Start + Math.Round(depth * 0.25);
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96 | break;
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97 | case (int)Ranges.Standard:
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98 | depthRange.Start = depthOffset + Math.Round(depth * 0.25);
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99 | depthRange.End = depthRange.Start + Math.Round(depth * 0.5);
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100 | break;
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101 | case (int)Ranges.Lowlevel:
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102 | depthRange.Start = depthOffset + Math.Round(depth * 0.75);
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103 | depthRange.End = Math.Max(depthRange.Start, depth);
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104 | break;
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105 | }
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106 |
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107 | var crossoverPoints0 = new List<CutPoint>();
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108 | parent0.Root.ForEachNodePostfix((n) => {
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109 | if (n.Subtrees.Any() && n != parent0.Root)
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110 | crossoverPoints0.AddRange(from s in n.Subtrees
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111 | where parent0.Root.GetBranchLevel(s) >= depthRange.Start && parent0.Root.GetBranchLevel(s) <= depthRange.End
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112 | select new CutPoint(n, s));
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113 | });
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114 |
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115 | if (crossoverPoints0.Count == 0)
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116 | throw new Exception("No crossover points available in the first parent");
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117 |
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118 | CutPoint crossoverPoint0 = crossoverPoints0.SelectRandom(random);
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119 | int level = parent0.Root.GetBranchLevel(crossoverPoint0.Child);
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120 | int length = parent0.Root.GetLength() - crossoverPoint0.Child.GetLength();
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121 |
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122 | var allowedBranches = new List<ISymbolicExpressionTreeNode>();
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123 | parent1.Root.ForEachNodePostfix((n) => {
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124 | if (n.Subtrees.Any() && n != parent1.Root) {
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125 | allowedBranches.AddRange(from s in n.Subtrees
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126 | let branchLevel = parent1.Root.GetBranchLevel(s)
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127 | where branchLevel >= depthRange.Start && branchLevel <= depthRange.End && s.GetDepth() + level <= maxDepth && s.GetLength() + length <= maxLength
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128 | select s);
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129 | }
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130 | });
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131 |
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132 | if (allowedBranches.Count == 0)
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133 | return parent0;
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134 |
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135 | var selectedBranch = allowedBranches.SelectRandom(random);
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136 |
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137 | swap(crossoverPoint0, selectedBranch);
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138 |
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139 | return parent0;
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140 | }
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141 |
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142 | private static void swap(CutPoint crossoverPoint, ISymbolicExpressionTreeNode selectedBranch) {
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143 | // perform the actual swap
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144 | if (crossoverPoint.Child != null) {
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145 | // manipulate the tree of parent0 in place
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146 | // replace the branch in tree0 with the selected branch from tree1
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147 | crossoverPoint.Parent.RemoveSubtree(crossoverPoint.ChildIndex);
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148 | if (selectedBranch != null) {
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149 | crossoverPoint.Parent.InsertSubtree(crossoverPoint.ChildIndex, selectedBranch);
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150 | }
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151 | } else {
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152 | // child is null (additional child should be added under the parent)
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153 | if (selectedBranch != null) {
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154 | crossoverPoint.Parent.AddSubtree(selectedBranch);
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155 | }
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156 | }
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157 | }
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158 | }
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159 | }
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