1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2008 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 System.Text;
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26 | using HeuristicLab.Core;
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27 | using HeuristicLab.Operators;
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28 | using HeuristicLab.Random;
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29 | using HeuristicLab.Data;
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30 | using HeuristicLab.Constraints;
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31 | using System.Diagnostics;
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32 |
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33 | namespace HeuristicLab.GP {
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34 | /// <summary>
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35 | /// Implementation of a homologous uniform crossover operator as described in:
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36 | /// R. Poli and W. B. Langdon. On the Search Properties of Different Crossover Operators in Genetic Programming.
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37 | /// In Proceedings of Genetic Programming '98, Madison, Wisconsin, 1998.
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38 | /// </summary>
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39 | public class UniformCrossover : OperatorBase {
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40 | public override string Description {
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41 | get {
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42 | return @"Uniform crossover as defined by Poli and Langdon";
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43 | }
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44 | }
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45 | public UniformCrossover()
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46 | : base() {
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47 | AddVariableInfo(new VariableInfo("Random", "Pseudo random number generator", typeof(MersenneTwister), VariableKind.In));
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48 | AddVariableInfo(new VariableInfo("OperatorLibrary", "The operator library containing all available operators", typeof(GPOperatorLibrary), VariableKind.In));
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49 | AddVariableInfo(new VariableInfo("FunctionTree", "The tree to mutate", typeof(IFunctionTree), VariableKind.In | VariableKind.New));
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50 | AddVariableInfo(new VariableInfo("TreeSize", "The size (number of nodes) of the tree", typeof(IntData), VariableKind.In | VariableKind.New));
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51 | AddVariableInfo(new VariableInfo("TreeHeight", "The height of the tree", typeof(IntData), VariableKind.In | VariableKind.New));
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52 | }
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53 |
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54 | public override IOperation Apply(IScope scope) {
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55 | MersenneTwister random = GetVariableValue<MersenneTwister>("Random", scope, true);
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56 | GPOperatorLibrary opLibrary = GetVariableValue<GPOperatorLibrary>("OperatorLibrary", scope, true);
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57 | TreeGardener gardener = new TreeGardener(random, opLibrary);
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58 |
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59 | if ((scope.SubScopes.Count % 2) != 0)
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60 | throw new InvalidOperationException("Number of parents is not even");
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61 |
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62 | CompositeOperation initOperations = new CompositeOperation();
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63 |
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64 | int children = scope.SubScopes.Count / 2;
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65 | for (int i = 0; i < children; i++) {
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66 | IScope parent1 = scope.SubScopes[0];
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67 | scope.RemoveSubScope(parent1);
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68 | IScope parent2 = scope.SubScopes[0];
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69 | scope.RemoveSubScope(parent2);
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70 | IScope child = new Scope(i.ToString());
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71 | IOperation childInitOperation = Cross(scope, random, gardener, parent1, parent2, child);
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72 | initOperations.AddOperation(childInitOperation);
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73 | scope.AddSubScope(child);
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74 | }
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75 |
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76 | return initOperations;
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77 | }
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78 |
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79 | private IOperation Cross(IScope scope, MersenneTwister random, TreeGardener gardener, IScope parent1, IScope parent2, IScope child) {
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80 | IFunctionTree newTree = Cross(random, gardener, parent1, parent2);
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81 | Debug.Assert(gardener.IsValidTree(newTree));
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82 | int newTreeSize = newTree.Size;
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83 | int newTreeHeight = newTree.Height;
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84 | child.AddVariable(new HeuristicLab.Core.Variable(scope.TranslateName("FunctionTree"), newTree));
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85 | child.AddVariable(new HeuristicLab.Core.Variable(scope.TranslateName("TreeSize"), new IntData(newTreeSize)));
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86 | child.AddVariable(new HeuristicLab.Core.Variable(scope.TranslateName("TreeHeight"), new IntData(newTreeHeight)));
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87 |
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88 | return null;
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89 | }
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90 |
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91 |
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92 | private IFunctionTree Cross(MersenneTwister random, TreeGardener gardener, IScope f, IScope g) {
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93 | IFunctionTree tree0 = f.GetVariableValue<IFunctionTree>("FunctionTree", false);
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94 | int tree0Height = f.GetVariableValue<IntData>("TreeHeight", false).Data;
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95 | int tree0Size = f.GetVariableValue<IntData>("TreeSize", false).Data;
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96 |
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97 | IFunctionTree tree1 = g.GetVariableValue<IFunctionTree>("FunctionTree", false);
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98 | int tree1Height = g.GetVariableValue<IntData>("TreeHeight", false).Data;
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99 | int tree1Size = g.GetVariableValue<IntData>("TreeSize", false).Data;
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100 |
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101 | List<CrossoverPoint> allowedCrossOverPoints = GetCrossOverPoints(gardener, tree0, tree1);
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102 | foreach (CrossoverPoint p in allowedCrossOverPoints) {
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103 | Debug.Assert(gardener.GetAllowedSubFunctions(p.parent0.Function, p.childIndex).Contains(p.parent1.SubTrees[p.childIndex].Function));
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104 | Debug.Assert(gardener.GetAllowedSubFunctions(p.parent1.Function, p.childIndex).Contains(p.parent0.SubTrees[p.childIndex].Function));
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105 | }
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106 | // iterate through the list of crossover points and swap nodes with p=0.5
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107 | foreach (CrossoverPoint crossoverPoint in allowedCrossOverPoints) {
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108 | if (random.NextDouble() < 0.5) {
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109 | IFunctionTree parent0 = crossoverPoint.parent0;
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110 | IFunctionTree parent1 = crossoverPoint.parent1;
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111 | IFunctionTree branch0 = crossoverPoint.parent0.SubTrees[crossoverPoint.childIndex];
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112 | IFunctionTree branch1 = crossoverPoint.parent1.SubTrees[crossoverPoint.childIndex];
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113 |
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114 | // if we are at an internal node of the common region swap only the node but not the subtrees
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115 | if (branch0.SubTrees.Count == branch1.SubTrees.Count) {
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116 | if (parent0 != null) {
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117 | Debug.Assert(parent1 != null); Debug.Assert(branch0 != null); Debug.Assert(branch0 != null);
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118 | Debug.Assert(gardener.GetAllowedSubFunctions(parent0.Function, crossoverPoint.childIndex).Contains(branch1.Function));
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119 | Debug.Assert(gardener.GetAllowedSubFunctions(parent1.Function, crossoverPoint.childIndex).Contains(branch0.Function));
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120 | // we are not at the root => exchange the branches in the parent
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121 | parent0.RemoveSubTree(crossoverPoint.childIndex);
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122 | parent1.RemoveSubTree(crossoverPoint.childIndex);
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123 | parent0.InsertSubTree(crossoverPoint.childIndex, branch1);
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124 | parent1.InsertSubTree(crossoverPoint.childIndex, branch0);
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125 | }
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126 | // always exchange all children
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127 | List<IFunctionTree> branch0Children = new List<IFunctionTree>(branch0.SubTrees); // create backup lists
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128 | List<IFunctionTree> branch1Children = new List<IFunctionTree>(branch1.SubTrees);
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129 | while (branch0.SubTrees.Count > 0) branch0.RemoveSubTree(0); // remove all children
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130 | while (branch1.SubTrees.Count > 0) branch1.RemoveSubTree(0);
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131 | foreach (IFunctionTree subTree in branch1Children) {
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132 | Debug.Assert(gardener.GetAllowedSubFunctions(branch0.Function, branch0.SubTrees.Count).Contains(subTree.Function));
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133 | branch0.AddSubTree(subTree); // append children of branch1 to branch0
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134 | }
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135 | foreach (IFunctionTree subTree in branch0Children) {
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136 | Debug.Assert(gardener.GetAllowedSubFunctions(branch1.Function, branch1.SubTrees.Count).Contains(subTree.Function));
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137 | branch1.AddSubTree(subTree); // and vice versa
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138 | }
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139 | } else {
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140 | // If we are at a node at the border of the common region then exchange the whole branch.
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141 | // If we are at the root node and the number of children is already different we can't do anything now but
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142 | // at the end either tree0 or tree1 must be returned with p=0.5.
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143 |
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144 | // However if we are not at the root => exchange the branches in the parent
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145 | if (parent0 != null) {
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146 | Debug.Assert(parent1 != null); Debug.Assert(branch0 != null); Debug.Assert(branch1 != null);
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147 | Debug.Assert(gardener.GetAllowedSubFunctions(parent0.Function, crossoverPoint.childIndex).Contains(branch1.Function));
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148 | Debug.Assert(gardener.GetAllowedSubFunctions(parent1.Function, crossoverPoint.childIndex).Contains(branch0.Function));
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149 | parent0.RemoveSubTree(crossoverPoint.childIndex);
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150 | parent1.RemoveSubTree(crossoverPoint.childIndex);
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151 | parent0.InsertSubTree(crossoverPoint.childIndex, branch1);
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152 | parent1.InsertSubTree(crossoverPoint.childIndex, branch0);
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153 | }
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154 | }
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155 | }
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156 | }
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157 | if (random.NextDouble() < 0.5) return tree0; else return tree1;
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158 | }
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159 |
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160 | class CrossoverPoint {
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161 | public IFunctionTree parent0;
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162 | public IFunctionTree parent1;
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163 | public int childIndex;
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164 | }
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165 |
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166 | private List<CrossoverPoint> GetCrossOverPoints(TreeGardener gardener, IFunctionTree branch0, IFunctionTree branch1) {
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167 | List<CrossoverPoint> results = new List<CrossoverPoint>();
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168 | if (branch0.SubTrees.Count != branch1.SubTrees.Count) return results;
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169 |
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170 | for (int i = 0; i < branch0.SubTrees.Count; i++) {
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171 | // if the branches fit to the parent
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172 | if (gardener.GetAllowedSubFunctions(branch0.Function, i).Contains(branch1.SubTrees[i].Function) &&
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173 | gardener.GetAllowedSubFunctions(branch1.Function, i).Contains(branch0.SubTrees[i].Function)) {
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174 | // if the point is at the border of the common region we don't care about the children
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175 | // however if the point is not on the border of the common region we also have to check if
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176 | // the children of the branches fit together
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177 | bool fit = true;
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178 | if (branch0.SubTrees[i].SubTrees.Count == branch1.SubTrees[i].SubTrees.Count) {
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179 | for (int j = 0; j < branch0.SubTrees[i].SubTrees.Count; j++) {
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180 | fit = fit & gardener.GetAllowedSubFunctions(branch0.SubTrees[i].Function, j).Contains(branch1.SubTrees[i].SubTrees[j].Function);
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181 | fit = fit & gardener.GetAllowedSubFunctions(branch1.SubTrees[i].Function, j).Contains(branch0.SubTrees[i].SubTrees[j].Function);
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182 | }
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183 | }
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184 | if (fit) {
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185 | CrossoverPoint p = new CrossoverPoint();
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186 | p.childIndex = i;
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187 | p.parent0 = branch0;
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188 | p.parent1 = branch1;
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189 | results.Add(p);
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190 | }
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191 | }
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192 | results.AddRange(GetCrossOverPoints(gardener, branch0.SubTrees[i], branch1.SubTrees[i]));
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193 | }
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194 | return results;
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195 | }
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196 | }
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197 | }
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