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 HeuristicLab.Functions;
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32 |
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33 | namespace HeuristicLab.StructureIdentification {
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34 | public class ChangeNodeTypeManipulation : OperatorBase {
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35 | public ChangeNodeTypeManipulation()
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36 | : base() {
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37 | AddVariableInfo(new VariableInfo("Random", "Uniform random number generator", typeof(MersenneTwister), VariableKind.In));
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38 | AddVariableInfo(new VariableInfo("OperatorLibrary", "The operator library containing all available operators", typeof(GPOperatorLibrary), VariableKind.In));
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39 | AddVariableInfo(new VariableInfo("MaxTreeHeight", "The maximal allowed height of the tree", typeof(IntData), VariableKind.In));
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40 | AddVariableInfo(new VariableInfo("MaxTreeSize", "The maximal allowed size (number of nodes) of the tree", typeof(IntData), VariableKind.In));
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41 | AddVariableInfo(new VariableInfo("BalancedTreesRate", "Determines how many trees should be balanced", typeof(DoubleData), VariableKind.In));
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42 | AddVariableInfo(new VariableInfo("FunctionTree", "The tree to mutate", typeof(IFunctionTree), VariableKind.In | VariableKind.Out));
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43 | AddVariableInfo(new VariableInfo("TreeSize", "The size (number of nodes) of the tree", typeof(IntData), VariableKind.In | VariableKind.Out));
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44 | AddVariableInfo(new VariableInfo("TreeHeight", "The height of the tree", typeof(IntData), VariableKind.In | VariableKind.Out));
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45 | }
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46 |
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47 |
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48 | public override IOperation Apply(IScope scope) {
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49 | IFunctionTree root = GetVariableValue<IFunctionTree>("FunctionTree", scope, false);
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50 | MersenneTwister random = GetVariableValue<MersenneTwister>("Random", scope, true);
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51 | GPOperatorLibrary library = GetVariableValue<GPOperatorLibrary>("OperatorLibrary", scope, true);
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52 | double balancedTreesRate = GetVariableValue<DoubleData>("BalancedTreesRate", scope, true).Data;
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53 | IntData treeSize = GetVariableValue<IntData>("TreeSize", scope, false);
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54 | IntData treeHeight = GetVariableValue<IntData>("TreeHeight", scope, false);
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55 | int maxTreeSize = GetVariableValue<IntData>("MaxTreeSize", scope, true).Data;
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56 | int maxTreeHeight = GetVariableValue<IntData>("MaxTreeHeight", scope, true).Data;
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57 |
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58 | TreeGardener gardener = new TreeGardener(random, library);
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59 | IFunctionTree parent = gardener.GetRandomParentNode(root);
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60 |
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61 | IFunctionTree selectedChild;
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62 | int selectedChildIndex;
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63 | if (parent == null) {
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64 | selectedChildIndex = 0;
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65 | selectedChild = root;
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66 | } else {
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67 | selectedChildIndex = random.Next(parent.SubTrees.Count);
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68 | selectedChild = parent.SubTrees [selectedChildIndex];
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69 | }
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70 |
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71 | if (selectedChild.SubTrees.Count == 0) {
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72 | IFunctionTree newTerminal = ChangeTerminalType(parent, selectedChild, selectedChildIndex, gardener, random);
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73 |
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74 | if (parent == null) {
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75 | // no parent means the new child is the initial operator
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76 | // and we have to update the value in the variable
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77 | scope.GetVariable(scope.TranslateName("FunctionTree")).Value = newTerminal;
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78 | } else {
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79 | parent.RemoveSubTree(selectedChildIndex);
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80 | parent.InsertSubTree(selectedChildIndex, newTerminal);
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81 | // updating the variable is not necessary because it stays the same
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82 | }
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83 |
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84 | // size and height stays the same when changing a terminal so no need to update the variables
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85 | // schedule an operation to initialize the new terminal
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86 | return gardener.CreateInitializationOperation(gardener.GetAllSubTrees(newTerminal), scope);
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87 | } else {
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88 | List<IFunctionTree> uninitializedBranches;
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89 | IFunctionTree newFunction = ChangeFunctionType(parent, selectedChild, selectedChildIndex, gardener, random, balancedTreesRate, out uninitializedBranches);
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90 |
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91 | if (parent == null) {
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92 | // no parent means the new function is the initial operator
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93 | // and we have to update the value in the variable
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94 | scope.GetVariable(scope.TranslateName("FunctionTree")).Value = newFunction;
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95 | root = newFunction;
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96 | } else {
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97 | // remove the old child
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98 | parent.RemoveSubTree(selectedChildIndex);
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99 | // add the new child as sub-tree of parent
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100 | parent.InsertSubTree(selectedChildIndex, newFunction);
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101 | }
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102 |
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103 | // recalculate size and height
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104 | treeSize.Data = gardener.GetTreeSize(root);
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105 | treeHeight.Data = gardener.GetTreeHeight(root);
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106 |
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107 | // check if the size of the new tree is still in the allowed bounds
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108 | if (treeHeight.Data > maxTreeHeight ||
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109 | treeSize.Data > maxTreeSize) {
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110 | throw new InvalidProgramException();
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111 | }
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112 |
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113 | // check if whole tree is ok
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114 | if (!gardener.IsValidTree(root)) {
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115 | throw new InvalidProgramException();
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116 | }
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117 |
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118 | // return a composite operation that initializes all created sub-trees
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119 | return gardener.CreateInitializationOperation(uninitializedBranches, scope);
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120 | }
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121 | }
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122 |
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123 |
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124 | private IFunctionTree ChangeTerminalType(IFunctionTree parent, IFunctionTree child, int childIndex, TreeGardener gardener, MersenneTwister random) {
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125 |
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126 | IList<IFunction> allowedChildren;
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127 | if (parent == null) {
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128 | allowedChildren = gardener.Terminals;
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129 | } else {
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130 | SubOperatorsConstraintAnalyser analyser = new SubOperatorsConstraintAnalyser();
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131 | analyser.AllPossibleOperators = gardener.Terminals.Cast<IOperator>().ToArray();
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132 | allowedChildren = analyser.GetAllowedOperators(parent.Function, childIndex).Cast<IFunction>().ToList();
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133 | }
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134 |
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135 | // selecting from the terminals should always work since the current child was also a terminal
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136 | // so in the worst case we will just create a new terminal of the same type again.
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137 | return gardener.CreateRandomTree(allowedChildren[random.Next(allowedChildren.Count)], 1, 1, false);
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138 | }
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139 |
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140 | private IFunctionTree ChangeFunctionType(IFunctionTree parent, IFunctionTree child, int childIndex, TreeGardener gardener, MersenneTwister random,
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141 | double balancedTreesRate, out List<IFunctionTree> uninitializedBranches) {
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142 | // since there are subtrees, we have to check which
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143 | // and how many of the existing subtrees we can reuse
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144 |
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145 | // let's choose the function we want to use instead of the old child. For this we have to determine the
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146 | // pool of allowed functions based on constraints of the parent if there is one.
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147 | IList<IFunction> allowedFunctions;
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148 | SubOperatorsConstraintAnalyser analyser = new SubOperatorsConstraintAnalyser();
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149 | analyser.AllPossibleOperators = gardener.AllFunctions.Cast<IOperator>().ToArray();
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150 | if (parent == null) {
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151 | allowedFunctions = gardener.AllFunctions;
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152 | } else {
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153 | allowedFunctions = analyser.GetAllowedOperators(parent.Function, childIndex).Cast<IFunction>().ToList();
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154 | }
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155 |
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156 | // try to make a tree with the same arity as the old child.
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157 | int actualArity = child.SubTrees.Count;
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158 | // arity of the selected operator
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159 | int minArity;
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160 | int maxArity;
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161 |
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162 | allowedFunctions = allowedFunctions.Where(f => {
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163 | gardener.GetMinMaxArity(f, out minArity, out maxArity);
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164 | return minArity <= actualArity;
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165 | }).ToList();
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166 |
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167 | IFunctionTree newTree = new FunctionTree(allowedFunctions[random.Next(allowedFunctions.Count)]);
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168 |
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169 | gardener.GetMinMaxArity(newTree.Function, out minArity, out maxArity);
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170 | // if the old child had too many sub-trees then make the new child with the maximal arity
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171 | if (actualArity > maxArity)
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172 | actualArity = maxArity;
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173 |
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174 | // get the allowed size and height for new sub-trees
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175 | // use the size of the smallest subtree as the maximal allowed size for new subtrees to
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176 | // prevent that we ever create trees over the MaxTreeSize limit
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177 | int maxSubTreeSize = child.SubTrees.Select(subTree => gardener.GetTreeSize(subTree)).Min();
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178 | int maxSubTreeHeight = gardener.GetTreeHeight(child) - 1;
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179 |
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180 | // create a list that holds old sub-trees that we can reuse in the new tree
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181 | List<IFunctionTree> availableSubTrees = new List<IFunctionTree>(child.SubTrees);
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182 | List<IFunctionTree> freshSubTrees = new List<IFunctionTree>() { newTree };
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183 |
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184 | // randomly select the sub-trees that we keep
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185 | for (int i = 0; i < actualArity; i++) {
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186 | // fill all sub-tree slots of the new tree
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187 | // if for a given slot i there are existing sub-trees that can be used in that slot
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188 | // then use a random existing sub-tree. When there are no existing sub-trees
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189 | // that fit in the given slot then create a new random tree and use it for the slot
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190 | IList<IFunction> allowedOperators = analyser.GetAllowedOperators(newTree.Function, i).Cast<IFunction>().ToList();
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191 | var matchingSubTrees = availableSubTrees.Where(subTree => allowedOperators.Contains(subTree.Function));
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192 |
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193 | if (matchingSubTrees.Count() > 0) {
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194 | IFunctionTree selectedSubTree = matchingSubTrees.ElementAt(random.Next(matchingSubTrees.Count()));
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195 | // we can just add it as subtree
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196 | newTree.InsertSubTree(i, selectedSubTree);
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197 | availableSubTrees.Remove(selectedSubTree); // the branch shouldn't be available for the following slots
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198 | } else {
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199 | IFunctionTree freshTree;
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200 | if(random.NextDouble() <= balancedTreesRate) {
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201 | freshTree = gardener.CreateRandomTree(allowedOperators, maxSubTreeSize, maxSubTreeHeight, true);
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202 | } else {
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203 | freshTree = gardener.CreateRandomTree(allowedOperators, maxSubTreeSize, maxSubTreeHeight, false);
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204 | }
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205 | freshSubTrees.AddRange(gardener.GetAllSubTrees(freshTree));
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206 |
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207 | newTree.InsertSubTree(i, freshTree);
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208 | }
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209 | }
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210 |
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211 | uninitializedBranches = freshSubTrees;
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212 | return newTree;
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213 | }
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214 | }
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215 | }
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