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 |
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32 | namespace HeuristicLab.StructureIdentification {
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33 | public class ChangeNodeTypeManipulation : OperatorBase {
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34 |
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35 | public override string Description {
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36 | get {
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37 | return @"This manipulation operator selects a random tree-node and changes the function type.
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38 | If this leads to a constraint-violation (wrong number or type of sub-trees) the sub-trees are repaired
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39 | resulting in a valid tree again.";
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40 | }
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41 | }
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42 |
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43 | public ChangeNodeTypeManipulation()
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44 | : base() {
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45 | AddVariableInfo(new VariableInfo("Random", "Uniform random number generator", typeof(MersenneTwister), VariableKind.In));
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46 | AddVariableInfo(new VariableInfo("OperatorLibrary", "The operator library containing all available operators", typeof(GPOperatorLibrary), VariableKind.In));
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47 | AddVariableInfo(new VariableInfo("MaxTreeHeight", "The maximal allowed height of the tree", typeof(IntData), VariableKind.In));
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48 | AddVariableInfo(new VariableInfo("MaxTreeSize", "The maximal allowed size (number of nodes) of the tree", typeof(IntData), VariableKind.In));
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49 | AddVariableInfo(new VariableInfo("BalancedTreesRate", "Determines how many trees should be balanced", typeof(DoubleData), VariableKind.In));
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50 | AddVariableInfo(new VariableInfo("OperatorTree", "The tree to mutate", typeof(IOperator), VariableKind.In));
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51 | AddVariableInfo(new VariableInfo("TreeSize", "The size (number of nodes) of the tree", typeof(IntData), VariableKind.In));
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52 | AddVariableInfo(new VariableInfo("TreeHeight", "The height of the tree", typeof(IntData), VariableKind.In));
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53 | }
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54 |
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55 |
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56 | public override IOperation Apply(IScope scope) {
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57 | IOperator rootOperator = GetVariableValue<IOperator>("OperatorTree", scope, false);
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58 | MersenneTwister random = GetVariableValue<MersenneTwister>("Random", scope, true);
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59 | GPOperatorLibrary library = GetVariableValue<GPOperatorLibrary>("OperatorLibrary", scope, true);
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60 | double balancedTreesRate = GetVariableValue<DoubleData>("BalancedTreesRate", scope, true).Data;
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61 | IntData treeSize = GetVariableValue<IntData>("TreeSize", scope, false);
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62 | IntData treeHeight = GetVariableValue<IntData>("TreeHeight", scope, false);
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63 | int maxTreeSize = GetVariableValue<IntData>("MaxTreeSize", scope, true).Data;
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64 | int maxTreeHeight = GetVariableValue<IntData>("MaxTreeHeight", scope, true).Data;
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65 |
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66 | TreeGardener gardener = new TreeGardener(random, library);
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67 |
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68 | IOperator parent = gardener.GetRandomParentNode(rootOperator);
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69 |
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70 | IOperator selectedChild;
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71 | int selectedChildIndex;
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72 | if (parent == null) {
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73 | selectedChildIndex = 0;
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74 | selectedChild = rootOperator;
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75 | } else {
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76 | selectedChildIndex = random.Next(parent.SubOperators.Count);
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77 | selectedChild = parent.SubOperators[selectedChildIndex];
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78 | }
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79 |
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80 | if (selectedChild.SubOperators.Count == 0) {
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81 | IOperator newTerminal = ChangeTerminalType(parent, selectedChild, selectedChildIndex, gardener, random);
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82 |
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83 | if (parent == null) {
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84 | // no parent means the new child is the initial operator
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85 | // and we have to update the value in the variable
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86 | scope.GetVariable("OperatorTree").Value = newTerminal;
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87 | } else {
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88 | parent.RemoveSubOperator(selectedChildIndex);
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89 | parent.AddSubOperator(newTerminal, selectedChildIndex);
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90 | // updating the variable is not necessary because it stays the same
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91 | }
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92 |
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93 | // size and height stays the same when changing a terminal so no need to update the variables
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94 | // schedule an operation to initialize the new terminal
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95 | return gardener.CreateInitializationOperation(gardener.GetAllOperators(newTerminal), scope);
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96 | } else {
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97 | List<IOperator> uninitializedOperators;
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98 | IOperator newFunction = ChangeFunctionType(parent, selectedChild, selectedChildIndex, gardener, random, balancedTreesRate, out uninitializedOperators);
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99 |
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100 | if (parent == null) {
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101 | // no parent means the new function is the initial operator
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102 | // and we have to update the value in the variable
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103 | scope.GetVariable("OperatorTree").Value = newFunction;
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104 | rootOperator = newFunction;
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105 | } else {
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106 | // remove the old child
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107 | parent.RemoveSubOperator(selectedChildIndex);
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108 | // add the new child as sub-tree of parent
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109 | parent.AddSubOperator(newFunction, selectedChildIndex);
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110 | }
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111 |
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112 | // recalculate size and height
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113 | treeSize.Data = gardener.GetTreeSize(rootOperator);
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114 | treeHeight.Data = gardener.GetTreeHeight(rootOperator);
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115 |
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116 | // check if the size of the new tree is still in the allowed bounds
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117 | if (treeHeight.Data > maxTreeHeight ||
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118 | treeSize.Data > maxTreeSize) {
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119 | throw new InvalidProgramException();
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120 | }
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121 |
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122 | // check if whole tree is ok
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123 | if (!gardener.IsValidTree(rootOperator)) {
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124 | throw new InvalidProgramException();
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125 | }
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126 |
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127 | // return a composite operation that initializes all created sub-trees
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128 | return gardener.CreateInitializationOperation(uninitializedOperators, scope);
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129 | }
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130 | }
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131 |
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132 |
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133 | private IOperator ChangeTerminalType(IOperator parent, IOperator child, int childIndex, TreeGardener gardener, MersenneTwister random) {
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134 |
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135 | IList<IOperator> allowedChildren;
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136 | if (parent == null) {
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137 | allowedChildren = gardener.Terminals;
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138 | } else {
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139 | SubOperatorsConstraintAnalyser analyser = new SubOperatorsConstraintAnalyser();
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140 | analyser.AllPossibleOperators = gardener.Terminals;
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141 | allowedChildren = analyser.GetAllowedOperators(parent, childIndex);
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142 | }
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143 |
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144 | // selecting from the terminals should always work since the current child was also a terminal
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145 | // so in the worst case we will just create a new terminal of the same type again.
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146 | return gardener.CreateRandomTree((IOperator)allowedChildren[random.Next(allowedChildren.Count)].Clone(), 1, 1, false);
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147 | }
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148 |
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149 | private IOperator ChangeFunctionType(IOperator parent, IOperator child, int childIndex, TreeGardener gardener, MersenneTwister random,
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150 | double balancedTreesRate, out List<IOperator> uninitializedOperators) {
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151 | // since there are suboperators, we have to check which
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152 | // and how many of the existing suboperators we can reuse
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153 |
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154 | // let's choose the operator we want to use instead of the old child. For this we have to determine the
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155 | // pool of allowed operators based on constraints of the parent if there is one.
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156 | IList<IOperator> allowedSubOperators;
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157 | SubOperatorsConstraintAnalyser analyser = new SubOperatorsConstraintAnalyser();
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158 | analyser.AllPossibleOperators = gardener.AllOperators;
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159 | if (parent == null) {
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160 | allowedSubOperators = gardener.AllOperators;
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161 | } else {
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162 | allowedSubOperators = analyser.GetAllowedOperators(parent, childIndex);
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163 | }
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164 |
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165 | // try to make a tree with the same arity as the old child.
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166 | int actualArity = child.SubOperators.Count;
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167 | // arity of the selected operator
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168 | int minArity;
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169 | int maxArity;
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170 |
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171 | allowedSubOperators = allowedSubOperators.Where(f => {
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172 | gardener.GetMinMaxArity(f, out minArity, out maxArity);
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173 | return minArity <= actualArity;
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174 | }).ToList();
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175 |
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176 | IOperator newOperator = (IOperator)allowedSubOperators[random.Next(allowedSubOperators.Count)].Clone();
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177 |
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178 | gardener.GetMinMaxArity(newOperator, out minArity, out maxArity);
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179 | // if the old child had too many sub-operators then make the new child with the maximal arity
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180 | if (actualArity > maxArity)
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181 | actualArity = maxArity;
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182 |
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183 | // get the allowed size and height for new sub-trees
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184 | // use the size of the smallest subtree as the maximal allowed size for new subtrees to
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185 | // prevent that we ever create trees over the MaxTreeSize limit
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186 | int maxSubTreeSize = child.SubOperators.Select(subOp => gardener.GetTreeSize(subOp)).Min();
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187 | int maxSubTreeHeight = gardener.GetTreeHeight(child) - 1;
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188 |
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189 | // create a list that holds old sub-trees that we can reuse in the new tree
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190 | List<IOperator> availableSubOperators = new List<IOperator>(child.SubOperators);
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191 | List<IOperator> freshSubTrees = new List<IOperator>() { newOperator };
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192 |
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193 | // randomly select the suboperators that we keep
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194 | for (int i = 0; i < actualArity; i++) {
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195 | // fill all sub-operator slots of the new operator
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196 | // if for a given slot i there are existing sub-operators that can be used in that slot
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197 | // then use a random existing sub-operator. When there are no existing sub-operators
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198 | // that fit in the given slot then create a new random tree and use it for the slot
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199 | IList<IOperator> allowedOperators = analyser.GetAllowedOperators(newOperator, i);
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200 | var matchingOperators = availableSubOperators.Where(subOp => allowedOperators.Contains(subOp, new TreeGardener.OperatorEqualityComparer()));
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201 |
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202 | if (matchingOperators.Count() > 0) {
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203 | IOperator selectedSubOperator = matchingOperators.ElementAt(random.Next(matchingOperators.Count()));
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204 | // we can just add it as suboperator
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205 | newOperator.AddSubOperator(selectedSubOperator, i);
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206 | availableSubOperators.Remove(selectedSubOperator); // the operator shouldn't be available for the following slots
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207 | } else {
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208 | IOperator freshOperatorTree;
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209 | if(random.NextDouble() <= balancedTreesRate) {
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210 | freshOperatorTree = gardener.CreateRandomTree(allowedOperators, maxSubTreeSize, maxSubTreeHeight, true);
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211 | } else {
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212 | freshOperatorTree = gardener.CreateRandomTree(allowedOperators, maxSubTreeSize, maxSubTreeHeight, false);
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213 | }
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214 | freshSubTrees.AddRange(gardener.GetAllOperators(freshOperatorTree));
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215 |
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216 | newOperator.AddSubOperator(freshOperatorTree, i);
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217 | }
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218 | }
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219 |
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220 | uninitializedOperators = freshSubTrees;
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221 | return newOperator;
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222 | }
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223 | }
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224 | }
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