1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2012 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.Common;
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26 | using HeuristicLab.Core;
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27 | using HeuristicLab.EvolutionaryTracking;
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28 | using HeuristicLab.Parameters;
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29 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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30 |
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31 | using CloneMapType = HeuristicLab.Core.ItemDictionary<HeuristicLab.Core.IItem, HeuristicLab.Core.IItem>;
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32 | using TraceMapType = HeuristicLab.Core.ItemDictionary<HeuristicLab.Core.IItem, HeuristicLab.Core.IItemList<HeuristicLab.Core.IItem>>;
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33 |
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34 | namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
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35 | /// <summary>
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36 | /// A base class for operators that perform a crossover of symbolic expression trees.
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37 | /// </summary>
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38 | [Item("SymbolicExpressionTreeCrossover", "A base class for operators that perform a crossover of symbolic expression trees.")]
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39 | [StorableClass]
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40 | public abstract class TracingSymbolicExpressionTreeCrossover : SymbolicExpressionTreeOperator, ISymbolicExpressionTreeCrossover {
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41 | private const string ParentsParameterName = "Parents";
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42 | private const string ChildParameterName = "Child";
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43 | private const string GlobalTraceMapParameterName = "GlobalTraceMap";
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44 | private const string GlobalCloneMapParameterName = "GlobalCloneMap";
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45 | private const string GlobalFragmentMapParameterName = "GlobalFragmentMap";
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46 |
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47 | #region Parameter Properties
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48 | public ILookupParameter<ItemArray<ISymbolicExpressionTree>> ParentsParameter {
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49 | get { return (ScopeTreeLookupParameter<ISymbolicExpressionTree>)Parameters[ParentsParameterName]; }
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50 | }
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51 | public ILookupParameter<ISymbolicExpressionTree> ChildParameter {
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52 | get { return (ILookupParameter<ISymbolicExpressionTree>)Parameters[ChildParameterName]; }
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53 | }
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54 | public LookupParameter<CloneMapType> GlobalCloneMapParameter {
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55 | get { return (LookupParameter<CloneMapType>)Parameters[GlobalCloneMapParameterName]; }
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56 | }
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57 | public LookupParameter<TraceMapType> GlobalTraceMapParameter {
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58 | get { return (LookupParameter<TraceMapType>)Parameters[GlobalTraceMapParameterName]; }
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59 | }
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60 | public LookupParameter<CloneMapType> GlobalFragmentMapParameter {
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61 | get { return (LookupParameter<CloneMapType>)Parameters[GlobalFragmentMapParameterName]; }
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62 | }
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63 | #endregion
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64 |
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65 | #region Properties
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66 | public ItemArray<ISymbolicExpressionTree> Parents {
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67 | get { return ParentsParameter.ActualValue; }
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68 | }
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69 | public ISymbolicExpressionTree Child {
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70 | get { return ChildParameter.ActualValue; }
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71 | set { ChildParameter.ActualValue = value; }
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72 | }
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73 | public CloneMapType GlobalCloneMap {
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74 | get { return GlobalCloneMapParameter.ActualValue; }
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75 | }
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76 | public TraceMapType GlobalTraceMap {
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77 | get { return GlobalTraceMapParameter.ActualValue; }
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78 | }
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79 | public CloneMapType GlobalFragmentMap {
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80 | get { return GlobalFragmentMapParameter.ActualValue; }
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81 | }
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82 | #endregion
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83 |
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84 | [StorableConstructor]
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85 | protected TracingSymbolicExpressionTreeCrossover(bool deserializing)
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86 | : base(deserializing) {
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87 | }
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88 |
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89 | protected TracingSymbolicExpressionTreeCrossover(TracingSymbolicExpressionTreeCrossover original, Cloner cloner)
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90 | : base(original, cloner) {
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91 | }
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92 |
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93 | protected TracingSymbolicExpressionTreeCrossover()
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94 | : base() {
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95 | Parameters.Add(new ScopeTreeLookupParameter<ISymbolicExpressionTree>(ParentsParameterName, "The parent symbolic expression trees which should be crossed."));
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96 | Parameters.Add(new LookupParameter<ISymbolicExpressionTree>(ChildParameterName, "The child symbolic expression tree resulting from the crossover."));
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97 | Parameters.Add(new LookupParameter<CloneMapType>(GlobalCloneMapParameterName, "A global map keeping track of trees and their clones (made during selection)."));
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98 | Parameters.Add(new LookupParameter<CloneMapType>(GlobalFragmentMapParameterName, "A global map keeping track of tree fragments received via crossover."));
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99 | Parameters.Add(new LookupParameter<TraceMapType>(GlobalTraceMapParameterName, "A global cache containing tracing info."));
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100 | }
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101 |
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102 | public sealed override IOperation Apply() {
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103 | if (Parents.Length != 2)
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104 | throw new ArgumentException("Number of parents must be exactly two for symbolic expression tree crossover operators.");
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105 |
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106 | // add global trace cache if not already present in global scope
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107 | var gScope = ExecutionContext.Scope;
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108 | while (gScope.Parent != null)
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109 | gScope = gScope.Parent;
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110 | if (GlobalTraceMap == null)
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111 | gScope.Variables.Add(new Variable(GlobalTraceMapParameterName, new TraceMapType()));
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112 | if (GlobalFragmentMap == null)
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113 | gScope.Variables.Add(new Variable(GlobalFragmentMapParameterName, new CloneMapType()));
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114 |
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115 | // get original parents (this info will be needed later to construct the genealogy graph)
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116 | var originalParents = new ItemList<IItem>(Parents.Select(x => GlobalCloneMap[x]));
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117 |
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118 | // save the nodes of parent0 in a list so we can track what modifications are made by crossover
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119 | var nodes0 = Parents[0].IterateNodesBreadth() as List<ISymbolicExpressionTreeNode>;
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120 |
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121 | //perform crossover
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122 | Child = Crossover(Random, Parents[0], Parents[1]);
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123 |
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124 | // create another list of parent0's nodes, so we can compare it with the first list to see what changed
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125 | var nodes1 = Child.IterateNodesBreadth() as List<ISymbolicExpressionTreeNode>;
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126 |
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127 | // compare the two nodes lists and check the difference (comparing node references so we avoid false functional identity).
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128 | // if no difference is found, then it is assumed that the whole tree was swapped with itself (it can happen), so the index is 0
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129 | int i, min = Math.Min(nodes0.Count, nodes1.Count);
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130 | for (i = 0; i != min; ++i)
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131 | if (nodes0[i] != nodes1[i]) break;
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132 | if (i == min) i = 0;
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133 |
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134 | // add heredity information into the global variables
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135 | GlobalTraceMap[Child] = originalParents; // map child to its corresponding parents from the previous generation
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136 | GlobalFragmentMap[Child] = new GenericWrapper<ISymbolicExpressionTreeNode>(nodes1[i]); // map child to the index of its fragment
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137 | return base.Apply();
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138 | }
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139 |
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140 | public abstract ISymbolicExpressionTree Crossover(IRandom random, ISymbolicExpressionTree parent0, ISymbolicExpressionTree parent1);
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141 | }
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142 | }
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