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.Linq;
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24 | using HeuristicLab.Common;
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25 | using HeuristicLab.Core;
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26 | using HeuristicLab.Data;
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27 | using HeuristicLab.Parameters;
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28 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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29 | using HeuristicLab.PluginInfrastructure;
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30 |
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31 | namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
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32 | [NonDiscoverableType]
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33 | [StorableClass]
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34 | [Item("GrowTreeCreator", "An operator that creates new symbolic expression trees using the 'Grow' method")]
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35 | public class GrowTreeCreator : SymbolicExpressionTreeCreator,
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36 | ISymbolicExpressionTreeSizeConstraintOperator,
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37 | ISymbolicExpressionTreeGrammarBasedOperator {
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38 | private const string MaximumSymbolicExpressionTreeLengthParameterName = "MaximumSymbolicExpressionTreeLength";
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39 | private const string MaximumSymbolicExpressionTreeDepthParameterName = "MaximumSymbolicExpressionTreeDepth";
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40 | private const string SymbolicExpressionTreeGrammarParameterName = "SymbolicExpressionTreeGrammar";
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41 | private const string ClonedSymbolicExpressionTreeGrammarParameterName = "ClonedSymbolicExpressionTreeGrammar";
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42 |
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43 | #region Parameter Properties
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44 | public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeLengthParameter {
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45 | get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeLengthParameterName]; }
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46 | }
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47 |
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48 | public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeDepthParameter {
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49 | get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeDepthParameterName]; }
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50 | }
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51 |
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52 | public IValueLookupParameter<ISymbolicExpressionGrammar> SymbolicExpressionTreeGrammarParameter {
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53 | get { return (IValueLookupParameter<ISymbolicExpressionGrammar>)Parameters[SymbolicExpressionTreeGrammarParameterName]; }
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54 | }
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55 |
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56 | public ILookupParameter<ISymbolicExpressionGrammar> ClonedSymbolicExpressionTreeGrammarParameter {
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57 | get { return (ILookupParameter<ISymbolicExpressionGrammar>)Parameters[ClonedSymbolicExpressionTreeGrammarParameterName]; }
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58 | }
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59 |
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60 | #endregion
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61 | #region Properties
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62 | public IntValue MaximumSymbolicExpressionTreeDepth {
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63 | get { return MaximumSymbolicExpressionTreeDepthParameter.ActualValue; }
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64 | }
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65 |
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66 | public IntValue MaximumSymbolicExpressionTreeLength {
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67 | get { return MaximumSymbolicExpressionTreeLengthParameter.ActualValue; }
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68 | }
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69 |
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70 | public ISymbolicExpressionGrammar ClonedSymbolicExpressionTreeGrammar {
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71 | get { return ClonedSymbolicExpressionTreeGrammarParameter.ActualValue; }
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72 | }
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73 |
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74 | #endregion
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75 |
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76 | [StorableConstructor]
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77 | protected GrowTreeCreator(bool deserializing) : base(deserializing) { }
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78 | protected GrowTreeCreator(GrowTreeCreator original, Cloner cloner) : base(original, cloner) { }
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79 |
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80 | public GrowTreeCreator()
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81 | : base() {
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82 | Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeLengthParameterName,
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83 | "The maximal length (number of nodes) of the symbolic expression tree (this parameter is ignored)."));
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84 | Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeDepthParameterName,
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85 | "The maximal depth of the symbolic expression tree (a tree with one node has depth = 0)."));
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86 | Parameters.Add(new ValueLookupParameter<ISymbolicExpressionGrammar>(SymbolicExpressionTreeGrammarParameterName,
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87 | "The tree grammar that defines the correct syntax of symbolic expression trees that should be created."));
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88 | Parameters.Add(new LookupParameter<ISymbolicExpressionGrammar>(ClonedSymbolicExpressionTreeGrammarParameterName,
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89 | "An immutable clone of the concrete grammar that is actually used to create and manipulate trees."));
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90 | }
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91 |
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92 | public override IDeepCloneable Clone(Cloner cloner) {
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93 | return new GrowTreeCreator(this, cloner);
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94 | }
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95 |
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96 | public override IOperation Apply() {
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97 | if (ClonedSymbolicExpressionTreeGrammarParameter.ActualValue == null) {
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98 | SymbolicExpressionTreeGrammarParameter.ActualValue.ReadOnly = true;
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99 | IScope globalScope = ExecutionContext.Scope;
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100 | while (globalScope.Parent != null)
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101 | globalScope = globalScope.Parent;
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102 |
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103 | globalScope.Variables.Add(new Variable(ClonedSymbolicExpressionTreeGrammarParameterName,
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104 | (ISymbolicExpressionGrammar)SymbolicExpressionTreeGrammarParameter.ActualValue.Clone()));
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105 | }
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106 | return base.Apply();
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107 | }
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108 |
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109 | protected override ISymbolicExpressionTree Create(IRandom random) {
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110 | return Create(random, ClonedSymbolicExpressionTreeGrammar,
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111 | MaximumSymbolicExpressionTreeLength.Value, MaximumSymbolicExpressionTreeDepth.Value);
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112 | }
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113 |
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114 | public override ISymbolicExpressionTree CreateTree(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
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115 | return Create(random, grammar, maxTreeLength, maxTreeDepth);
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116 | }
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117 |
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118 | /// <summary>
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119 | /// Create a symbolic expression tree using the 'Grow' method.
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120 | /// All symbols are allowed for nodes, so the resulting trees can be of any shape and size.
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121 | /// </summary>
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122 | /// <param name="random">Random generator</param>
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123 | /// <param name="grammar">Available tree grammar</param>
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124 | /// <param name="maxTreeDepth">Maximum tree depth</param>
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125 | /// <param name="maxTreeLength">Maximum tree length. This parameter is not used.</param>
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126 | /// <returns></returns>
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127 | public static ISymbolicExpressionTree Create(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
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128 | var tree = new SymbolicExpressionTree();
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129 | var rootNode = (SymbolicExpressionTreeTopLevelNode)grammar.ProgramRootSymbol.CreateTreeNode();
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130 | rootNode.SetGrammar(new SymbolicExpressionTreeGrammar(grammar));
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131 | if (rootNode.HasLocalParameters) rootNode.ResetLocalParameters(random);
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132 |
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133 | var startNode = (SymbolicExpressionTreeTopLevelNode)grammar.StartSymbol.CreateTreeNode();
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134 | if (startNode.HasLocalParameters) startNode.ResetLocalParameters(random);
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135 | startNode.SetGrammar(new SymbolicExpressionTreeGrammar(grammar));
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136 |
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137 | rootNode.AddSubtree(startNode);
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138 |
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139 | Create(random, startNode, maxTreeDepth - 2);
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140 | tree.Root = rootNode;
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141 | return tree;
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142 | }
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143 |
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144 | public static void Create(IRandom random, ISymbolicExpressionTreeNode seedNode, int maxDepth) {
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145 | // make sure it is possible to create a trees smaller than maxDepth
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146 | if (seedNode.Grammar.GetMinimumExpressionDepth(seedNode.Symbol) > maxDepth)
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147 | throw new ArgumentException("Cannot create trees of depth " + maxDepth + " or smaller because of grammar constraints.", "maxDepth");
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148 |
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149 | var arity = SampleArity(random, seedNode);
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150 | // throw an exception if the seedNode happens to be a terminal, since in this case we cannot grow a tree
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151 | if (arity <= 0)
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152 | throw new ArgumentException("Cannot grow tree. Seed node shouldn't have arity zero.");
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153 |
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154 | var allowedSymbols = seedNode.Grammar.AllowedSymbols
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155 | .Where(s => s.InitialFrequency > 0.0)
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156 | .ToList();
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157 |
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158 | for (var i = 0; i < arity; i++) {
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159 | var possibleSymbols = allowedSymbols
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160 | .Where(s => seedNode.Grammar.IsAllowedChildSymbol(seedNode.Symbol, s, i))
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161 | .ToList();
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162 | var selectedSymbol = possibleSymbols.SelectRandom(random);
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163 | var tree = selectedSymbol.CreateTreeNode();
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164 | if (tree.HasLocalParameters) tree.ResetLocalParameters(random);
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165 | seedNode.AddSubtree(tree);
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166 | }
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167 |
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168 | // Only iterate over the non-terminal nodes (those which have arity > 0)
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169 | // Start from depth 2 since the first two levels are formed by the rootNode and the seedNode
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170 | foreach (var subTree in seedNode.Subtrees)
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171 | if (subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) > 0)
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172 | RecursiveCreate(random, subTree, 2, maxDepth);
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173 | }
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174 |
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175 | private static void RecursiveCreate(IRandom random, ISymbolicExpressionTreeNode root, int currentDepth, int maxDepth) {
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176 | var arity = SampleArity(random, root);
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177 | if (arity <= 0)
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178 | throw new ArgumentException("Cannot grow node of arity zero. Expected a function node.");
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179 |
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180 | var allowedSymbols = root.Grammar.AllowedSymbols
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181 | .Where(s => s.InitialFrequency > 0.0)
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182 | .ToList();
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183 |
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184 | for (var i = 0; i < arity; i++) {
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185 | var possibleSymbols = allowedSymbols
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186 | .Where(s => root.Grammar.IsAllowedChildSymbol(root.Symbol, s, i) &&
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187 | root.Grammar.GetMinimumExpressionDepth(s) - 1 <= maxDepth - currentDepth)
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188 | .ToList();
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189 | if (!possibleSymbols.Any())
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190 | throw new InvalidOperationException("No symbols are available for the tree.");
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191 | var selectedSymbol = possibleSymbols.SelectRandom(random);
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192 | var tree = selectedSymbol.CreateTreeNode();
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193 | if (tree.HasLocalParameters) tree.ResetLocalParameters(random);
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194 | root.AddSubtree(tree);
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195 | }
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196 |
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197 | foreach (var subTree in root.Subtrees)
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198 | if (subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) != 0)
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199 | RecursiveCreate(random, subTree, currentDepth + 1, maxDepth);
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200 | }
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201 |
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202 | private static int SampleArity(IRandom random, ISymbolicExpressionTreeNode node) {
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203 | var minArity = node.Grammar.GetMinimumSubtreeCount(node.Symbol);
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204 | var maxArity = node.Grammar.GetMaximumSubtreeCount(node.Symbol);
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205 |
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206 | return random.Next(minArity, maxArity + 1);
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207 | }
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208 | }
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209 | } |
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