[645] | 1 | #region License Information
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| 2 | /* HeuristicLab
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[9732] | 3 | * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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[645] | 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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[3462] | 22 | using System;
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[4068] | 23 | using System.Collections.Generic;
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[3462] | 24 | using System.Linq;
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[4722] | 25 | using HeuristicLab.Common;
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[645] | 26 | using HeuristicLab.Core;
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| 27 | using HeuristicLab.Data;
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[5521] | 28 | using HeuristicLab.Parameters;
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[4068] | 29 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
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[7012] | 30 | using HeuristicLab.PluginInfrastructure;
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[645] | 31 |
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[5499] | 32 | namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
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[7012] | 33 | [NonDiscoverableType]
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[3223] | 34 | [StorableClass]
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[5549] | 35 | [Item("ProbabilisticTreeCreator", "An operator that creates new symbolic expression trees with uniformly distributed length")]
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[5618] | 36 | public class ProbabilisticTreeCreator : SymbolicExpressionTreeCreator,
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[5686] | 37 | ISymbolicExpressionTreeSizeConstraintOperator, ISymbolicExpressionTreeGrammarBasedOperator {
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[3369] | 38 | private const int MAX_TRIES = 100;
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[5499] | 39 | private const string MaximumSymbolicExpressionTreeLengthParameterName = "MaximumSymbolicExpressionTreeLength";
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| 40 | private const string MaximumSymbolicExpressionTreeDepthParameterName = "MaximumSymbolicExpressionTreeDepth";
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| 41 | private const string SymbolicExpressionTreeGrammarParameterName = "SymbolicExpressionTreeGrammar";
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[6233] | 42 | private const string ClonedSymbolicExpressionTreeGrammarParameterName = "ClonedSymbolicExpressionTreeGrammar";
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[5499] | 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 | public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeDepthParameter {
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| 48 | get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeDepthParameterName]; }
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| 49 | }
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[5686] | 50 | public IValueLookupParameter<ISymbolicExpressionGrammar> SymbolicExpressionTreeGrammarParameter {
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| 51 | get { return (IValueLookupParameter<ISymbolicExpressionGrammar>)Parameters[SymbolicExpressionTreeGrammarParameterName]; }
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[5499] | 52 | }
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[6233] | 53 | public ILookupParameter<ISymbolicExpressionGrammar> ClonedSymbolicExpressionTreeGrammarParameter {
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| 54 | get { return (ILookupParameter<ISymbolicExpressionGrammar>)Parameters[ClonedSymbolicExpressionTreeGrammarParameterName]; }
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| 55 | }
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[5499] | 56 | #endregion
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| 57 | #region Properties
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| 58 | public IntValue MaximumSymbolicExpressionTreeLength {
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| 59 | get { return MaximumSymbolicExpressionTreeLengthParameter.ActualValue; }
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| 60 | }
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| 61 | public IntValue MaximumSymbolicExpressionTreeDepth {
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| 62 | get { return MaximumSymbolicExpressionTreeDepthParameter.ActualValue; }
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| 63 | }
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[5686] | 64 | public ISymbolicExpressionGrammar SymbolicExpressionTreeGrammar {
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[6233] | 65 | get { return ClonedSymbolicExpressionTreeGrammarParameter.ActualValue; }
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[5499] | 66 | }
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| 67 | #endregion
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| 68 |
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[4722] | 69 | [StorableConstructor]
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[5618] | 70 | protected ProbabilisticTreeCreator(bool deserializing) : base(deserializing) { }
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| 71 | protected ProbabilisticTreeCreator(ProbabilisticTreeCreator original, Cloner cloner) : base(original, cloner) { }
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[5499] | 72 | public ProbabilisticTreeCreator()
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| 73 | : base() {
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| 74 | Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeLengthParameterName, "The maximal length (number of nodes) of the symbolic expression tree."));
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| 75 | Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeDepthParameterName, "The maximal depth of the symbolic expression tree (a tree with one node has depth = 0)."));
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[5686] | 76 | Parameters.Add(new ValueLookupParameter<ISymbolicExpressionGrammar>(SymbolicExpressionTreeGrammarParameterName, "The tree grammar that defines the correct syntax of symbolic expression trees that should be created."));
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[6233] | 77 | Parameters.Add(new LookupParameter<ISymbolicExpressionGrammar>(ClonedSymbolicExpressionTreeGrammarParameterName, "An immutable clone of the concrete grammar that is actually used to create and manipulate trees."));
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[5499] | 78 | }
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[3338] | 79 |
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[4722] | 80 | public override IDeepCloneable Clone(Cloner cloner) {
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| 81 | return new ProbabilisticTreeCreator(this, cloner);
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[645] | 82 | }
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[6233] | 83 | [StorableHook(HookType.AfterDeserialization)]
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| 84 | private void AfterDeserialization() {
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| 85 | if (!Parameters.ContainsKey(ClonedSymbolicExpressionTreeGrammarParameterName))
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| 86 | Parameters.Add(new LookupParameter<ISymbolicExpressionGrammar>(ClonedSymbolicExpressionTreeGrammarParameterName, "An immutable clone of the concrete grammar that is actually used to create and manipulate trees."));
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| 87 | }
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[645] | 88 |
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[6233] | 89 | public override IOperation Apply() {
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| 90 | if (ClonedSymbolicExpressionTreeGrammarParameter.ActualValue == null) {
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| 91 | SymbolicExpressionTreeGrammarParameter.ActualValue.ReadOnly = true;
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| 92 | IScope globalScope = ExecutionContext.Scope;
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| 93 | while (globalScope.Parent != null)
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| 94 | globalScope = globalScope.Parent;
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| 95 |
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| 96 | globalScope.Variables.Add(new Variable(ClonedSymbolicExpressionTreeGrammarParameterName, (ISymbolicExpressionGrammar)SymbolicExpressionTreeGrammarParameter.ActualValue.Clone()));
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| 97 | }
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| 98 | return base.Apply();
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| 99 | }
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| 100 |
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[5510] | 101 | protected override ISymbolicExpressionTree Create(IRandom random) {
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[5686] | 102 | return Create(random, SymbolicExpressionTreeGrammar, MaximumSymbolicExpressionTreeLength.Value, MaximumSymbolicExpressionTreeDepth.Value);
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[2447] | 103 | }
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| 104 |
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[7012] | 105 | public override ISymbolicExpressionTree CreateTree(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
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| 106 | return Create(random, grammar, maxTreeLength, maxTreeDepth);
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| 107 | }
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| 108 |
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| 109 | public static ISymbolicExpressionTree Create(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
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[3223] | 110 | SymbolicExpressionTree tree = new SymbolicExpressionTree();
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[5686] | 111 | var rootNode = (SymbolicExpressionTreeTopLevelNode)grammar.ProgramRootSymbol.CreateTreeNode();
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[3442] | 112 | if (rootNode.HasLocalParameters) rootNode.ResetLocalParameters(random);
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[4249] | 113 | rootNode.SetGrammar(new SymbolicExpressionTreeGrammar(grammar));
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[5686] | 114 | var startNode = (SymbolicExpressionTreeTopLevelNode)grammar.StartSymbol.CreateTreeNode();
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| 115 | startNode.SetGrammar(new SymbolicExpressionTreeGrammar(grammar));
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| 116 | if (startNode.HasLocalParameters) startNode.ResetLocalParameters(random);
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[5733] | 117 | rootNode.AddSubtree(startNode);
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[5686] | 118 | PTC2(random, startNode, maxTreeLength, maxTreeDepth);
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| 119 | tree.Root = rootNode;
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[3223] | 120 | return tree;
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| 121 | }
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| 122 |
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[3338] | 123 | private class TreeExtensionPoint {
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[5499] | 124 | public ISymbolicExpressionTreeNode Parent { get; set; }
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[3338] | 125 | public int ChildIndex { get; set; }
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| 126 | public int ExtensionPointDepth { get; set; }
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[6911] | 127 | public int MaximumExtensionLength { get; set; }
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| 128 | public int MinimumExtensionLength { get; set; }
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[3223] | 129 | }
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[3360] | 130 |
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[5686] | 131 | public static void PTC2(IRandom random, ISymbolicExpressionTreeNode seedNode,
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| 132 | int maxLength, int maxDepth) {
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[6009] | 133 | // make sure it is possible to create a trees smaller than maxLength and maxDepth
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| 134 | if (seedNode.Grammar.GetMinimumExpressionLength(seedNode.Symbol) > maxLength)
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| 135 | throw new ArgumentException("Cannot create trees of length " + maxLength + " or shorter because of grammar constraints.", "maxLength");
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| 136 | if (seedNode.Grammar.GetMinimumExpressionDepth(seedNode.Symbol) > maxDepth)
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| 137 | throw new ArgumentException("Cannot create trees of depth " + maxDepth + " or smaller because of grammar constraints.", "maxDepth");
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| 138 |
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[5549] | 139 | // tree length is limited by the grammar and by the explicit size constraints
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[5686] | 140 | int allowedMinLength = seedNode.Grammar.GetMinimumExpressionLength(seedNode.Symbol);
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[6911] | 141 | int allowedMaxLength = Math.Min(maxLength, seedNode.Grammar.GetMaximumExpressionLength(seedNode.Symbol, maxDepth));
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[3369] | 142 | int tries = 0;
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| 143 | while (tries++ < MAX_TRIES) {
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[5549] | 144 | // select a target tree length uniformly in the possible range (as determined by explicit limits and limits of the grammar)
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| 145 | int targetTreeLength;
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| 146 | targetTreeLength = random.Next(allowedMinLength, allowedMaxLength + 1);
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[5686] | 147 | if (targetTreeLength <= 1 || maxDepth <= 1) return;
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[3369] | 148 |
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[6911] | 149 | bool success = TryCreateFullTreeFromSeed(random, seedNode, targetTreeLength - 1, maxDepth - 1);
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[3369] | 150 |
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[4189] | 151 | // if successful => check constraints and return the tree if everything looks ok
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[5549] | 152 | if (success && seedNode.GetLength() <= maxLength && seedNode.GetDepth() <= maxDepth) {
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[5686] | 153 | return;
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[3369] | 154 | } else {
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| 155 | // clean seedNode
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[5733] | 156 | while (seedNode.Subtrees.Count() > 0) seedNode.RemoveSubtree(0);
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[3360] | 157 | }
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[5549] | 158 | // try a different length MAX_TRIES times
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[3369] | 159 | }
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[3825] | 160 | throw new ArgumentException("Couldn't create a random valid tree.");
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[3338] | 161 | }
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| 162 |
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[6911] | 163 | private static bool TryCreateFullTreeFromSeed(IRandom random, ISymbolicExpressionTreeNode root,
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[5686] | 164 | int targetLength, int maxDepth) {
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[3338] | 165 | List<TreeExtensionPoint> extensionPoints = new List<TreeExtensionPoint>();
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[6911] | 166 | int currentLength = 0;
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| 167 | int actualArity = SampleArity(random, root, targetLength, maxDepth);
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[5727] | 168 | if (actualArity < 0) return false;
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| 169 |
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[3223] | 170 | for (int i = 0; i < actualArity; i++) {
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| 171 | // insert a dummy sub-tree and add the pending extension to the list
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[3338] | 172 | var dummy = new SymbolicExpressionTreeNode();
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[5733] | 173 | root.AddSubtree(dummy);
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[6911] | 174 | var x = new TreeExtensionPoint { Parent = root, ChildIndex = i, ExtensionPointDepth = 0 };
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| 175 | FillExtensionLengths(x, maxDepth);
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| 176 | extensionPoints.Add(x);
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[3223] | 177 | }
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[8311] | 178 | //necessary to use long data type as the extension point length could be int.MaxValue
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| 179 | long minExtensionPointsLength = extensionPoints.Select(x => (long)x.MinimumExtensionLength).Sum();
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| 180 | long maxExtensionPointsLength = extensionPoints.Select(x => (long)x.MaximumExtensionLength).Sum();
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[6911] | 181 |
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[3223] | 182 | // while there are pending extension points and we have not reached the limit of adding new extension points
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[6911] | 183 | while (extensionPoints.Count > 0 && minExtensionPointsLength + currentLength <= targetLength) {
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[3294] | 184 | int randomIndex = random.Next(extensionPoints.Count);
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[3338] | 185 | TreeExtensionPoint nextExtension = extensionPoints[randomIndex];
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[3294] | 186 | extensionPoints.RemoveAt(randomIndex);
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[5499] | 187 | ISymbolicExpressionTreeNode parent = nextExtension.Parent;
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[3338] | 188 | int argumentIndex = nextExtension.ChildIndex;
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| 189 | int extensionDepth = nextExtension.ExtensionPointDepth;
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[6911] | 190 |
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| 191 | if (parent.Grammar.GetMinimumExpressionDepth(parent.Symbol) > maxDepth - extensionDepth) {
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[5686] | 192 | ReplaceWithMinimalTree(random, root, parent, argumentIndex);
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[6911] | 193 | int insertedTreeLength = parent.GetSubtree(argumentIndex).GetLength();
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| 194 | currentLength += insertedTreeLength;
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| 195 | minExtensionPointsLength -= insertedTreeLength;
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| 196 | maxExtensionPointsLength -= insertedTreeLength;
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[3223] | 197 | } else {
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[6911] | 198 | //remove currently chosen extension point from calculation
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| 199 | minExtensionPointsLength -= nextExtension.MinimumExtensionLength;
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| 200 | maxExtensionPointsLength -= nextExtension.MaximumExtensionLength;
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| 201 |
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| 202 | var symbols = from s in parent.Grammar.GetAllowedChildSymbols(parent.Symbol, argumentIndex)
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| 203 | where s.InitialFrequency > 0.0
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| 204 | where parent.Grammar.GetMinimumExpressionDepth(s) <= maxDepth - extensionDepth
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| 205 | where parent.Grammar.GetMinimumExpressionLength(s) <= targetLength - currentLength - minExtensionPointsLength
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| 206 | select s;
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| 207 | if (maxExtensionPointsLength < targetLength - currentLength)
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| 208 | symbols = from s in symbols
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| 209 | where parent.Grammar.GetMaximumExpressionLength(s, maxDepth - extensionDepth) >= targetLength - currentLength - maxExtensionPointsLength
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| 210 | select s;
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| 211 | var allowedSymbols = symbols.ToList();
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| 212 |
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[6233] | 213 | if (allowedSymbols.Count == 0) return false;
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[5499] | 214 | var weights = allowedSymbols.Select(x => x.InitialFrequency).ToList();
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| 215 | var selectedSymbol = allowedSymbols.SelectRandom(weights, random);
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| 216 | ISymbolicExpressionTreeNode newTree = selectedSymbol.CreateTreeNode();
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[3442] | 217 | if (newTree.HasLocalParameters) newTree.ResetLocalParameters(random);
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[5733] | 218 | parent.RemoveSubtree(argumentIndex);
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| 219 | parent.InsertSubtree(argumentIndex, newTree);
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[3338] | 220 |
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[5686] | 221 | var topLevelNode = newTree as SymbolicExpressionTreeTopLevelNode;
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| 222 | if (topLevelNode != null)
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| 223 | topLevelNode.SetGrammar((ISymbolicExpressionTreeGrammar)root.Grammar.Clone());
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[3338] | 224 |
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[5549] | 225 | currentLength++;
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[6911] | 226 | actualArity = SampleArity(random, newTree, targetLength - currentLength, maxDepth - extensionDepth);
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[5727] | 227 | if (actualArity < 0) return false;
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[3223] | 228 | for (int i = 0; i < actualArity; i++) {
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| 229 | // insert a dummy sub-tree and add the pending extension to the list
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[3338] | 230 | var dummy = new SymbolicExpressionTreeNode();
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[5733] | 231 | newTree.AddSubtree(dummy);
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[6911] | 232 | var x = new TreeExtensionPoint { Parent = newTree, ChildIndex = i, ExtensionPointDepth = extensionDepth + 1 };
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| 233 | FillExtensionLengths(x, maxDepth);
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| 234 | extensionPoints.Add(x);
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| 235 | maxExtensionPointsLength += x.MaximumExtensionLength;
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| 236 | minExtensionPointsLength += x.MinimumExtensionLength;
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[3223] | 237 | }
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| 238 | }
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| 239 | }
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| 240 | // fill all pending extension points
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[3294] | 241 | while (extensionPoints.Count > 0) {
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| 242 | int randomIndex = random.Next(extensionPoints.Count);
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[3338] | 243 | TreeExtensionPoint nextExtension = extensionPoints[randomIndex];
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[3294] | 244 | extensionPoints.RemoveAt(randomIndex);
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[5499] | 245 | ISymbolicExpressionTreeNode parent = nextExtension.Parent;
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[3338] | 246 | int a = nextExtension.ChildIndex;
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[5686] | 247 | ReplaceWithMinimalTree(random, root, parent, a);
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[3223] | 248 | }
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[5727] | 249 | return true;
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[2210] | 250 | }
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[3223] | 251 |
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[5499] | 252 | private static void ReplaceWithMinimalTree(IRandom random, ISymbolicExpressionTreeNode root, ISymbolicExpressionTreeNode parent,
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[5686] | 253 | int childIndex) {
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[3338] | 254 | // determine possible symbols that will lead to the smallest possible tree
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[5686] | 255 | var possibleSymbols = (from s in parent.Grammar.GetAllowedChildSymbols(parent.Symbol, childIndex)
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[5925] | 256 | where s.InitialFrequency > 0.0
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[5686] | 257 | group s by parent.Grammar.GetMinimumExpressionLength(s) into g
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[3338] | 258 | orderby g.Key
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[5499] | 259 | select g).First().ToList();
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| 260 | var weights = possibleSymbols.Select(x => x.InitialFrequency).ToList();
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| 261 | var selectedSymbol = possibleSymbols.SelectRandom(weights, random);
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[3338] | 262 | var tree = selectedSymbol.CreateTreeNode();
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[3442] | 263 | if (tree.HasLocalParameters) tree.ResetLocalParameters(random);
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[5733] | 264 | parent.RemoveSubtree(childIndex);
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| 265 | parent.InsertSubtree(childIndex, tree);
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[5686] | 266 |
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| 267 | var topLevelNode = tree as SymbolicExpressionTreeTopLevelNode;
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| 268 | if (topLevelNode != null)
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| 269 | topLevelNode.SetGrammar((ISymbolicExpressionTreeGrammar)root.Grammar.Clone());
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| 270 |
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| 271 | for (int i = 0; i < tree.Grammar.GetMinimumSubtreeCount(tree.Symbol); i++) {
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[3338] | 272 | // insert a dummy sub-tree and add the pending extension to the list
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| 273 | var dummy = new SymbolicExpressionTreeNode();
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[5733] | 274 | tree.AddSubtree(dummy);
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[3338] | 275 | // replace the just inserted dummy by recursive application
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[5686] | 276 | ReplaceWithMinimalTree(random, root, tree, i);
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[3338] | 277 | }
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| 278 | }
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[3360] | 279 |
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[6911] | 280 | private static void FillExtensionLengths(TreeExtensionPoint extension, int maxDepth) {
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| 281 | var grammar = extension.Parent.Grammar;
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| 282 | int maxLength = int.MinValue;
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| 283 | int minLength = int.MaxValue;
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| 284 | foreach (ISymbol s in grammar.GetAllowedChildSymbols(extension.Parent.Symbol, extension.ChildIndex)) {
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| 285 | if (s.InitialFrequency > 0.0) {
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| 286 | int max = grammar.GetMaximumExpressionLength(s, maxDepth - extension.ExtensionPointDepth);
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| 287 | maxLength = Math.Max(maxLength, max);
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| 288 | int min = grammar.GetMinimumExpressionLength(s);
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| 289 | minLength = Math.Min(minLength, min);
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| 290 | }
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| 291 | }
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| 292 |
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| 293 | extension.MaximumExtensionLength = maxLength;
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| 294 | extension.MinimumExtensionLength = minLength;
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[3338] | 295 | }
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| 296 |
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[6911] | 297 | private static int SampleArity(IRandom random, ISymbolicExpressionTreeNode node, int targetLength, int maxDepth) {
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[3223] | 298 | // select actualArity randomly with the constraint that the sub-trees in the minimal arity can become large enough
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[5686] | 299 | int minArity = node.Grammar.GetMinimumSubtreeCount(node.Symbol);
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| 300 | int maxArity = node.Grammar.GetMaximumSubtreeCount(node.Symbol);
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[5549] | 301 | if (maxArity > targetLength) {
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| 302 | maxArity = targetLength;
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[3223] | 303 | }
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[6911] | 304 | if (minArity == maxArity) return minArity;
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| 305 |
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[5549] | 306 | // the min number of sub-trees has to be set to a value that is large enough so that the largest possible tree is at least tree length
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| 307 | // if 1..3 trees are possible and the largest possible first sub-tree is smaller larger than the target length then minArity should be at least 2
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[3237] | 308 | long aggregatedLongestExpressionLength = 0;
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[3223] | 309 | for (int i = 0; i < maxArity; i++) {
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[5686] | 310 | aggregatedLongestExpressionLength += (from s in node.Grammar.GetAllowedChildSymbols(node.Symbol, i)
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[5925] | 311 | where s.InitialFrequency > 0.0
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[6911] | 312 | select node.Grammar.GetMaximumExpressionLength(s, maxDepth)).Max();
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[6803] | 313 | if (i > minArity && aggregatedLongestExpressionLength < targetLength) minArity = i + 1;
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[3223] | 314 | else break;
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| 315 | }
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| 316 |
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[5549] | 317 | // the max number of sub-trees has to be set to a value that is small enough so that the smallest possible tree is at most tree length
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| 318 | // if 1..3 trees are possible and the smallest possible first sub-tree is already larger than the target length then maxArity should be at most 0
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[3237] | 319 | long aggregatedShortestExpressionLength = 0;
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[3223] | 320 | for (int i = 0; i < maxArity; i++) {
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[5686] | 321 | aggregatedShortestExpressionLength += (from s in node.Grammar.GetAllowedChildSymbols(node.Symbol, i)
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[5925] | 322 | where s.InitialFrequency > 0.0
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[5686] | 323 | select node.Grammar.GetMinimumExpressionLength(s)).Min();
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[5549] | 324 | if (aggregatedShortestExpressionLength > targetLength) {
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[3223] | 325 | maxArity = i;
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| 326 | break;
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| 327 | }
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| 328 | }
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[5727] | 329 | if (minArity > maxArity) return -1;
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[3223] | 330 | return random.Next(minArity, maxArity + 1);
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| 331 | }
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[6911] | 332 |
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[2447] | 333 | }
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[645] | 334 | } |
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