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source: trunk/sources/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/Creators/FullTreeCreator.cs @ 12844

Last change on this file since 12844 was 12844, checked in by mkommend, 7 years ago

#2458: Adapted tree creators to work with the same depth restriction as the PTC2 (excluding the root symbol).

File size: 7.4 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2015 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using System.Linq;
24using HeuristicLab.Common;
25using HeuristicLab.Core;
26using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
27using HeuristicLab.PluginInfrastructure;
28
29namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
30  [NonDiscoverableType]
31  [StorableClass]
32  [Item("FullTreeCreator", "An operator that creates new symbolic expression trees using the 'Full' method")]
33  public class FullTreeCreator : SymbolicExpressionTreeCreator,
34                                 ISymbolicExpressionTreeSizeConstraintOperator,
35                                 ISymbolicExpressionTreeGrammarBasedOperator {
36
37    [StorableConstructor]
38    protected FullTreeCreator(bool deserializing) : base(deserializing) { }
39    protected FullTreeCreator(FullTreeCreator original, Cloner cloner) : base(original, cloner) { }
40
41    public FullTreeCreator() : base() { }
42
43    public override IDeepCloneable Clone(Cloner cloner) {
44      return new FullTreeCreator(this, cloner);
45    }
46
47
48    protected override ISymbolicExpressionTree Create(IRandom random) {
49      return Create(random, ClonedSymbolicExpressionTreeGrammarParameter.ActualValue,
50          MaximumSymbolicExpressionTreeLengthParameter.ActualValue.Value, MaximumSymbolicExpressionTreeDepthParameter.ActualValue.Value);
51    }
52
53    public override ISymbolicExpressionTree CreateTree(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
54      return Create(random, grammar, maxTreeLength, maxTreeDepth);
55    }
56
57    /// <summary>
58    /// Create a symbolic expression tree using the 'Full' method.
59    /// Function symbols are used for all nodes situated on a level above the maximum tree depth.
60    /// Nodes on the last tree level will have Terminal symbols.
61    /// </summary>
62    /// <param name="random">Random generator</param>
63    /// <param name="grammar">Available tree grammar</param>
64    /// <param name="maxTreeDepth">Maximum tree depth</param>
65    /// <param name="maxTreeLength">Maximum tree length. This parameter is not used.</param>
66    /// <returns></returns>
67    public static ISymbolicExpressionTree Create(IRandom random, ISymbolicExpressionGrammar grammar, int maxTreeLength, int maxTreeDepth) {
68      var tree = new SymbolicExpressionTree();
69      var rootNode = (SymbolicExpressionTreeTopLevelNode)grammar.ProgramRootSymbol.CreateTreeNode();
70      if (rootNode.HasLocalParameters) rootNode.ResetLocalParameters(random);
71      rootNode.SetGrammar(grammar.CreateExpressionTreeGrammar());
72
73      var startNode = (SymbolicExpressionTreeTopLevelNode)grammar.StartSymbol.CreateTreeNode();
74      if (startNode.HasLocalParameters) startNode.ResetLocalParameters(random);
75      startNode.SetGrammar(grammar.CreateExpressionTreeGrammar());
76
77      rootNode.AddSubtree(startNode);
78
79      Create(random, startNode, maxTreeDepth-1);
80      tree.Root = rootNode;
81      return tree;
82    }
83
84    public static void Create(IRandom random, ISymbolicExpressionTreeNode seedNode, int maxDepth) {
85      // make sure it is possible to create a trees smaller than maxDepth
86      if (seedNode.Grammar.GetMinimumExpressionDepth(seedNode.Symbol) > maxDepth)
87        throw new ArgumentException("Cannot create trees of depth " + maxDepth + " or smaller because of grammar constraints.", "maxDepth");
88
89
90      int arity = seedNode.Grammar.GetMaximumSubtreeCount(seedNode.Symbol);
91      // Throw an exception if the seedNode happens to be a terminal, since in this case we cannot grow a tree.
92      if (arity <= 0)
93        throw new ArgumentException("Cannot grow tree. Seed node shouldn't have arity zero.");
94
95      var allowedSymbols = seedNode.Grammar.AllowedSymbols
96        .Where(s => s.InitialFrequency > 0.0 && seedNode.Grammar.GetMaximumSubtreeCount(s) > 0)
97        .ToList();
98
99      for (var i = 0; i < arity; i++) {
100        var possibleSymbols = allowedSymbols
101          .Where(s => seedNode.Grammar.IsAllowedChildSymbol(seedNode.Symbol, s, i)
102                   && seedNode.Grammar.GetMinimumExpressionDepth(s) <= maxDepth
103                   && seedNode.Grammar.GetMaximumExpressionDepth(s) >= maxDepth)
104          .ToList();
105        var weights = possibleSymbols.Select(s => s.InitialFrequency).ToList();
106
107#pragma warning disable 612, 618
108        var selectedSymbol = possibleSymbols.SelectRandom(weights, random);
109#pragma warning restore 612, 618
110
111        var tree = selectedSymbol.CreateTreeNode();
112        if (tree.HasLocalParameters) tree.ResetLocalParameters(random);
113        seedNode.AddSubtree(tree);
114      }
115
116      // Only iterate over the non-terminal nodes (those which have arity > 0)
117      // Start from depth 2 since the first two levels are formed by the rootNode and the seedNode
118      foreach (var subTree in seedNode.Subtrees)
119        if (subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) > 0)
120          RecursiveCreate(random, subTree, 2, maxDepth);
121    }
122
123    private static void RecursiveCreate(IRandom random, ISymbolicExpressionTreeNode root, int currentDepth, int maxDepth) {
124      var arity = root.Grammar.GetMaximumSubtreeCount(root.Symbol);
125      // In the 'Full' grow method, we cannot have terminals on the intermediate tree levels.
126      if (arity <= 0)
127        throw new ArgumentException("Cannot grow node of arity zero. Expected a function node.");
128
129      var allowedSymbols = root.Grammar.AllowedSymbols
130        .Where(s => s.InitialFrequency > 0.0)
131        .ToList();
132
133      for (var i = 0; i < arity; i++) {
134        var possibleSymbols = allowedSymbols
135          .Where(s => root.Grammar.IsAllowedChildSymbol(root.Symbol, s, i) &&
136            root.Grammar.GetMinimumExpressionDepth(s) - 1 <= maxDepth - currentDepth &&
137            root.Grammar.GetMaximumExpressionDepth(s) > maxDepth - currentDepth)
138          .ToList();
139        if (!possibleSymbols.Any())
140          throw new InvalidOperationException("No symbols are available for the tree.");
141        var weights = possibleSymbols.Select(s => s.InitialFrequency).ToList();
142
143#pragma warning disable 612, 618
144        var selectedSymbol = possibleSymbols.SelectRandom(weights, random);
145#pragma warning restore 612, 618
146
147        var tree = selectedSymbol.CreateTreeNode();
148        if (tree.HasLocalParameters) tree.ResetLocalParameters(random);
149        root.AddSubtree(tree);
150      }
151
152      //additional levels should only be added if the maximum depth is not reached yet
153      if (maxDepth > currentDepth) {
154        foreach (var subTree in root.Subtrees)
155          if (subTree.Grammar.GetMaximumSubtreeCount(subTree.Symbol) > 0)
156            RecursiveCreate(random, subTree, currentDepth + 1, maxDepth);
157      }
158    }
159  }
160}
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