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 |
|
---|
22 | using System;
|
---|
23 | using System.Linq;
|
---|
24 | using HeuristicLab.Common;
|
---|
25 | using HeuristicLab.Core;
|
---|
26 | using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
|
---|
27 | using HeuristicLab.PluginInfrastructure;
|
---|
28 |
|
---|
29 | namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
|
---|
30 | [NonDiscoverableType]
|
---|
31 | [StorableClass("924958FB-7A65-4432-8334-0AB6CE4DA37C")]
|
---|
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 | }
|
---|