source: branches/HeuristicLab.DataAnalysis.Symbolic.LinearInterpreter/HeuristicLab.Encodings.SymbolicExpressionTreeEncoding/3.4/ArchitectureManipulators/ArgumentCreater.cs @ 9732

Last change on this file since 9732 was 9732, checked in by bburlacu, 6 years ago

#2021: Merged trunk changes for HeuristicLab.Encodings.SymbolicExpressionTreeEncoding and HeuristicLab.Problems.DataAnalysis.Symbolic. Replaced prefix iteration of nodes in the linear interpretation with breadth iteration for simplified logic and extra performance. Reversed unnecessary changes to other projects.

File size: 11.9 KB
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1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2013 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.Collections.Generic;
24using System.Linq;
25using HeuristicLab.Common;
26using HeuristicLab.Core;
27using HeuristicLab.Data;
28using HeuristicLab.Parameters;
29using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
30
31namespace HeuristicLab.Encodings.SymbolicExpressionTreeEncoding {
32  /// <summary>
33  /// Creates a new argument within one function-defining branch of a symbolic expression tree.
34  /// As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 106
35  /// </summary>
36  [Item("ArgumentCreater", "Manipulates a symbolic expression by creating a new argument within one function-defining branch. As described in Koza, Bennett, Andre, Keane, Genetic Programming III - Darwinian Invention and Problem Solving, 1999, pp. 106")]
37  [StorableClass]
38  public sealed class ArgumentCreater : SymbolicExpressionTreeArchitectureManipulator, ISymbolicExpressionTreeSizeConstraintOperator {
39    private const string MaximumSymbolicExpressionTreeLengthParameterName = "MaximumSymbolicExpressionTreeLength";
40    private const string MaximumSymbolicExpressionTreeDepthParameterName = "MaximumSymbolicExpressionTreeDepth";
41    #region Parameter Properties
42    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeLengthParameter {
43      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeLengthParameterName]; }
44    }
45    public IValueLookupParameter<IntValue> MaximumSymbolicExpressionTreeDepthParameter {
46      get { return (IValueLookupParameter<IntValue>)Parameters[MaximumSymbolicExpressionTreeDepthParameterName]; }
47    }
48    #endregion
49    #region Properties
50    public IntValue MaximumSymbolicExpressionTreeLength {
51      get { return MaximumSymbolicExpressionTreeLengthParameter.ActualValue; }
52    }
53    public IntValue MaximumSymbolicExpressionTreeDepth {
54      get { return MaximumSymbolicExpressionTreeDepthParameter.ActualValue; }
55    }
56    #endregion
57    [StorableConstructor]
58    private ArgumentCreater(bool deserializing) : base(deserializing) { }
59    private ArgumentCreater(ArgumentCreater original, Cloner cloner) : base(original, cloner) { }
60    public ArgumentCreater()
61      : base() {
62      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeLengthParameterName, "The maximal length (number of nodes) of the symbolic expression tree."));
63      Parameters.Add(new ValueLookupParameter<IntValue>(MaximumSymbolicExpressionTreeDepthParameterName, "The maximal depth of the symbolic expression tree (a tree with one node has depth = 0)."));
64    }
65
66    public override sealed void ModifyArchitecture(
67      IRandom random,
68      ISymbolicExpressionTree symbolicExpressionTree,
69      IntValue maxFunctionDefinitions, IntValue maxFunctionArguments) {
70      CreateNewArgument(random, symbolicExpressionTree, MaximumSymbolicExpressionTreeLength.Value, MaximumSymbolicExpressionTreeDepth.Value, maxFunctionDefinitions.Value, maxFunctionArguments.Value);
71    }
72
73    public override IDeepCloneable Clone(Cloner cloner) {
74      return new ArgumentCreater(this, cloner);
75    }
76
77    public static bool CreateNewArgument(
78      IRandom random,
79      ISymbolicExpressionTree symbolicExpressionTree,
80      int maxTreeLength, int maxTreeDepth,
81      int maxFunctionDefinitions, int maxFunctionArguments) {
82      // work on a copy in case we find out later that the tree would be too big
83      // in this case it's easiest to simply return the original tree.
84      ISymbolicExpressionTree clonedTree = (ISymbolicExpressionTree)symbolicExpressionTree.Clone();
85
86      var functionDefiningBranches = clonedTree.IterateNodesPrefix().OfType<DefunTreeNode>();
87      if (functionDefiningBranches.Count() == 0)
88        // no function defining branch found => abort
89        return false;
90
91      // select a random function defining branch
92      var selectedDefunBranch = functionDefiningBranches.SelectRandom(random);
93      var definedArguments = (from symbol in selectedDefunBranch.Grammar.Symbols.OfType<Argument>()
94                              select symbol.ArgumentIndex).Distinct();
95      if (definedArguments.Count() >= maxFunctionArguments)
96        // max number of arguments reached => abort
97        return false;
98
99      var allowedArgumentIndexes = Enumerable.Range(0, maxFunctionArguments);
100      var newArgumentIndex = allowedArgumentIndexes.Except(definedArguments).First();
101      ArgumentTreeNode newArgumentNode = MakeArgumentNode(newArgumentIndex);
102
103      // this operation potentially creates very big trees so the access to the length property might throw overflow exception
104      try {
105        if (CreateNewArgumentForDefun(random, clonedTree, selectedDefunBranch, newArgumentNode) && clonedTree.Length <= maxTreeLength && clonedTree.Depth <= maxTreeDepth) {
106
107          // size constraints are fulfilled
108          // replace root of original tree with root of manipulated tree
109          symbolicExpressionTree.Root = clonedTree.Root;
110          return true;
111        } else {
112          // keep originalTree
113          return false;
114        }
115      }
116      catch (OverflowException) {
117        // keep original tree
118        return false;
119      }
120    }
121
122    private static bool CreateNewArgumentForDefun(IRandom random, ISymbolicExpressionTree tree, DefunTreeNode defunBranch, ArgumentTreeNode newArgumentNode) {
123      // select a random cut point in the function defining branch
124      // the branch at the cut point is to be replaced by a new argument node
125      var cutPoints = (from node in defunBranch.IterateNodesPrefix()
126                       where node.Subtrees.Count() > 0 &&
127                             !node.IterateNodesPrefix().OfType<ArgumentTreeNode>().Any() &&
128                             !node.IterateNodesPrefix().OfType<InvokeFunctionTreeNode>().Any()
129                       from subtree in node.Subtrees
130                       select new CutPoint(node, subtree)).ToList();
131
132      if (cutPoints.Count() == 0)
133        // no cut point found => abort;
134        return false;
135      var selectedCutPoint = cutPoints[random.Next(cutPoints.Count)];
136      // replace the branch at the cut point with an argument node
137      var replacedBranch = selectedCutPoint.Child;
138      selectedCutPoint.Parent.RemoveSubtree(selectedCutPoint.ChildIndex);
139      selectedCutPoint.Parent.InsertSubtree(selectedCutPoint.ChildIndex, newArgumentNode);
140
141      // find all old invocations of the selected ADF and attach a cloned version of the replaced branch (with all argument-nodes expanded)
142      // iterate in post-fix order to make sure that the subtrees of n are already adapted when n is processed
143      var invocationNodes = (from node in tree.IterateNodesPostfix().OfType<InvokeFunctionTreeNode>()
144                             where node.Symbol.FunctionName == defunBranch.FunctionName
145                             where node.Subtrees.Count() == defunBranch.NumberOfArguments
146                             select node).ToList();
147      // do this repeatedly until no matching invocations are found     
148      while (invocationNodes.Count > 0) {
149        List<ISymbolicExpressionTreeNode> newlyAddedBranches = new List<ISymbolicExpressionTreeNode>();
150        foreach (var invocationNode in invocationNodes) {
151          // check that the invocation node really has the correct number of arguments
152          if (invocationNode.Subtrees.Count() != defunBranch.NumberOfArguments) throw new InvalidOperationException();
153          // append a new argument branch after expanding all argument nodes
154          var clonedBranch = (ISymbolicExpressionTreeNode)replacedBranch.Clone();
155          clonedBranch = ReplaceArgumentsInBranch(clonedBranch, invocationNode.Subtrees);
156          invocationNode.InsertSubtree(newArgumentNode.Symbol.ArgumentIndex, clonedBranch);
157          newlyAddedBranches.Add(clonedBranch);
158        }
159        // iterate in post-fix order to make sure that the subtrees of n are already adapted when n is processed
160        invocationNodes = (from newlyAddedBranch in newlyAddedBranches
161                           from node in newlyAddedBranch.IterateNodesPostfix().OfType<InvokeFunctionTreeNode>()
162                           where node.Symbol.FunctionName == defunBranch.FunctionName
163                           where node.Subtrees.Count() == defunBranch.NumberOfArguments
164                           select node).ToList();
165      }
166      // increase expected number of arguments of function defining branch
167      // it's possible that the number of actually referenced arguments was reduced (all references were replaced by a single new argument)
168      // but the number of expected arguments is increased anyway
169      defunBranch.NumberOfArguments++;
170      defunBranch.Grammar.AddSymbol(newArgumentNode.Symbol);
171      defunBranch.Grammar.SetSubtreeCount(newArgumentNode.Symbol, 0, 0);
172      // allow the argument as child of any other symbol
173      GrammarModifier.SetAllowedParentSymbols(defunBranch.Grammar, selectedCutPoint.Child.Symbol, newArgumentNode.Symbol);
174
175      foreach (var subtree in tree.Root.Subtrees) {
176        // when the changed function is known in the branch then update the number of arguments
177        var matchingSymbol = subtree.Grammar.Symbols.OfType<InvokeFunction>().Where(s => s.FunctionName == defunBranch.FunctionName).SingleOrDefault();
178        if (matchingSymbol != null) {
179          subtree.Grammar.SetSubtreeCount(matchingSymbol, defunBranch.NumberOfArguments, defunBranch.NumberOfArguments);
180          foreach (var symb in subtree.Grammar.Symbols) {
181            if (symb is StartSymbol || symb is ProgramRootSymbol) continue;
182            if (symb.Name == matchingSymbol.Name) continue; //don't allow invoke as child of invoke
183            if (subtree.Grammar.IsAllowedChildSymbol(selectedCutPoint.Parent.Symbol, symb, selectedCutPoint.ChildIndex))
184              subtree.Grammar.AddAllowedChildSymbol(matchingSymbol, symb, newArgumentNode.Symbol.ArgumentIndex);
185          }
186        }
187      }
188
189      return true;
190    }
191
192    private static ISymbolicExpressionTreeNode ReplaceArgumentsInBranch(ISymbolicExpressionTreeNode branch, IEnumerable<ISymbolicExpressionTreeNode> argumentTrees) {
193      ArgumentTreeNode argNode = branch as ArgumentTreeNode;
194      if (argNode != null) {
195        // replace argument nodes by a clone of the original subtree that provided the result for the argument node
196        return (SymbolicExpressionTreeNode)argumentTrees.ElementAt(argNode.Symbol.ArgumentIndex).Clone();
197      } else {
198        // call recursively for all subtree
199        List<ISymbolicExpressionTreeNode> subtrees = new List<ISymbolicExpressionTreeNode>(branch.Subtrees);
200        while (branch.Subtrees.Count() > 0) branch.RemoveSubtree(0);
201        foreach (var subtree in subtrees) {
202          branch.AddSubtree(ReplaceArgumentsInBranch(subtree, argumentTrees));
203        }
204        return branch;
205      }
206    }
207
208    private static ArgumentTreeNode MakeArgumentNode(int argIndex) {
209      var node = (ArgumentTreeNode)(new Argument(argIndex)).CreateTreeNode();
210      return node;
211    }
212  }
213}
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