1 | #region License Information
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2 | /* HeuristicLab
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3 | * Copyright (C) 2002-2008 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.Collections.Generic;
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23 | using System.Linq;
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24 | using HeuristicLab.Core;
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25 | using HeuristicLab.Data;
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26 | using HeuristicLab.Operators;
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27 | using HeuristicLab.Random;
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28 | using System;
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29 | using System.Diagnostics;
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30 | using HeuristicLab.GP.Interfaces;
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31 |
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32 | namespace HeuristicLab.GP {
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33 | public class CutOutNodeManipulation : GPManipulatorBase {
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34 | public override string Description {
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35 | get {
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36 | return @"Takes a tree, selects a random node of the tree and then tries to replace a random sub-tree
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37 | of that node with one of the childs of the selected child.
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38 |
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39 | O O
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40 | / \ / \
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41 | O X O 2
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42 | / \ 2 is selected => / \
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43 | 1 2 4 5
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44 | / / \
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45 | 3 4 5
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46 | ";
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47 | }
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48 | }
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49 |
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50 | public CutOutNodeManipulation()
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51 | : base() {
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52 | }
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53 |
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54 |
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55 | internal override IOperation Manipulate(MersenneTwister random, IGeneticProgrammingModel gpModel, FunctionLibrary library, int maxTreeSize, int maxTreeHeight, IScope scope) {
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56 | TreeGardener gardener = new TreeGardener(random, library);
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57 | IFunctionTree parent = gardener.GetRandomParentNode(gpModel.FunctionTree);
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58 | // parent == null means we should cut out the root node
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59 | // => return a random sub-tree of the root
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60 | if (parent == null) {
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61 | // when there are sub-trees then replace the old tree with a random sub-tree
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62 | if (gpModel.FunctionTree.SubTrees.Count > 0) {
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63 | gpModel.FunctionTree = gpModel.FunctionTree.SubTrees[random.Next(gpModel.FunctionTree.SubTrees.Count)];
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64 | Debug.Assert(gardener.IsValidTree(gpModel.FunctionTree));
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65 | // we reused a sub-tree so we don't have to schedule initialization operations
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66 | return null;
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67 | } else {
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68 | // we want to cut the root node and there are no sub-trees => create a new random terminal
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69 | gpModel.FunctionTree = gardener.CreateRandomTree(gardener.Terminals, 1, 1);
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70 | Debug.Assert(gardener.IsValidTree(gpModel.FunctionTree));
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71 |
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72 | // schedule an operation to initialize the whole tree
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73 | return TreeGardener.CreateInitializationOperation(TreeGardener.GetAllSubTrees(gpModel.FunctionTree), scope);
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74 | }
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75 | }
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76 |
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77 | // select a child to cut away
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78 | int childIndex = random.Next(parent.SubTrees.Count);
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79 | IFunctionTree child = parent.SubTrees[childIndex];
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80 | // match the sub-trees of the child with the allowed sub-trees of the parent
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81 | ICollection<IFunction> allowedFunctions = gardener.GetAllowedSubFunctions(parent.Function, childIndex);
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82 | IFunctionTree[] possibleChilds = child.SubTrees.Where(t => allowedFunctions.Contains(t.Function)).ToArray();
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83 | if (possibleChilds.Length > 0) {
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84 | // replace child with a random child of that child
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85 | IFunctionTree selectedChild = possibleChilds[random.Next(possibleChilds.Length)];
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86 | parent.RemoveSubTree(childIndex);
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87 | parent.InsertSubTree(childIndex, selectedChild);
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88 | Debug.Assert(gardener.IsValidTree(gpModel.FunctionTree));
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89 | // recalculate the size and height of our tree
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90 | gpModel.Size = gpModel.FunctionTree.GetSize();
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91 | gpModel.Height = gpModel.FunctionTree.GetHeight();
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92 | // don't need to schedule initialization operations
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93 | return null;
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94 | } else {
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95 | // can't reuse an existing branch => create a new tree
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96 | // determine the level of the parent
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97 | int parentLevel = gardener.GetBranchLevel(gpModel.FunctionTree, parent);
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98 | // first remove the old child (first step essential!)
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99 | parent.RemoveSubTree(childIndex);
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100 | // then determine the number of nodes left over after the child has been removed!
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101 | int remainingNodes = gpModel.FunctionTree.GetSize();
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102 | allowedFunctions = gardener.GetAllowedSubFunctions(parent.Function, childIndex);
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103 | IFunctionTree newFunctionTree = gardener.CreateRandomTree(allowedFunctions, maxTreeSize - remainingNodes, maxTreeHeight - parentLevel);
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104 | parent.InsertSubTree(childIndex, newFunctionTree);
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105 | Debug.Assert(gardener.IsValidTree(gpModel.FunctionTree));
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106 | // recalculate size and height
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107 | gpModel.Size = gpModel.FunctionTree.GetSize();
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108 | gpModel.Height = gpModel.FunctionTree.GetHeight();
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109 | // schedule an initialization operation for the new function-tree
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110 | return TreeGardener.CreateInitializationOperation(TreeGardener.GetAllSubTrees(newFunctionTree), scope);
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111 | }
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112 | }
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113 | }
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114 | }
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