[11239] | 1 | #region License Information
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[11887] | 2 |
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[11239] | 3 | /* HeuristicLab
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[15583] | 4 | * Copyright (C) 2002-2018 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
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[11239] | 5 | *
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| 6 | * This file is part of HeuristicLab.
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| 7 | *
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| 8 | * HeuristicLab is free software: you can redistribute it and/or modify
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| 9 | * it under the terms of the GNU General Public License as published by
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| 10 | * the Free Software Foundation, either version 3 of the License, or
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| 11 | * (at your option) any later version.
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| 12 | *
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| 13 | * HeuristicLab is distributed in the hope that it will be useful,
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| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 16 | * GNU General Public License for more details.
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| 17 | *
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| 18 | * You should have received a copy of the GNU General Public License
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| 19 | * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
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| 20 | */
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[11887] | 21 |
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[11239] | 22 | #endregion
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| 23 |
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| 24 | using System;
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[10562] | 25 | using System.Collections.Generic;
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| 26 | using System.Linq;
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| 27 | using HeuristicLab.Encodings.SymbolicExpressionTreeEncoding;
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| 28 | //using HeuristicLab.EvolutionTracking;
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| 29 |
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| 30 | namespace HeuristicLab.Problems.DataAnalysis.Symbolic {
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| 31 | public static class SymbolicExpressionTreeMatching {
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[11910] | 32 | public static bool ContainsSubtree(this ISymbolicExpressionTreeNode root, ISymbolicExpressionTreeNode subtree, SymbolicExpressionTreeNodeEqualityComparer comparer) {
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[10562] | 33 | return FindMatches(root, subtree, comparer).Any();
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| 34 | }
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[11910] | 35 | public static IEnumerable<ISymbolicExpressionTreeNode> FindMatches(ISymbolicExpressionTree tree, ISymbolicExpressionTreeNode subtree, SymbolicExpressionTreeNodeEqualityComparer comparer) {
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[10562] | 36 | return FindMatches(tree.Root, subtree, comparer);
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| 37 | }
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| 38 |
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[11910] | 39 | public static IEnumerable<ISymbolicExpressionTreeNode> FindMatches(ISymbolicExpressionTreeNode root, ISymbolicExpressionTreeNode subtree, SymbolicExpressionTreeNodeEqualityComparer comp) {
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[10562] | 40 | var fragmentLength = subtree.GetLength();
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| 41 | // below, we use ">=" for Match(n, subtree, comp) >= fragmentLength because in case of relaxed conditions,
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| 42 | // we can have multiple matches of the same node
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| 43 |
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| 44 | return root.IterateNodesBreadth().Where(n => n.GetLength() >= fragmentLength && Match(n, subtree, comp) == fragmentLength);
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| 45 | }
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| 46 |
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| 47 | ///<summary>
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| 48 | /// Finds the longest common subsequence in quadratic time and linear space
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| 49 | /// Variant of:
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| 50 | /// D. S. Hirschberg. A linear space algorithm for or computing maximal common subsequences. 1975.
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| 51 | /// http://dl.acm.org/citation.cfm?id=360861
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| 52 | /// </summary>
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| 53 | /// <returns>Number of pairs that were matched</returns>
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[11239] | 54 | public static int Match(ISymbolicExpressionTreeNode a, ISymbolicExpressionTreeNode b, ISymbolicExpressionTreeNodeSimilarityComparer comp) {
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[10562] | 55 | if (!comp.Equals(a, b)) return 0;
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| 56 | int m = a.SubtreeCount;
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| 57 | int n = b.SubtreeCount;
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| 58 | if (m == 0 || n == 0) return 1;
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| 59 | var matrix = new int[m + 1, n + 1];
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| 60 | for (int i = 1; i <= m; ++i) {
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| 61 | var ai = a.GetSubtree(i - 1);
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| 62 | for (int j = 1; j <= n; ++j) {
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| 63 | var bj = b.GetSubtree(j - 1);
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| 64 | int match = Match(ai, bj, comp);
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| 65 | matrix[i, j] = Math.Max(Math.Max(matrix[i, j - 1], matrix[i - 1, j]), matrix[i - 1, j - 1] + match);
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| 66 | }
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| 67 | }
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| 68 | return matrix[m, n] + 1;
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| 69 | }
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[11887] | 70 |
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| 71 | /// <summary>
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| 72 | /// Calculates the difference between two symbolic expression trees.
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| 73 | /// </summary>
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| 74 | /// <param name="tree">The first symbolic expression tree</param>
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| 75 | /// <param name="other">The second symbolic expression tree</param>
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| 76 | /// <returns>Returns the root of the subtree (from T1) by which T1 differs from T2, or null if no difference is found.</returns>
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| 77 | public static ISymbolicExpressionTreeNode Difference(this ISymbolicExpressionTree tree, ISymbolicExpressionTree other) {
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| 78 | return Difference(tree.Root, other.Root);
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| 79 | }
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| 80 |
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| 81 | public static ISymbolicExpressionTreeNode Difference(this ISymbolicExpressionTreeNode node, ISymbolicExpressionTreeNode other) {
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| 82 | var a = node.IterateNodesPrefix().ToList();
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| 83 | var b = other.IterateNodesPrefix().ToList();
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| 84 | var list = new List<ISymbolicExpressionTreeNode>();
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| 85 | for (int i = 0, j = 0; i < a.Count && j < b.Count; ++i, ++j) {
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| 86 | var s1 = a[i].ToString();
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| 87 | var s2 = b[j].ToString();
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| 88 | if (s1 == s2) continue;
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| 89 | list.Add(a[i]);
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| 90 | // skip subtrees since the parents are already different
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| 91 | i += a[i].SubtreeCount;
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| 92 | j += b[j].SubtreeCount;
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| 93 | }
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| 94 | ISymbolicExpressionTreeNode result = list.Count > 0 ? LowestCommonAncestor(node, list) : null;
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| 95 | return result;
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| 96 | }
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| 97 |
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| 98 | private static ISymbolicExpressionTreeNode LowestCommonAncestor(ISymbolicExpressionTreeNode root, List<ISymbolicExpressionTreeNode> nodes) {
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| 99 | if (nodes.Count == 0)
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| 100 | throw new ArgumentException("The nodes list should contain at least one element.");
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| 101 |
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| 102 | if (nodes.Count == 1)
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| 103 | return nodes[0];
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| 104 |
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| 105 | int minLevel = nodes.Min(x => root.GetBranchLevel(x));
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| 106 |
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| 107 | // bring the nodes in the nodes to the same level (relative to the root)
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| 108 | for (int i = 0; i < nodes.Count; ++i) {
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| 109 | var node = nodes[i];
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| 110 | var level = root.GetBranchLevel(node);
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| 111 | for (int j = minLevel; j < level; ++j)
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| 112 | node = node.Parent;
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| 113 | nodes[i] = node;
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| 114 | }
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| 115 |
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| 116 | // while not all the elements in the nodes are equal, go one level up
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| 117 | while (nodes.Any(x => x != nodes[0])) {
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| 118 | for (int i = 0; i < nodes.Count; ++i)
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| 119 | nodes[i] = nodes[i].Parent;
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| 120 | }
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| 121 |
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| 122 | return nodes[0];
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| 123 | }
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[10562] | 124 | }
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| 125 | }
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