1 | using System;
|
---|
2 | using System.Collections.Generic;
|
---|
3 | using System.Diagnostics;
|
---|
4 | using System.Linq;
|
---|
5 |
|
---|
6 | namespace HeuristicLab.Algorithms.DataAnalysis.SymRegGrammarEnumeration.GrammarEnumeration {
|
---|
7 | public abstract class Hasher<THashType> {
|
---|
8 | protected Hasher(Grammar grammar) {
|
---|
9 | Grammar = grammar;
|
---|
10 | }
|
---|
11 |
|
---|
12 | protected Grammar Grammar { get; }
|
---|
13 |
|
---|
14 | protected abstract THashType AggregateHashes(Symbol operatorSym, THashType[] hashes);
|
---|
15 |
|
---|
16 | public int CalcHashCode(SymbolString sentence) {
|
---|
17 | Debug.Assert(sentence.Any(), "Trying to evaluate empty sentence!");
|
---|
18 |
|
---|
19 | Stack<Symbol> parseStack = new Stack<Symbol>(sentence);
|
---|
20 |
|
---|
21 | Symbol peek = parseStack.Peek();
|
---|
22 | return AggregateHashes(peek, GetSubtreeHashes(parseStack)).GetHashCode();
|
---|
23 | }
|
---|
24 |
|
---|
25 | private THashType[] GetSubtreeHashes(Stack<Symbol> parseStack) {
|
---|
26 | Symbol currentSymbol = parseStack.Pop();
|
---|
27 |
|
---|
28 | // ADDITION
|
---|
29 | if (currentSymbol == Grammar.Addition) {
|
---|
30 | return GetAdditionSubtreeHashes(parseStack);
|
---|
31 | }
|
---|
32 |
|
---|
33 | // MULTIPLICATION
|
---|
34 | if (currentSymbol == Grammar.Multiplication) {
|
---|
35 | return GetMultiplicationSubtreeHashes(parseStack);
|
---|
36 | }
|
---|
37 |
|
---|
38 | // LOG, EXP, SIN, INV
|
---|
39 | if (currentSymbol == Grammar.Log || currentSymbol == Grammar.Exp ||
|
---|
40 | currentSymbol == Grammar.Sin || currentSymbol == Grammar.Cos ||
|
---|
41 | currentSymbol == Grammar.Inv) {
|
---|
42 | // Directly aggregate the single subtree
|
---|
43 | return new[] { AggregateHashes(parseStack.Peek(), GetSubtreeHashes(parseStack)) };
|
---|
44 | }
|
---|
45 |
|
---|
46 | // var or nonterminal symbol
|
---|
47 | return new[] { AggregateHashes(currentSymbol, new THashType[0]) };
|
---|
48 | }
|
---|
49 |
|
---|
50 | private THashType[] GetAdditionSubtreeHashes(Stack<Symbol> parseStack) {
|
---|
51 | var uniqueChildHashes = new HashSet<THashType>();
|
---|
52 |
|
---|
53 | // First subtree
|
---|
54 | if (parseStack.Peek() == Grammar.Addition) {
|
---|
55 | uniqueChildHashes.UnionWith(GetSubtreeHashes(parseStack));
|
---|
56 | } else {
|
---|
57 | var peek = parseStack.Peek();
|
---|
58 | uniqueChildHashes.Add(AggregateHashes(peek, GetSubtreeHashes(parseStack)));
|
---|
59 | }
|
---|
60 | // Second subtree
|
---|
61 | if (parseStack.Peek() == Grammar.Addition) {
|
---|
62 | uniqueChildHashes.UnionWith(GetSubtreeHashes(parseStack));
|
---|
63 | } else {
|
---|
64 | var peek = parseStack.Peek();
|
---|
65 | uniqueChildHashes.Add(AggregateHashes(peek, GetSubtreeHashes(parseStack)));
|
---|
66 | }
|
---|
67 |
|
---|
68 | var result = uniqueChildHashes.ToArray();
|
---|
69 | Array.Sort(result);
|
---|
70 | return result;
|
---|
71 | }
|
---|
72 |
|
---|
73 | public THashType[] GetMultiplicationSubtreeHashes(Stack<Symbol> parseStack) {
|
---|
74 | var childHashes = new List<THashType>();
|
---|
75 |
|
---|
76 | // First subtree
|
---|
77 | if (parseStack.Peek() == Grammar.Multiplication) {
|
---|
78 | childHashes.AddRange(GetSubtreeHashes(parseStack));
|
---|
79 | } else {
|
---|
80 | childHashes.Add(AggregateHashes(parseStack.Peek(), GetSubtreeHashes(parseStack)));
|
---|
81 | }
|
---|
82 | // Second subtree
|
---|
83 | if (parseStack.Peek() == Grammar.Multiplication) {
|
---|
84 | childHashes.AddRange(GetSubtreeHashes(parseStack));
|
---|
85 | } else {
|
---|
86 | childHashes.Add(AggregateHashes(parseStack.Peek(), GetSubtreeHashes(parseStack)));
|
---|
87 | }
|
---|
88 |
|
---|
89 | // Sort due to commutativity
|
---|
90 | childHashes.Sort();
|
---|
91 |
|
---|
92 | // Cancel out inverse factors.
|
---|
93 | bool[] isFactorRemaining = Enumerable.Repeat(true, childHashes.Count).ToArray();
|
---|
94 |
|
---|
95 | for (int i = 0; i < isFactorRemaining.Length; i++) {
|
---|
96 | if (!isFactorRemaining[i]) continue;
|
---|
97 | if (isFactorRemaining.Length <= 2) break; // Until we have constants, we can't cancel out all terms.
|
---|
98 |
|
---|
99 | var currFactor = childHashes[i];
|
---|
100 | var invFactor = AggregateHashes(Grammar.Inv, new[] { currFactor });
|
---|
101 |
|
---|
102 | int indexOfInv = childHashes.IndexOf(invFactor);
|
---|
103 | if (indexOfInv >= 0 && isFactorRemaining[indexOfInv]) {
|
---|
104 | isFactorRemaining[i] = isFactorRemaining[indexOfInv] = false;
|
---|
105 | }
|
---|
106 | }
|
---|
107 |
|
---|
108 | return childHashes
|
---|
109 | .Where((c, i) => isFactorRemaining[i])
|
---|
110 | .ToArray();
|
---|
111 | }
|
---|
112 |
|
---|
113 |
|
---|
114 | }
|
---|
115 |
|
---|
116 | public class IntHasher : Hasher<int> {
|
---|
117 | public IntHasher(Grammar grammar) : base(grammar) { }
|
---|
118 |
|
---|
119 | protected override int AggregateHashes(Symbol operatorSym, int[] hashes) {
|
---|
120 | int start;
|
---|
121 | if ((operatorSym == Grammar.Addition || operatorSym == Grammar.Multiplication) && hashes.Length <= 1) {
|
---|
122 | start = 0;
|
---|
123 |
|
---|
124 | } else if (operatorSym is NonterminalSymbol || operatorSym is VariableTerminalSymbol) {
|
---|
125 | return operatorSym.StringRepresentation.GetHashCode();
|
---|
126 |
|
---|
127 | } else {
|
---|
128 | start = operatorSym.StringRepresentation.GetHashCode();
|
---|
129 | }
|
---|
130 |
|
---|
131 | for (int i = 0; i < hashes.Length; i++) {
|
---|
132 | start = ((start << 5) + start) ^ hashes[i];
|
---|
133 | }
|
---|
134 | return start;
|
---|
135 | }
|
---|
136 | }
|
---|
137 |
|
---|
138 | public class StringHasher : Hasher<string> {
|
---|
139 | public StringHasher(Grammar grammar) : base(grammar) { }
|
---|
140 |
|
---|
141 | protected override string AggregateHashes(Symbol operatorSym, string[] hashes) {
|
---|
142 | var hashesArray = hashes.ToArray();
|
---|
143 |
|
---|
144 | if ((operatorSym == Grammar.Addition || operatorSym == Grammar.Multiplication) && hashesArray.Length <= 1) {
|
---|
145 | return hashesArray[0];
|
---|
146 | }
|
---|
147 | if (operatorSym is NonterminalSymbol || operatorSym is VariableTerminalSymbol) {
|
---|
148 | return operatorSym.StringRepresentation;
|
---|
149 | }
|
---|
150 |
|
---|
151 | return $"[{operatorSym.StringRepresentation} ° {string.Join(" ° ", hashesArray)}]";
|
---|
152 | }
|
---|
153 | }
|
---|
154 | }
|
---|