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1 | using System;
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2 | using System.Collections.Generic;
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3 | using System.Diagnostics;
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4 | using System.Linq;
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5 | using System.Text;
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6 | using System.Text.RegularExpressions;
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7 |
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8 | namespace HeuristicLab.Problems.GrammaticalOptimization {
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9 | // 4-bit even parity
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10 | public class EvenParityProblem : IProblem {
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11 | // + == OR
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12 | // * == AND
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13 | private const string grammarString = @"
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14 | G(S):
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15 | S -> N | N*S | N+S | !S | (S)
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16 | N -> a | b | c | d
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17 | ";
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18 |
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19 | private readonly IGrammar grammar;
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20 | private readonly ExpressionInterpreter interpreter = new ExpressionInterpreter();
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21 | public EvenParityProblem() {
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22 | this.grammar = new Grammar (grammarString);
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23 | }
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24 |
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25 | public double BestKnownQuality(int maxLen) {
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26 | // for now only an upper bound is returned, ideally all fitness cases are predicted correctly
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27 | return Math.Pow(2, 4);
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28 | }
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29 |
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30 | public IGrammar Grammar {
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31 | get { return grammar; }
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32 | }
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33 |
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34 | public double Evaluate(string sentence) {
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35 | var vars = new bool[4];
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36 | var nCorrect = 0;
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37 | for (int b0 = 0; b0 <= 1; b0++)
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38 | for (int b1 = 0; b1 <= 1; b1++)
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39 | for (int b2 = 0; b2 <= 1; b2++)
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40 | for (int b3 = 0; b3 <= 1; b3++) {
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41 | vars[0] = b0 > 0;
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42 | vars[1] = b1 > 0;
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43 | vars[2] = b2 > 0;
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44 | vars[3] = b3 > 0;
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45 |
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46 | var pred = interpreter.Interpret(sentence, vars);
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47 | var target = (b0 > 0) ^ (b1 > 0) ^ (b2 > 0) ^ (b3 > 0);
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48 | if (pred == target) nCorrect++;
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49 | }
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50 | return nCorrect;
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51 | }
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52 |
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53 | public string CanonicalRepresentation(string terminalPhrase) {
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54 | return terminalPhrase;
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55 | }
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56 | }
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57 | }
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