1 | package de.ugoe.cs.quest.coverage;
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2 |
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3 | import java.security.InvalidParameterException;
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4 | import java.util.Collection;
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5 | import java.util.LinkedHashMap;
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6 | import java.util.LinkedHashSet;
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7 | import java.util.LinkedList;
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8 | import java.util.List;
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9 | import java.util.Map;
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10 | import java.util.Set;
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11 |
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12 | import de.ugoe.cs.quest.eventcore.Event;
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13 | import de.ugoe.cs.quest.usageprofiles.IStochasticProcess;
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14 |
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15 | /**
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16 | * <p>
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17 | * This class gathers some helper functions to work with sequences.
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18 | * </p>
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19 | *
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20 | * @author Steffen Herbold
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21 | * @version 1.0
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22 | */
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23 | public class SequenceTools {
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24 |
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25 | /**
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26 | * <p>
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27 | * Private constructor to prevent initializing of the class.
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28 | * </p>
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29 | */
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30 | private SequenceTools() {
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31 |
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32 | }
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33 |
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34 | /**
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35 | * <p>
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36 | * Calculates the weights for all sequences passed to this function as defined by the stochastic
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37 | * process and stores them in a {@link Map}. The weights are normalized, i.e., the sum of all
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38 | * weights contained in this map is 1.
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39 | * </p>
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40 | *
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41 | * @param process
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42 | * process used for weight calculation
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43 | * @param sequences
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44 | * sequences for which the weights are calculated
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45 | * @return {@link Map} of weights
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46 | */
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47 | public static Map<List<Event>, Double> generateWeights(IStochasticProcess process,
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48 | Collection<List<Event>> sequences)
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49 | {
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50 | Map<List<Event>, Double> subSeqWeights = new LinkedHashMap<List<Event>, Double>();
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51 | if (sequences != null && !sequences.isEmpty()) {
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52 | if (process != null) {
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53 | double sum = 0.0;
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54 | for (List<Event> sequence : sequences) {
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55 | double prob = process.getProbability(sequence);
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56 | subSeqWeights.put(sequence, prob);
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57 | sum += prob;
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58 | }
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59 | if (sum < 1.0) {
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60 | for (Map.Entry<List<Event>, Double> entry : subSeqWeights.entrySet()) {
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61 | entry.setValue(entry.getValue() / sum);
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62 | }
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63 | }
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64 | }
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65 | else {
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66 | for (List<Event> sequence : sequences) {
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67 | subSeqWeights.put(sequence, 0.0d);
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68 | }
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69 | }
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70 | }
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71 | return subSeqWeights;
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72 | }
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73 |
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74 | /**
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75 | * <p>
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76 | * Calculates the number of all existing sequences of a given length, regardless whether they
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77 | * are possible or not.
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78 | * </p>
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79 | *
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80 | * @param process
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81 | * stochastic process whose symbols are the basis for this calculation
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82 | * @param length
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83 | * lenght of the sequences
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84 | * @return numStates^length
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85 | * @throws InvalidParameterException
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86 | * thrown if length less or equal to 0
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87 | */
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88 | public static long numSequences(IStochasticProcess process, int length) {
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89 | if (length <= 0) {
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90 | throw new InvalidParameterException("length must be a positive integer");
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91 | }
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92 | long result = 0;
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93 | if (process != null) {
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94 | result = (long) Math.pow(process.getNumSymbols(), length);
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95 | }
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96 | return result;
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97 | }
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98 |
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99 | /**
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100 | * <p>
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101 | * Creates a {@link Set} of all subsequences of a given length that are contained in a sequence
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102 | * collection.
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103 | * </p>
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104 | *
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105 | * @param sequences
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106 | * sequences from which the subsequences are extracted
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107 | * @param length
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108 | * length of the subsequences
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109 | * @return {@link Set} of all subsequences
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110 | * @throws InvalidParameterException
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111 | * thrown if length less or equal to 0
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112 | */
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113 | public static Set<List<Event>> containedSubSequences(Collection<List<Event>> sequences,
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114 | int length)
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115 | {
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116 | if (length <= 0) {
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117 | throw new InvalidParameterException("length must be a positive integer");
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118 | }
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119 | Set<List<Event>> containedSubSeqs = new LinkedHashSet<List<Event>>();
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120 | if (sequences != null) {
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121 | for (List<Event> sequence : sequences) {
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122 | List<Event> subSeq = new LinkedList<Event>();
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123 | boolean minLengthReached = false;
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124 | for (Event event : sequence) {
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125 | subSeq.add(event);
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126 | if (!minLengthReached) {
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127 | if (subSeq.size() == length) {
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128 | minLengthReached = true;
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129 | }
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130 | }
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131 | else {
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132 | subSeq.remove(0);
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133 | }
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134 | if (minLengthReached) {
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135 | if (!containedSubSeqs.contains(subSeq)) {
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136 | containedSubSeqs.add(new LinkedList<Event>(subSeq));
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137 | }
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138 | }
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139 | }
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140 | }
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141 | }
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142 | return containedSubSeqs;
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143 | }
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144 | }
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