1 | package de.ugoe.cs.eventbench.models;
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2 |
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3 | import java.util.LinkedList;
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4 | import java.util.List;
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5 | import java.util.Random;
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6 |
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7 | import de.ugoe.cs.eventbench.data.Event;
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8 | import de.ugoe.cs.eventbench.models.Trie.Edge;
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9 | import de.ugoe.cs.eventbench.models.Trie.TrieVertex;
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10 | import edu.uci.ics.jung.graph.Tree;
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11 |
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12 | public abstract class TrieBasedModel implements IStochasticProcess {
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13 |
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14 | protected int trieOrder;
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15 |
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16 | protected abstract double getProbability(List<Event<?>> context, Event<?> symbol);
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17 |
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18 | protected Trie<Event<?>> trie;
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19 | protected final Random r;
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20 |
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21 |
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22 | public TrieBasedModel(int markovOrder, Random r) {
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23 | super();
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24 | this.trieOrder = markovOrder+1;
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25 | this.r = r;
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26 | }
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27 |
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28 | public void train(List<List<Event<?>>> sequences) {
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29 | trie = new Trie<Event<?>>();
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30 |
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31 | for(List<Event<?>> sequence : sequences) {
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32 | List<Event<?>> currentSequence = new LinkedList<Event<?>>(sequence); // defensive copy
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33 | currentSequence.add(0, Event.STARTEVENT);
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34 | currentSequence.add(Event.ENDEVENT);
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35 |
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36 | trie.train(currentSequence, trieOrder);
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37 | }
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38 | }
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39 |
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40 | /* (non-Javadoc)
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41 | * @see de.ugoe.cs.eventbench.models.IStochasticProcess#randomSequence()
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42 | */
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43 | @Override
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44 | public List<? extends Event<?>> randomSequence() {
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45 | List<Event<?>> sequence = new LinkedList<Event<?>>();
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46 |
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47 | IncompleteMemory<Event<?>> context = new IncompleteMemory<Event<?>>(trieOrder-1);
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48 | context.add(Event.STARTEVENT);
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49 |
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50 | Event<?> currentState = Event.STARTEVENT;
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51 |
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52 | boolean endFound = false;
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53 |
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54 | while(!endFound) {
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55 | double randVal = r.nextDouble();
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56 | double probSum = 0.0;
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57 | List<Event<?>> currentContext = context.getLast(trieOrder);
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58 | for( Event<?> symbol : trie.getKnownSymbols() ) {
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59 | probSum += getProbability(currentContext, symbol);
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60 | if( probSum>=randVal ) {
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61 | endFound = (symbol==Event.ENDEVENT);
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62 | if( !(symbol==Event.STARTEVENT || symbol==Event.ENDEVENT) ) {
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63 | // only add the symbol the sequence if it is not START or END
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64 | context.add(symbol);
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65 | currentState = symbol;
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66 | sequence.add(currentState);
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67 | }
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68 | break;
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69 | }
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70 | }
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71 | }
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72 | return sequence;
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73 | }
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74 |
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75 | public String getTrieDotRepresentation() {
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76 | return trie.getDotRepresentation();
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77 | }
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78 |
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79 | public Tree<TrieVertex, Edge> getTrieGraph() {
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80 | return trie.getGraph();
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81 | }
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82 |
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83 | @Override
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84 | public String toString() {
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85 | return trie.toString();
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86 | }
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87 |
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88 | public int getNumStates() {
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89 | return trie.getNumSymbols();
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90 | }
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91 |
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92 | public String[] getStateStrings() {
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93 | String[] stateStrings = new String[getNumStates()];
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94 | int i=0;
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95 | for( Event<?> symbol : trie.getKnownSymbols() ) {
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96 | stateStrings[i] = symbol.toString();
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97 | i++;
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98 | }
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99 | return stateStrings;
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100 | }
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101 |
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102 | } |
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