[432] | 1 | package de.ugoe.cs.quest.models;
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[258] | 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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[432] | 7 | import de.ugoe.cs.quest.data.Event;
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| 8 | import de.ugoe.cs.quest.data.ReplayableEvent;
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[258] | 9 |
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| 10 | /**
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| 11 | * <p>
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| 12 | * This class provides functions to create flattened first-order Markov models
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| 13 | * from {@link HighOrderMarkovModel}s and {@link PredictionByPartialMatch}
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| 14 | * models through state splitting.
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| 15 | * </p>
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| 16 | * <p>
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| 17 | * If possible, the normal high-order markov model should be used, as the Events
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| 18 | * may be broken by the flattener, as, e.g., the information
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| 19 | * {@link ReplayableEvent}s contain is not preserved.
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| 20 | * </p>
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| 21 | *
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| 22 | * @author Steffen Herbold
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| 23 | * @version 1.0
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| 24 | */
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| 25 | public class ModelFlattener {
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| 26 |
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| 27 | private static final String EVENT_SEPARATOR = "-=-";
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| 28 |
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| 29 | Trie<Event<?>> firstOrderTrie;
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| 30 |
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| 31 | /**
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| 32 | * <p>
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| 33 | * Takes a {@link HighOrderMarkovModel} and returns a
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| 34 | * {@link FirstOrderMarkovModel} that conserves the high-order memory
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| 35 | * through state splitting.
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| 36 | * </p>
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| 37 | *
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| 38 | * @param model
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| 39 | * model that is flattened
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| 40 | * @return flattened first-order Markov model
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| 41 | */
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| 42 | public FirstOrderMarkovModel flattenHighOrderMarkovModel(
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| 43 | HighOrderMarkovModel model) {
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| 44 | int markovOrder = model.trieOrder - 1;
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| 45 | FirstOrderMarkovModel firstOrderModel = new FirstOrderMarkovModel(
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| 46 | new Random());
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| 47 | firstOrderModel.trieOrder = 2;
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[361] | 48 | if (markovOrder == 1) {
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| 49 | firstOrderModel.trie = new Trie<Event<?>>(model.trie);
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| 50 | firstOrderModel.trieOrder = 2;
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| 51 | } else {
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| 52 | firstOrderTrie = new Trie<Event<?>>();
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| 53 | TrieNode<Event<?>> rootNode = model.trie.find(null);
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| 54 | generateFirstOrderTrie(rootNode, new LinkedList<String>(), markovOrder);
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| 55 | firstOrderTrie.updateKnownSymbols();
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| 56 | firstOrderModel.trie = firstOrderTrie;
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| 57 | }
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[258] | 58 |
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| 59 | return firstOrderModel;
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| 60 | }
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| 61 |
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| 62 | /**
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| 63 | * <p>
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| 64 | * <b>This method is not available yet and always return null!</b>
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| 65 | * </p>
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| 66 | * <p>
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| 67 | * Takes a {@link PredictionByPartialMatch} model and returns a
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| 68 | * {@link FirstOrderMarkovModel} that conserves the high-order memory
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| 69 | * through state splitting.
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| 70 | * </p>
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| 71 | *
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| 72 | * @param model
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| 73 | * model that is flattened
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| 74 | * @return flattened first-order Markov model
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| 75 | */
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| 76 | public FirstOrderMarkovModel flattenPredictionByPartialMatch(
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| 77 | PredictionByPartialMatch model) {
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| 78 | // TODO implement method
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| 79 | return null;
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| 80 | }
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| 81 |
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| 82 | /**
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| 83 | * <p>
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| 84 | * Converts all nodes of the given depth into first-order node through
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| 85 | * state-splitting. For each node at the given depth a new node is created
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| 86 | * and appropriate transitions will be added.
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| 87 | * </p>
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| 88 | * <p>
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| 89 | * This method traverses through the tree recursively. If the recursion
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| 90 | * reaches the desired depth in the tree, node are added.
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| 91 | * </p>
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| 92 | *
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| 93 | * @param currentNode
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| 94 | * node whose sub-trie is currently traversed
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| 95 | * @param parentIDs
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| 96 | * ID strings of the ancestors of the currentNode
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| 97 | * @param depth
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| 98 | * depth to go - NOT the current depth.
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| 99 | */
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| 100 | private void generateFirstOrderTrie(TrieNode<Event<?>> currentNode,
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| 101 | List<String> parentIDs, int depth) {
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| 102 | for (TrieNode<Event<?>> child : currentNode.getChildren()) {
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| 103 | String currentId = child.getSymbol().getStandardId();
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| 104 | if (depth > 1) {
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| 105 | List<String> childParentIDs = new LinkedList<String>(parentIDs);
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| 106 | childParentIDs.add(currentId);
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| 107 | generateFirstOrderTrie(child, childParentIDs, depth - 1);
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| 108 |
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| 109 | } else {
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| 110 | StringBuilder firstOrderID = new StringBuilder();
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| 111 | for (String parentID : parentIDs) {
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| 112 | firstOrderID.append(parentID + EVENT_SEPARATOR);
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| 113 | }
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| 114 | firstOrderID.append(currentId);
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| 115 | TrieNode<Event<?>> firstOrderNode = firstOrderTrie
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| 116 | .getChildCreate(new Event<Object>(firstOrderID
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| 117 | .toString()));
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| 118 | firstOrderNode.setCount(child.getCount());
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| 119 | for (TrieNode<Event<?>> transitionChild : child.getChildren()) {
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| 120 | StringBuilder transitionID = new StringBuilder();
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| 121 | for (String parentID : parentIDs.subList(1,
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| 122 | parentIDs.size())) {
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| 123 | transitionID.append(parentID + EVENT_SEPARATOR);
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| 124 | }
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| 125 | transitionID.append(currentId + EVENT_SEPARATOR);
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| 126 | transitionID.append(transitionChild.getSymbol()
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| 127 | .getStandardId());
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| 128 | TrieNode<Event<?>> firstOrderTransitionChild = firstOrderNode
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| 129 | .getChildCreate(new Event<Object>(transitionID
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| 130 | .toString()));
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| 131 | firstOrderTransitionChild.setCount(transitionChild
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| 132 | .getCount());
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| 133 | }
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| 134 | }
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| 135 | }
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| 136 | }
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| 137 | }
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