Examples of org.apache.mahout.cf.taste.model.PreferenceArray

Package org.apache.mahout.cf.taste.model

Examples of org.apache.mahout.cf.taste.model.PreferenceArray

org.apache.mahout.cf.taste.model.PreferenceArray
An alternate representation of an array of {@link Preference}. Implementations, in theory, can produce a more memory-efficient representation.

  public PreferenceArray getPreferencesForItem(long itemID) throws NoSuchItemException {
    FastIDSet userIDs = preferenceForItems.get(itemID);
    if (userIDs == null) {
      throw new NoSuchItemException();
    }
    PreferenceArray prefArray = new BooleanItemPreferenceArray(userIDs.size());
    int i = 0;
    LongPrimitiveIterator it = userIDs.iterator();
    while (it.hasNext()) {
      prefArray.setUserID(i, it.next());
      prefArray.setItemID(i, itemID);
      i++;
    }
    return prefArray;
  }

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  private synchronized void recompute() throws TasteException {
    Counters itemPreferenceCounts = new Counters();
    int numUsers = 0;
    LongPrimitiveIterator it = dataModel.getUserIDs();
    while (it.hasNext()) {
      PreferenceArray prefs = dataModel.getPreferencesFromUser(it.nextLong());
      int size = prefs.length();
      for (int i = 0; i < size; i++) {
        itemPreferenceCounts.increment(prefs.getItemID(i));
      }
      numUsers++;
    }
    FastByIDMap<Double> newIufFactors = new FastByIDMap<Double>(itemPreferenceCounts.size());
    double logFactor = Math.log(logBase);

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    while (it.hasNext()) {
      long userID = it.nextLong();
      if (random.nextDouble() < evaluationPercentage) {
        long start = System.currentTimeMillis();
        FastIDSet relevantItemIDs = new FastIDSet(at);
        PreferenceArray prefs = dataModel.getPreferencesFromUser(userID);
        int size = prefs.length();
        if (size < 2 * at) {
          // Really not enough prefs to meaningfully evaluate this user
          continue;
        }
        
        // List some most-preferred items that would count as (most) "relevant" results
        double theRelevanceThreshold = Double.isNaN(relevanceThreshold) ?
            computeThreshold(prefs) : relevanceThreshold;
        prefs.sortByValueReversed();
        for (int i = 0; (i < size) && (relevantItemIDs.size() < at); i++) {
          if (prefs.getValue(i) >= theRelevanceThreshold) {
            relevantItemIDs.add(prefs.getItemID(i));
          }
        }
        int numRelevantItems = relevantItemIDs.size();
        if (numRelevantItems > 0) {
          FastByIDMap<PreferenceArray> trainingUsers = new FastByIDMap<PreferenceArray>(dataModel

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  private static void processOtherUser(long id,
                                       FastIDSet relevantItemIDs,
                                       FastByIDMap<PreferenceArray> trainingUsers,
                                       long userID2,
                                       DataModel dataModel) throws TasteException {
    PreferenceArray prefs2Array = dataModel.getPreferencesFromUser(userID2);
    if (id == userID2) {
      List<Preference> prefs2 = new ArrayList<Preference>(prefs2Array.length());
      for (Preference pref : prefs2Array) {
        prefs2.add(pref);
      }
      for (Iterator<Preference> iterator = prefs2.iterator(); iterator.hasNext();) {
        Preference pref = iterator.next();

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  private DataModel createModel() {
    FastByIDMap<PreferenceArray> data = new FastByIDMap<PreferenceArray>(NUM_USERS);
    for (int i = 0; i < NUM_USERS; i++) {
      int numPrefs = random.nextInt(NUM_PREFS) + 1;
      PreferenceArray prefs = new GenericUserPreferenceArray(numPrefs);
      for (int j = 0; j < numPrefs; j++) {
        prefs.set(j, new GenericPreference(i, random.nextInt(NUM_ITEMS), random.nextFloat()));
      }
      data.put(i, prefs);
    }
    return new GenericDataModel(data);
  }

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                    {1.0, 1.0, 1.0, 1.0, 1.0},
            });


    InverseUserFrequency iuf = new InverseUserFrequency(dataModel, 10.0);


    PreferenceArray user5Prefs = dataModel.getPreferencesFromUser(5);


    for (int i = 0; i < 5; i++) {
      Preference pref = user5Prefs.get(i);
      assertNotNull(pref);
      assertEquals(Math.log(5.0 / (double) (5 - i)) / Math.log(iuf.getLogBase()),
          iuf.getTransformedValue(pref),
          EPSILON);
    }

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    writer.println(recommender);
    writer.println();
    writer.print("Top ");
    writer.print(NUM_TOP_PREFERENCES);
    writer.println(" Preferences:");
    PreferenceArray rawPrefs = dataModel.getPreferencesFromUser(userID);
    int length = rawPrefs.length();
    PreferenceArray sortedPrefs = rawPrefs.clone();
    sortedPrefs.sortByValueReversed();
    // Cap this at NUM_TOP_PREFERENCES just to be brief
    int max = Math.min(NUM_TOP_PREFERENCES, length);
    for (int i = 0; i < max; i++) {
      Preference pref = sortedPrefs.get(i);
      writer.print(pref.getValue());
      writer.print('\t');
      writer.println(pref.getItemID());
    }
    writer.println();

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    // Yeah ignoring items that only the plus-one user knows about... can't really happen
  }
  
  @Override
  public PreferenceArray getPreferencesForItem(long itemID) throws TasteException {
    PreferenceArray delegatePrefs = delegate.getPreferencesForItem(itemID);
    for (int i = 0; i < tempPrefs.length(); i++) {
      if (tempPrefs.getItemID(i) == itemID) {
        int length = delegatePrefs.length();
        PreferenceArray newPreferenceArray = new GenericItemPreferenceArray(length + 1);
        for (int j = 0; j < length; j++) {
          newPreferenceArray.setUserID(j, delegatePrefs.getUserID(j));
          newPreferenceArray.setItemID(j, delegatePrefs.getItemID(j));
          newPreferenceArray.setValue(j, delegatePrefs.getValue(j));
        }
        newPreferenceArray.setUserID(length, tempPrefs.getUserID(i));
        newPreferenceArray.setItemID(length, tempPrefs.getItemID(i));
        newPreferenceArray.setValue(length, tempPrefs.getValue(i));
        newPreferenceArray.sortByUser();
        return newPreferenceArray;
      }
    }
    return delegatePrefs;
  }

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  }




  public void testTranspose() throws Exception {
    FileDataModel tModel = new FileDataModel(testFile, true);
    PreferenceArray userPrefs = tModel.getPreferencesFromUser(456);
    assertNotNull("user prefs are null and it shouldn't be", userPrefs);
    PreferenceArray pref = tModel.getPreferencesForItem(123);
    assertNotNull("pref is null and it shouldn't be", pref);
    assertEquals("pref Size: " + pref.length() + " is not: " + 3, 3, pref.length());
  }

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      // good
    }
  }


  public void testPreferencesForItem() throws Exception {
    PreferenceArray prefs = model.getPreferencesForItem(456);
    assertNotNull(prefs);
    Preference pref1 = prefs.get(0);
    assertEquals(123, pref1.getUserID());
    assertEquals(456, pref1.getItemID());
    Preference pref2 = prefs.get(1);
    assertEquals(456, pref2.getUserID());
    assertEquals(456, pref2.getItemID());
    assertEquals(2, prefs.length());
  }

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