@Override
public double userSimilarity(long userID1, long userID2) throws TasteException {
FastIDSet prefs1 = dataModel.getItemIDsFromUser(userID1);
FastIDSet prefs2 = dataModel.getItemIDsFromUser(userID2);
int prefs1Size = prefs1.size();
int prefs2Size = prefs2.size();
int intersectionSize =
prefs1Size < prefs2Size ? prefs2.intersectionSize(prefs1) : prefs1.intersectionSize(prefs2);
if (intersectionSize == 0) {
return Double.NaN;
}
// int numItems = dataModel.getNumItems();
// int numItems = Math.max(prefs1Size, prefs2Size);
// int numItems = prefs1Size;
// double distance1 = (double) (prefs1Size - intersectionSize)/(double) 2;
// double distance2 = (double) (prefs2Size - intersectionSize)/(double) 2;
// double distance = (distance1 + distance2);
double distance = (double) (prefs1Size - intersectionSize);
double similarity = 1.0 / (1.0 + distance);
////// System.out.println( prefs1Size + ", " + prefs2Size + ", " + intersectionSize + ", " +
// similarity);
return similarity;
}
@Override
public int getNumUsersWithPreferenceFor(long itemID1, long itemID2) {
FastIDSet userIDs1 = preferenceForItems.get(itemID1);
if (userIDs1 == null) {
return 0;
}
FastIDSet userIDs2 = preferenceForItems.get(itemID2);
if (userIDs2 == null) {
return 0;
}
return userIDs1.size() < userIDs2.size()
? userIDs2.intersectionSize(userIDs1)
: userIDs1.intersectionSize(userIDs2);
}
@Test
public void testStrategy() throws TasteException {
FastIDSet itemIDsFromUser123 = new FastIDSet();
itemIDsFromUser123.add(1L);
FastIDSet itemIDsFromUser456 = new FastIDSet();
itemIDsFromUser456.add(1L);
itemIDsFromUser456.add(2L);
List<Preference> prefs = new ArrayList<Preference>();
prefs.add(new GenericPreference(123L, 1L, 1.0f));
prefs.add(new GenericPreference(456L, 1L, 1.0f));
PreferenceArray preferencesForItem1 = new GenericItemPreferenceArray(prefs);
DataModel dataModel = EasyMock.createMock(DataModel.class);
EasyMock.expect(dataModel.getPreferencesForItem(1L)).andReturn(preferencesForItem1);
EasyMock.expect(dataModel.getItemIDsFromUser(123L)).andReturn(itemIDsFromUser123);
EasyMock.expect(dataModel.getItemIDsFromUser(456L)).andReturn(itemIDsFromUser456);
PreferenceArray prefArrayOfUser123 =
new GenericUserPreferenceArray(Arrays.asList(new GenericPreference(123L, 1L, 1.0f)));
CandidateItemsStrategy strategy = new PreferredItemsNeighborhoodCandidateItemsStrategy();
EasyMock.replay(dataModel);
FastIDSet candidateItems = strategy.getCandidateItems(123L, prefArrayOfUser123, dataModel);
assertEquals(1, candidateItems.size());
assertTrue(candidateItems.contains(2L));
EasyMock.verify(dataModel);
}
@Override
public double userSimilarity(long userID1, long userID2) throws TasteException {
FastIDSet prefs1 = dataModel.getItemIDsFromUser(userID1);
FastIDSet prefs2 = dataModel.getItemIDsFromUser(userID2);
int prefs1Size = prefs1.size();
int prefs2Size = prefs2.size();
int intersectionSize =
prefs1Size < prefs2Size ? prefs2.intersectionSize(prefs1) : prefs1.intersectionSize(prefs2);
if (intersectionSize == 0) {
return Double.NaN;
}
int numItems = dataModel.getNumItems();
double logLikelihood =
twoLogLambda(
intersectionSize, prefs1Size - intersectionSize, prefs2Size, numItems - prefs2Size);
return 1.0 - 1.0 / (1.0 + logLikelihood);
}
@Override
public double userSimilarity(long userID1, long userID2) throws TasteException {
DataModel dataModel = getDataModel();
FastIDSet xPrefs = dataModel.getItemIDsFromUser(userID1);
FastIDSet yPrefs = dataModel.getItemIDsFromUser(userID2);
int xPrefsSize = xPrefs.size();
int yPrefsSize = yPrefs.size();
if (xPrefsSize == 0 && yPrefsSize == 0) {
return Double.NaN;
}
if (xPrefsSize == 0 || yPrefsSize == 0) {
return 0.0;
}
double intersection = 0.0;
double union = 0.0;
for (LongPrimitiveIterator it_item = xPrefs.iterator(); it_item.hasNext(); ) {
long itemID = (long) it_item.nextLong();
double weight = (double) getDataModel().getNumUsers() / mItemPrefNum.get(itemID);
if (yPrefs.contains(itemID)) {
intersection += weight;
union -= weight;
}
union += weight;
}
for (LongPrimitiveIterator it_item = yPrefs.iterator(); it_item.hasNext(); ) {
long itemID = (long) it_item.nextLong();
double weight = (double) getDataModel().getNumUsers() / mItemPrefNum.get(itemID);
union += weight;
}
return Math.log(intersection) / Math.log(union);
}
@Override
public PreferenceArray getPreferencesForItem(long itemID) throws NoSuchItemException {
FastIDSet userIDs = preferenceForItems.get(itemID);
if (userIDs == null) {
throw new NoSuchItemException(itemID);
}
PreferenceArray prefArray = new BooleanItemPreferenceArray(userIDs.size());
int i = 0;
LongPrimitiveIterator it = userIDs.iterator();
while (it.hasNext()) {
prefArray.setUserID(i, it.nextLong());
prefArray.setItemID(i, itemID);
i++;
}
return prefArray;
}
@Override
public int getNumUsersWithPreferenceFor(long itemID) {
FastIDSet userIDs1 = preferenceForItems.get(itemID);
return userIDs1 == null ? 0 : userIDs1.size();
}