@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);
}
private double doItemSimilarity(long itemID1, long itemID2, FastIDSet preferring1)
throws TasteException {
double intersection = 0.0;
double union = 0.0;
for (Preference pref : getDataModel().getPreferencesForItem(itemID2)) {
long userID = pref.getUserID();
double weight = (double) getDataModel().getNumItems() / mUserPrefNum.get(userID);
if (preferring1.contains(userID)) {
intersection += weight;
union -= weight;
}
union += weight;
}
for (LongPrimitiveIterator it_user = preferring1.iterator(); it_user.hasNext(); ) {
long userID = (long) it_user.nextLong();
double weight = (double) getDataModel().getNumItems() / mUserPrefNum.get(userID);
union += weight;
}
if (intersection == 0) {
return Double.NaN;
}
return Math.log(intersection) / Math.log(union);
}
@Override
public Float getPreferenceValue(long userID, long itemID) throws NoSuchUserException {
FastIDSet itemIDs = preferenceFromUsers.get(userID);
if (itemIDs == null) {
throw new NoSuchUserException(userID);
}
if (itemIDs.contains(itemID)) {
return 1.0f;
}
return null;
}
@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);
}