@Override
public List<RecommendedItem> recommend(
long userID, int howMany, IDRescorer rescorer, boolean includeKnownItems)
throws TasteException {
Preconditions.checkArgument(howMany >= 1, "howMany must be at least 1");
log.debug("Recommending items for user ID '{}'", userID);
PreferenceArray preferencesFromUser = getDataModel().getPreferencesFromUser(userID);
FastIDSet possibleItemIDs = getAllOtherItems(userID, preferencesFromUser, includeKnownItems);
TopItems.Estimator<Long> estimator = new Estimator(userID);
List<RecommendedItem> topItems =
TopItems.getTopItems(howMany, possibleItemIDs.iterator(), rescorer, estimator);
log.debug("Recommendations are: {}", topItems);
return topItems;
}
@Test
public void testTopItems() throws Exception {
long[] ids = new long[100];
for (int i = 0; i < 100; i++) {
ids[i] = i;
}
LongPrimitiveIterator possibleItemIds = new LongPrimitiveArrayIterator(ids);
TopItems.Estimator<Long> estimator =
new TopItems.Estimator<Long>() {
@Override
public double estimate(Long thing) {
return thing;
}
};
List<RecommendedItem> topItems = TopItems.getTopItems(10, possibleItemIds, null, estimator);
int gold = 99;
for (RecommendedItem topItem : topItems) {
assertEquals(gold, topItem.getItemID());
assertEquals(gold--, topItem.getValue(), 0.01);
}
}
@Test
public void testTopItemsRandom() throws Exception {
long[] ids = new long[100];
for (int i = 0; i < 100; i++) {
ids[i] = i;
}
LongPrimitiveIterator possibleItemIds = new LongPrimitiveArrayIterator(ids);
final Random random = RandomUtils.getRandom();
TopItems.Estimator<Long> estimator =
new TopItems.Estimator<Long>() {
@Override
public double estimate(Long thing) {
return random.nextDouble();
}
};
List<RecommendedItem> topItems = TopItems.getTopItems(10, possibleItemIds, null, estimator);
assertEquals(10, topItems.size());
double last = 2.0;
for (RecommendedItem topItem : topItems) {
assertTrue(topItem.getValue() <= last);
last = topItem.getItemID();
}
}