/**
* Creates a new {@link GenericDataModel} from the given users (and their preferences). This
* {@link DataModel} retains all this information in memory and is effectively immutable.
*
* @param userData users to include
* @param timestamps optionally, provided timestamps of preferences as milliseconds since the
* epoch. User IDs are mapped to maps of item IDs to Long timestamps.
*/
public GenericBooleanPrefDataModel(
FastByIDMap<FastIDSet> userData, FastByIDMap<FastByIDMap<Long>> timestamps) {
Preconditions.checkArgument(userData != null, "userData is null");
this.preferenceFromUsers = userData;
this.preferenceForItems = new FastByIDMap<>();
FastIDSet itemIDSet = new FastIDSet();
for (Map.Entry<Long, FastIDSet> entry : preferenceFromUsers.entrySet()) {
long userID = entry.getKey();
FastIDSet itemIDs = entry.getValue();
itemIDSet.addAll(itemIDs);
LongPrimitiveIterator it = itemIDs.iterator();
while (it.hasNext()) {
long itemID = it.nextLong();
FastIDSet userIDs = preferenceForItems.get(itemID);
if (userIDs == null) {
userIDs = new FastIDSet(2);
preferenceForItems.put(itemID, userIDs);
}
userIDs.add(userID);
}
}
this.itemIDs = itemIDSet.toArray();
itemIDSet = null; // Might help GC -- this is big
Arrays.sort(itemIDs);
this.userIDs = new long[userData.size()];
int i = 0;
LongPrimitiveIterator it = userData.keySetIterator();
while (it.hasNext()) {
userIDs[i++] = it.next();
}
Arrays.sort(userIDs);
this.timestamps = timestamps;
}
