/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.cf.taste.impl.eval;
import com.google.common.collect.Lists;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.eval.RelevantItemsDataSplitter;
import org.apache.mahout.cf.taste.impl.common.FastByIDMap;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.impl.model.GenericUserPreferenceArray;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.model.Preference;
import org.apache.mahout.cf.taste.model.PreferenceArray;
import java.util.Iterator;
import java.util.List;
/**
* Picks relevant items to be those with the strongest preference, and
* includes the other users' preferences in full.
*/
public final class GenericRelevantItemsDataSplitter implements RelevantItemsDataSplitter {
@Override
public FastIDSet getRelevantItemsIDs(long userID,
int at,
double relevanceThreshold,
DataModel dataModel) throws TasteException {
PreferenceArray prefs = dataModel.getPreferencesFromUser(userID);
FastIDSet relevantItemIDs = new FastIDSet(at);
prefs.sortByValueReversed();
for (int i = 0; i < prefs.length() && relevantItemIDs.size() < at; i++) {
if (prefs.getValue(i) >= relevanceThreshold) {
relevantItemIDs.add(prefs.getItemID(i));
}
}
return relevantItemIDs;
}
@Override
public void processOtherUser(long userID,
FastIDSet relevantItemIDs,
FastByIDMap<PreferenceArray> trainingUsers,
long otherUserID,
DataModel dataModel) throws TasteException {
PreferenceArray prefs2Array = dataModel.getPreferencesFromUser(otherUserID);
// If we're dealing with the very user that we're evaluating for precision/recall,
if (userID == otherUserID) {
// then must remove all the test IDs, the "relevant" item IDs
List<Preference> prefs2 = Lists.newArrayListWithCapacity(prefs2Array.length());
for (Preference pref : prefs2Array) {
prefs2.add(pref);
}
for (Iterator<Preference> iterator = prefs2.iterator(); iterator.hasNext();) {
Preference pref = iterator.next();
if (relevantItemIDs.contains(pref.getItemID())) {
iterator.remove();
}
}
if (!prefs2.isEmpty()) {
trainingUsers.put(otherUserID, new GenericUserPreferenceArray(prefs2));
}
} else {
// otherwise just add all those other user's prefs
trainingUsers.put(otherUserID, prefs2Array);
}
}
}