/**
* 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.example.kddcup.track2;
import java.io.File;
import java.io.IOException;
import java.util.Collection;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.similarity.AbstractItemSimilarity;
import org.apache.mahout.cf.taste.impl.similarity.LogLikelihoodSimilarity;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.similarity.ItemSimilarity;
final class HybridSimilarity extends AbstractItemSimilarity {
private final ItemSimilarity cfSimilarity;
private final ItemSimilarity contentSimilarity;
HybridSimilarity(DataModel dataModel, File dataFileDirectory) throws IOException {
super(dataModel);
cfSimilarity = new LogLikelihoodSimilarity(dataModel);
contentSimilarity = new TrackItemSimilarity(dataFileDirectory);
}
@Override
public double itemSimilarity(long itemID1, long itemID2) throws TasteException {
return contentSimilarity.itemSimilarity(itemID1, itemID2) * cfSimilarity.itemSimilarity(itemID1, itemID2);
}
@Override
public double[] itemSimilarities(long itemID1, long[] itemID2s) throws TasteException {
double[] result = contentSimilarity.itemSimilarities(itemID1, itemID2s);
double[] multipliers = cfSimilarity.itemSimilarities(itemID1, itemID2s);
for (int i = 0; i < result.length; i++) {
result[i] *= multipliers[i];
}
return result;
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
cfSimilarity.refresh(alreadyRefreshed);
}
}