/**
* 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.recommender.svd;
import java.util.Collection;
import java.util.concurrent.Callable;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastByIDMap;
import org.apache.mahout.cf.taste.impl.common.LongPrimitiveIterator;
import org.apache.mahout.cf.taste.impl.common.RefreshHelper;
import org.apache.mahout.cf.taste.model.DataModel;
/**
* base class for {@link Factorizer}s, provides ID to index mapping
*/
public abstract class AbstractFactorizer implements Factorizer {
private final DataModel dataModel;
private FastByIDMap<Integer> userIDMapping;
private FastByIDMap<Integer> itemIDMapping;
private final RefreshHelper refreshHelper;
protected AbstractFactorizer(DataModel dataModel) throws TasteException {
this.dataModel = dataModel;
buildMappings();
refreshHelper = new RefreshHelper(new Callable<Object>() {
@Override
public Object call() throws TasteException {
buildMappings();
return null;
}
});
refreshHelper.addDependency(dataModel);
}
private void buildMappings() throws TasteException {
userIDMapping = createIDMapping(dataModel.getNumUsers(), dataModel.getUserIDs());
itemIDMapping = createIDMapping(dataModel.getNumItems(), dataModel.getItemIDs());
}
protected Factorization createFactorization(double[][] userFeatures, double[][] itemFeatures) {
return new Factorization(userIDMapping, itemIDMapping, userFeatures, itemFeatures);
}
protected Integer userIndex(long userID) {
Integer userIndex = userIDMapping.get(userID);
if (userIndex == null) {
userIndex = userIDMapping.size();
userIDMapping.put(userID, userIndex);
}
return userIndex;
}
protected Integer itemIndex(long itemID) {
Integer itemIndex = itemIDMapping.get(itemID);
if (itemIndex == null) {
itemIndex = itemIDMapping.size();
itemIDMapping.put(itemID, itemIndex);
}
return itemIndex;
}
private static FastByIDMap<Integer> createIDMapping(int size, LongPrimitiveIterator idIterator) {
FastByIDMap<Integer> mapping = new FastByIDMap<Integer>(size);
int index = 0;
while (idIterator.hasNext()) {
mapping.put(idIterator.nextLong(), index++);
}
return mapping;
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
refreshHelper.refresh(alreadyRefreshed);
}
}