/**
* 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.neighborhood;
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.common.Cache;
import org.apache.mahout.cf.taste.impl.common.RefreshHelper;
import org.apache.mahout.cf.taste.impl.common.Retriever;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.neighborhood.UserNeighborhood;
import com.google.common.base.Preconditions;
/** A caching wrapper around an underlying {@link UserNeighborhood} implementation. */
public final class CachingUserNeighborhood implements UserNeighborhood {
private final UserNeighborhood neighborhood;
private final Cache<Long,long[]> neighborhoodCache;
public CachingUserNeighborhood(UserNeighborhood neighborhood, DataModel dataModel) throws TasteException {
Preconditions.checkArgument(neighborhood != null, "neighborhood is null");
this.neighborhood = neighborhood;
int maxCacheSize = dataModel.getNumUsers(); // just a dumb heuristic for sizing
this.neighborhoodCache = new Cache<Long,long[]>(new NeighborhoodRetriever(neighborhood), maxCacheSize);
}
@Override
public long[] getUserNeighborhood(long userID) throws TasteException {
return neighborhoodCache.get(userID);
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
neighborhoodCache.clear();
alreadyRefreshed = RefreshHelper.buildRefreshed(alreadyRefreshed);
RefreshHelper.maybeRefresh(alreadyRefreshed, neighborhood);
}
private static final class NeighborhoodRetriever implements Retriever<Long,long[]> {
private final UserNeighborhood neighborhood;
private NeighborhoodRetriever(UserNeighborhood neighborhood) {
this.neighborhood = neighborhood;
}
@Override
public long[] get(Long key) throws TasteException {
return neighborhood.getUserNeighborhood(key);
}
}
}