/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.grouplens.lenskit.data.snapshot;
import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
import it.unimi.dsi.fastutil.longs.Long2ObjectMaps;
import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
import org.grouplens.lenskit.data.pref.IndexedPreference;
import org.grouplens.lenskit.data.pref.Preferences;
import org.grouplens.lenskit.vectors.SparseVector;
import javax.annotation.OverridingMethodsMustInvokeSuper;
import java.util.Collection;
/**
* Base class for implementing preference snapshots.
*/
public abstract class AbstractPreferenceSnapshot implements PreferenceSnapshot {
/**
* The user vector cache.
*/
protected Long2ObjectMap<SparseVector> cache;
/**
* Initialize the snapshot.
*/
public AbstractPreferenceSnapshot() {
cache = Long2ObjectMaps.synchronize(new Long2ObjectOpenHashMap<SparseVector>());
}
@Override
public SparseVector userRatingVector(long userId) {
// FIXME Don't make this so locky
synchronized (cache) {
SparseVector data = cache.get(userId);
if (data != null) {
return data;
} else {
Collection<IndexedPreference> prefs = this.getUserRatings(userId);
data = Preferences.userPreferenceVector(prefs).freeze();
cache.put(userId, data);
return data;
}
}
}
@Override
@OverridingMethodsMustInvokeSuper
public void close() {
cache = null;
}
}