/*
* 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.basic;
import it.unimi.dsi.fastutil.longs.LongLists;
import org.grouplens.lenskit.ItemScorer;
import org.grouplens.lenskit.vectors.MutableSparseVector;
import org.grouplens.lenskit.vectors.SparseVector;
import javax.annotation.Nonnull;
import java.util.Collection;
/**
* Base class to make item scorers easier to implement. Delegates all score methods to
* {@link #score(long, MutableSparseVector)}.
*
* @author <a href="http://www.grouplens.org">GroupLens Research</a>
*/
public abstract class AbstractItemScorer implements ItemScorer {
/**
* {@inheritDoc}
* <p>Delegates to {@link #score(long, MutableSparseVector)}.
*/
@Nonnull
@Override
public SparseVector score(long user, @Nonnull Collection<Long> items) {
MutableSparseVector scores = MutableSparseVector.create(items);
score(user, scores);
// FIXME Create a more efficient way of "releasing" mutable sparse vectors
return scores.freeze();
}
/**
* {@inheritDoc}
* <p>Delegates to {@link #score(long, Collection)}.
*/
@Override
public double score(long user, long item) {
SparseVector v = score(user, LongLists.singleton(item));
return v.get(item, Double.NaN);
}
}