/*
* 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.baseline;
import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
import it.unimi.dsi.fastutil.longs.LongSet;
import it.unimi.dsi.fastutil.longs.LongSets;
import org.grouplens.lenskit.ItemScorer;
import org.grouplens.lenskit.basic.AbstractItemScorer;
import org.grouplens.lenskit.symbols.TypedSymbol;
import org.grouplens.lenskit.vectors.MutableSparseVector;
import org.grouplens.lenskit.vectors.VectorEntry;
import javax.annotation.Nonnull;
import javax.inject.Inject;
/**
* Item scorer that combines a primary scorer with a baseline. This scorer is comprised of two
* other scorers, a primary scorer and a baseline scorer. It first scores items using the primary
* scorer, and then consults the baseline scorer for any items that the primary scorer could not
* score.
*
* @author <a href="http://www.grouplens.org">GroupLens Research</a>
*/
public class FallbackItemScorer extends AbstractItemScorer {
public static final TypedSymbol<ScoreSource> SCORE_SOURCE_SYMBOL =
TypedSymbol.of(ScoreSource.class, "org.grouplens.lenskit.baseline.ScoreSource");
private final ItemScorer primaryScorer;
private final ItemScorer baselineScorer;
@Inject
public FallbackItemScorer(@PrimaryScorer ItemScorer primary,
@BaselineScorer ItemScorer baseline) {
primaryScorer = primary;
baselineScorer = baseline;
}
@Override
public void score(long user, @Nonnull MutableSparseVector output) {
primaryScorer.score(user, output);
LongSet fallbackKeys = LongSets.EMPTY_SET;
if (output.size() != output.keyDomain().size()) {
fallbackKeys = output.unsetKeySet();
MutableSparseVector blpreds = MutableSparseVector.create(fallbackKeys);
baselineScorer.score(user, blpreds);
output.set(blpreds);
}
// FIXME Make this faster
Long2ObjectMap<ScoreSource> chan = output.getOrAddChannel(SCORE_SOURCE_SYMBOL);
for (VectorEntry e: output) {
long key = e.getKey();
ScoreSource source = ScoreSource.PRIMARY;
if (fallbackKeys.contains(key)) {
source = ScoreSource.BASELINE;
}
chan.put(key, source);
}
}
/**
* Get the primary scorer from this item scorer.
* @return The scorer's primary scorer.
* @see PrimaryScorer
*/
@Nonnull
public ItemScorer getPrimaryScorer() {
return primaryScorer;
}
/**
* Get the baseline scorer from this item scorer.
* @return The scorer's baseline scorer.
* @see BaselineScorer
*/
@Nonnull
public ItemScorer getBaselineScorer() {
return baselineScorer;
}
}