/*
* 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.LongArrayList;
import it.unimi.dsi.fastutil.longs.LongList;
import org.grouplens.lenskit.ItemScorer;
import org.grouplens.lenskit.RatingPredictor;
import org.grouplens.lenskit.baseline.FallbackItemScorer;
import org.grouplens.lenskit.baseline.ScoreSource;
import org.grouplens.lenskit.data.pref.PreferenceDomain;
import org.grouplens.lenskit.vectors.MutableSparseVector;
import org.junit.Before;
import org.junit.Test;
import static org.hamcrest.Matchers.closeTo;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.nullValue;
import static org.junit.Assert.assertThat;
public class SimpleRatingPredictorTest {
RatingPredictor pred;
RatingPredictor unclamped;
private static final double EPSILON = 1.0e-5;
@Before
public void setUp() throws Exception {
ItemScorer scorer = PrecomputedItemScorer.newBuilder()
.addScore(40, 1, 4.0)
.addScore(40, 2, 5.5)
.addScore(40, 3, -1)
.build();
PreferenceDomain domain = new PreferenceDomain(1, 5, 1);
pred = new SimpleRatingPredictor(scorer, null, domain);
unclamped = new SimpleRatingPredictor(scorer, null, null);
}
@Test
public void testBasicPredict() {
assertThat(pred.predict(40, 1),
closeTo(4.0, EPSILON));
}
@Test
public void testBasicPredictHigh() {
assertThat(pred.predict(40, 2),
closeTo(5.0, EPSILON));
}
@Test
public void testBasicPredictLow() {
assertThat(pred.predict(40, 3),
closeTo(1.0, EPSILON));
}
@Test
public void testUnclampedPredict() {
assertThat(unclamped.predict(40, 1),
closeTo(4.0, EPSILON));
}
@Test
public void testUnclampedPredictHigh() {
assertThat(unclamped.predict(40, 2),
closeTo(5.5, EPSILON));
}
@Test
public void testUnclampedPredictLow() {
assertThat(unclamped.predict(40, 3),
closeTo(-1, EPSILON));
}
@Test
public void testVectorPredict() {
LongList keys = new LongArrayList();
keys.add(1);
keys.add(2);
keys.add(3);
keys.add(4);
MutableSparseVector v = MutableSparseVector.create(keys);
pred.predict(40, v);
assertThat(v.get(1),
closeTo(4.0, EPSILON));
assertThat(v.get(2),
closeTo(5.0, EPSILON));
assertThat(v.get(3),
closeTo(1.0, EPSILON));
assertThat(v.get(4, 0.0), closeTo(0.0, EPSILON));
assertThat(v.getChannel(SimpleRatingPredictor.PREDICTION_SOURCE_SYMBOL).get(1),
equalTo(ScoreSource.PRIMARY));
}
/**
* Make sure that score sources are routed properly through the rating predictor and
* fallback scorer.
*/
@Test
public void testDoubleFallback() {
ItemScorer primary = PrecomputedItemScorer.newBuilder()
.addScore(42, 1, 3.5)
.build();
ItemScorer base1 = PrecomputedItemScorer.newBuilder()
.addScore(42, 1, 2.5)
.addScore(42, 2, 2.5)
.build();
ItemScorer base2 = PrecomputedItemScorer.newBuilder()
.addScore(42, 1, 3.0)
.addScore(42, 2, 3.0)
.addScore(42, 3, 3.0)
.build();
ItemScorer scorer = new FallbackItemScorer(primary, base1);
RatingPredictor pred = new SimpleRatingPredictor(scorer, base2, null);
MutableSparseVector vec = MutableSparseVector.create(1, 2, 3);
pred.predict(42, vec);
assertThat(vec.size(), equalTo(3));
assertThat(vec.get(1), equalTo(3.5));
assertThat(vec.get(2), equalTo(2.5));
assertThat(vec.get(3), equalTo(3.0));
assertThat(vec.getChannel(FallbackItemScorer.SCORE_SOURCE_SYMBOL).get(1),
equalTo(ScoreSource.PRIMARY));
assertThat(vec.getChannel(FallbackItemScorer.SCORE_SOURCE_SYMBOL).get(2),
equalTo(ScoreSource.BASELINE));
assertThat(vec.getChannel(FallbackItemScorer.SCORE_SOURCE_SYMBOL).get(3),
nullValue());
assertThat(vec.getChannel(SimpleRatingPredictor.PREDICTION_SOURCE_SYMBOL).get(1),
equalTo(ScoreSource.PRIMARY));
assertThat(vec.getChannel(SimpleRatingPredictor.PREDICTION_SOURCE_SYMBOL).get(2),
equalTo(ScoreSource.PRIMARY));
assertThat(vec.getChannel(SimpleRatingPredictor.PREDICTION_SOURCE_SYMBOL).get(3),
equalTo(ScoreSource.BASELINE));
}
}