/**
* 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.similarity;
import com.google.common.collect.Lists;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.similarity.ItemSimilarity;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
/** <p>Tests {@link GenericItemSimilarity}.</p> */
public final class GenericItemSimilarityTest extends SimilarityTestCase {
@Test
public void testSimple() {
List<GenericItemSimilarity.ItemItemSimilarity> similarities = Lists.newArrayList();
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(1, 2, 0.5));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(2, 1, 0.6));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(1, 1, 0.5));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(1, 3, 0.3));
GenericItemSimilarity itemCorrelation = new GenericItemSimilarity(similarities);
assertEquals(1.0, itemCorrelation.itemSimilarity(1, 1), EPSILON);
assertEquals(0.6, itemCorrelation.itemSimilarity(1, 2), EPSILON);
assertEquals(0.6, itemCorrelation.itemSimilarity(2, 1), EPSILON);
assertEquals(0.3, itemCorrelation.itemSimilarity(1, 3), EPSILON);
assertTrue(Double.isNaN(itemCorrelation.itemSimilarity(3, 4)));
}
@Test
public void testFromCorrelation() throws Exception {
DataModel dataModel = getDataModel(
new long[] {1, 2, 3},
new Double[][] {
{1.0, 2.0},
{2.0, 5.0},
{3.0, 6.0},
});
ItemSimilarity otherSimilarity = new PearsonCorrelationSimilarity(dataModel);
ItemSimilarity itemSimilarity = new GenericItemSimilarity(otherSimilarity, dataModel);
assertCorrelationEquals(1.0, itemSimilarity.itemSimilarity(0, 0));
assertCorrelationEquals(0.960768922830523, itemSimilarity.itemSimilarity(0, 1));
}
@Test
public void testAllSimilaritiesWithoutIndex() throws TasteException {
List<GenericItemSimilarity.ItemItemSimilarity> itemItemSimilarities =
Arrays.asList(new GenericItemSimilarity.ItemItemSimilarity(1L, 2L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(1L, 3L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(2L, 1L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(3L, 5L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(3L, 4L, 0.2));
ItemSimilarity similarity = new GenericItemSimilarity(itemItemSimilarities);
assertTrue(containsExactly(similarity.allSimilarItemIDs(1L), 2L, 3L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(2L), 1L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(3L), 1L, 5L, 4L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(4L), 3L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(5L), 3L));
}
@Test
public void testAllSimilaritiesWithIndex() throws TasteException {
List<GenericItemSimilarity.ItemItemSimilarity> itemItemSimilarities =
Arrays.asList(new GenericItemSimilarity.ItemItemSimilarity(1L, 2L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(1L, 3L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(2L, 1L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(3L, 5L, 0.2),
new GenericItemSimilarity.ItemItemSimilarity(3L, 4L, 0.2));
ItemSimilarity similarity = new GenericItemSimilarity(itemItemSimilarities);
assertTrue(containsExactly(similarity.allSimilarItemIDs(1L), 2L, 3L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(2L), 1L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(3L), 1L, 5L, 4L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(4L), 3L));
assertTrue(containsExactly(similarity.allSimilarItemIDs(5L), 3L));
}
private static boolean containsExactly(long[] allIDs, long... shouldContainID) {
return new FastIDSet(allIDs).intersectionSize(new FastIDSet(shouldContainID)) == shouldContainID.length;
}
}