/**
* 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.hadoop;
import org.apache.mahout.cf.taste.impl.TasteTestCase;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
import org.apache.mahout.common.MahoutTestCase;
import org.junit.Test;
import java.util.List;
public class TopItemsQueueTest extends TasteTestCase {
@Test
public void topK() {
float[] ratings = {0.5f, 0.6f, 0.7f, 2.0f, 0.0f};
List<RecommendedItem> topItems = findTop(ratings, 2);
assertEquals(2, topItems.size());
assertEquals(3L, topItems.get(0).getItemID());
assertEquals(2.0f, topItems.get(0).getValue(), MahoutTestCase.EPSILON);
assertEquals(2L, topItems.get(1).getItemID());
assertEquals(0.7f, topItems.get(1).getValue(), MahoutTestCase.EPSILON);
}
@Test
public void topKInputSmallerThanK() {
float[] ratings = {0.7f, 2.0f};
List<RecommendedItem> topItems = findTop(ratings, 3);
assertEquals(2, topItems.size());
assertEquals(1L, topItems.get(0).getItemID());
assertEquals(2.0f, topItems.get(0).getValue(), MahoutTestCase.EPSILON);
assertEquals(0L, topItems.get(1).getItemID());
assertEquals(0.7f, topItems.get(1).getValue(), MahoutTestCase.EPSILON);
}
private static List<RecommendedItem> findTop(float[] ratings, int k) {
TopItemsQueue queue = new TopItemsQueue(k);
for (int item = 0; item < ratings.length; item++) {
MutableRecommendedItem top = queue.top();
if (ratings[item] > top.getValue()) {
top.set(item, ratings[item]);
queue.updateTop();
}
}
return queue.getTopItems();
}
}