/**
* 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.recommender;
import java.io.Serializable;
import java.util.Comparator;
import org.apache.mahout.cf.taste.recommender.IDRescorer;
import org.apache.mahout.cf.taste.recommender.RecommendedItem;
/**
* <p>
* Defines ordering on {@link RecommendedItem} by the rescored value of the recommendations' estimated
* preference value, from high to low.
* </p>
*/
final class ByRescoreComparator implements Comparator<RecommendedItem>, Serializable {
private final IDRescorer rescorer;
ByRescoreComparator(IDRescorer rescorer) {
this.rescorer = rescorer;
}
@Override
public int compare(RecommendedItem o1, RecommendedItem o2) {
double rescored1;
double rescored2;
if (rescorer == null) {
rescored1 = o1.getValue();
rescored2 = o2.getValue();
} else {
rescored1 = rescorer.rescore(o1.getItemID(), o1.getValue());
rescored2 = rescorer.rescore(o2.getItemID(), o2.getValue());
}
if (rescored1 < rescored2) {
return 1;
} else if (rescored1 > rescored2) {
return -1;
} else {
return 0;
}
}
@Override
public String toString() {
return "ByRescoreComparator[rescorer:" + rescorer + ']';
}
}