/**
* 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.neighborhood;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.similarity.AbstractItemSimilarity;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.similarity.PreferenceInferrer;
import org.apache.mahout.cf.taste.similarity.UserSimilarity;
import java.util.Collection;
final class DummySimilarity extends AbstractItemSimilarity implements UserSimilarity {
DummySimilarity(DataModel dataModel) {
super(dataModel);
}
@Override
public double userSimilarity(long userID1, long userID2) throws TasteException {
DataModel dataModel = getDataModel();
return 1.0 / (1.0 + Math.abs(dataModel.getPreferencesFromUser(userID1).get(0).getValue()
- dataModel.getPreferencesFromUser(userID2).get(0).getValue()));
}
@Override
public double itemSimilarity(long itemID1, long itemID2) {
// Make up something wacky
return 1.0 / (1.0 + Math.abs(itemID1 - itemID2));
}
@Override
public double[] itemSimilarities(long itemID1, long[] itemID2s) {
int length = itemID2s.length;
double[] result = new double[length];
for (int i = 0; i < length; i++) {
result[i] = itemSimilarity(itemID1, itemID2s[i]);
}
return result;
}
@Override
public void setPreferenceInferrer(PreferenceInferrer inferrer) {
throw new UnsupportedOperationException();
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
// do nothing
}
}