/*
* 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.math;
import java.io.Serializable;
import java.util.Comparator;
/**
* Orders {@link WeightedVector} by {@link WeightedVector#getWeight()}.
*/
public final class WeightedVectorComparator implements Comparator<WeightedVector>, Serializable {
private static final double DOUBLE_EQUALITY_ERROR = 1.0e-8;
@Override
public int compare(WeightedVector a, WeightedVector b) {
if (a == b) {
return 0;
}
double aWeight = a.getWeight();
double bWeight = b.getWeight();
int r = Double.compare(aWeight, bWeight);
if (r != 0 && Math.abs(aWeight - bWeight) >= DOUBLE_EQUALITY_ERROR) {
return r;
}
double diff = a.minus(b).norm(1);
if (diff < 1.0e-12) {
return 0;
}
for (Vector.Element element : a.all()) {
r = Double.compare(element.get(), b.get(element.index()));
if (r != 0) {
return r;
}
}
return 0;
}
}