org.codelibs.elasticsearch.taste.common.FullRunningAverage Maven / Gradle / Ivy
/**
* 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.codelibs.elasticsearch.taste.common;
import java.io.Serializable;
/**
*
* A simple class that can keep track of a running average of a series of numbers. One can add to or remove
* from the series, as well as update a datum in the series. The class does not actually keep track of the
* series of values, just its running average, so it doesn't even matter if you remove/change a value that
* wasn't added.
*
*/
public class FullRunningAverage implements RunningAverage, Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private int count;
private double average;
public FullRunningAverage() {
this(0, Double.NaN);
}
public FullRunningAverage(final int count, final double average) {
this.count = count;
this.average = average;
}
/**
* @param datum
* new item to add to the running average
*/
@Override
public synchronized void addDatum(final double datum) {
if (++count == 1) {
average = datum;
} else {
average = average * (count - 1) / count + datum / count;
}
}
/**
* @param datum
* item to remove to the running average
* @throws IllegalStateException
* if count is 0
*/
@Override
public synchronized void removeDatum(final double datum) {
if (count == 0) {
throw new IllegalStateException();
}
if (--count == 0) {
average = Double.NaN;
} else {
average = average * (count + 1) / count - datum / count;
}
}
/**
* @param delta
* amount by which to change a datum in the running average
* @throws IllegalStateException
* if count is 0
*/
@Override
public synchronized void changeDatum(final double delta) {
if (count == 0) {
throw new IllegalStateException();
}
average += delta / count;
}
@Override
public synchronized int getCount() {
return count;
}
@Override
public synchronized double getAverage() {
return average;
}
@Override
public RunningAverage inverse() {
return new InvertedRunningAverage(this);
}
@Override
public synchronized String toString() {
return String.valueOf(average);
}
}