org.apache.solr.util.stats.Snapshot 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.
*/
/*
* Forked from https://github.com/codahale/metrics
*/
package org.apache.solr.util.stats;
import java.util.Arrays;
import java.util.Collection;
import static java.lang.Math.floor;
/**
* A statistical snapshot of a {@link Snapshot}.
*/
public class Snapshot {
private static final double MEDIAN_Q = 0.5;
private static final double P75_Q = 0.75;
private static final double P95_Q = 0.95;
private static final double P98_Q = 0.98;
private static final double P99_Q = 0.99;
private static final double P999_Q = 0.999;
private final double[] values;
/**
* Create a new {@link Snapshot} with the given values.
*
* @param values an unordered set of values in the sample
*/
public Snapshot(Collection values) {
final Object[] copy = values.toArray();
this.values = new double[copy.length];
for (int i = 0; i < copy.length; i++) {
this.values[i] = (Long) copy[i];
}
Arrays.sort(this.values);
}
/**
* Create a new {@link Snapshot} with the given values.
*
* @param values an unordered set of values in the sample
*/
public Snapshot(double[] values) {
this.values = new double[values.length];
System.arraycopy(values, 0, this.values, 0, values.length);
Arrays.sort(this.values);
}
/**
* Returns the value at the given quantile.
*
* @param quantile a given quantile, in {@code [0..1]}
* @return the value in the distribution at {@code quantile}
*/
public double getValue(double quantile) {
if (quantile < 0.0 || quantile > 1.0) {
throw new IllegalArgumentException(quantile + " is not in [0..1]");
}
if (values.length == 0) {
return 0.0;
}
final double pos = quantile * (values.length + 1);
if (pos < 1) {
return values[0];
}
if (pos >= values.length) {
return values[values.length - 1];
}
final double lower = values[(int) pos - 1];
final double upper = values[(int) pos];
return lower + (pos - floor(pos)) * (upper - lower);
}
/**
* Returns the number of values in the snapshot.
*
* @return the number of values in the snapshot
*/
public int size() {
return values.length;
}
/**
* Returns the median value in the distribution.
*
* @return the median value in the distribution
*/
public double getMedian() {
return getValue(MEDIAN_Q);
}
/**
* Returns the value at the 75th percentile in the distribution.
*
* @return the value at the 75th percentile in the distribution
*/
public double get75thPercentile() {
return getValue(P75_Q);
}
/**
* Returns the value at the 95th percentile in the distribution.
*
* @return the value at the 95th percentile in the distribution
*/
public double get95thPercentile() {
return getValue(P95_Q);
}
/**
* Returns the value at the 98th percentile in the distribution.
*
* @return the value at the 98th percentile in the distribution
*/
public double get98thPercentile() {
return getValue(P98_Q);
}
/**
* Returns the value at the 99th percentile in the distribution.
*
* @return the value at the 99th percentile in the distribution
*/
public double get99thPercentile() {
return getValue(P99_Q);
}
/**
* Returns the value at the 99.9th percentile in the distribution.
*
* @return the value at the 99.9th percentile in the distribution
*/
public double get999thPercentile() {
return getValue(P999_Q);
}
/**
* Returns the entire set of values in the snapshot.
*
* @return the entire set of values in the snapshot
*/
public double[] getValues() {
return Arrays.copyOf(values, values.length);
}
}