cz.cuni.mff.d3s.spl.data.BenchmarkRunSummary.java Source code

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Here is the source code for cz.cuni.mff.d3s.spl.data.BenchmarkRunSummary.java

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/*
 * Copyright 2015 Charles University in Prague
 * Copyright 2015 Vojtech Horky
 * 
 * Licensed 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 cz.cuni.mff.d3s.spl.data;

import org.apache.commons.math3.stat.descriptive.moment.Mean;
import org.apache.commons.math3.stat.descriptive.moment.Variance;

/** Statistical summary of a benchmark run.
 * 
 * <p>
 * This class aggregates the whole benchmark run into few values such as
 * mean, variance or number of data samples.
 * 
 * <p>
 * This class is in essence immutable but it uses caching to improve
 * performance (hopefully).
 * Also, it makes copy of the original benchmark run and the changes in
 * the original run are not taken into account when user retrieves the values.
 */
public class BenchmarkRunSummary {
    private final double[] data;
    private Double cacheMean = null;
    private Double cacheVariance = null;

    /** Create a new summary from a benchmark run.
     * 
     * <p>
     * The data from the given run are copied and further changes to the
     * run are ignored when the statistical values are retrived. 
     * 
     * @param run Benchmark run from which to compute the summary.
     */
    public BenchmarkRunSummary(BenchmarkRun run) {
        synchronized (run) {
            data = new double[run.getSampleCount()];
            for (int i = 0; i < data.length; i++) {
                data[i] = run.getSample(i);
            }
        }
    }

    /** Compute artihmetic mean of the samples.
     * 
     * @return Arithmetic mean of the data in the original benchmark run.
     */
    public synchronized double getMean() {
        if (cacheMean == null) {
            Mean mean = new Mean();
            cacheMean = mean.evaluate(data);
        }
        return cacheMean;
    }

    /** Compute variance of the samples.
     * 
     * @return Variance of the data in the original benchmark run.
     */
    public synchronized double getVariance() {
        if (cacheVariance == null) {
            Variance mean = new Variance();
            cacheVariance = mean.evaluate(data);
        }
        return cacheVariance;
    }

    /** Tell number of data samples.
     * 
     * @return Number of samples in the original benchmark run.
     */
    public long getSize() {
        return data.length;
    }
}