Java tutorial
/* * 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.jackrabbit.oak.commons.benchmark; import java.util.concurrent.TimeUnit; import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics; /** * Poor man's micro benchmark suite. * <p> * Implementations of {@link Benchmark} are executed by the {@link #run(Benchmark)} method. * Execution consists of a warm up phase followed by the actual benchmark run. */ public final class MicroBenchmark { private MicroBenchmark() { } /** * Benchmark base class. */ public abstract static class Benchmark { /** * The benchmark runner calls this method first and exactly once by for setting up * the test fixture. */ public void setup() throws Exception { } /** * The benchmark runner calls the method before every call to the {@code run} * method for setting the scope of the subsequent call to {@code run}. */ public void beforeRun() throws Exception { } /** * The benchmark runner calls this method a number of times to measure its * runtime performance. */ public abstract void run() throws Exception; /** * The benchmark runner calls the method after every call to the {@code run} * method for tearing down the scope of the previous call to {@code run}. */ public void afterRun() throws Exception { } /** * The benchmark runner calls this method exactly once and only if the benchmark * did not result in an error. This default implementation tabulates * the percentiles of the gathered test statistics. */ public void result(DescriptiveStatistics statistics) { System.out.println(this); if (statistics.getN() > 0) { System.out.format("%6s %6s %6s %6s %6s %6s %6s %6s%n", "min", "10%", "50%", "90%", "max", "mean", "stdev", "N"); System.out.format("%6.0f %6.0f %6.0f %6.0f %6.0f %6.0f %6.0f %6d%n", statistics.getMin() / 1000000, statistics.getPercentile(10.0) / 1000000, statistics.getPercentile(50.0) / 1000000, statistics.getPercentile(90.0) / 1000000, statistics.getMax() / 1000000, statistics.getMean() / 1000000, statistics.getStandardDeviation() / 1000000, statistics.getN()); } else { System.out.println("No results"); } } /** * The benchmark runner calls this method last and exactly once for tearing down * the test fixture. */ public void tearDown() throws Exception { } } /** * Run a {@code benchmark} * @param benchmark * @throws Exception */ public static void run(Benchmark benchmark) throws Exception { benchmark.setup(); try { // Warm up runTest(benchmark); // Run the test benchmark.result(runTest(benchmark)); } finally { benchmark.tearDown(); } } private static DescriptiveStatistics runTest(Benchmark benchmark) throws Exception { final DescriptiveStatistics statistics = new DescriptiveStatistics(); long runtimeEnd = System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(60); while (System.currentTimeMillis() < runtimeEnd) { statistics.addValue(execute(benchmark)); } return statistics; } private static double execute(Benchmark benchmark) throws Exception { benchmark.beforeRun(); try { long start = System.nanoTime(); benchmark.run(); return System.nanoTime() - start; } finally { benchmark.afterRun(); } } }