com.fillumina.performance.producer.timer.PerformanceTimer Maven / Gradle / Ivy

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Configurable tool to easily compare performances of different code snippets and to take performance telemetry of a running application.
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package com.fillumina.performance.producer.timer;

import com.fillumina.performance.producer.LoopPerformances;
import com.fillumina.performance.producer.LoopPerformancesHolder;

/**
 * This is the base class for all the performance tests. It delegates
 * the test execution to a given {@link PerformanceExecutor} and can be
 * instrumented to execute tests in a specific way (i.e. repeat the test
 * until a target results stability is reached).
 *
 * 
 * WARNING:
 * Performance tests are subject to many factors that may
 * hinder their accuracy:
 * 

 * System load;
 * 
CPUs heat level;
 * 
JDK version and brand;
 * 
Garbage collector
 * 
 * So if a test fails randomly try to increase the iteration number,
 * relax the tolerance and close demanding background processes.
 *
 * @author Francesco Illuminati
 */
public class PerformanceTimer
        extends AbstractPerformanceTimer {
    private static final long serialVersionUID = 1L;

    private final PerformanceExecutor executor;

    /**
     * Executes the tests using the specified executor.
     */
    public PerformanceTimer(final PerformanceExecutor executor) {
        this.executor = executor;
    }

    /**
     * Run exactly the same tests as {@link #execute()} without taking
     * any statistics. It's used to warm up the JVM into compiling the code.
     */
    @Override
    public PerformanceTimer warmup() {
        final LoopPerformances lp = executeTests();
        // this check avoids JVM cutting out dead code
        if (lp.getStatistics().min() < 0) {
            throw new AssertionError("elapsed time cannot be negative");
        }
        return this;
    }

    /**
     * Executes the performance test.
     * Instead of specifying the number of iterations
     * (with {@link #setIterations(long) }) and than {@link #execute()}
     * you may use the shorter (and recommended) {@link #iterate(int) }.
     * 
     * Hint:It may be convenient to run a small amount of iterations
     * before the actual test
     * to warm up the JVM and let it do the necessary optimizations
     * up front (see {@link AbstractPerformanceTimer#warmup(int) }). At any
     * rate if you use
     * {@link com.fillumina.performance.producer.progression.AutoProgressionPerformanceInstrumenter}
     * the value will be found automatically.
     *
     * @see AbstractPerformanceTimer#iterate(int)
     * @see AbstractPerformanceTimer#warmup(int)
     */
    @Override
    public LoopPerformancesHolder execute() {
        LoopPerformances loopPerformances = executeTests();
        // makes loopPerformances available to consumers
        consume(null, loopPerformances);
        return new LoopPerformancesHolder(loopPerformances);
    }

    private LoopPerformances executeTests() {
        final long iterations = getIterations();
        if (iterations <= 0) {
            throw new IllegalStateException("invalid iteration number, you should " +
                    "have called setIteration() before calling execute() or " +
                    "directly iterate() or instrument this object with " +
                    "instrumentBy()");
        }
        initTests();
        final LoopPerformances loopPerformances =
                executor.executeTests(iterations, getTests());
        return loopPerformances;
    }
}