org.openjdk.jmh.samples.JMHSample_26_BatchSize Maven / Gradle / Ivy
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package org.openjdk.jmh.samples;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.GenerateMicroBenchmark;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;
import java.util.LinkedList;
import java.util.List;
@State(Scope.Thread)
public class JMHSample_26_BatchSize {
/*
* Sometimes you need to evaluate operation which doesn't have
* the steady state. The cost of a benchmarked operation may
* significantly vary from invocation to invocation.
*
* In this case, using the timed measurements is not a good idea,
* and the only acceptable benchmark mode is a single shot. On the
* other hand, the operation may be too small for reliable single
* shot measurement.
*
* We can use "batch size" parameter to describe the number of
* benchmark calls to do per one invocation without looping the method
* manually and protect from problems described in JMHSample_11_Loops.
*/
/*
* Suppose we want to measure insertion in the middle of the list.
*/
List list = new LinkedList();
@GenerateMicroBenchmark
@Warmup(iterations = 5, time = 1)
@Measurement(iterations = 5, time = 1)
@BenchmarkMode(Mode.AverageTime)
public List measureWrong_1() {
list.add(list.size() / 2, "something");
return list;
}
@GenerateMicroBenchmark
@Warmup(iterations = 5, time = 5)
@Measurement(iterations = 5, time = 5)
@BenchmarkMode(Mode.AverageTime)
public List measureWrong_5() {
list.add(list.size() / 2, "something");
return list;
}
/*
* This is what you do with JMH.
*/
@GenerateMicroBenchmark
@Warmup(iterations = 5, batchSize = 5000)
@Measurement(iterations = 5, batchSize = 5000)
@BenchmarkMode(Mode.SingleShotTime)
public List measureRight() {
list.add(list.size() / 2, "something");
return list;
}
@Setup(Level.Iteration)
public void setup(){
list.clear();
}
/*
* ============================== HOW TO RUN THIS TEST: ====================================
*
* You can see completely different results for measureWrong_1 and measureWrong_5; this
* is because the workload has no steady state. The result of the workload is dependent
* on the measurement time. measureRight does not have this drawback, because it measures
* the N invocations of the test method and measures it's time.
*
* We measure batch of 5000 invocations and consider the batch as the single operation.
*
* You can run this test:
*
* a) Via the command line:
* $ mvn clean install
* $ java -jar target/microbenchmarks.jar ".*JMHSample_26.*" -f 1
*
* b) Via the Java API:
*/
public static void main(String[] args) throws RunnerException {
Options opt = new OptionsBuilder()
.include(".*" + JMHSample_26_BatchSize.class.getSimpleName() + ".*")
.forks(1)
.build();
new Runner(opt).run();
}
}