ExpBenchmark.java

import org.apache.commons.math3.util.FastMath;
import org.openjdk.jmh.annotations.*;
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.Random;
import java.util.concurrent.TimeUnit;
import java.util.function.DoubleUnaryOperator;

/**
 * @author Dmitry Groshev
 * @date 11/08/2014
 */
@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Warmup(iterations = 5)
@Measurement(iterations = 5)
@State(Scope.Benchmark)
public class ExpBenchmark {
  int arrayLen = 1000;

  double[] logValues;
  double[] values;

  @Setup
  public void prepare() {
    logValues = new double[arrayLen];
    final Random gen = new Random(42);
    for (int i = 0; i < arrayLen; i++) {
      logValues[i] = gen.nextDouble();
    }
    transformInPlace(logValues, Math::log);
  }

  public static double[] transform(final double[] values, final DoubleUnaryOperator op) {
    final double[] res = values.clone();
    transformInPlace(res, op);
    return res;
  }

  public static void transformInPlace(final double[] values, final DoubleUnaryOperator op) {
    for (int i = 0; i < values.length; i++) {
      values[i] = op.applyAsDouble(values[i]);
    }
  }

  @Benchmark
  public void jvmMathExpArray() {
    values = transform(logValues, Math::exp);
  }

  @Benchmark
  public void fastMathExpArray() {
    values = transform(logValues, FastMath::exp);
  }


  public static void main(final String[] args) throws RunnerException {
    final Options opts = new OptionsBuilder()
        .include(".*" + ExpBenchmark.class.getSimpleName() + ".*")
        .forks(1)
        .build();

    new Runner(opts).run();
  }

}