JavaStringBenchmark.java

package org.qwwdfsad.benchmarks;

import org.openjdk.jmh.annotations.*;

import java.util.concurrent.TimeUnit;
import java.util.stream.IntStream;

/**
 * @author Tolstopyatov Vsevolod
 * @since 01/10/16
 */
@Fork(value = 1) //jvmArgsAppend = arrayOf("-XX:TieredStopAtLevel=1"))
@Measurement(iterations = 10)
@Warmup(iterations = 10)
@State(Scope.Benchmark)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class JavaStringBenchmark {

  @Param({"5", "10", "25", "50", "100"})
  int stringLength;
  String string;

  @Setup
  public void init() {
    string = IntStream.range(0, stringLength)
      .map(i -> 'a' + (i % ('z' - 'a' + 1)))
      .collect(StringBuilder::new,
        StringBuilder::appendCodePoint, StringBuilder::append)
      .toString();
  }

  @Benchmark
  public int charAt() {
    String cs = string;
    for (int i = 0; i < cs.length(); i++) {
      if (cs.charAt(i) == '|') {
        return 1;
      }
    }

    return 0;
  }
}

results.txt

Unpatched, C2:
Benchmark                   (stringLength)  Mode  Cnt   Score   Error  Units
JavaStringBenchmark.charAt               5  avgt   10   4.291 ? 0.025  ns/op
JavaStringBenchmark.charAt              10  avgt   10   5.812 ? 0.110  ns/op
JavaStringBenchmark.charAt              25  avgt   10   8.171 ? 0.038  ns/op
JavaStringBenchmark.charAt              50  avgt   10  12.595 ? 0.221  ns/op
JavaStringBenchmark.charAt             100  avgt   10  20.174 ? 0.673  ns/op
StringBenchmark.charAt                   5  avgt   10   6.297 ? 0.007  ns/op
StringBenchmark.charAt                  10  avgt   10   6.156 ? 0.041  ns/op
StringBenchmark.charAt                  25  avgt   10  10.142 ? 0.023  ns/op
StringBenchmark.charAt                  50  avgt   10  12.668 ? 0.019  ns/op
StringBenchmark.charAt                 100  avgt   10  20.199 ? 0.024  ns/op
StringBenchmark.string                   5  avgt   10   6.666 ? 0.029  ns/op
StringBenchmark.string                  10  avgt   10   9.391 ? 0.070  ns/op
StringBenchmark.string                  25  avgt   10  11.625 ? 0.344  ns/op
StringBenchmark.string                  50  avgt   10  17.167 ? 0.211  ns/op
StringBenchmark.string                 100  avgt   10  28.717 ? 0.068  ns/op

Unpatched, C1:
Benchmark                   (stringLength)  Mode  Cnt    Score   Error  Units
JavaStringBenchmark.charAt               5  avgt   10    6.547 ? 0.003  ns/op
JavaStringBenchmark.charAt              10  avgt   10   10.072 ? 0.009  ns/op
JavaStringBenchmark.charAt              25  avgt   10   28.487 ? 1.721  ns/op
JavaStringBenchmark.charAt              50  avgt   10   49.782 ? 0.069  ns/op
JavaStringBenchmark.charAt             100  avgt   10   88.735 ? 1.999  ns/op
StringBenchmark.charAt                   5  avgt   10    6.643 ? 0.014  ns/op
StringBenchmark.charAt                  10  avgt   10    9.885 ? 0.103  ns/op
StringBenchmark.charAt                  25  avgt   10   27.667 ? 0.233  ns/op
StringBenchmark.charAt                  50  avgt   10   44.377 ? 0.126  ns/op
StringBenchmark.charAt                 100  avgt   10   76.319 ? 0.755  ns/op
StringBenchmark.string                   5  avgt   10   29.300 ? 0.092  ns/op
StringBenchmark.string                  10  avgt   10   51.920 ? 0.080  ns/op
StringBenchmark.string                  25  avgt   10  129.637 ? 0.234  ns/op
StringBenchmark.string                  50  avgt   10  243.009 ? 0.499  ns/op
StringBenchmark.string                 100  avgt   10  469.338 ? 0.675  ns/op



Patched C2:
Benchmark                   (stringLength)  Mode  Cnt   Score   Error  Units
JavaStringBenchmark.charAt               5  avgt   10   4.306 ? 0.065  ns/op
JavaStringBenchmark.charAt              10  avgt   10   6.264 ? 0.928  ns/op
JavaStringBenchmark.charAt              25  avgt   10   8.184 ? 0.018  ns/op
JavaStringBenchmark.charAt              50  avgt   10  12.562 ? 0.050  ns/op
JavaStringBenchmark.charAt             100  avgt   10  19.847 ? 0.041  ns/op
StringBenchmark.charAt                   5  avgt   10   6.304 ? 0.035  ns/op
StringBenchmark.charAt                  10  avgt   10   6.148 ? 0.012  ns/op
StringBenchmark.charAt                  25  avgt   10  10.143 ? 0.063  ns/op
StringBenchmark.charAt                  50  avgt   10  12.681 ? 0.066  ns/op
StringBenchmark.charAt                 100  avgt   10  20.209 ? 0.041  ns/op
StringBenchmark.string                   5  avgt   10   4.590 ? 0.085  ns/op
StringBenchmark.string                  10  avgt   10   5.802 ? 0.009  ns/op
StringBenchmark.string                  25  avgt   10   8.362 ? 0.125  ns/op
StringBenchmark.string                  50  avgt   10  12.628 ? 0.027  ns/op
StringBenchmark.string                 100  avgt   10  19.993 ? 0.045  ns/op

Patched C1:
Benchmark                   (stringLength)  Mode  Cnt   Score   Error  Units
JavaStringBenchmark.charAt               5  avgt   10   6.551 ? 0.006  ns/op
JavaStringBenchmark.charAt              10  avgt   10  10.061 ? 0.005  ns/op
JavaStringBenchmark.charAt              25  avgt   10  28.540 ? 1.098  ns/op
JavaStringBenchmark.charAt              50  avgt   10  49.835 ? 0.169  ns/op
JavaStringBenchmark.charAt             100  avgt   10  87.446 ? 0.072  ns/op
StringBenchmark.charAt                   5  avgt   10   6.668 ? 0.029  ns/op
StringBenchmark.charAt                  10  avgt   10   9.835 ? 0.018  ns/op
StringBenchmark.charAt                  25  avgt   10  27.941 ? 1.341  ns/op
StringBenchmark.charAt                  50  avgt   10  44.641 ? 0.893  ns/op
StringBenchmark.charAt                 100  avgt   10  75.886 ? 0.043  ns/op
StringBenchmark.string                   5  avgt   10   6.350 ? 0.007  ns/op
StringBenchmark.string                  10  avgt   10   9.815 ? 0.003  ns/op
StringBenchmark.string                  25  avgt   10  27.527 ? 0.330  ns/op
StringBenchmark.string                  50  avgt   10  42.557 ? 0.041  ns/op
StringBenchmark.string                 100  avgt   10  73.943 ? 0.042  ns/op

StringBenchmark.kt

package org.qwwdfsad.benchmarks

import org.openjdk.jmh.annotations.*
import java.util.concurrent.TimeUnit

/**
 * @author Tolstopyatov Vsevolod
 * @since 28/09/16
 */
@Fork(value = 1) //jvmArgsAppend = arrayOf("-XX:TieredStopAtLevel=1"))
@Measurement(iterations = 10)
@Warmup(iterations = 10)
@State(Scope.Benchmark)
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
open class StringBenchmark() {

    @Param("5", "10", "25", "50", "100")
    var stringLength: Int = 0
    var string: String = ""


    @Setup
    fun init() {
        string = (0 until stringLength).map { 'a' + (it % ('z' - 'a' + 1)) }.joinToString("", "", "")
    }

    @Benchmark
    fun string(): Int {
        val cs = string
        for (c in cs) {
            // Dead branch, trick DCE without BH#consume
            if (c == '|') {
                return 1
            }
        }

        return 0
    }

    @Benchmark
    fun charAt(): Int {
        val cs = string
        for (i in 0..cs.length - 1) {
            // Dead branch, trick DCE without BH#consume
            if (cs[i] == '|') {
                return 1
            }
        }

        return 0
    }
}