How can I use JMH for Scala benchmarks together with sbt? - scala

Question

I have tried to use jmh together with sbt, but so far I have not managed to set it up properly so that .scala based benchmarks work.
As the combination sbt + .java based benchmarks works, I tried to start from that base.
I am using sbt 0.13.1.
.java based benchmarks using sbt
build.sbt
import AssemblyKeys._
name := "scala-benchmark"
version := "1.0"
scalaVersion := "2.10.3"
scalacOptions += "-deprecation"
libraryDependencies += "org.openjdk.jmh" % "jmh-core" % "0.5.5"
libraryDependencies += "org.openjdk.jmh" % "jmh-java-benchmark-archetype" % "0.5.5"
libraryDependencies += "org.openjdk.jmh" % "jmh-generator-annprocess" % "0.5.5"
libraryDependencies += "org.openjdk.jmh" % "jmh-generator-bytecode" % "0.5.5"
assemblySettings
jarName in assembly := "microbenchmarks.jar"
test in assembly := {}
mainClass in assembly := Some("org.openjdk.jmh.Main")
To get a single "fat" jar at the end, the sbt-assembly plugin is required:
project/assembly.sbt
addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.11.2")
A simple benchmark:
src/main/java/app/benchmark/java/benchmark2/Benchmark2.java
package app.benchmark.java.benchmark2;
import org.openjdk.jmh.annotations.GenerateMicroBenchmark;
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;
public class Benchmark2 {
#GenerateMicroBenchmark
public int run() {
int result = 0;
for (int i = 0; i < 10; i++) {
result += i * i;
}
return result;
}
}
Running sbt assembly gives this output:
$ sbt assembly
[...]
[info] Compiling 2 Scala sources and 2 Java sources to ...
[warn] warning: Supported source version 'RELEASE_6' from annotation processor 'org.openjdk.jmh.generators.GenerateMicroBenchmarkProcessor' less than -source '1.8'
[warn] 1 warning
[info] Including: jmh-java-benchmark-archetype-0.5.5.jar
[info] Including: jmh-generator-bytecode-0.5.5.jar
[info] Including: jopt-simple-4.6.jar
[info] Including: jmh-generator-reflection-0.5.5.jar
[info] Including: jmh-generator-annprocess-0.5.5.jar
[info] Including: asm-4.2.jar
[info] Including: commons-math3-3.2.jar
[info] Including: jmh-core-0.5.5.jar
[info] Including: scala-library.jar
[...]
[info] Packaging /home/scala-2.10/vc/rhaag/scala/scala-benchmark/target/scala-2.10/microbenchmarks.jar ...
and the resulting microbenchmarks.jar contains everything required to run the benchmarks:
$ java -jar target/scala-2.10/microbenchmarks.jar -wi 3 -i 3 -f 1 app.benchmark.java.benchmark2.Benchmark2.run
[...]
Benchmark Mode Samples Mean Mean error Units
a.b.j.b.Benchmark2.run thrpt 3 607555,968 70243,275 ops/ms
So far so good.
Scala benchmarks using sbt
From that base I tried to switch to .scala based benchmarks:
build.sbt
Replacing the Java archetype with the Scala one
libraryDependencies += "org.openjdk.jmh" % "jmh-scala-benchmark-archetype" % "0.5.5"
does not work, as the download fails.
This works:
libraryDependencies += "org.openjdk.jmh" % "jmh-scala-benchmark-archetype" % "0.5.5" from "http://repo1.maven.org/maven2/org/openjdk/jmh/jmh-scala-benchmark-archetype/0.5.5/jmh-scala-benchmark-archetype-0.5.5.jar"
Another simple benchmark:
src/main/scala/app/benchmark/scala/benchmark2/Benchmark2.scala
package app.benchmark.scala.benchmark2
import org.openjdk.jmh.annotations.GenerateMicroBenchmark
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
class Benchmark2 {
#GenerateMicroBenchmark
def run() = {
Seq.range(0, 10).map(i => i * i).sum
}
}
Now sbt assembly creates the jar file, but target/scala-2.10/microbenchmarks.jar#META-INF/MicroBenchmarks does not list the Scala benchmarks, and these are not shown by java -jar target/scala-2.10/microbenchmarks.jar -l either.
Resources:
JMH with maven (there is a link to an ant based approach as well)
A Japanese page where I got the inital sbt setup from
JMH with gradle
How can I integrate the (bytecode based) JMH processor for Scala?
Or from another perspective: Why is the (annotation based) JMH processor picked up automatically and produces Java based benchmarks?

Answer 1

I have implemented an sbt-jmh plugin that actually works: https://github.com/ktoso/sbt-jmh
Currently building benchmarks.jar is not supported, but you can simply type run -i 10 .*MyBenchmark.* and it will work as expected (doing all the multi-step compilation for you).
I hope this helps, cheers!