2018-02-07

Kotlin's scoped extensions micro-benchmarked

How do they get compiled, what is the runtime cost we can expect?

My last post was about an approach to use Kotlin's scoped extension methods to implement an application with data oriented design paradigm. Yes, I'm still coding that game engine, that's why I had to do a simple benchmark, just to get a feeling how performance could get better or worse. See it as a brain dump. Very unprofessional benchmark with the println statement, but I wanted to get the relation between the simple baseline implementation and the extension method version, like this:

import org.openjdk.jmh.annotations.Benchmark

interface Extension<ELEMENT>{
    fun ELEMENT.prettyPrint() { println("Default pretty " + this) }
}

object StringListExtension : Extension<String>

fun <T> someFrameWorkFunction(parameter : T, extensionProvider: Extension<T>) {
    with(extensionProvider) {
        parameter.prettyPrint()
    }
}

@Benchmark
fun extension() {
    someFrameWorkFunction("asd", StringListExtension)
}

fun String.prettyPrint() { println("Default pretty " + this) }

@Benchmark
fun baseline() {
    "asd".prettyPrint()
}

Surprising results again:

Benchmark                            Mode  Cnt       Score       Error  Units
BenchmarkRunner.benchmarkBaseline   thrpt  200  269087.160 ± 17915.393  ops/s
BenchmarkRunner.benchmarkExtension  thrpt  200  329648.131 ± 19646.005  ops/s

Once again, the opposite of my expectations.