Bench.scala

package scalaz.effect

import java.util.concurrent.TimeUnit
import org.openjdk.jmh.annotations._
import scala.concurrent.Await

import IOBenchmarks._

@State(Scope.Thread)
@BenchmarkMode(Array(Mode.Throughput))
@OutputTimeUnit(TimeUnit.SECONDS)
class IODeepFlatMapBenchmark {
  @Param(Array("20"))
  var depth: Int = _

  @Benchmark
  def futureDeepFlatMap(): BigInt = {
    import scala.concurrent.Future
    import scala.concurrent.duration.Duration.Inf

    def fib(n: Int): Future[BigInt] =
      if (n <= 1) Future.successful(n) else
        fib(n-1).flatMap { a =>
          fib(n-2).flatMap(b => Future.successful(a + b))
        }

    Await.result(fib(depth), Inf)
  }

  @Benchmark
  def scalazDeepFlatMap(): BigInt = {
    def fib(n: Int): IO[BigInt] =
      if (n <= 1) IO.now(n) else
        fib(n-1).flatMap { a =>
          fib(n-2).flatMap(b => IO.now(a + b))
        }

    unsafePerformIO(fib(depth))
  }

}

scores.txt

[info] Benchmark                                 (depth)   Mode  Cnt     Score    Error  Units
[info] IODeepFlatMapBenchmark.futureDeepFlatMap       20  thrpt  200    23.213 ±  0.523  ops/s
[info] IODeepFlatMapBenchmark.scalazDeepFlatMap       20  thrpt  200  1390.392 ± 59.044  ops/s