akka-future-pi.scala

import scalaz._,Scalaz._

import akka.scalaz.futures._
import akka.dispatch._

import System.{currentTimeMillis => now}

object Pi extends App {
  val nrOfElements = 10000
  val nrOfMessages = 10000

  val startTime = now

  // Single threaded and mutable
  var piSeq = 0.0
  0 until (nrOfMessages * nrOfElements) foreach (i =>
    piSeq += 4 * math.pow(-1, i) / (2 * i + 1))

  val seqTime = now

  // Using Akka Future
  val piFuture = (0 until nrOfMessages).foldLeft(Future(0.0))((result, n) =>
    Future(((n * nrOfElements) until ((n + 1) * nrOfElements)).foldLeft(0.0)((acc, i) =>
      acc + (4 * math.pow(-1, i) / (2 * i + 1)))) flatMap (acc => result map (_ + acc))).get

  val futureTime = now

  // Using Akka Future 2
  val piFuture2 = (0 until nrOfMessages).foldLeft(Future(0.0))((result, n) =>
    Future {
      var acc = 0.0
      ((n * nrOfElements) until ((n + 1) * nrOfElements)).foreach(i =>
        acc += (4 * math.pow(-1, i) / (2 * i + 1)))
      acc
    } flatMap (acc => result map (_ + acc))).get

  val future2Time = now

  // Using Akka Future and Scalaz
  val piScalaz = (0 until nrOfMessages).foldMap(n =>
    Future((n * nrOfElements) until ((n + 1) * nrOfElements) foldMap (i =>
      4 * math.pow(-1, i) / (2 * i + 1)))).get

  val scalazTime = now

  // Parallel Collections
  val piPar = (0 until nrOfMessages).par.map(n =>
    ((n * nrOfElements) until ((n + 1) * nrOfElements)).foldLeft(0.0)((acc, i) =>
      acc + (4 * math.pow(-1, i) / (2 * i + 1)))).sum

  val parTime = now

  // Parallel Collections with a mutable var
  val piPar2 = (0 until nrOfMessages).par.map { n =>
    var acc = 0.0
    ((n * nrOfElements) until ((n + 1) * nrOfElements)).foreach(i =>
      acc += (4 * math.pow(-1, i) / (2 * i + 1)))
    acc
  }.sum

  println("\n\tSingle threaded with a mutable var")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piSeq, (seqTime - startTime)))
  println("\n\tAkka Future")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piFuture, (futureTime - seqTime)))
  println("\n\tAkka Future with a mutable var")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piFuture2, (future2Time - futureTime)))
  println("\n\tAkka Future and Scalaz")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piScalaz, (scalazTime - future2Time)))
  println("\n\tParallel Collections")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piPar, (parTime - scalazTime)))
  println("\n\tParallel Collections with a mutable var")
  println("\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis".format(piPar2, (now - parTime)))

  println("\n\tPi actual:   \t\t%s".format(scala.math.Pi))

}