arjanblokzijl/gist:7feee095093d3229d824

## gistfile1.scala
package test

import annotation.tailrec

object ConcurrentTest extends App {

  import concurrent._, duration._, ExecutionContext.Implicits.global

  def banner(str: String) = {
    val line = "=" * 80
    println(s"\n\n$line\n$str\n$line\n")
  }

  def expensiveCalc() {
    @tailrec
    def loop(i: Int, accum: Double): Double =
      if (i == 0) accum else loop(i - 1, math.pow(math.sqrt(accum), 2.00001))
    loop(100000000, 42)
  }

  def expensiveCalcs() = {
    def loop(i: Int) {
      println(s"loop $i")
      val results = List(1, 2, 3, 4) map {
        j =>
          future {
            println(s"(i, j) = ($i, $j): ${Thread.currentThread}")
            expensiveCalc()
          }
      }
      val f = Future.sequence(results)
      val result = Await.result(f, Duration.Inf)

      // the real app needs to check `result` here, so has to block
      def continue(result: Any): Boolean =
        i > 0
      if (!continue(result)) () else loop(i - 1)
    }
    loop(3)
  }

  banner(s"Start Direct Call ")
  (1 to 10).map(_ =>  expensiveCalcs())
  banner(s"End Direct Call ")
   //All CPUs are utilized here

  banner(s"Parallel Call ")
  (1 to 10).par.map(_ =>  expensiveCalcs())
  banner(s"End Parallel Call ")
  //scala 2.10: all CPU's utilized
  //scala 2.11: one CPU utilized

}
	package test

	import annotation.tailrec

	object ConcurrentTest extends App {

	import concurrent._, duration._, ExecutionContext.Implicits.global

	def banner(str: String) = {
	val line = "=" * 80
	println(s"\n\n$line\n$str\n$line\n")
	}

	def expensiveCalc() {
	@tailrec
	def loop(i: Int, accum: Double): Double =
	if (i == 0) accum else loop(i - 1, math.pow(math.sqrt(accum), 2.00001))
	loop(100000000, 42)
	}

	def expensiveCalcs() = {
	def loop(i: Int) {
	println(s"loop $i")
	val results = List(1, 2, 3, 4) map {
	j =>
	future {
	println(s"(i, j) = ($i, $j): ${Thread.currentThread}")
	expensiveCalc()
	}
	}
	val f = Future.sequence(results)
	val result = Await.result(f, Duration.Inf)

	// the real app needs to check `result` here, so has to block
	def continue(result: Any): Boolean =
	i > 0
	if (!continue(result)) () else loop(i - 1)
	}
	loop(3)
	}

	banner(s"Start Direct Call ")
	(1 to 10).map(_ => expensiveCalcs())
	banner(s"End Direct Call ")
	//All CPUs are utilized here

	banner(s"Parallel Call ")
	(1 to 10).par.map(_ => expensiveCalcs())
	banner(s"End Parallel Call ")
	//scala 2.10: all CPU's utilized
	//scala 2.11: one CPU utilized

	}