scala primes

ParallelPrimesCompute.scala

import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Await
import scala.concurrent.duration.DurationInt

object ParallelPrimesCompute extends App {
  val primes: Stream[Long] =
    2L #:: Stream.range(3, Long.MaxValue, 2).filter(
      n => primes.takeWhile(_ <= Math.sqrt(n)).forall(n % _ != 0))

  def runAll(functions: Iterable[() => Long]): Future[Any] = {
    val futures = functions.map(f => Future { f() })
    for {
      collection <- Future.sequence(futures)
    } yield collection.sum
  }

  val costlyCalls = (1 to 60 * 1000).map(i => sumNprimes(i) _)
  val res = Await.result(runAll(costlyCalls), 50.seconds)
  println(res)

  def sumNprimes(n: Int)(): Long = {
    val name = Thread.currentThread.getName
    val res = primes.take(n).sum
    println(s"$n $name => $res")
    res
  }
}

primes.scala

val primes:Stream[Int] =
  2 #:: Stream.from(3,2).filter(
     n => !primes.takeWhile(_ <= Math.sqrt(n)).exists(n % _ ==0))
primes take 100 foreach println