CPU-bound tasks for experimenting in the Scala REPL

CPUboundTasks.scala

// a CPU-intensive task
def isPrime(i: Long): Boolean = {
  if (i == 2) return true
  if (i < 2 || i % 2 == 0) return false
  var k = 3L
  val half = i / 2
  while (k <= half) {
    if (i % k == 0) return false
    k += 2
  }
  true
}

// running two tasks sequentially
// about 18 seconds on a MacBook Air
val t0 = System.currentTimeMillis
isPrime(1500450271)
isPrime(1500450271)
System.currentTimeMillis - t0

// running two tasks concurrently
// about 12 seconds on a MacBook Air
val p1 = new java.lang.Thread { override def run() = { isPrime(1500450271) } }
val p2 = new java.lang.Thread { override def run() = { isPrime(1500450271) } }
val t0 = System.currentTimeMillis
p1.start()
p2.start()
p1.join()
p2.join()
System.currentTimeMillis - t0