Test MonteCarlo Pi en Scala

MonteCarlo.scala

package io.github.ilaborie.loops.samples

import java.text.NumberFormat

import scala.annotation.tailrec
import scala.util.Random

object MonteCarlo {

  def main(args: Array[String]): Unit = {
    val format = NumberFormat.getIntegerInstance()
    (2 to 7)
      .map(e => Math.pow(10.0, e.toDouble).toInt)
      .foreach { count =>
        System.out.printf("Compute with %s ...%n", format.format(count.toLong))
        val pi = monteCarloStreamParallel(count)
        println(s"Result: $pi")
      }
  }

  private val rnd = new Random()

  case class Point(x: Double, y: Double) {
    def inCircle(): Boolean =
      x * x + y * y <= 1
  }

  private def compute(count: Int, inCircle: Int): Double =
    inCircle.toDouble / count * 4

  def monteCarloFor(count: Int): Double = {
    var inCircle = 0
    for (_ <- 1 to count) {
      val p = Point(rnd.nextDouble(), rnd.nextDouble())

      if (p.inCircle()) {
        inCircle += 1
      }
    }
    compute(count, inCircle)
  }

  def monteCarloRecursion(count: Int): Double = {
    @tailrec
    def aux(count: Int, inCircle: Int): Int =
      if (count == 0) inCircle
      else {
        val p = Point(rnd.nextDouble(), rnd.nextDouble())
        aux(count - 1, inCircle + if (p.inCircle()) 1 else 0)
      }

    val inCircle = aux(count, 0)
    compute(count, inCircle)
  }

  def monteCarloStream(count: Int): Double = {
    val inCircle = Stream.continually(Point(rnd.nextDouble(), rnd.nextDouble()))
      .take(count)
      .count(_.inCircle())

    compute(count, inCircle)
  }

  def monteCarloStreamParallel(count: Int): Double = {
    val inCircle = Stream.continually(Point(rnd.nextDouble(), rnd.nextDouble()))
      .par
      .take(count)
      .count(_.inCircle())

    compute(count, inCircle)
  }

}