LocalPi

1. 计算PI  = count / total * 4

2. 编程

import scala.math.random

 var count = 0
    for (i <- 1 to 100000) {
      val x = random * 2 - 1
      val y = random * 2 - 1
      if (x*x + y*y < 1) count += 1
    }
    println("Pi is roughly " + 4 * count / 100000.0)
  }

3. 并行化

object SparkPi {
  def main(args: Array[String]) {
    val conf = new SparkConf().setAppName("Spark Pi")
    val spark = new SparkContext(conf)
    val slices = if (args.length > 0) args(0).toInt else 2 
    val n = 100000 * slices
    val count = spark.parallelize(1 to n, slices).map { i =>
      val x = random * 2 - 1
      val y = random * 2 - 1
      if (x*x + y*y < 1) 1 else 0
    }.reduce(_ + _)
    println("Pi is roughly " + 4.0 * count / n)
    spark.stop()
  }
}