randomclicker.scala

RandomClick.scala

package com.yieldmo.simulation.actor

import akka.actor.{ Actor, ActorSystem, Props, ActorLogging }
import com.yieldmo.simulation.TrafficSimulationProtocol._

class RandomClick extends Actor with ActorLogging {
  // uses  30K in memory per instance. Use wisely
  // described http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng.pdf
  // better than marsene twister
  private val rand = new org.apache.commons.math3.random.Well44497b(scala.compat.Platform.currentTime)
  def pickCreative(creatives: Array[Creative]): Option[Creative] = {
    def tail(j: Int): Double = {
      if (j < 0) 1.0
      else (1 - creatives(j).ctr) * tail(j - 1)
    }

    val probabilities = creatives.zipWithIndex.map {
      case (creative, i) =>
        // p_i(head) * for all i --> do p_(i-1)(tail)
        (creative, creative.ctr * tail(i - 1))
    }

    // pick a probability at random
    val p = rand.nextDouble

    probabilities.collectFirst { case (creative, probabilityOfClick) if p < probabilityOfClick => creative }
  }

  def receive = {
    case arr: Array[Creative] =>
      pickCreative(arr) foreach (sender ! _)
  }
}