136 lines
3.4 KiB
Scala
136 lines
3.4 KiB
Scala
//#imports
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package akka.tutorial.scala.first
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import _root_.akka.routing.{RoutedProps, Routing, CyclicIterator}
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import akka.actor.{Actor, PoisonPill}
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import Actor._
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import Routing._
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import System.{currentTimeMillis => now}
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import java.util.concurrent.CountDownLatch
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//#imports
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//#app
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object Pi extends App {
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calculate(nrOfWorkers = 4, nrOfElements = 10000, nrOfMessages = 10000)
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//#actors-and-messages
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// ====================
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// ===== Messages =====
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// ====================
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//#messages
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sealed trait PiMessage
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case object Calculate extends PiMessage
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case class Work(start: Int, nrOfElements: Int) extends PiMessage
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case class Result(value: Double) extends PiMessage
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//#messages
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// ==================
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// ===== Worker =====
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// ==================
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//#worker
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class Worker extends Actor {
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//#calculate-pi
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def calculatePiFor(start: Int, nrOfElements: Int): Double = {
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var acc = 0.0
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for (i <- start until (start + nrOfElements))
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acc += 4.0 * math.pow(-1, i) / (2 * i + 1)
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acc
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}
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//#calculate-pi
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def receive = {
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case Work(start, nrOfElements) =>
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self reply Result(calculatePiFor(start, nrOfElements)) // perform the work
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}
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}
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//#worker
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// ==================
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// ===== Master =====
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// ==================
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//#master
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class Master(
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nrOfWorkers: Int, nrOfMessages: Int, nrOfElements: Int, latch: CountDownLatch)
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extends Actor {
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var pi: Double = _
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var nrOfResults: Int = _
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var start: Long = _
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//#create-workers
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// create the workers
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val workers = Vector.fill(nrOfWorkers)(actorOf[Worker].start())
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// wrap them with a load-balancing router
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val router = Routing.actorOf(
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RoutedProps.apply
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.withRoundRobinRouter
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.withConnections(workers)
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.withDeployId("pi")
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)
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loadBalancerActor(CyclicIterator(workers)).start()
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//#create-workers
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//#master-receive
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// message handler
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def receive = {
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//#message-handling
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case Calculate =>
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// schedule work
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for (i <- 0 until nrOfMessages) router ! Work(i * nrOfElements, nrOfElements)
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// send a PoisonPill to all workers telling them to shut down themselves
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router ! Broadcast(PoisonPill)
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// send a PoisonPill to the router, telling him to shut himself down
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router ! PoisonPill
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case Result(value) =>
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// handle result from the worker
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pi += value
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nrOfResults += 1
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if (nrOfResults == nrOfMessages) self.stop()
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//#message-handling
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}
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//#master-receive
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override def preStart() {
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start = now
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}
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override def postStop() {
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// tell the world that the calculation is complete
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println(
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"\n\tPi estimate: \t\t%s\n\tCalculation time: \t%s millis"
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.format(pi, (now - start)))
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latch.countDown()
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}
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}
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//#master
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//#actors-and-messages
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// ==================
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// ===== Run it =====
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// ==================
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def calculate(nrOfWorkers: Int, nrOfElements: Int, nrOfMessages: Int) {
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// this latch is only plumbing to know when the calculation is completed
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val latch = new CountDownLatch(1)
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// create the master
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val master = actorOf(
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new Master(nrOfWorkers, nrOfMessages, nrOfElements, latch)).start()
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// start the calculation
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master ! Calculate
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// wait for master to shut down
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latch.await()
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}
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}
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//#app
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