Akka消息传递时间

时间：2015-05-24 02:15:24

标签： scala akka artificial-life

我正在与Scala和Akka一起进行人工生命模拟，到目前为止，我对两者都非常满意。我有一些时间方面的问题，但我无法解释。

目前，模拟中的每只动物都是一对演员（动物+大脑）。通常，这两个演员轮流（动物将传感器输入发送到大脑，等待结果，作用于它并重新开始）。然而，不时地，动物需要彼此互动以互相吃饭或繁殖。

对我来说奇怪的一点是时机。事实证明，从一只动物向另一只动物发送信息比从动物发送到大脑要慢很多（大约100倍）。这使得我的可怜的食肉动物和性活跃的动物处于劣势，而不是素食者和无性动物（免责声明：我自己也吃素，但我认为成为素食主义者的理由比在尝试捕食时陷入困境更好。 ）。

我提取了一个演示问题的最小代码段：

package edu.blindworld.test

import java.util.concurrent.TimeUnit

import akka.actor.{ActorRef, ActorSystem, Props, Actor}
import akka.pattern.ask
import akka.util.Timeout

import scala.concurrent.Await
import scala.concurrent.duration.Duration
import scala.util.Random

class Animal extends Actor {
  val brain = context.actorOf(Props(classOf[Brain]))
  var animals: Option[List[ActorRef]] = None

  var brainCount = 0
  var brainRequestStartTime = 0L
  var brainNanos = 0L

  var peerCount = 0
  var peerRequestStartTime = 0L
  var peerNanos = 0L

  override def receive = {
    case Go(all) =>
      animals = Some(all)
      performLoop()
    case BrainResponse =>
      brainNanos += (System.nanoTime() - brainRequestStartTime)
      brainCount += 1
      // Animal interactions are rare
      if (Random.nextDouble() < 0.01) {
        // Send a ping to a random other one (or ourselves). Defer our own loop
        val randomOther = animals.get(Random.nextInt(animals.get.length))
        peerRequestStartTime = System.nanoTime()
        randomOther ! PeerRequest
      } else {
        performLoop()
      }
    case PeerResponse =>
      peerNanos += (System.nanoTime() - peerRequestStartTime)
      peerCount += 1
      performLoop()
    case PeerRequest =>
      sender() ! PeerResponse
    case Stop =>
      sender() ! StopResult(brainCount, brainNanos, peerCount, peerNanos)
      context.stop(brain)
      context.stop(self)
  }

  def performLoop() = {
    brain ! BrainRequest
    brainRequestStartTime = System.nanoTime()
  }
}

class Brain extends Actor {
  override def receive = {
    case BrainRequest =>
      sender() ! BrainResponse
  }
}

case class Go(animals: List[ActorRef])
case object Stop
case class StopResult(brainCount: Int, brainNanos: Long, peerCount: Int, peerNanos: Long)

case object BrainRequest
case object BrainResponse

case object PeerRequest
case object PeerResponse

object ActorTest extends App {
  println("Sampling...")
  val system = ActorSystem("Test")
  val animals = (0 until 50).map(i => system.actorOf(Props(classOf[Animal]))).toList
  animals.foreach(_ ! Go(animals))
  Thread.sleep(5000)
  implicit val timeout = Timeout(5, TimeUnit.SECONDS)
  val futureStats = animals.map(_.ask(Stop).mapTo[StopResult])
  val stats = futureStats.map(Await.result(_, Duration(5, TimeUnit.SECONDS)))
  val brainCount = stats.foldLeft(0)(_ + _.brainCount)
  val brainNanos = stats.foldLeft(0L)(_ + _.brainNanos)
  val peerCount = stats.foldLeft(0)(_ + _.peerCount)
  val peerNanos = stats.foldLeft(0L)(_ + _.peerNanos)
  println("Average time for brain request: " + (brainNanos / brainCount) / 1000000.0 + "ms (sampled from " + brainCount + " requests)")
  println("Average time for peer pings: " + (peerNanos / peerCount) / 1000000.0 + "ms (sampled from " + peerCount + " requests)")
  system.shutdown()
}

这就是这里发生的事情：

  • 我正在创造50对动物/大脑演员
  • 它们全部启动并运行5秒
  • 每只动物做一个无限循环，轮流用它的大脑
  • 在所有跑步的1％中，动物向其他随机动物发送ping并等待其回复。然后，它继续其大脑循环
  • 测量每个对大脑和同伴的请求，以便我们得到平均值
  • 5秒后，一切都停止了，比较大脑请求和同伴ping的时间

在我的双核i7上，我看到了这些数字：

  

大脑请求的平均时间：0.004708ms（从21073859请求中抽样）

     

对等ping的平均时间：0.66866ms（从211167个请求中采样）

因此对同行的ping比对大脑的请求慢165倍。我一直在尝试很多东西来解决这个问题（例如优先邮箱和热身JIT），但是还没有能够弄清楚发生了什么。有没有人有想法？

1 个答案:

答案 0 :(得分：0)

我认为您应该使用ask模式来处理消息。在你的代码中，BrainRequest被发送给大脑演员，然后它发送回BrainResponse。问题出在这里。 BrainResponse并不是BrainRequest的回应。也许这是之前BrainRequest的回应。

以下代码使用ask模式，perf结果几乎相同。

package edu.blindworld.test

import java.util.concurrent.TimeUnit

import akka.actor.{ActorRef, ActorSystem, Props, Actor}
import akka.pattern.ask
import akka.util.Timeout

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Await
import scala.concurrent.duration._
import scala.util.Random

class Animal extends Actor {
  val brain = context.actorOf(Props(classOf[Brain]))
  var animals: Option[List[ActorRef]] = None

  var brainCount = 0
  var brainRequestStartTime = 0L
  var brainNanos = 0L

  var peerCount = 0
  var peerRequestStartTime = 0L
  var peerNanos = 0L

  override def receive = {
    case Go(all) =>
      animals = Some(all)
      performLoop()
    case PeerRequest =>
      sender() ! PeerResponse
    case Stop =>
      sender() ! StopResult(brainCount, brainNanos, peerCount, peerNanos)
      context.stop(brain)
      context.stop(self)
  }

  def performLoop(): Unit = {
    brainRequestStartTime = System.nanoTime()
    brain.ask(BrainRequest)(10.millis) onSuccess {
      case _ =>
        brainNanos += (System.nanoTime() - brainRequestStartTime)
        brainCount += 1
        // Animal interactions are rare
        if (Random.nextDouble() < 0.01) {
          // Send a ping to a random other one (or ourselves). Defer our own loop
          val randomOther = animals.get(Random.nextInt(animals.get.length))
          peerRequestStartTime = System.nanoTime()
          randomOther.ask(PeerRequest)(10.millis) onSuccess {
            case _ =>
              peerNanos += (System.nanoTime() - peerRequestStartTime)
              peerCount += 1
              performLoop()
          }
        } else {
          performLoop()
        }
    }
  }
}

class Brain extends Actor {
  override def receive = {
    case BrainRequest =>
      sender() ! BrainResponse
  }
}

case class Go(animals: List[ActorRef])
case object Stop
case class StopResult(brainCount: Int, brainNanos: Long, peerCount: Int, peerNanos: Long)

case object BrainRequest
case object BrainResponse

case object PeerRequest
case object PeerResponse

object ActorTest extends App {
  println("Sampling...")
  val system = ActorSystem("Test")
  val animals = (0 until 50).map(i => system.actorOf(Props(classOf[Animal]))).toList
  animals.foreach(_ ! Go(animals))
  Thread.sleep(5000)
  implicit val timeout = Timeout(5, TimeUnit.SECONDS)
  val futureStats = animals.map(_.ask(Stop).mapTo[StopResult])
  val stats = futureStats.map(Await.result(_, Duration(5, TimeUnit.SECONDS)))
  val brainCount = stats.foldLeft(0)(_ + _.brainCount)
  val brainNanos = stats.foldLeft(0L)(_ + _.brainNanos)
  val peerCount = stats.foldLeft(0)(_ + _.peerCount)
  val peerNanos = stats.foldLeft(0L)(_ + _.peerNanos)
  println("Average time for brain request: " + (brainNanos / brainCount) / 1000000.0 + "ms (sampled from " + brainCount + " requests)")
  println("Average time for peer pings: " + (peerNanos / peerCount) / 1000000.0 + "ms (sampled from " + peerCount + " requests)")
  system.shutdown()
}
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