scala – 如何使用actor重写具有共享依赖关系的for循环
发布时间：2020-12-16 18:14:57 所属栏目：安全 来源：网络整理
导读：我们有一些代码需要运行得更快.它已经分析了,所以我们想要使用多个线程.通常我会设置一个内存队列,并有许多线程从事队列的工作并计算结果.对于共享数据,我将使用ConcurrentHashMap或类似的. 我真的不想再去那条路了.从我所看到的使用演员将导致更清晰的代码,
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我们有一些代码需要运行得更快.它已经分析了,所以我们想要使用多个线程.通常我会设置一个内存队列,并有许多线程从事队列的工作并计算结果.对于共享数据,我将使用ConcurrentHashMap或类似的.
我真的不想再去那条路了.从我所看到的使用演员将导致更清晰的代码,如果我使用akka迁移到超过1 jvm应该更容易.真的吗？ 但是,我不知道如何在演员中思考,所以我不知道从哪里开始. 为了更好地了解问题,这里有一些示例代码： case class Trade(price:Double,volume:Int,stock:String) {
def value(priceCalculator:PriceCalculator) =
(priceCalculator.priceFor(stock)-> price)*volume
}
class PriceCalculator {
def priceFor(stock:String) = {
Thread.sleep(20)//a slow operation which can be cached
50.0
}
}
object ValueTrades {
def valueAll(trades:List[Trade],priceCalculator:PriceCalculator):List[(Trade,Double)] = {
trades.map { trade => (trade,trade.value(priceCalculator)) }
}
def main(args:Array[String]) {
val trades = List(
Trade(30.5,10,"Foo"),Trade(30.5,20,"Foo")
//usually much longer
)
val priceCalculator = new PriceCalculator
val values = valueAll(trades,priceCalculator)
}
}
如果有经验的玩家可以建议如何映射演员,我会很感激. 解决方法
这是对我对昂贵计算的共享结果的评论的补充.这里是：
import scala.actors._
import Actor._
import Futures._
case class PriceFor(stock: String) // Ask for result
// The following could be an "object" as well,if it's supposed to be singleton
class PriceCalculator extends Actor {
val map = new scala.collection.mutable.HashMap[String,Future[Double]]()
def act = loop {
react {
case PriceFor(stock) => reply(map getOrElseUpdate (stock,future {
Thread.sleep(2000) // a slow operation
50.0
}))
}
}
}
这是一个用法示例： scala> val pc = new PriceCalculator; pc.start
pc: PriceCalculator = PriceCalculator@141fe06
scala> class Test(stock: String) extends Actor {
| def act = {
| println(System.currentTimeMillis().toString+": Asking for stock "+stock)
| val f = (pc !? PriceFor(stock)).asInstanceOf[Future[Double]]
| println(System.currentTimeMillis().toString+": Got the future back")
| val res = f.apply() // this blocks until the result is ready
| println(System.currentTimeMillis().toString+": Value: "+res)
| }
| }
defined class Test
scala> List("abc","def","abc").map(new Test(_)).map(_.start)
1269310737461: Asking for stock abc
res37: List[scala.actors.Actor] = List(Test@6d888e,Test@1203c7f,Test@163d118)
1269310737461: Asking for stock abc
1269310737461: Asking for stock def
1269310737464: Got the future back
scala> 1269310737462: Got the future back
1269310737465: Got the future back
1269310739462: Value: 50.0
1269310739462: Value: 50.0
1269310739465: Value: 50.0
scala> new Test("abc").start // Should return instantly
1269310755364: Asking for stock abc
res38: scala.actors.Actor = Test@15b5b68
1269310755365: Got the future back
scala> 1269310755367: Value: 50.0
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