adding dataflow concurrency support
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Jonas Boner
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1 changed files with 371 additions and 0 deletions
371
kernel/src/main/scala/DataFlowVariable.scala
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371
kernel/src/main/scala/DataFlowVariable.scala
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/**
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* Copyright (C) 2009 Scalable Solutions.
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*/
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package com.scalablesolutions.akka.kernel
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import scala.actors.Actor
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import scala.actors.OutputChannel
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import scala.actors.Future
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import scala.actors.Actor._
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import java.util.concurrent.atomic.AtomicReference
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import java.util.concurrent.{ConcurrentLinkedQueue, LinkedBlockingQueue}
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object DataFlow {
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def thread(body: => Unit) = {
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val thread = new IsolatedEventBasedThread(body).start
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thread ! 'start
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thread
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}
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def thread[MessageType, ReturnType](body: MessageType => ReturnType) =
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new ReactiveEventBasedThread(body).start
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private class IsolatedEventBasedThread(body: => Unit) extends Actor {
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def act = loop {
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react {
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case 'start => body
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case 'exit => exit()
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}
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}
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}
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private class ReactiveEventBasedThread[MessageType, ReturnType](body: MessageType => ReturnType) extends Actor {
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def act = loop {
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react {
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case message: MessageType => sender ! body(message)
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case 'exit => exit()
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}
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}
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}
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sealed class DataFlowVariable[T] {
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private sealed abstract class DataFlowVariableMessage
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private case class Set[T](value: T) extends DataFlowVariableMessage
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private case object Get extends DataFlowVariableMessage
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private val value = new AtomicReference[Option[T]](None)
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private val blockedReaders = new ConcurrentLinkedQueue[Actor]
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private class In[T](dataFlow: DataFlowVariable[T]) extends Actor {
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def act = loop { react {
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case Set(v) =>
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if (dataFlow.value.compareAndSet(None, Some(v.asInstanceOf[T]))) {
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val iterator = dataFlow.blockedReaders.iterator
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while (iterator.hasNext) iterator.next ! Set(v)
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dataFlow.blockedReaders.clear
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} else throw new DataFlowVariableException(
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"Attempt to change data flow variable (from [" + dataFlow.value.get + "] to [" + v + "])")
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case 'exit => exit()
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}}
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}
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private class Out[T](dataFlow: DataFlowVariable[T]) extends Actor {
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var reader: Option[OutputChannel[Any]] = None
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def act = loop { react {
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case Get =>
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val ref = dataFlow.value.get
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if (ref.isDefined) reply(ref.get) else reader = Some(sender)
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case Set(v) => if (reader.isDefined) reader.get ! v
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case 'exit => exit()
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}}
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}
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private[this] val in = { val in = new In(this); in.start; in }
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def <<(ref: DataFlowVariable[T]) = in ! Set(ref())
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def <<(value: T) = in ! Set(value)
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def apply(): T = {
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val ref = value.get
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if (ref.isDefined) ref.get
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else {
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val out = { val out = new Out(this); out.start; out }
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blockedReaders.offer(out)
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val future: Future[T] = out !! (Get, {case t: T => t})
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val result = future()
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out ! 'exit
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result
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}
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}
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def shutdown = in ! 'exit
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}
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class DataFlowStream[T] extends Seq[T] {
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private[this] val queue = new LinkedBlockingQueue[DataFlowVariable[T]]
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def <<<(ref: DataFlowVariable[T]) = queue.offer(ref)
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def <<<(value: T) = {
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val ref = new DataFlowVariable[T]
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ref << value
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queue.offer(ref)
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}
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def apply(): T = {
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val ref = queue.take
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ref()
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}
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def take: DataFlowVariable[T] = queue.take
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//==== For Seq ====
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def length: Int = queue.size
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def apply(i: Int): T = {
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if (i == 0) apply()
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else throw new UnsupportedOperationException("Access by index other than '0' is not supported by DataFlowSream")
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}
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override def elements: Iterator[T] = new Iterator[T] {
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private val iter = queue.iterator
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def hasNext: Boolean = iter.hasNext
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def next: T = { val ref = iter.next; ref() }
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}
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override def toList: List[T] = queue.toArray.toList.asInstanceOf[List[T]]
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}
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class DataFlowVariableException(msg: String) extends RuntimeException(msg)
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}
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// ==========================
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// ======== EXAMPLES ========
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// ==========================
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object Test1 extends Application {
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// =======================================
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// This example is rom Oz wikipedia page: http://en.wikipedia.org/wiki/Oz_(programming_language)
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/*
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thread
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Z = X+Y % will wait until both X and Y are bound to a value.
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{Browse Z} % shows the value of Z.
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end
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thread X = 40 end
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thread Y = 2 end
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*/
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import DataFlow._
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val x, y, z = new DataFlowVariable[Int]
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thread {
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z << x() + y()
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println("z = " + z())
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}
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thread { x << 40 }
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thread { y << 2 }
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}
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// =======================================
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object Test2 extends Application {
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/*
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fun {Ints N Max}
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if N == Max then nil
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else
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{Delay 1000}
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N|{Ints N+1 Max}
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end
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end
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fun {Sum S Stream}
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case Stream of nil then S
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[] H|T then S|{Sum H+S T} end
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end
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local X Y in
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thread X = {Ints 0 1000} end
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thread Y = {Sum 0 X} end
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{Browse Y}
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end
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*/
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import DataFlow._
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def ints(n: Int, max: Int): List[Int] =
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if (n == max) Nil
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else n :: ints(n + 1, max)
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def sum(s: Int, stream: List[Int]): List[Int] = stream match {
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case Nil => s :: Nil
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case h :: t => s :: sum(h + s, t)
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}
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val x = new DataFlowVariable[List[Int]]
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val y = new DataFlowVariable[List[Int]]
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thread { x << ints(0, 1000) }
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thread { y << sum(0, x()) }
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thread { println("List of sums: " + y()) }
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}
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// =======================================
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object Test3 extends Application {
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// Using DataFlowStream and foldLeft to calculate sum
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/*
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fun {Ints N Max}
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if N == Max then nil
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else
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{Delay 1000}
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N|{Ints N+1 Max}
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end
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end
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fun {Sum S Stream}
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case Stream of nil then S
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[] H|T then S|{Sum H+S T} end
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end
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local X Y in
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thread X = {Ints 0 1000} end
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thread Y = {Sum 0 X} end
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{Browse Y}
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end
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*/
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import DataFlow._
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def ints(n: Int, max: Int, stream: DataFlowStream[Int]): Unit = if (n != max) {
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println("Generating int: " + n)
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stream <<< n
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ints(n + 1, max, stream)
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}
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def sum(s: Int, in: DataFlowStream[Int], out: DataFlowStream[Int]): Unit = {
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println("Calculating: " + s)
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out <<< s
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sum(in() + s, in, out)
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}
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def printSum(stream: DataFlowStream[Int]): Unit = {
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println("Result: " + stream())
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printSum(stream)
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}
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val producer = new DataFlowStream[Int]
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val consumer = new DataFlowStream[Int]
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thread { ints(0, 1000, producer) }
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thread {
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Thread.sleep(1000)
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println("Sum: " + producer.map(x => x * x).foldLeft(0)(_ + _))
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}
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}
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// =======================================
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object Test4 extends Application {
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// Using DataFlowStream and recursive function to calculate sum
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/*
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fun {Ints N Max}
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if N == Max then nil
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else
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{Delay 1000}
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N|{Ints N+1 Max}
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end
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end
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fun {Sum S Stream}
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case Stream of nil then S
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[] H|T then S|{Sum H+S T} end
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end
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local X Y in
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thread X = {Ints 0 1000} end
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thread Y = {Sum 0 X} end
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{Browse Y}
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end
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*/
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import DataFlow._
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def ints(n: Int, max: Int, stream: DataFlowStream[Int]): Unit = if (n != max) {
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println("Generating int: " + n)
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stream <<< n
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ints(n + 1, max, stream)
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}
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def sum(s: Int, in: DataFlowStream[Int], out: DataFlowStream[Int]): Unit = {
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println("Calculating: " + s)
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out <<< s
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sum(in() + s, in, out)
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}
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def printSum(stream: DataFlowStream[Int]): Unit = {
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println("Result: " + stream())
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printSum(stream)
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}
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val producer = new DataFlowStream[Int]
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val consumer = new DataFlowStream[Int]
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thread { ints(0, 1000, producer) }
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thread { sum(0, producer, consumer) }
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thread { printSum(consumer) }
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}
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// =======================================
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object Test5 extends Application {
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import DataFlow._
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// create four 'Int' data flow variables
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val x, y, z, v = new DataFlowVariable[Int]
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val main = thread {
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println("Thread 'main'")
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x << 1
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println("'x' set to: " + x())
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println("Waiting for 'y' to be set...")
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if (x() > y()) {
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z << x
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println("'z' set to 'x': " + z())
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} else {
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z << y
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println("'z' set to 'y': " + z())
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}
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// main completed, shut down the data flow variables
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x.shutdown
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y.shutdown
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z.shutdown
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v.shutdown
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}
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val setY = thread {
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println("Thread 'setY', sleeping...")
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Thread.sleep(5000)
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y << 2
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println("'y' set to: " + y())
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}
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val setV = thread {
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println("Thread 'setV'")
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v << y
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println("'v' set to 'y': " + v())
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}
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// shut down the threads
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main ! 'exit
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setY ! 'exit
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setV ! 'exit
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//System.gc
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}
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