Akka actor infinite loop - scala

Question

I'm trying to write a simple matrix multiplication program with concurrent processing using Scala and Akka actors. I've not even written 10% of the code and I'm running into trouble. I created two actors - master and worker. I'm trying to communicate between them but its runs into an infinite loop. Any suggestions are really appreciated. As you can see, the code below does nothing, it prints 2 10X10 matrices in the master, after that the worker is called. But the worker's workDone message never comes back to the master. I also suspect this has to do something with a warning I'm getting:
patterns after a variable pattern cannot match (inside receive of master for case "masterSend")
import akka.actor.{ActorRef, Actor, ActorSystem, Props}
import scala.Array._
import scala.util.Random
case object masterSend
case object workSend
case object workDone
object MatrixMultiply {
val usage = """
Usage: MainStart <matrix-dimension> <high-value>
"""
def main(args: Array[String]) {
if (args.length != 2) {
println(usage)
System.exit(1)
}
val Dim = args(0).toInt
val Max = args(1).toInt
val system = ActorSystem("ComputeSystem")
val worker = system.actorOf(Props[Worker], name = "worker")
val master = system.actorOf(Props(new Master(Dim, Max, worker)), name = "master")
master ! masterSend
}
class Master(Dim: Int, Max: Int, worker : ActorRef) extends Actor {
def receive = {
case masterSend =>
val r = new Random(34636)
val matrixA = ofDim[Int](Dim,Dim)
val matrixB = ofDim[Int](Dim,Dim)
println("Matrix A: ")
for (i <- 0 to Dim - 1) {
for (j <- 0 to Dim - 1) {
matrixA(i)(j) = r.nextInt(Max)
print(matrixA(i)(j) + " ")
}
println()
}
r.setSeed(23535)
println("Matrix B: ")
for (i <- 0 to Dim - 1) {
for (j <- 0 to Dim - 1) {
matrixB(i)(j) = r.nextInt(Max)
print(matrixB(i)(j) + " ")
}
println()
}
worker ! workSend
case workDone =>
println("Work was done!!")
context.system.shutdown()
}
}
class Worker extends Actor {
def receive = {
case workSend =>
println("Work Done")
sender ! workDone
}
}
}

Answer 1

The problem is with pattern matching on objects you've created. It's matching inproperly. Do not bother yourself with objects. Use strings for example:
object A {
val masterSend = "masterSend"
val workSend = "workSend"
val workDone = "workDone"
}
object MatrixMultiply {
val usage = """
Usage: MainStart <matrix-dimension> <high-value>
"""
def main(args: Array[String]) {
val Dim = 3
val Max = 2
val system = ActorSystem("ComputeSystem")
val worker = system.actorOf(Props[Worker], name = "worker")
val master = system.actorOf(Props(new Master(Dim, Max, worker)), name = "master")
master ! A.masterSend
}
class Master(Dim: Int, Max: Int, worker : ActorRef) extends Actor {
def receive = {
case A.masterSend =>
println("Master sent")
worker ! A.workSend
case A.workDone =>
println("Work was done!!")
context.system.shutdown()
}
}
class Worker extends Actor {
def receive = {
case A.workSend =>
println("Work Done")
sender ! A.workDone
}
}
}
You've named your object from lower case letter.
object messageSend
But pattern matching consider it not as an object but as a some new variable instead.
case messageSend => messageSend - is a variable
You'd be able to write anything here case magicBall => will also compile.