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Copyright Tristan Aubrey-Jones May 2008.
Abstract: A project investigating and developing an implicitly concurrent programming language, based on a metaphor taken from the physical world is reported. Uses a programming paradigm where programs consist of systems of autonomous agents, or active objects which communicate via message passing. A language enhancing Java with actors and linear types is presented. Example programs are written, compiled, and executed to evaluate the usefulness of the language. The language found to provide a familiar notation for implicit parallelism, and a compelling new model for concurrency, combining the performance of shared variables with the elegance of message passing.
Introductory Slides (PDF),
Report (PDF),
ActiveJava compiler prototype (ajavac),
ActiveJava runtime library (ajava_lang).
Examples:
calc - pocket calculator actor program
dining - dining philosophers actor program (never deadlocks)
sort - parallel quicksort implementation ("SortBenchmark" sorts 10,000 random integers using actors, java threads, and sequentially and compares)
To compile examples use:compile.bat ./calc compile.bat ./sort compile.bat ./diningTo run examples use:
run ./calc Main run ./dining Main run ./dining Main fast run ./sort Main run ./sort SortingBenchmark
import java.util.*;
import org.taj.ajava.lang.*;
public class Event extends Actor
{
private List subscribers;
public Event()
{
subscribers = new ArrayList();
}
public static class Subscribe
{
Actor a;
public Subscribe(Actor a)
{
this.a = a;
}
}
private void react_0(Subscribe s)
{
subscribers.add(s.a);
}
public void deliver(Subscribe s)
{
bufferMessage(new org.taj.ajava.runtime.ActorMessage(s, 0));
}
protected void react(Subscribe s)
{
react_0(s);
}
public static class Unsubscribe
{
Actor a;
public Unsubscribe(Actor a)
{
this.a = a;
}
}
private void react_1(Unsubscribe s)
{
subscribers.remove(s.a);
}
public void deliver(Unsubscribe s)
{
bufferMessage(new org.taj.ajava.runtime.ActorMessage(s, 1));
}
protected void react(Unsubscribe s)
{
react_1(s);
}
private static class SendAll extends ListIterator
{
private Object msg;
public SendAll(List list, Object msg)
{
super(list);
this.msg = msg;
}
private void react_3(Object target)
{
Actor.sendMessage(target, msg);
}
public void deliver(Object target)
{
bufferMessage(new org.taj.ajava.runtime.ActorMessage(target, 3));
}
protected void react(Object target)
{
react_3(target);
}
protected void processMessage(org.taj.ajava.runtime.ActorMessage msg)
{
switch (msg.reactorId) {
case 3:
{
react_3(((Object)msg.payload));
return;
}
default:
{
super.processMessage(msg);
return;
}
}
}
}
private void react_2(Object msg)
{
SendAll sndr = new SendAll(subscribers, msg);
sndr.deliver(new ListIterator.Run());
}
public void deliver(Object msg)
{
bufferMessage(new org.taj.ajava.runtime.ActorMessage(msg, 2));
}
protected void react(Object msg)
{
react_2(msg);
}
protected void processMessage(org.taj.ajava.runtime.ActorMessage msg)
{
switch (msg.reactorId) {
case 0:
{
react_0(((Subscribe)msg.payload));
return;
}
case 1:
{
react_1(((Unsubscribe)msg.payload));
return;
}
case 2:
{
react_2(((Object)msg.payload));
return;
}
default:
{
super.processMessage(msg);
return;
}
}
}
}