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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.*;
public aclass Event {
// current list of subscribers
private List subscribers;
public Event() {
subscribers = new ArrayList();
}
// registers a subscriber
public static class Subscribe {
Actor a;
public Subscribe(Actor a) {
this.a = a;
}
}
public react (Subscribe s) {
subscribers.add(s.a);
}
// unsubscribe
public static class Unsubscribe {
Actor a;
public Unsubscribe(Actor a) {
this.a = a;
}
}
public react (Unsubscribe s) {
subscribers.remove(s.a);
}
// sends to all subscribers
private aclass SendAll extends ListIterator {
private Object msg;
public SendAll(List list, Object msg) {
super(list);
this.msg = msg;
}
public react(Object target) {
Actor.sendMessage(target, msg);
}
}
// receives a message to send out
react (Object msg) {
SendAll sndr = new SendAll(subscribers, msg);
sndr <-- new ListIterator.Run();
}
}