Implementation of Join Semantics in Java

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Implementation of Join Semantics in Java

• G Stewart von Itzstein
• University of South Australia

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Overview

• Motivation
• Syntax Changes
• Asynchronous Methods
• Message Passing
• State Charts/Diagram

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Motivation

• Despite the relative simplicity of Javas
  threading model, writing concurrent programs in
  Java can still be strange and confusing.
• Tim Lindholm, Javasoft

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Motivation

• Why is there no message passing in Java threads?
• Shared memory model defeats encapsulation
• Concurrent application are hard to understand.
• Visualise, Barrier Synchronisation, Thread Pools
• We need a higher level of abstraction to
  represent more complex concurrent problems.

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Syntax

• Chemical Abstract Machine
• Two changes to the Java Syntax
• signal return representing asynchronous
  operation.
• Compound method signatures (join patterns)
• A Method body is not executed until all methods
  have been called.
• The first method can be synchronous (normal Java)
  or asynchronous (signal return type).
• The second and subsequent methods must be
  asynchronous.

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Chemical Abstract Machine

• All Join Patterns Represent Available Molecules
• A Method is an Atom.
• When you make a call to a method is made the call
  is placed into the chemical machine.
• When a complete join pattern is in the machine it
  reacts changing the composition of the pool
  (executing the code associated with the join
  pattern)

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Asynchronous Methods

• class threader
• signal thread1()
• //code
• System.out.println(Hello World)
• //code
• public static void main(String argv)
• threader x new threader()
• x.thread1()
• x.thread1()

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Message Passing

• class Message
• public Message() thread1()thread2()
• String receiver() sender(String value)
• return value
• signal thread1()
• //do some work that produces a string value
• sender(value)
• signal thread2()
• String value receiver()
• //use value

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State Diagrams

• Conversion of State Diagrams to Code

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State Diagram Code

• class statediagram
• public statediagram() A()
• void x() A() C()
• void b() A() B()
• void a() B() A()
• void y() C() B()

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State Charts

• Conversion of State Charts to Code

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State Chart Code

• class StateChart
• public StateChart() inA() inD() D() A()
• void y() D() inD()
• E() inD()
• void x() A() inA()
• B() inA()
• void c() inA() inD()
• //clean up
• void leaveA() A()
• void leaveA() B()

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Compiler

• Translation of Join Patterns
• Tree Structure Representation.

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Next Steps

• Add Synchronous Trailing Methods.
• Benchmarking.
• Add parent types?
• eg A() B() -gt partOfInA