Kevin Doyle

With Jenna Lau, Jonathan Ostroff and Faraz Ahmadi Torshizi.Department of Computer Science and Engineering, York University, 4700 Keele Street, Toronto, Canada M3J 1P3



CREATING A JSCOOP PROJECT

JSCOOP Projects are Java Projects with an additional JSCOOP Project NatureJSCOOP Projects can be created in Eclipse using the New Project Wizard to select the JSCOOP Project Wizard

USING THE @SEPARATE ANNOTATION

The @separate annotation can be used to decorate fields, local variables and method parametersObjects decorated by the @separate annotation are considered separate with respect to the current object

The @separate annotation takes in an argument dir to provide support for arrays used in the separate context

USING THE @AWAIT ANNOTATION

The @await annotation can be used to decorate method declarations and takes in an argument pre to specify boolean conditionsPreconditions specified in @await declarations will be treated as wait conditions

1) private @separate JObject o;

2) @separate JObject o = new JObject();

3) public void aMethod(@separate JObject arg) {}

1) Non-separate array, Non-separate elements

JObject[] o = new JObject[#]();

2) Separate array, Non-separate elements

@separate(dir=“@separate JObject[] o”)JObject[] o = new JObject[#]();

3) Non-separate array, Separate elements

@separate(dir=“JObject[@separate] o”)JObject[] o = new JObject[#]();

4) Separate array, Separate elements

@separate(dir=“@separate JObject[@separate] o”)JObject[] o = new JObject[#]();

@await(pre=“list.isEmpty() && arg1 != null)public void aMethod(@separate Jlist list,

@separate JObject arg1) {…

}

CORRECTNESS CHECKING FOR @SEPARATE

JSCOOP Eclipse tooling provides correctness checking for the following cases:

Incorrect placement of annotationIncorrect use of directive (dir)Introduction of traitors on:

Variable declarationsAssignmentsMethod calls

Note: The concept of a “traitor” is taken from the SCOOP model. Traitors are introduced when separate objects are used where a non-separate object is expectedErrors are highlighted in the Eclipse development environment as follows:

CORRECTNESS CHECKING FOR @AWAIT

Valid precondition strings specified in the @await annotation correspond to valid boolean expressions for Java assert statements

HOW TO MANIPULATE THE ECLIPSE AST

In order to take advantage of existing Eclipse tools for Java, annotations were chosen over keywords for JSCOOP A JSCOOP_CompilationParticipant was created to act on compilation events (specifically save reconciles) To parse the Eclipse AST, a class extending ASTVisitor is required. The ASTVisitor provides capability for visiting all nodes of the DOM created from a parsed Java document, including:

Variable DeclarationsAssignment StatementsMethod DeclarationsMethod Invocations

The Eclipse AST can be altered for the purpose of correctness checking of @await statements and automated translation of JSCOOP Projects to Java code

JSCOOP PLUG-IN

The tooling is broken down into two packages within this plug-in:

edu.yorku.jscoopThis package is responsible for correctness checking and GUI support for JSCOOP Project creation. A single visitor class is used to parse JSCOOP files for problem determination

edu.yorku.jscoop.translatorThis package is responsible for the automated translation of JSCOOP code to Java code.Basic framework for automated translation has been designed with the anticipation of future development to fully implement this feature

JSCOOP Project File

Copy of File Original AST Rewritten AST

Await Processing:Copy of File is a hidden file, which is processedfor errors and reported back to the original JSCOOP project file, then deleted.

Translation File Creation:Copy of File is a new file the translation creates from processing the current JSCOOPproject file.

ABSTRACT

The real world is concurrent. Several things may happen at the same time. Computer systems must increasingly contend with concurrent applications.

SCOOP is a concurrent programming language with a new semantics for contracts that applies equally well in concurrent and sequential contexts. SCOOP eliminates race conditions and atomicity violations by construction.

In this work we describe JSCOOP – an equivalent solution in Java. This solution introduces new annotations modeled after SCOOP keywords as well as several core library classes which provide the backend support necessary to mirror SCOOP semantics.

JAC (Java with Annotated Concurrency via JML) is a prior attempt to port SCOOP notions to Java.

OBJECTIVE

JSCOOP extends Java’s concurrent behaviour by hiding the notion of threads, semaphores and synchronization. This is achieved by adding two annotated keywords (@separate and @await). These keywords have the same meaning as separate and require in SCOOP.

The goal in creating the JSCOOP library was to provide a base set of classes similar to SCOOPLI for SCOOP. These classes are intended to provide support for major SCOOP concepts, including a fair scheduling algorithm that eliminates race conditions, separate processor functionality, and mechanisms to mirror Eiffel’s agents for wrapping calls.

Consider an excerpt of JSCOOP code using the new keywords for the classic Dining Philosophers example:

Advantages

• No explicit thread declarations• No synchronized blocks• No semaphores or explicit waits

Support developed for JSCOOP includes:

(a) An Eclipse JSCOOP plug-in that supports the two new keywords as annotations and does automated syntax type checking for “traitors” (that prevent atomicity or race violations). This is described in this poster.

(b) Prototype runtime translation to translate JSCOOP to multithreaded Java. A core library for the translation has been developed that provides support for the translation, with proof of concept on some examples. See sister poster.

public class Philosopher {

private @separate Fork left, right;

@await(pre="!l.isInUse() && !r.isInUse()") public void eat(@separate Fork l, @separate Fork r) { l.pickUp(); r.pickUp(); if(l.isInUse() && r.isInUse()) status = EATING; l.putDown(); r.putDown(); if(!l.isInUse() && !r.isInUse()) status = IDLE; } …}

Eclipse

Resource Markers

Help Table of Contents

New Wizards

JDT Compilation Participant

Resource Natures

Pop Up Menus

edu.yorku.jscoop

JSCOOPProjectWizard

edu.yorku.jscoop

JSCOOP_CompilationParticipantJSCOOP_ToolingVisitorJSCOOP_Problem

edu.yorku.jscoop

JSCOOPProjectNature

edu.yorku.jscoop.translator

TranslateActionJSCOOP_InitiralTranslationVisitorJSCOOP_MainClassTranslationVisitorJSCOOP_TranslatorVisitor

toc.xmltopics_GettignStarted.xmltopics_JSCOOPDevelopersGuide.xmltopics_JSCOOPToolingDevelopersGuide.xmltopics_UsersGuide.xmlhtml/*

edu.yorku.jscoop

JSCOOPProjectNature