asynchronous and deterministic objects

ASYNCHRONOUS AND DETERMINISTIC OBJECTS

ASP: Asynchronous Sequential Processes Distributed objects Asynchronous method calls Futures and Wait-by-necessity Determinism properties

Denis CAROMEL, Ludovic HENRIO, Bernard Paul SERPETTE

I3S - INRIA - Univ Nice Sophia-Antipolis

Context

-calculus Objects, not concurrent Some concurrent extensions, not our way to determinism

-calculus Communications, channel based, not object structured Linear(ized) channels(o), no implicit synchronization

Process Networks Processes, channel based, not object oriented Determinism, no implicit synchronization

Context

Contents

1 - ASP Principles

2 - Syntax and Semantics

3 - Confluence and Determinacy

4 - Conclusion

f3

f1

Structure

1- ASP Principles

foo

foo

f2

Active(a)

foo

beta.foo(b)

result=beta.foo(b)

Sending Requests ( REQUEST )

1- ASP Principles

foo

beta.foo(b)result

Sending Requests ( REQUEST )

1- ASP Principles

result=beta.foo(b)

foo

beta.foo(b)

Serve(foo);...

result

Serving Requests ( SERVE )

Serve(foo);...

bar

1- ASP Principles

beta.foo(b)result

Serving Requests ( SERVE )

Serve(foo)

barfoo ...foo

1- ASP Principles

Serve(foo);...

...foo

End of Service ( ENDSERVICE )

value

1- ASP Principles

foo

End of Service ( ENDSERVICE )

...

1- ASP Principles

foo

Sending Results ( REPLY )

1- ASP Principles

Sending Results ( REPLY )

foo

1- ASP Principles

delta.send(result)

Wait by Necessity

1- ASP Principles

delta.send(result)result.bar()result.bar()

Wait by Necessity

1- ASP Principles

Wait by Necessity

result.bar()Futures updates can occur at any time

Futures updates can occur at any time

1- ASP Principles

1 - ASP Principles



4 - Conclusion

Contents

ASP Syntax : source terms

2- Syntax and Semantics

Imperative-calculus

ASP parallelism primitives

2- Syntax and Semantics

Local

CreatingActivity

Sendingrequest

Receivingreplies

Service

Contents

1 - ASP Principles



4 - Conclusion

Compatibility

delta.foo()

foo

….Serve(foo,bar)

…Serve(foo,gee)

bar

gee

3- Confluence and Determinacy

Serves the oldest request on foo OR bar

Confluence

Potential services:


P0

P Q

R

RSL definition:

Compatibility Confluence

Configuration Compatibility:Execution characterized

by the order of Request SendersExecution characterized

by the order of Request Senders

Deterministic Object Networks

{foo,bar} , {foo,gee}

delta.gee(a)

gee

delta.bar(a)bar

{bar,gee} , {foo}

gee barbar gee


DON(P):

Static DON

{foo,bar} , {gee}

{foo,bar} , {gee}

{gee}, {f,g}

{bar} , {gee}

{foo,bar} , {gee}

foo

bar

f{foo}, {bar}

{gee}, {f,g}

{f,g}{gee}, {f,g}f

g

gee

f

g

{gee}, {f,g}


g

Contents

1 - ASP Principles



4 - Conclusion

Conclusion

An Asynchronous Object Calculus : Structured asynchronous activities Structured communications with futures Data-driven synchronization

ASP Confluence and Determinacy Future updates can occur at any time

Execution characterized by the order of request senders

Determinacy of programs communicating over trees, …

4- Conclusion

Thank You

Any Question?

Thank You

Any Question?

Perspectives

Approximation of confluence property Static analysis

Generalization of confluence property Functional behavior Scheduling of requests

Extensions of ASP Group communication Component calculus Mobility and other features

Related Work

Futures and Wait by Necessity: MultiLisp by Halstead Wait-By-Necessity by Caromel

Determinism: by JonesLinearized channels Process Networks by Kahn and MacQueen

Objects and concurrency: Obliq, Gordon-Hankin-Lassen Actors -calculus, blue calculus, join-calculus

Terms:

Configuration: Request queue: Futures list: Store:

Intermediate Structures

Static DON versus Process Networks

{foo,bar} , {gee}

{foo,bar} , {gee}

{gee}, {f},{g}

{bar} , {gee}

{foo,bar} , {gee}

foo

bar

f{foo}, {bar}

{gee}, {f},{g}

{f},{g}{gee}, {f},{g}f

g

gee

f

g

put

get

Active(a)

newact=Active(a)

newact

Activity Creation ( NEWACT )

Objects Topology

Equivalence Modulo Futures Updates

f1

f2

f3

More Futures

...result.bar()

More Futures

result.bar()

More Futures

result.bar()Futures updates can occur at any time

Futures updates can occur at any time

Concurrent Constraint Programming

Constraint programming, different notion of store

Shared memory

No internal state in the store (functional agents)

Data-driven / constraint driven synchronization:

Blocking Ask

Determinate case

Active(a,s)

newact=Active(a,s)


Active(a,s)

newact=Active(a,s)

newact


ao.s()


f1

f2

f3

f1

f2


f2

f3

f1

f1

f2

f1

Store Partitioning

Serve(foo)

Serve(foo);...

bar foo

Request Service ( SERVE )

Serve(foo)

barfoo

Serve(foo);...

...foo

Request Service ( SERVE )

Objectives

Model of the following features Object orientation (activities, communications) Asynchronous communications with futures Service policy

Confluence and determinacy Identify sources of non-determinism Characterize equivalent executions Give general properties Find some properties easy to verify

value

foo bar

...

End Of Service ( ENDSERVICE )

value

barfoo

...

...

End Of Service ( ENDSERVICE )

asynchronous and deterministic objects

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