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Troisieme partie Cours EJC 2003, AUSSOIS, www.inria.fr/oasis/ProActive

Denis Caromel

OASIS TeamINRIA -- CNRS - I3S -- Univ. of Nice Sophia-Antipolis

EJCP , Lundi 2 juin 2003

ASP: Asynchronous Sequential Processes

An Imperative and Parallel Object Calculus

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The ASP calculus: Asynchronous Sequential Processes

Together with Ludovic Henrio, and Bernard Serpette

Objectives:

• Formally study the ProActive model

• Investigate various strategies for asynchronous calls

• Prove some equivalence between Sequential and Parallel programs

• Demonstrate the deterministic nature of sub-sets of the model

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ASP principles and Sequential CalculusImperative sigma-calculus a la Abadi-Cardelli

Sequential Language:

Example: a point object

A call to a point:

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Principles of Reduction

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The Heap -- StoreReduced objects: all

fields are reduced to a location

Heap Reference: Locations

Heap Sequential Configuration

Heap Well Formed properties

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Reduction Context

From A. D. Gordon, P. D. Hankin, and S. B. Lassen,

Compilation Equivalence of Imperative Objects, FST+TCS’97, LNCS

Reduction context = an expression with a hole :

provides a deterministic order of evaluation:

• Target object before parameters

• Fields of objects: left to right

• Assignment: left before right

Abbreviation of substitution

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Sequential Transition System

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Sequential TS Properties

From Gordon-Hankin-Lassen:

Sequential reduction preserves well-formdness:

Sequential reduction is deterministic (modulo renaming):

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Parallel calculus

Language:

Intuitive semantics:• Object activation: copy together with a deep copy of its reachable objects

• Asynchronous calls: a Request Queue per Activity

• M is a list of method labels (names) used to specify the request to be served

• A list of already computed futures per activity

• At any time, a full or partial reply may be send back (not eager)

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Parallel Binary Tree

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Example of a parallel configuration

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Structure of Activities (3)

Parallel configurations:

• name of activity [• a current expression being evaluated

• its own heap

• a reference towards the Active Object in the heap (root)

• a list of request to execute in FIFO order:

• a list of futures already computed (future Id --> obj in heap)• A current future: Id associated to the current service

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3 additions to the Sequential Calculus

In the store: Remote Objects (proxy) and Futures (proxy for futures)

Reduction contexts: to reduce within an Active expression

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Deep (Parallel) Copy

Basic ideas:• upon an active object OA(alpha) , or a future Fut(f beta->alpha)

• the parallel copy stops copying, but pass the OA or Fut as is

It means we pass futures as parameters of communications

Transition System: Deep Copy (more operational def. exists)

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Parallel

Transition System

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Properties

The PTS is correct with respect to the well formed properties:

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Store partitioning

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A confluence property (1)

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A confluence property (2)

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A confluence property (3)

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A confluence property (4)

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A confluence property (5)

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Deterministic Object Networks (1)

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Deterministic Object Networks (2)

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Tree Topology Determinism

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Conclusion• A library: ProActive 100% Java

• Parallelism, distribution, synchronization (CSCW), and mobility

• Reuse -- seamless• Polymorphism with existing class types

• Asynchrony -- Wait-by-necessity

• An interactive tool towards Metacomputing: IC2D

• A calculus:ASP: Asynchronous Sequential Processes• Capture the semantics, and demonstrates the independence of activities

• Results of confluence and determinism

• Mobility to be added

ProActive vs. RMI alone : - 30% of code www.inria.fr/oasis/ProActive