University of Birmingham > Talks@bham > Computer Science Departmental Series > Cycle-based Programming of Distributed Systems: The Synchrony Hypothesis and Constructive Circuits.

Cycle-based Programming of Distributed Systems: The Synchrony Hypothesis and Constructive Circuits.

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If you have a question about this talk, please contact Mohammad Tayarani.

Host: Dr. Dan R. Ghica

The synchronous model of programming, which emerged in the 1980ies and has led to the development of well-known languages such as Esterel, Signal, Lustre, has made the programming of concurrent systems with deterministic and bounded reaction a routine exercise. The synchronous approach draws its success from the fact that it is founded on a simple and well-understood mathematical model of computation, the Mealy automaton. However, validity of this model is not for free. It depends on the Synchrony Hypothesis according to which a system is invariably faster than its environment. Under this hypothesis the system’s reactions to input stimuli can be abstracted into atomic and instantaneous input-output actions, the so-called synchronous steps. Since in a distributed system each node is in the environment of the every other node, it follows that each node must be faster than every other and hence faster than itself. Solving this paradox requires global assumptions on timing and scheduling which refine the classical Mealy model by constructive notions of input-output causality. >> This talk reviews some of the more prominent constructive interpretations of the Synchrony Hypothesis which amount to different ways of organizing asynchronous computations inside clocked synchronous cycles. In particular, the talk introduces the class of “constructive circuits”, for which signals settle to a unique value in bounded time, for any input, under up-bounded non-inertial (UN) delays. This class is important, because, as recently discovered, constructive circuits can be analyzed correctly and efficiently by the well-known technique of timed ternary simulation.

This talk is part of the Computer Science Departmental Series series.

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