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Synchronous Programming Techniques: from Research to Industry

Gerard Berry

Chief Scientist, Esterel Technologies

Synchronous programming languages were born in the 80's to deal with reactive systems. They describe cycle-base computations, where the cycle can be of various kinds: sampling cycle for signal and continuous control applications, interaction cycle for state machines, clock cycle for hardware circuits. Within a cycle, computation is assumed zero-delay. Cycle-base synchrony is mathematically simple and compositional by nature. It makes it possible to build concurrent systems whose behavior remains fully deterministic, unlike for more classical asynchronous techniques.

Synchronous languages originally came in two flavors: data-flow based (Lustre, Signal) and control-flow based (Esterel, SyncCharts, Reactive C). These two flavors are now unified in two industrial products, SCADE and Esterel Studio. SCADE is devoted to certified safety-critical applications in avionics and automotive. It is extensively used by companies such as Airbus and Eurocopter for flight control and numerous other functions. Esterel Studio is devoted to hardware circuit design. It is used by companies such as Texas Instruments and Philips.

In the talk, we concentrate on the interaction between the scientific aspects of synchronous languages and their industrial usage. Synchronous languages and tools are strongly based on the mathematical semantics of synchrony and are linked to formal verification engines, which makes them very rigorous. However, for industrial applications, rigor is not enough.Tools must fit into complex verification or certification flows. In particular, we discuss cosimulation and generated code traceability, which are key practical issues. We also briefly discuss current extensions of the synchronous models to distributed systems and multiclock circuits, which become the rule.

Wednesday Seminars

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