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Section: Partnerships and Cooperations
International Initiatives
Inria Associate Teams
POLYCORE
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Title: Models of computation for embedded software design of multi-core architectures
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See also: http://www.irisa.fr/espresso/Polycore
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Anyone experienced with multi-threaded programming would recognize the difficulty of designing and implementing such software. Resolving concurrency, synchronization, and coordination issues, and tackling the non-determinism germane in multi-threaded software is extremely difficult. Ensuring correctness with respect to the specification and deterministic behavior is necessary for safe execution of such code. It is therefore desirable to synthesize multi-threaded code from formal specifications using a provably “correct-by-construction” approach. In Europe, it has been widely claimed that the embedded software for “fly-by-wire” was mostly automatically generated using French tools based on the synchronous programming models. Unfortunately, software generated in those contexts usually operate in a time-triggered execution model. Such models are simpler but less efficient than multi-threaded software on multi-core processors. Normally they run on multiple processors communicating over a time-triggered bus. Hence the execution is less efficient than it could be. While time-triggered programming model simplifies code generation, we feel that multi-rate event driven execution model is much more efficient. Code synthesis for such execution model must be thoroughly investigated. The multi-threaded software generation is inspired by a recent shift in the hardware design paradigms from single-core to multi-core processors. This shift has brought parallel and concurrent programming to the desktop and embedded arena. In the desktop market, most processors now being sold are multi-core, and very soon this trend might conquer the embedded world as well. We plan to develop formal models, methods, algorithms and techniques for generating provably correct multi-threaded reactive real-time embedded software for mission-critical applications. For scalable modeling of larger embedded software systems, the specification formalism has to be compositional and hierarchical. Our proposed formalism entails a model of computation (MoC) based on a multi-rate synchronous dataflow paradigm: Polychrony.
Inria International Partners
The University of Hong Kong, Emerging Technologies Institute
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Title: Virtual prototyping of embedded software architectures
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Embedded software architectures are modeling objects at the crossing of several design viewpoints: the physical environment, the embedded software and the hardware architecture. These viewpoints present different perceptions of time: continuous and discrete, event-based and clock-based. They are further represented by high-level models that significantly alter this perception: in the model of the environment, evolution over time is represented by differential equations whose resolution alters discrete simulation time; in the model of the embedded software, hardware/operating-system events are sampled by periodic reaction loops; in the model of the hardware, instruction clock time is usually approximated by coarser periods or transactions. Providing a mathematical framework, verification and synthesis tools, to understand, compose and orchestrate them would prove invaluable to system architects. The architect operates from design focus point around which all components of the system under design—software, middleware, hardware and environment—need to be analyzed, profiled, composed, simulated, validated. It is the aim of our project to propose a formal design methodology to that purpose.
Beihang University, Institute of Computer Architectures
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Title: Certifiable development of a synchronous compiler for multi-core platforms
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The synchronous paradigm is a widely accepted approach for the design of safety-critical applications, such as digital circuits or embedded software. The well-defined notions of time and causality at specification-level provide a simple way to model, analyze and verify systems. The synchronous programming paradigm is made popular because of its role at the joint point of 1) computer science and language design, 2) control theory and reactive systems, and 3) microelectronic (synchronous) circuit design. It provides a sound semantic background with a notion of discrete instants and successive reactions, together with high-level structuring primitives which help defining subthreads whose activations (defined by signals or clocks) model over/sub-sampling. Exploiting the semantic independence of various computations to allow the generation of concurrent, potentially distributed code from synchronous and polychronous specifications is a notoriously difficult subject. It amounts to determining which part of the system-wide synchronization specific to the synchronous model can be removed while preserving the specified functionality. In this context, the objective of the proposed project consists in the design of a certifiable compiler from a synchronous language to a multicore platform. However, even if the compilation of endochronous systems to a sequential architecture has been widely studied for twenty years, targeting multicore architectures is more recent and exploiting weak endochrony has not yet been deeply explored. Three main points will be addressed: the architecture of a compiler of weakly-endochronous programs to a virtual parallel machine; the formal verification of some of these compilation steps as well as the formal modeling of the target; the study of multicore platforms, of their synchronization primitives and the implementation of the virtual machine on such a platform.
Participation In other International Programs
USAF Office for Scientific Grant FA8655-13-1-3049
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Title: Co-Modeling of Safety-Critical Multi-threaded Embedded Software for Multi-Core Embedded Platforms
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See also: http://www.irisa.fr/espresso/Polycore
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The aim of the USAF OSR Grant FA8655-13-1-3049 is to support collaborative research entitled “Co-Modeling of safety-critical multi-threaded embedded software for multi-core embedded platforms” between Inria project-team ESPRESSO, the VTRL Fermat Laboratory and the TUKL embedded system research group, under the program of the Polycore associate-project.