Section: Software and Platforms

Lopht

Participants : Thomas Carle, Manel Djemal, Zhen Zhang, Dumitru Potop Butucaru [correspondant] .

The Lopht (Logical to Physical Time Compiler) has been designed as an implementation of the AAA methodology. Lopht is similar to SynDEx by relying on off-line allocation and scheduling techniques to allow real-time implementation of dataflow synchronous specifications onto multiprocessor systems. But it has two significant originality points: a stronger focus on efficiency (but without compromising correctness), and a focus on novel target architectures (many-core chips and time-triggered embedded systems).

Improved efficiency is attained through the use of classical and novel data structures and optimization algorithms pertaining to 3 fields: synchronous language compilation, classical compiler theory, and real-time scheduling. A finer representation of execution conditions allows us to make a better use of double resource reservation and thus improve latency and throughput. The use of software pipelining allows the improvement of computation throughput. The use of post-scheduling optimisations allows a reduction in the number of preemptions. The focus on novel architectures means that architecture descriptions need to define novel communication media such as the networks-on-chips (NoCs), and that real-time characteristics must include those specific to a time-triggered execution model, such as the Major Time Frame (MTF).

Significant contributions to the Lopht tool have been brought by T. Carle (the extensions concerning time-triggered platforms), M. Djemal (the extensions concerning many-core platforms), and Zhen Zhang under the supervision of D. Potop Butucaru. The tool has been used and extended during the PARSEC project. It is currently used in the IRT SystemX/FSF project, in the collaboration with Astrium Space Transportation (Airbus Defence and Space), and in the collaboration with Kalray SA. It has been developed in OCaml.