Section: Software

ID.Fix: Infrastructure for the Design of Fixed-point Systems

Participants : Daniel Menard [correspondant] , Olivier Sentieys, Romuald Rocher, Nicolas Simon, Quentin Meunier.

The different techniques proposed by the team for fixed-point conversion are implemented on the ID.Fix infrastructure. The application is described with a C code using floating-point data types and different pragmas, used to specify parameters (dynamic, input/output word-length, delay operations) for the fixed-point conversion. This tool determines and optimizes the fixed-point specification and then, generates a C code using fixed-point data types (ac_fixed ) from Mentor Graphics. The infrastructure is made-up of three main modules corresponding to the fixed-point conversion (Fix.Conv), the accuracy evaluation (Acc.Eval) and the dynamic range evaluation (Dyn.Eval).

The different developments carried-out in 2011 allow obtaining a fixed-point conversion tool handling functions, conditional structures and repetitive structures having a fixed number of iterations during time. For the accuracy evaluation (Acc.Eval), conditional structures and correlation between noise sources have been considered. For the dynamic range evaluation (Dyn.Eval), the method based on the Karhunen-Loève Expansion (KLE) have been implemented. It allows determining the dynamic range for a given overflow probability.

The development of this tool has been achieved thanks to an INRIA post-doc in the context of S2S4HLS project until August 2011, and a University of Rennes graduate engineer from November 2011 in the context of DEFIS ANR project and different students during their training period.