Shortening design time through multiplatform simulations with a portable OpenCL golden-model: the LDPC decoder case

Gabriel Falcao1,  Muhsen Owaida2,  David Novo3,  Madhura Purnaprajna3,  Nikolaos Bellas2,  Christos D. Antonopoulos2,  Georgios Karakonstantis3,  Andreas Burg3,  Paolo Ienne3
1Department of Electrical and Computer Engineering, University of Coimbra, Portugal, 2Department of Computer and Communication Engineering, University of Thessaly, Volos, Greece, 3Ecole Polytechnique Fédéral de Lausanne (EPFL), Switzerland


Abstract

Hardware designers and engineers typically need to explore a multi-parametric design space in order to find the best configuration for their designs using simulations that can take weeks to months to complete. For example, designers of special purpose chips need to explore parameters such as the optimal bitwidth and data representation. This is the case for the development of complex algorithms such as Low-Density Parity-Check (LDPC) decoders used in modern communication systems. Modern high-performance computing offers a wide set of acceleration options, that range from multicore CPUs to graphics processing units (GPUs) and FPGAs. Depending on the simulation requirements, the ideal architecture to use can vary. In this paper we propose a new design flow based on OpenCL, a unified multiplatform programming model, which accelerates LDPC decoding simulations, thereby significantly reducing architectural exploration and design time. OpenCL-based parallel kernels are used without modifications or code tuning on multicore CPUs, GPUs and FPGAs. We use SOpenCL (Silicon to OpenCL), a tool that automatically converts OpenCL kernels to RTL for mapping the simulations into FPGAs. To the best of our knowledge, this is the first time that a single, unmodified OpenCL code is used to target those three different platforms. We show that, depending on the design parameters to be explored in the simulation and on the dimension of the design, the GPU or the FPGA may suit different purposes more conveniently, providing different acceleration factors. For example, although simulations generated with SOpenCL typically can execute faster on FPGAs than GPU ones, the overhead of circuit synthesis often outweighs the benefits of FPGA-accelerated execution.