Section: Overall Objectives

Introduction

Keywords:

Compilation, code analysis, code optimization, memory optimization, combinatorial optimization, algorithmics, polyhedral optimization, hardware accelerators, high-level synthesis, high-performance computing.

Compsys develops compilation techniques, more precisely code analysis and code optimization techniques, to help programming or designing “embedded computing systems” or platforms for “small” HPC (High-Performance Computing). The team focuses on both low-level (back-end) optimizations and high-level (front-end, mainly source-to-source) transformations, for specialized processors, programmable hardware accelerators (GPU, multicores), and FPGA platforms (high-level synthesis). Recent activities include a shift towards the analysis of parallel languages, and links with abstract interpretation and program termination. The main characteristic of Compsys is its use of algorithmic and formal methods (with graph algorithms, linear programming, polyhedral optimizations) to address code analysis and optimization problems (e.g., termination, register allocation, memory optimizations, scheduling, automatic generation of interfaces) and the validation of these techniques through the development of compilation tools.

Compsys started as an Inria project in 2004, after 2 years of maturation. This first period of Compsys, Compsys I, was positively evaluated in Spring 2007 after its first 4 years period (2004-2007). It was again evaluated by AERES in 2009, as part of the general evaluation of Lip, and got the best possible mark, A+. The second period (2007-2012), Compsys II, was again evaluated positively by Inria in Spring 2012 and formally prolonged into Compsys III at the very end of 2012. In 2013, Fabrice Rastello moved to Grenoble first to expand the activities of Compsys in the context of Giant, a R&D technology center with several industrial and academic actors. He left officially the team in 2014 to work on his own. The research directions of Compsys III followed the lines presented in the synthesis report provided for the 2012 evaluation (See http://www.ens-lyon.fr/LIP/COMPSYS/wordpress/wp-content/uploads/2013/09/ficheSynthese.pdf ), including a shift towards the compilation of streaming programming, the analysis and optimizations of parallel languages, and an even stronger focus on polyhedral optimizations and their extensions. Christophe Alias was mostly involved in the development of the Zettice/XtremLogic start-up. The hiring of Laure Gonnord (in 2013) and Tomofumi Yuki (in 2014) added new forces on the code analysis research aspects and on HPC polyhedral-related topics. However, Christophe Alias and Laure Gonnord left the team in Sep. 2015. The project-team itself ended officially in Dec. 2015, reaching the limit of 12 years. Nevertheless, it will be evaluated again by Inria in Spring 2016. It has been extended as an Inria team until Dec. 2016.

Section  2.2 defines the general context of the team's activities. Section  2.3 presents the research objectives and main achievements in Compsys I, i.e., until 2007, and how its research directions were modified for Compsys II. Section  2.4 briefly presents the main achievements of Compsys II and of the first years of Compsys III, referring to the annual reports from 2008 to 2014 for details. As for the highlights of the past year, i.e., 2015, they are given in Section  5.1 .