Vous êtes cordialement invités à venir assister à la soutenance de thèse de Jaechul LEE, équipe TARAN, le jeudi 08 décembre 2022 à 10h00 en salle Métivier.
Energy – Performance Trade-Off for Optical Network-on-Chip
Over the years, System-on-Chip (SoC) has evolved from a single processor in a chip to multi/many processors in chips containing billions of transistors. With the evolution of SoC, new research topics have risen on interconnect between processors in a chip. Network-on-Chip(NoC) has been proposed as a solution for more dynamic communication links to connect large number of Intellectual Property (IP)s. Secondly, to overcome drawbacks of electrical NoC, Optical communication link has been proposed as a promising solution. This type of NoC provides low latency and high bandwidth, but it suffers from low power efficiency.
In this thesis, we address this topic and we aim to develop techniques to manage laser power consumption. To address this challenge, we exploit the approximation concept and we apply it to the ONoC to propose two types of communications: Accurate and Approximate communication. Our proposal is applied to Floating-Point (FP) numbers by using low-power optical signals for LSB, at the cost of higher error rate. These approximate optical signals allow a drastic reduction in the laser power consumption. In parallel, to ensure the communication accuracy on MSBs, the laser power levels are remained using high power signals. Simulations results demonstrate that a reduction of to 42\% of laser power can be obtained for Streamcluster application with a limited degradation at the application level. Furthermore, we propose to manage the communications according to the distance between source and destination cores. However, this fine-grain distance-aware management could be too costly, so we propose a low overhead distance-aware technique based on only two distances Short/Long classes. The results of our evaluation show drastic laser power reduction of 20\%for example for Streamcluster application.
Camel TANOUGAST, Professeur des universités, Université de Lorraine
Frédéric PETROT, Professeur des universités, Université Grenoble Alpes
Angeliki KRITIKAKOU, Maître de conférences HDR, Université de Rennes 1
Daniel CHILLET, Professeur des universités, Université de Rennes 1
Cédric KILLIAN, Maître de Conférences HDR, Université de Rennes 1