PhD Defence: “Dynamic Heterogeneous Memory Allocation for embedded devices”, Tristan Delizy, Chappe Amphitheater, CITI, 19th of December 2019 at 10h00


Dynamic Heterogeneous Memory Allocation for embedded devices


Reducing energy consumption is a key challenge to the realisation of the Internet of Things. While emerging memory technologies may offer power reduction and high integration density, they come with major drawbacks such as high latency or limited endurance. As a result, system designers tend to juxtapose several memory technologies on the same chip. We aim to provide the embedded application programmer with a transparent software mechanism to leverage this memory heterogeneity. This work studies the interaction between dynamic memory allocation and memory heterogeneity. We provide cycle accurate simulation of embedded platforms with various memory technologies and we show that different dynamic allocation strategies have a major impact on performance. We demonstrates that interesting performance gains can be achieved even for a low fraction of memory using low latency technology, but only with a clever placement strategy between memory banks. We propose an efficient strategy based on application profiling in our simulator.



  • Olivier Sentieys, Professeur des Universités, Université de Rennes – Examinateur
  • Cécile Belleudy, Maitre de Conférence HDR, Université de Nice Sophia Antipolis – Rapporteure
  • Lionel Torres, Professeur des Universités, Université de Montpellier – Rapporteur
  • Guillaume Salagnac, Maitre de Conférences, INSA de Lyon – Examinateur, Encadrant
  • Tanguy Risset, Professeur des Universités, INSA de Lyon – Examinateur, Co-directeur de thèse
  • Matthieu Moy, Maitre de Conférences HDR, Université Claude Bernard Lyon 1 – Examinateur, Co-directeur de thèse

Journées Nationales de la Recherche en Robotique

Du 14 au 17 octobre, Olivier Simonin a co-présidé avec François Charpillet (Inria Nancy) les JNRR 2019 Journées Nationales de la Recherche en Robotique, qui se sont tenues à Vittel et parrainées par le GDR Robotique. Le 13 octobre était également organisée la Journée des Jeunes Chercheurs en Robotique JJCR, et les 17/18 un tutoriel Apprentissage & Robotique était organisé par Christian Wolf et David Filliat.

L’événement, qui a lieu tous les 2 ans, a eu un fort succès en accueillant 200 participants, qui ont pu suivre 27 exposés scientifiques sur 3 jours.

Site des JNRR 2019 (accès au programme) :

CITI seminar – John Manuel Delgado and Michael Puentes (TInteresaLab de Unidades Tecnológicas de Santander) – 22/11 at 9:00AM

Title: Pedestrian Behavior Modeling and Simulation from Real Time Data Information

Date and Place: 22 / 11 / 2019 09:00 in TD-D

Speaker: John Manuel Delgado and Michael Puentes (TInteresaLab de Unidades Tecnológicas de Santander – UTS, Colombia)

Host: Oscar Carrillo

Accidents of pedestrians sometimes take lives, in Bucaramanga since 2012 pedestrian died by accidents are 179, and 2873 hurt, In a city like Bucaramanga-Colombia, this means each day at least one pedestrian is involved in an accident. Therefore is necessary to know the causes of accidents in the way to decrease the accidents. One of many reasons to know the causes is with system dynamics, simulating the events of the Pedestrian behavior when accidents occur in risen cities. The implementation simulation joint with technology and research looking for saving lives, reducing the accidental rate, and to implementing or suggesting new policies from the government. This project is looking for the implementation of technology in video records and Deep Learning analysis for the service of the citizens, where a simulation model will be revealing the main variables which intervene in the pedestrian’s behavior. As initials results, shows the methodology here implemented, can reach data which was insufficient before thanks to the cameras and software of objects detection, those are the data input for the simulation model, which after to implement a change in a particular spot of Bucaramanga is possible to decrease the accident rate in 80% where pedestrians could be involved.


PhD Defence: “High-level synthesis and arithmetic optimizations”, Yohann Uguen, Chappe Amphitheater, CITI, 13th of November 2019 at 13h30


High-level synthesis and arithmetic optimizations


High-level synthesis (HLS) tools offer increased productivity regarding FPGA programming. However, due to their relatively young nature, they still lack many arithmetic optimizations. This thesis proposes safe arithmetic optimizations that should always be applied. These optimizations are simple operator specializations, following the C semantic. Other require to a lift the semantic embedded in high-level input program languages, which are inherited from software programming, for an improved accuracy/cost/performance ratio. To demonstrate this claim, the sum-of-product of floating-point numbers is used as a case study. The sum is performed on a fixed-point format, which is tailored to the application, according to the context in which the operator is instantiated.

In some cases, there is not enough information about the input data to tailor the fixed-point accumulator. The fall-back strategy used in this thesis is to generate an accumulator covering the entire floating-point range. This thesis explores different strategies for implementing such a large accumulator, including new ones. The use of a 2’s complement representation instead of a sign+magnitude is demonstrated to save resources and to reduce the accumulation loop delay.

Based on a tapered precision scheme and an exact accumulator, the posit number systems claims to be a candidate to replace the IEEE floating-point format. A throughout analysis of posit operators is performed, using the same level of hardware optimization as state-of-the-art floating-point operators. Their cost remains much higher that their floating-point counterparts in terms of resource usage and performance.

Finally, this thesis presents a compatibility layer for HLS tools that allows one code to be deployed on multiple tools. This library implements a strongly typed custom size integer type along side a set of optimized custom operators.



  • Philippe Coussy, Professeur des Universités, UBS, Lorient, France : Rapporteur
  • Olivier Sentieys, Professeur des Universités, Univ. Rennes, Inria, IRISA, Rennes : Rapporteur
  • Laure Gonnord, Maître de conférence, Université Lyon 1, France : Examinatrice
  • Frédéric Pétrot, Professeur des Universités, TIMA, Grenoble, France : Examinateur
  • Martin Kumm, Professeur des Universités, Université de Fulda, Allemagne : Examinateur
  • Florent de Dinechin, Professeur des Universités, INSA Lyon, France : Directeur de thèse

CITI seminar – Martin Kumm (University of Applied Sciences Fulda, Germany) – 13/11 at 10:30AM

Title: Design of Optimal Multiplierless FIR Filters

Date and Place: 13 / 11 / 2019 10:30 in TD-C

Speaker: Martin Kumm (University of Applied Sciences Fulda, Germany)

Host: Florent de Dinechin

In this talk we present a novel method for the simultaneous design of digital filters adhering to a given frequency specification and its dedicated (hardware) implementation. Our methods are based on an integer linear programming (ILP) problem and aim to minimize the number of adders used to implement a digital filter. In the first part, an overview is given about the structure of finite impulse response (FIR) filters which typically contain many costly multiplications. As these are usually multiplications by a constant, they can be reduced to additions, subtractions and bit-shifts, leading to a multiplierless realization. A brief overview of state-of-the-art methods for optimizing constant multiplications is presented. In the second part, novel extensions are presented that also consider the frequency specification of the digital filter in the optimization. Compared to previous multiplierless FIR approaches, the methods introduced here ensure adder count optimality. We show the effectiveness by solving established design problems: our results either prove existing heuristics to be optimal or improve their adder count.

Martin Kumm is full professor in the faculty of Applied Computer Science at the University of Applied Sciences Fulda in Germany. His research interests are arithmetic circuits and their optimization in the context of reconfigurable systems (FPGAs).

CITI Seminar of Erwan Le Merrer / Gilles Tredan (Inria-Rennes / LAAS-CNRS) on October 9 at 3pm

Title: The Bouncer Problem: Challenges to Remote Explainability

Date and Place: 09 / 10 / 2019 3PM in 432 (Antenne Inria)

Host: Privatics

The concept of explainability is envisioned to satisfy society’s demands for transparency on machine learning decisions. The concept is simple: like humans, algorithms should explain the rationale behind their decisions so that their fairness can be assessed. While this approach is promising in a local context (e.g. to explain a model during debugging at training time), we argue that this reasoning cannot simply be transposed in a remote context, where a trained model by a service provider is only accessible through its API. This is problematic as it constitutes precisely the target use-case requiring transparency from a societal perspective. Through an analogy with a club bouncer (which may provide untruthful explanations upon customer reject), we show that providing explanations cannot prevent a remote service from lying about the true reasons leading to its decisions.

More precisely, we prove the impossibility of remote explainability for single explanations, by constructing an attack on explanations that hides discriminatory features to the querying user. We provide an example implementation of this attack. We then show that the probability that an observer spots the attack, using several explanations for attempting to find incoherences, is low in practical settings. This undermines the very concept of remote explainability in general.

Erwan is on an “advanced research position” at Inria, in the WIDE team, since Nov. 2018. He was previously senior research scientist at Technicolor R&I (2009-2018). Gilles is a “chargé de recherches” at CNRS since 2011.

CITI Seminar of Subhash Lakshminarayana (University of Warwick’s School of Engineering) on September 19 at 2pm

Title: On False Data Injection Attacks Against Power Grids and Countermeasures

Date and Place: 19 / 09 / 2019 2PM in TD-C

Host: Samir M. Perlaza

The power grid state estimation (SE) has been shown to be vulnerable to false data injection (FDI) attacks, which can lead to severe consequences, e.g., transmission line trips, unsafe frequency excursions and/or economic losses. In this talk, we will examine the security of power gird SE from both the attacker and the defender’s perspective. For the former, we examine data-driven FDI attacks, i.e., constructing FDI attacks that can bypass the grid’s bad-data detector (BDD) by accessing its measurement data over a period of time. We characterize important tradeoffs for the attacker in this context between the attack’s spatial and temporal efficiency. The results provide us with an understanding for designing defense mechanism to thwart such attacks. For defense, we propose a hardened-attack detector based on moving-target defense (MTD) that actively perturbs transmission line reactances to invalidate the attacker’s knowledge. We present novel formal design criteria to select MTD reactance perturbations that are truly effective. Moreover, based on a key optimal power flow formulation, we find that the effective MTD may incur a non-trivial operational cost. Accordingly, we characterize important tradeoffs between the MTD’s detection capability and its associated required cost. Extensive simulations, using the MATPOWER simulator and benchmark IEEE bus systems, verify and illustrate the proposed design approach.

Subhash Lakshminarayana is an assistant professor in the University of Warwick’s School of Engineering since September 2018. Prior to joining Warwick, he worked as a research scientist at the Advanced Digital Sciences Center (ADSC) in Singapore between 2015-2018. Before that, he held joint post-doctoral researcher appointment at Princeton University and the Singapore University of Technology and Design (SUTD) between 2013-2015. He received his PhD in the field of Wireless Communications at the Department of Telecommunications at Ecole Superieure d’Electricite (Supelec) Paris, France, M.S. degree from The Ohio State University, USA and B.S. from Bangalore University in India. His research interests include cyber-physical system security (power grids and urban transportation) and wireless communications. His works have been selected among the Best Conference Papers at the IEEE Power Energy Society General Meeting (PESGM) 2015 conference, and the Best 50 Papers at the IEEE Globecom 2014 conference.

CITI Seminar of Christine Solnon (INSA-Lyon-LIRIS) on September 26 at 2pm

Title: Time-Dependent and Stochastic Vehicle Routing Problems

Date and Place: 26 / 09 / 2019 14:00 in TD-C

Host: Florent de Dinechin

Smart cities are equipped with sensors which monitor traffic speed. The exploitation of these data to optimise urban deliveries has given rise to new challenging problems, and I’ll focus on two of them: – Time-Dependent Vehicle Routing Problems, which take into account variations of travel speeds during the day; – Stochastic Vehicle Routing Problems, where uncertain data are represented by random variables.

Christine Solnon is Professor in the Computer Science Department of INSA Lyon, and member of the LIRIS lab.

PhD Defence: “Contributions Théoriques sur les Communications Furtives”, David KIBLOFF, Chappe Amphitheater, CITI, 17th of September 2019 at 14h00


Information Theoretic Contributions to Covert Communications


The problem of covert communications, also known as communications with low-probability of detection has gained interest in the information theory community in the last years. Since Bash et. al. showed in 2012 that the square-root law applied in the point-to-point case for such communications systems, the number of contributions on the topic did not cease to grow. In this thesis, two new problems of covert communications are introduced. First, the problem of covert communications over a point-to-point link where a warden observes only a fraction of channel outputs in order to try to detect the communications is studied. An achievability bound in the finite block-length regime is derived for this problem. Second, the problem of embedding covert information into a given broadcast code is introduced. Given a broadcast code to transmit a common message to two receivers, the goal is to determine the maximum number of information bits that can be reliably sent to one receiver while remaining covert with respect to the other receiver. For this problem, both an achievability and converse bound in the asymptotic block-length regime are derived for a particular class of channels, i.e., symmetric channels. Together these bounds characterize the maximum number of information bits that can be covertly embedded in a given broadcast code for symmetric channels.



  • Dr. Albert Guillen i Fabregas, Université Pompeu Fabra, Espagne. Rapporteur.
  • Dr. Aline Roumy, INRIA, France. Rapporteure.
  • Dr. Laurent Clavier, IMT Lille Douai, France. Examinateur.
  • Dr. Inbar Fijalkow, Université de Cergy-Pontoise, France. Examinatrice.
  • Dr. Jean-Marie Gorce, INSA de Lyon, France. Examinateur.
  • Dr. Ligong Wang, CNRS, France. Examinateur.
  • Dr. Guillaume Villemaud, INSA de Lyon, France. Directeur de thèse.
  • Dr. Samir M. Perlaza, INRIA, France. Encadrant de thèse.
  • Dr. Ronan Cosquer, DGA, France. Invité.

Save the date: Atelier “algorithmes en boite-noire” – October 10, Lyon

Atelier “algorithmes en boite-noire”
Etat des lieux et réaction face à une exposition massive aux décisions algorithmiques.
Le 10 Octobre 2019 à Lyon

Les technologies de l’information et de la communication transforment la
société. Les algorithmes sont au coeur de toutes les attentions: objets
industriels fondamentaux pour les entreprises, ils sont souvent perçus comme
des “boites-noires” par les utilisateurs confrontés à leurs décisions. Ce
constat ne va qu’en s’amplifiant avec le déploiement continu de solutions à
base d’apprentissage machine, dont les dernières avancées techniques
(réseaux de neurones profonds) fournissent des décisions qui sont
inexplicables par construction.

L’objectif de cet atelier est de questionner ces boites-noires, leur nature,
leur conception, et plus généralement leur impact sur leurs usagers et sur la
société. La visée pluridisciplinaire et transversale de l’atelier cherchera
par exemple à aborder des sujets tels que:

– Les biais de traitement des algorithmes, et les moyens de quantifier ce biais?
– L’implémentabilité de la notion de bien commun ?
– Quels outils et quelles métriques pour un audit citoyen des algorithmes ?
– Quelle responsabilité pour les concepteurs d’algorithmes opaques ?
– Les moyens pour l’utilisateur d’observer et d’appréhender les résultats des
algorithmes en boite-noire pour construire une compréhension.
– L’évolution de la société face au nombre grandissant de boites-noires à
visées décisionnelles automatiques, et le manque avéré d’explications des
– Quelles notions d’éthique dans le développement courant de ces
boites-noires? Sont elles suffisantes et satisfaisantes ?
– Le traitement des données personnelles des utilisateurs, la notion de
consentement et celle de la compréhension. Comment exercer un contrôle
critique sur le traitement de nos données critiques ?

Intervenants (confirmés):
* Dominique CARDON (sociologue, directeur du Médialab de Sciences Po)
* Loup CELLARD (designer, doctorant au Centre for Interdisciplinary
Methodologies de l’University of Warwick, UK)
* Claude KIRCHNER (directeur de recherches émérite d’Inria, membre de
plusieurs comités liés à l’éthique)
* Claire MATHIEU (directrice de recherches CNRS, spécialiste des algorithmes
et chargée de mission Parcoursup)
* Antoinette ROUVROY (Juriste et philosophe du droit, professeure à
l’université de Namur et chercheuse au FNRS, Belgique)
* Félix TREGUER (membre de la Quadrature du Net et chercheur au Centre
Internet et Société du CNRS et au CERI de Sciences Po)

Le programme courant est disponible ici :

Localisation :  Les Halles du Faubourg – 10 Impasse des Chalets, 69007 Lyon

Inscription (gratuite) :