Coati is a joint team between Inria Sophia Antipolis - Méditerranée and the I3S laboratory (Informatique Signaux et Systèmes de Sophia Antipolis) which itself belongs to CNRS (Centre National de la Recherche Scientifique) and UNS (Univ. Nice Sophia Antipolis). Its research fields are Algorithmics, Discrete Mathematics, and Combinatorial Optimization, with applications mainly in telecommunication networks.

The main objectives of the Coati project-team are to design networks and communication algorithms. In order to meet these objectives, the team studies various theoretical problems in Discrete Mathematics, Graph Theory, Algorithmics, and Operations Research and develops applied techniques and tools, especially for Combinatorial Optimization and Computer Simulation. In particular, Coati used in the last years both these theoretical and applied tools for the design of various networks, such as wdm, wireless (radio), satellite, overlay, and peer-to-peer networks. This research has been done within various industrial and international collaborations.

Coati also investigates other application areas such as bio-informatics, transportation networks and economics.

The research done in Coati results in the production of advanced software such as Grph, and in the contribution to large open source software such as Sagemath.

Members of Coati have a strong expertise in the design and management of wired and wireless backbone, backhaul, broadband, and complex networks. On the one hand, we cope with specific problems such as energy efficiency in backhaul and backbone networks, routing reconfiguration in connection oriented networks (mpls, wdm), traffic aggregation in sonet networks, compact routing in large-scale networks, survivability to single and multiple failures, etc. These specific problems often come from questions of our industrial partners. On the other hand, we study fundamental problems mainly related to routing and reliability that appear in many networks (not restricted to our main fields of applications) and that have been widely studied in the past. However, previous solutions do not take into account the constraints of current networks/traffic such as their huge size and their dynamics. Coati thus puts a significant research effort in the following directions:

**Energy efficiency and Software-Defined Networks (SDN)** at both the design and management levels. More
precisely, we plan to study the deployment of energy-efficient routing algorithm
within SDN. We developed new algorithms in order to take into account
the new constraints of SDN equipments and we evaluate their performance by simulation and by experimentation
on a fat-tree architecture.

**Larger networks:** Another challenge one has to face is the
increase in size of practical instances. It is
already difficult, if not impossible, to solve practical instances optimally
using existing tools. Therefore, we have to find new ways to solve
problems using reduction and decomposition methods, characterization of
polynomial instances (which are surprisingly often the practical ones), or
algorithms with acceptable practical performances.

**Stochastic behaviors:** Larger topologies mean frequent changes due
to traffic and radio fluctuations, failures, maintenance
operations, growth, routing policy changes, etc. We aim at including these
stochastic behaviors in our combinatorial optimization process to handle the
dynamics of the system and to obtain robust designs of networks.

Coati is mostly interested in telecommunications networks. Within this domain, we consider applications that follow the needs and interests of our industrial partners, in particular Orange Labs or Alcatel-Lucent Bell-Labs, but also SME like 3-Roam.

We focus on the design and management of heterogeneous networks. The project has kept working on the design of backbone networks (optical networks, radio networks, IP networks). We also study routing algorithms such as dynamic and compact routing schemes, as we did in the context of the FP7 EULER led by Alcatel-Lucent Bell-Labs (Belgium), and the evolution of the routing in case of any kind of topological modifications (maintenance operations, failures, capacity variations, etc.).

Our combinatorial tools may be well applied to solve many other problems in various areas (transport, biology, resource allocation, chemistry, smart-grids, speleology, etc.) and we intend to collaborate with experts of these other domains.

For instance, we have recently started a collaboration in Structural Biology with EPI ABS (Algorithms Biology Structure) from Sophia Antipolis (described in Section ). Furthermore, we are working on robot moving problems coming from Artificial Intelligence/Robotic in collaboration with Japan Advanced Institute of Science and Technology. In the area of transportation networks, we have started a collaboration with Amadeus on complex trip planning, and a collaboration with SME Instant-System on dynamic car-pooling combined with multi-modal transportation systems. Last, we have started a collaboration with GREDEG (Groupe de Recherche en Droit, Economie et Gestion, Univ. Nice Sophia Antipolis) on the analysis and the modeling of systemic risks in networks of financial institutions.

Bi Li, former PhD student of Coati, is recipient of the Chinese government award for outstanding self-financed students abroad, edition 2014, for her PhD thesis entitled "Tree Decompositions and Routing Problems".

Fatima Zahra Moataz received the best student paper award of the conference ALGOTEL 2015.

Functional Description

Grph is an open-source Java library for the manipulation of graphs. In 2015, the library has been maintained and augmented for users needs, especially with a new algorithm for iterating over the cycles of a given graph. This was requested by the EPI Aoste for the TimeSquare tool.

Functional Description

JourneyPlanner is a Java implementation of a recursive algorithm to solve a TSP problem on small dense graphs, where non-trivial constraints must be satisfied, that make commonly used paradigms (as dynamic programming) unfit to the task.

This work is done in collaboration with the R&D service of the "Train Transportation" division of Amadeus.

Scientific Description

Sagemath is a free open-source mathematics software system initially created by William Stein (Professor of mathematics at Washington University). It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more. Access their combined power through a common, Python-based language or directly via interfaces or wrappers.

Our contribution

We contribute the addition of new graph algorithms to Sagemath, along with their documentation and the improvement of underlying data structures.

URL : http://

Functional Description

TripPlanner is a tool for computing a minimum cost trip across multiple cities when neither the order in which to visit the cities nor the sojourn duration in these cities are fully specified. The cost of a trip includes both the price of all airplane tickets necessarily for the trip plus the price of the hotels (both costs depend on the exact travel date) at which the user will sojourn. The trip planner is also able to compute the

TripPlanner is written in Python and uses the linear programming interface of Sagemath.

This work is done in collaboration with the R&D service of the "Train Transportation" division of Amadeus.

BNF Antepedia Deposit 2015-09-23-16-11-18

Functional Description

The objective of BigGraphs is to provide a distributed platform for very large graphs processing. A typical data set for testing purpose is a sample of the Twitter graph with 3 millions of nodes and 200 millions of edges. Last year we started the project with the evaluation of existing middlewares (GraphX/Spark and Giraph/Hadoop). After having tested some useful algorithms (written in the BSP model) we decided to develop our own platform.

This platform is based on the existing BigGrph library and this year we have focused on the quality and the improvement of the code. In particular we have designed strong test suites and some non trivial bugs have been fixed. We also have implemented specific data structures for BSP and support for distributed debugging. This comes along with the implementation of algorithms such as BFS or strongly connected components that are run on the NEF cluster.

This project is a joint work of the three EPI Coati, Diana and Scale and is supported by an ADT grant.

URL: http://

The following software are useful tools that bring basic services to the platform (they are not dedicated to BigGrph).

Jac-a-boo: is a framework aiming at facilitating the deployment of distributed Java scientific applications over clusters and is used to start BigGrph. computers.

ldjo: (Live Distributed Java Objects) is a framework for the development and the deployment of Java distributed data structures

Octojus: provides an object-oriented RPC (Remote Procedure Call) implementation in Java

Participants : Luc Hogie [Contact], Nicolas Chleq

URL : http://

In the gathering problem, a particular node in a graph, the base station, aims at receiving messages from some nodes in the graph. At each step, a node can send one message to one of its neighbors (such an action is called a call ). However, a node cannot send and receive a message during the same step. Moreover, the communication is subject to interference constraints, more precisely, two calls interfere in a step, if one sender is at distance at most

To face the explosion of the Internet traffic, a new generation of optical networks is being developed; the Elastic optical Networks (EONs). The aim with EONs is to use the optical spectrum efficiently and flexibly. The benefit of the flexibility is, however, accompanied by more difficulty in the resource allocation problems. In , , , we study the problem of Spectrum Allocation in Elastic Optical Tree-Networks. In trees, even though the routing is fixed, the spectrum allocation is NP-hard. We survey the complexity and approximability results that have been established for the SA in trees and prove new results for stars and binary trees.

The notion of Shared Risk Link Groups (SRLG) captures survivability issues when a set of links of a network may fail simultaneously. The theory of survivable network design relies on basic combinatorial objects that are rather easy to compute in the classical graph models: shortest paths, minimum cuts, or pairs of disjoint paths. In the SRLG context, the optimization criterion for these objects is no longer the number of edges they use, but the number of SRLGs involved. Unfortunately, computing these combinatorial objects is NP-hard and hard to approximate with this objective in general. Nevertheless some objects can be computed in polynomial time when the SRLGs satisfy certain structural properties of locality which correspond to practical ones, namely the star property (all links affected by a given SRLG are incident to a unique node) and the span 1 property (the links affected by a given SRLG form a connected component of the network). The star property is defined in a multi-colored model where a link can be affected by several SRLGs while the span property is defined only in a mono-colored model where a link can be affected by at most one SRLG. In , we extend these notions to characterize new cases in which these optimization problems can be solved in polynomial time. We also investigate the computational impact of the transformation from the multi-colored model to the mono-colored one. Experimental results are presented to validate the proposed algorithms and principles.

Current switches have four ports. Obviously, the larger the number of ports, the more expensive will be the switches, but then fewer will be required. So the cost of such a network involves a trade-off between the total number of switches and their unit cost. In order to determine the minimum-cost network, we give some bounds on the minimum number

We first show

Due to the increasing impact of ICT (Information and Communication Technology) on power consumption and worldwide gas emissions, energy efficient ways to design and operate backbone networks are becoming a new concern for network operators. Recently, energy-aware routing (EAR) has gained an increasing popularity in the networking research community. The idea is that traffic demands are redirected over a subset of the network links, allowing other links to sleep to save energy. We studied variant of this problems.

In , we propose GreenRE – a new EAR model with the support of data redundancy elimination (RE). This technique, enabled within routers, can virtually increase the capacity of network links. Based on real experiments on a Orange Labs platform, we show that performing RE increases the energy consumption for routers. Therefore, it is important to determine which routers should enable RE and which links to put into sleep mode so that the power consumption of the network is minimized. We model the problem as a Mixed Integer Linear Program and propose greedy heuristic algorithms for large networks. Simulations on several network topologies show that the GreenRE model can gain further 37% of energy savings compared to the classical EAR model. In , we introduce an extended model of the classical multi-commodity flow problem with compressible flows which is also robust with fluctuation of traffic demand and compression rate. An heuristic built on this model allows for 16-28% extra energy saving.

To guarantee QoS while implementing EAR, all traffic demands should be routed without violating capacity constraints and the network should keep its connectivity. From the perspective of traffic engineering, we argue that stability in routing configuration also plays an important role in QoS. In details, frequent changes in network configuration (link weights, slept and activated links) to adapt with traffic fluctuation in daily time cause network oscillations. In , we propose a novel optimization method to adjust the link weights of Open Shortest Path First (OSPF) protocol while limiting the changes in network configurations when multi-period traffic matrices are considered.

Recently, there is a trend to introduce content caches as an inherent capacity of network equipment, with the objective of improving the efficiency of content distribution and reducing the network congestion. In , we study the impact of using in-network caches and content delivery network (CDN) cooperation on an EAR. We formulate this problem as Energy Efficient Content Distribution, we propose an integer linear program (ILP) and a heuristic algorithm to solve it. The objective of this problem is to find a feasible routing, so that the total energy consumption of the network is minimized while the constraints given by the demands and the link capacity are satisfied. We exhibit for which the range of parameters (size of caches, popularity of content, demand intensity, etc.) it is useful to use caches. Experimental results show that by placing a cache on each backbone router to store the most popular content, along with well choosing the best content provider server for each demand to a CDN, we can save about 20% of power in average of all the backbone networks considered.

Motivated by finding the best set of links that should be on for energy efficiency, we study the problem of determining the minimum forwarding index of a graph. The (edge) forwarding index of a graph is the minimum, over all possible routings of all the demands, of the maximum load of an edge. This metric is of a great interest since it captures the notion of global congestion in a precise way: the lesser the forwarding-index, the lesser the congestion. This parameter has been studied for different graph classes in the literature. In , we determine, for different numbers of edges, the best spanning graphs of a square grid, namely those with a low forwarding index. In , , we study the following design question: Given a number

*On the complexity of equal shortest path routing.*

Additionally, we studied the complexity of configuring the OSPF-ECMP (for Open Shortest Path First-Equal Cost Multiple Path) protocol. In , we show that the problem of maximizing even a single commodity flow for the OSPF-ECMP protocol cannot be approximated within any constant factor ratio. Besides this main theorem, we derive some positive results which include polynomial-time approximations and an exponential-time exact algorithm.

Software Defined Networking (SDN) is gaining momentum with the support of major manufacturers. While it brings flexibility in the management of flows within the data center fabric, this flexibility comes at the cost of smaller routing table capacities. In , we investigate compression techniques to reduce the forwarding information base (FIB) of SDN switches. We validate our algorithm, called MINNIE, on a real testbed able to emulate a 20 switches fat tree architecture. We demonstrate that even with a small number of clients, the limit in terms of number of rules is reached if no compression is performed, increasing the delay of all new incoming flows. MINNIE, on the other hand, reduces drastically the number of rules that need to be stored with a limited impact on the packet loss rate. We also evaluate the actual switching and reconfiguration times and the delay introduced by the communications with the controller. In parallel, we considered the algorithmic problem of compressing bidimensional routings table with priorities on the rules. We carry out in a study of the problem complexity, providing results of NP-completeness, of Fixed-Parameter Tractability and approximation algorithms. In , we then propose green routing schemes performing simultaneously the selection of the routes, the compression of the routing tables, and decide to put in sleep mode unused links. These algorithms are tested on networks from the SNDLib library.

Coati is also interested in the algorithmic aspects of Graph Theory. In general we try to find the most efficient algorithms to solve various problems of Graph Theory and telecommunication networks. We use graph theory to model various network problems. We study their complexity and then we investigate the structural properties of graphs that make these problems hard or easy. In particular, we try to find the most efficient algorithms to solve the problems, sometimes focusing on specific graph classes from which the problems are polynomial-time solvable. Many results introduced here are presented in detail in the PhD thesis of F. Z. Moataz .

The Gromov hyperbolicity is an important parameter for analyzing complex networks which expresses how the metric structure of a network looks like a tree (the smaller gap the better). It has recently been used to provide bounds on the expected stretch of greedy-routing algorithms in Internet-like graphs, and for various applications in network security, computational biology, the analysis of graph algorithms, and the classification of complex networks.

The best known theoretical algorithm computing this parameter runs in

Topologies for data center networks have been proposed in the literature through various graph classes and operations. A common trait to most existing designs is that they enhance the symmetric properties of the underlying graphs. Indeed, symmetry is a desirable property for interconnection networks because it minimizes congestion problems and it allows each entity to run the same routing protocol. However, despite sharing similarities these topologies all come with their own routing protocol. Recently, generic routing schemes have been introduced which can be implemented for any interconnection networks. The performances of such universal routing schemes are intimately related to the hyperbolicity of the topology. Motivated by the good performances in practice of these new routing schemes, we propose in the first general study of the hyperbolicity of data center interconnection networks. Our findings are disappointingly negative: we prove that the hyperbolicity of most data center topologies scales linearly with their diameter, that it the worst-case possible for hyperbolicity. To obtain these results, we introduce original connection between hyperbolicity and the properties of the endomorphism monoid of a graph. In particular, our results extend to all vertex and edge-transitive graphs. Additional results are obtained for de Bruijn and Kautz graphs, grid-like graphs and networks from the so-called Cayley model.

We study the computational complexity of different variants of tree-decompositions. We also study their relationship with various pursuit-evasion games.

Tree-decompositions are the cornerstone of many dynamic programming algorithms for solving graph problems. Since the complexity of such algorithms generally depends exponentially on the width (size of the bags) of the decomposition, much work has been devoted to compute tree-decompositions with small width. However, practical algorithms computing tree-decompositions only exist for graphs with treewidth less than 4. In such graphs, the time-complexity of dynamic programming algorithms is dominated by the size (number of bags) of the tree-decompositions. It is then interesting to minimize the size of the tree-decompositions. In , , we consider the problem of computing a tree-decomposition of a graph with width at most

Non-deterministic graph searching was introduced by Fomin et al. to provide a unified approach for pathwidth, treewidth, and their interpretations in terms of graph searching games. Given

Cops and robber games, introduced by Winkler and Nowakowski and independently defined by Quilliot, concern a team of cops that must capture a robber moving in a graph. We consider in the class of

The surveillance game models the problem of web-page prefetching as a pursuit evasion game played on a graph. This two-player game is played turn-by-turn. The first player, called the observer, can mark a fixed amount of vertices at each turn. The second one controls a surfer that stands at vertices of the graph and can slide along edges. The surfer starts at some initially marked vertex of the graph, its objective is to reach an unmarked node before all nodes of the graph are marked. The surveillance number

A set of autonomous robots have to collaborate in order to accomplish a common task in a ring-topology where neither nodes nor edges are labeled (that is, the ring is anonymous). In , we present a unified approach to solve three important problems: the exclusive perpetual exploration, the exclusive perpetual clearing, and the gathering problems. In the first problem, each robot aims at visiting each node infinitely often while avoiding that two robots occupy a same node (exclusivity property); in exclusive perpetual clearing (also known as searching), the team of robots aims at clearing the whole ring infinitely often (an edge is cleared if it is traversed by a robot or if both its endpoints are occupied); and in the gathering problem, all robots must eventually occupy the same node. We investigate these tasks in the Look-Compute-Move model where the robots cannot communicate but can perceive the positions of other robots. Each robot is equipped with visibility sensors and motion actuators, and it operates in asynchronous cycles. In each cycle, a robot takes a snapshot of the current global configuration (Look), then, based on the perceived configuration, takes a decision to stay idle or to move to one of its adjacent nodes (Compute), and in the latter case it eventually moves to this neighbor (Move). Moreover, robots are endowed with very weak capabilities. Namely, they are anonymous, asynchronous, oblivious, uniform (execute the same algorithm) and have no common sense of orientation. In this setting, we devise algorithms that, starting from an exclusive and rigid (i.e. aperiodic and asymmetric) configuration, solve the three above problems in anonymous ring-topologies.

A transition in a graph is a pair of adjacent edges. Given a graph

Motivated by some channel assignment problem, we study the following variation of graph colouring problem.
A function

The Grundy index of a graph

An *orientation* of a graph *indegree* of *proper* if *proper orientation number* of a graph

As an evidence to this, we prove that if

However, the proper orientation number has the drawback to be difficult to compute. We prove in that deciding whether *subcubic* graphs

Nevertheless, it might be interesting to bound the proper orientation number on some graph families.
In particular, if we prove that for a graph with treewidth at most

An important result in the Roberston and Seymour minor theory is the polynomial-time algorithm to solve the so-called Linkage Problem.
This implies in particular, that for any fixed graph

We consider the directed analogue

Consider a set of oligomers listing the subunits involved in sub-complexes of a macro-molecular assembly, obtained e.g. using native mass spectrometry or affinity purification. Given these oligomers, connectivity inference (CI) consists in finding the most plausible contacts between these subunits, and minimum connectivity inference (MCI) is the variant consisting in finding a set of contacts of smallest cardinality. MCI problems avoid speculating on the total number of contacts, but yield a subset of all contacts and do not allow exploiting a priori information on the likelihood of individual contacts. In this context, we present in two novel algorithms, MILP-W and MILP-WB. The former solves the minimum weight connectivity inference (MWCI), an optimization problem whose criterion mixes the number of contacts and their likelihood. The latter uses the former in a bootstrap fashion, to improve the sensitivity and the specificity of solution sets. Experiments on three systems (yeast exosome, yeast proteasome lid, human eiF3), for which reference contacts are known (crystal structure, cryo electron microscopy, cross-linking), show that our algorithms predict contacts with high specificity and sensitivity, yielding a very significant improvement over previous work, typically a twofold increase in sensitivity. The software accompanying this paper is made available, and should prove of ubiquitous interest whenever connectivity inference from oligomers is faced.

When an aircraft is approaching an airport, it gets a short time interval (called *slot*) that it can use to land. If the landing of the aircraft is delayed (because of bad weather, or if it arrives late, or if other aircrafts have to land first), it loses its slot and Air traffic controllers have to assign it a new slot. However, slots for landing are a scarce resource of the airports and, to avoid that an aircraft waits too much time, Air traffic controllers have to regularly modify the assignment of the slots of the aircrafts. Unfortunately, for legal and economical reasons, Air traffic controllers can modify the slot-assignment only using two kind of operations: either assign to aircraft

Big Data promises important societal progress but exacerbates the need for due process and accountability. Companies and institutions can now discriminate between users at an individual level using collected data or past behavior. Worse, today they can do so in near perfect opacity. The nascent field of web transparency aims to develop the tools and methods necessary to reveal how information is used, however today it lacks robust tools that let users and investigators identify targeting using multiple inputs. In , , we formalize for the first time the problem of detecting and identifying targeting on combinations of inputs and provide the first algorithm that is asymptotically exact. This algorithm is designed to serve as a theoretical foundational block to build future scalable and robust web transparency tools. It offers three key properties. First, our algorithm is service agnostic and applies to a variety of settings under a broad set of assumptions. Second, our algorithm's analysis delineates a theoretical detection limit that characterizes which forms of targeting can be distinguished from noise and which cannot. Third, our algorithm establishes fundamental tradeoffs that lead the way to new metrics for the science of web transparency. Understanding the tradeoff between effective targeting and targeting concealment lets us determine under which conditions predatory targeting can be made unprofitable by transparency tools.

Duration: May 2014 - April 2015

Inria teams: Coati, Scale

Abstract: This collaboration aims at assessing the benefits that digital technologies can bring in complex travel distribution applications. Indeed, these applications require both high performance algorithms and distributed programming methods to search for the best solutions among billions of combinations, in a very short time thanks to the simultaneous use of several hundreds (if not thousands) of computers. These benefits will be demonstrated in an application to build 'off the shelf' optimized packages, fully customized to best meet the complex demands of the traveler.

We have contracted with KONTRON (worldwide company which designs and manufactures embedded systems) a
"Convention de recherche encadrant une bourse CIFRE" on the topic *Graphic Processing Units for Signal Processing*, which work is a joint supervision with Aoste project.

Duration: November 2011 - April 2015

Coati is part of the joint laboratory Inria / Alcatel-Lucent Bell-labs France within the ADR Network Science and works on the fast computation of topological properties (hyperbolicity, covering, etc.).

Duration: January 2013 - December 2015

The Instant System startup company develop a platform in the area of Intelligent transportation systems (ITS). The partnership with Coati aims at designing algorithms for itinerary planning in multimodal transportation networks. The main objective is to combine public transport system and dynamic car-pooling.

Duration: December 2015 - November 2016 (12 man-month)

The STINT project (*STructures INTerdites*) is led by the MC2 group (LIP, ENS-Lyon) and involves the G-SCOP laboratory (Grenoble).

The aim of STINT is to answer the following fundamental question: *given a (possibly infinite) family $\psi $ of graphs, what properties does a $\psi $-free graph have?* To this end, it will firstly establish bounds on some classical graph parameters (e.g., clique number, stability number, chromatic number) for

The SYSTEMIC project was led by COATI and involves the LAMA (Paris Est), GREDEG (Sophia Antipolis) and CREM (Rennes) laboratories.

The aim of SYSTEMIC was to bring together the expertises of researchers in economics, graph theory and financial mathematics to propose new models to evaluate the systemic risk of networks of financial institutions, and to propose new methods to mitigate the risk of contagions in such networks. The novelty of the project was in particular to consider strategies for a dynamic control of heterogeneous networks.

Réseaux de communications, working group of GDR RSD, CNRS.

Action Graphes, working group of GDR IM, CNRS.

AOR (Vassilis Zissimopoulos) : University of Athens, Department of Informatics and Telecommunications (Greece)

Combinatorial Optimization, Games and Applications (COGA), June 2015- September 2016

Participants : Jean-Claude Bermond, David Coudert, Frédéric Giroire, Nicolas Nisse, Stéphane Pérennes

**Inria Chile**

Associate Team involved in the International Lab:

Title: Algorithm for large and Dynamic Networks

Inria principal investigator: Nicolas Nisse

International Partner (Institution - Laboratory - Researcher):

Universidad Adolfo Ibañez, Santiago, Chile

Facultad de Ingeniería y Ciencias

Karol Suchan

Duration: 2013 - 2015

The main goal of this Associate Team is to study the structure of networks (modeled by graphs) to design both efficient distributed algorithms and reliable network topologies suitable to applications. We are interested both in large-scale (Facebook, Internet, etc.) and in smaller networks (e.g., WDM) that handle heavy traffic. More precisely, we aim at designing new techniques of distributed and localized computing to test structural properties of networks and to compute structures (e.g., decompositions) to be used in applications. Concerning the applications, we will first focus on routing and subgraph packing problems.

Apart from formal collaboration Coati members maintain strong connections with the following international teams, with regular visits of both sides.

Univ. of Southern Denmark, Prof. Jorgen Bang Jensen

RWTH Aachen Univ., Lehrstuhl II für Mathematik, Germany, Prof. Arie M.C.A. Koster

Concordia Univ. - Montréal, Quebec, Canada, Prof. Brigitte Jaumard

Action ECOS-SUD: ALgorithmes Distribués pour le calcul de la structure des réseaux, with Chile, 2013-2015.

GAIATO : Graphs and Algorithms Applied to Telecommunications, International Cooperation FUNCAP/FAPs/Inria/INS2i-CNRS, no. INC-0083-00047.01.00/13, with Federal University of Ceará, Brasil, 2014-2016.

Jorgen Bang Jensen : Jan 31 - June 13, Univ. of Southern Denmark

Sylvain Leguay : Feb 2 - March 27, Univ. Paris XI, LRI, Orsay, France

Mauricio Abel Soto Gomez : Feb 23 - March 20, Univ. Adolfo Ibáñez, Santiago, Chile

Takako Kodate : March 23 - Apr 4, Tokyo Woman's Christian Univ., Japan

Min-Li (Joseph) Yu : March 3 - Apr 8, Univ. of the Fraser valley, Abbotsford, (BC), Canada

Medji Kaddour : May 4 - 15, Univ. d'Oran, Algérie

Nicolas De Almeida Martins : May 20 - July 30, Univ. Federal do Ceará, Fortaleza, Brazil

Samuel Nascimiento de Araujo : June - July, Univ. Federal do Ceará, Fortaleza, Brazil

Esteban H. Roman Catafau : Oct 1 - 10, Univ. Adolfo Ibáñez, Santiago, Chile

Arunabha Sen : Oct 12 - 17, Arizona State Univ., USA

Fabricio Benevides : Oct 19 - 31, Univ. Federal do Ceará, Fortaleza, Brazil

Victor Campos : Oct 19 - 31, Univ. Federal do Ceará, Fortaleza, Brazil

Eduardo Moreno : Nov 1 - 7, Univ. Adolfo Ibáñez, Santiago, Chile

David Coudert

Univ. Adolfo Ibañez and Univ. Chile, Santiago, Chile, in the context of Inria associated team AlDyNet, April 3-19 and November 21-December 5, 2015;

Department of Information Engineering at University of Florence, Italy, June 23-30, 2015;

Department of Informatics and Telecommunications of the National and Kapodistrian University of Athens, Greece, September 7-11, 2015.

Guillaume Ducoffe

Univ. Adolfo Ibañez and Univ. Chile, Santiago, Chile, in the context of Inria associated team AlDyNet, November 21-December 6, 2015.

Frédéric Giroire

Univ. Adolfo Ibañez and Univ. Chile, Santiago, Chile, in the context of Inria associated team AlDyNet, November 13-29, 2015.

Frédéric Havet

Univ. Federal do Ceará, Fortaleza, Brazil, May 5-10, 2015;

Univ. Orléans - LIFO, July 6-10 2015.

Nicolas Nisse

Univ. Federal do Ceará, Fortaleza, Brazil, May 4-17, 2015;

Univ. Aix-Marseille, June 29-July 2015;

Univ. Adolfo Ibañez and Univ. Chile, Santiago, Chile, in the context of Inria associated team AlDyNet, November 13-29, 2015.

Jean-Claude Bermond :

Mediterranean Days 2015 : February 18-20 (http://

Frédéric Havet :

SGT 2015 : 2nd French School on Graph Theory, Porquerolles, France, May 18-22 2015;

15th JCALM : 15th Journées Combinatoire et Algorithmes du Littoral Méditerranéen. Sophia Antipolis, France, March 10-11, 2015.

Nicolas Nisse :

GRASTA-MAC : joint Workshops 7th Workshop on GRAph Searching, Theory and Applications and 5th workshop on Moving And Computing, Montréal, Canada, October 19-23rd, 2015. Organizers: G. Hahn and N. Nisse.

David Coudert, Frédéric Havet (chair), Michel Syska : SGT 2015, 2nd French School on Graph Theory, Porquerolles, France, May 18-22 2015;

Frédéric Havet (chair) : 17th Journées Graphes et Algorithmes (JGA 2015), Orléans, France, November 4-6, 2015.

Frédéric Giroire

Algotel’15: 17es Rencontres Francophones sur les Aspects Algorithmiques de Télécommunications, Beaune, France, June 2-5, 2015; Chairs: L. Blin and F. Giroire.

David Coudert :

ONDM'15 : 19th International Conference on Optical Networking Design and Modeling, Pisa, Italy, May 11-14, 2015;

PHYSComNet : International Workshop on Physics Inspired Paradigms in Wireless Communications and Networks, Bombay, India, May 29, 2015;

IEEE ICC'15 : IEEE International Conference on Communications, London, UK, June 8-12, 2015;

SEA'15 : 14th International Symposium on Experimental Algorithms, Paris, France, June 29 - July 1, 2015;

USRR'15 : 3rd International Workshop on Understanding the Inter-play between Sustainability, Resilience and Robustness in networks, Munich, Germany, October 7, 2015;

IEEE Globecom'15 : IEEE Global Communications Conference, San Diego, CA, USA, December 6-10, 2015.

Nicolas Nisse :

International Conference on Ad Hoc Networks and Wireless (Ad-Hoc Now), track on Mobile Agents, Athens, Greece (June 29-July 1st 2015).

VIII Latin-American Algorithms, Graphs and Optimization Symposium (LAGOS), Praia das Fontes, Beberibe, Ceará, Brazil (11-15 May, 2015).

Jean-Claude Bermond :

Combinatorics Probability and Computing (Cambridge University Press);

Computer Science Reviews (Elsevier);

Discrete Applied Mathematics (Elsevier);

Discrete Mathematics (ScienceDirect);

Discrete Mathematics, Algorithms and Applications (World Scientific);

Journal of Graph Theory (Wiley);

Journal of Interconnection Networks (Advisory Board, World Scientific);

Mathématiques et Sciences Humaines (http://

Networks (Wiley);

Parallel Processing Letters (World Scientific);

SIAM's Discrete Mathematics and Applications Book Series (SIAM).

David Coudert :

Discrete Applied Mathematics (Elsevier);

Networks (Wiley).

Frédéric Havet :

Discrete Mathematics and Theoretical Computer Science (http://

Members of COATI have reviewed numerous manuscripts submitted to international journals, including: Algorithmica, Bulletin of the Malaysian Mathematical Sciences Society, Computer Communications, Computer Networks, Computers & Operations Research, Discrete Applied Mathematics, IEEE/OSA Journal of Lightwave Technology, Networks, Photonic Network Communications, The Computer Journal, Theoretical Computer Science, IEEE/ACM Transactions on Communications, IEEE/ACM Transactions on Networking, etc

Frédéric Havet :

VIII Latin-American Algorithms, Graphs and Optimization Symposium (LAGOS 2015), Beberibe, Brazil (May 11-15, 2015), "Induced subdigraphs of digraphs with large chromatic number";

2015 Barbados Graph Theory Workshop, Holetown, Barbados (March 27-April 3), "Subdigraphs of digraphs with large chromatic number".

Nicolas Nisse :

Journées du GDR IM, Bordeaux (Feb. 2nd, 2015), "Cops and robber games in graphs";

Réunion ANR Displexity, Arcachon (September 3rd, 2015), "Allowing each node to communicate only once in a distributed system";

GRASTA-MAC'15, Montréal, Canada (October 19th, 2015), "Cops and Robber Games";

Journées Graphes et Algorithmes (JGA) 2015, Orléans (November 4th, 2015), "Jeux de Gendarmes et Voleur dans les Graphes".

David Coudert :

Member of the steering committee of *Pôle ResCom du GDR RSD du CNRS* (since 2005);

Member of the steering committee of *Rencontres francophones sur les aspects algorithmiques des télécommunications* (AlgoTel).

Frédéric Giroire :

Member of the steering committee of *Action GREEN du GDR RSD du CNRS*.

Frédéric Havet :

Member of the steering committee of GT Graphes du GDR IM du CNRS;

Member of the steering committee of Journées Graphes et Algorithmes (JGA);

Member of the steering committee of Journée Combinatoire et Algorithmes du Littoral Méditerranéen (JCALM).

Jean-Claude Bermond :

Expert for DRTT-MESR (Crédit Impôt Recherche CIR);

Expert for an Eurostars application POF transceiver;

Evaluation of PISCOPIA Fellowship Programme Marie Curie Action, for the University of Padua (Italia).

Christelle Caillouet :

Member of the comité de sélection MCF of 27^{e} section of Univ. Nice Sophia Antipolis;

Member of the comité de sélection MCF of 27^{e} section of Univ. Toulon.

David Coudert :

Expert for the Future and Emerging Technologies Open Scheme (FET-Open) European program, and the ANR;

Member of the comité de sélection MCF of 27^{e} section of LIRMM, Univ. Montpellier.

Frédéric Havet :

Expert for the ANR.

Joanna Moulierac :

Member of the comité de sélection MCF of 27^{e} section of Univ. Nice Sophia Antipolis.

Nicolas Nisse :

Expert for the ANR.

Michel Syska :

Expert for DRTT PACA.

Jean-Claude Bermond :

Member of the doctoral school of the Univ. of Marseille;

Responsible of the Attractivity for Inria Sophia Antipolis - Méditerranée and more generally for the Campus Sophia Tech (in particular signature of bilateral agreements, contacts with French Embassies and creation of join grants).

Frédéric Giroire :

Elected member of I3S laboratory committee since 2012.

Frédéric Havet :

Responsible of Pôle ComRed of I3S laboratory.

The members of Coati are strongly involved in teaching with more than 1200 hours in various university levels.

**Licence**

Christelle Caillouet, *IT Tools*, 53h ETD, Level L1, IUT Nice Côte d’Azur, UNS;

Christelle Caillouet, *Database and advanced information system*, 36h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Christelle Caillouet, *Operations Research*, 81h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Christelle Caillouet, *Delivery Optimization*, 30h ETD, Level L3, IUT Nice Côte d’Azur, UNS;

Guillaume Ducoffe, *Introduction au Web*, 39h ETD, L2, Polytech'Nice, Univ. Nice Sophia Antipolis (UNS), France;

Guillaume Ducoffe, *Programmation Objet*, 25.5h ETD, L2, Polytech'Nice, UNS, France;

Guillaume Ducoffe, *Algorithmique et Structures de Données*, 39h ETD, L2, Polytech'Nice, UNS, France;

Nicolas Huin, *Networks*, 42h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Alvinice Kodjo, *Interfaces Homme Machine*, 24h ETD, Level L1, UNS;

Alvinice Kodjo, *Réseaux*, 15h ETD, Level L2, UNS;

Dimitris Letsios *Algorithmique et Programmation Impérative*, 36h ETD, Level L1, UNS;

Dimitris Letsios *Programmation Web*, 8h ETD, Level L1, UNS;

Dimitris Letsios *Informatique Fondamentale*, 36h ETD, Level L1, UNS;

Dimitris Letsios *Algorithmique et Programmation Objet*, 54h ETD, Level L2, UNS;

Dimitris Letsios *Programmation Orientée Objet Java*, 18h ETD, Level L2, UNS;

Dimitris Letsios *Mathématiques*, 18h ETD, Level L3, UNS;

Dimitris Letsios *Mathématiques*, 18h ETD, Level M1, UNS;

Fatima Zahra Moataz, *Programmation avec Python*, 12h ETD, Level L1, UNS;

Fatima Zahra Moataz, *Systèmes Informatiques*, 24h ETD, Level L1, UNS;

Benjamin Momège, *Mathématiques Discrètes*, 75h ETD, Level L3, Polytech'Nice, UNS;

Joanna Moulierac, *Introduction to Operating Systems*, 60h ETD, Level L1, IUT Nice Côte d’Azur, UNS;

Joanna Moulierac, *Networks*, 100h ETD, Level L1, IUT Nice Côte d’Azur, UNS;

Joanna Moulierac, *Algorithmics*, 60h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Nicolas Nisse, *Introduction à l'informatique*, 24h ETD, Classe préparatoire MPSI (Lycée international de Valbonne), France;

Michel Syska, *Operating Systems : Advanced Programming*, 90h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Michel Syska, *Algorithmics*, 90h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Michel Syska, *Distributed Programming*, 30h ETD, Level L2, IUT Nice Côte d’Azur, UNS;

Michel Syska, *Bash Scripting*, 40h ETD, Level L3, IUT Nice Côte d’Azur, UNS;

Michel Syska, *Introduction to Algorithms and Complexity*, 30h ETD, Level L3, IUT Nice Côte d’Azur, UNS;

Michel Syska, *Linux System Administration*, 40h ETD, Level L3, IUT Nice Côte d’Azur, UNS.

**Master**

David Coudert, *Algorithms for Telecoms*, 32h ETD, stream UbiNet of Master 2 IFI and Master RIF, UNS;

Frédéric Giroire, *Algorithmics of Telecommunications*, 18h ETD, stream UbiNet of Master 2 IFI, UNS;

Frédéric Giroire, *Green Networks*, 18h ETD, stream UbiNet of Master 2 IFI, UNS;

Frédéric Giroire, *Introduction to probability and statistics*, 15h ETD, International Master 1, UNS;

Frédéric Havet, *Combinatorial optimisation*, 24h ETD, M1 international, UNS, France;

Nicolas Nisse, *Resolution Methods*, 15h ETD, M1 international, UNS, France;

Nicolas Nisse, *Graph Algorithms*, 18h ETD, M2 IFI, parcours UBINET, UNS, France.

**Doctorate**

Nicolas Nisse, *Graph Theory and Optimization*, 27h ETD, University of Oulu, Finland, September 15-18th, 2015.

Paul Bertot : Nov 2014 - Feb 2015, IUT Nice Côte d’Azur, France

Flavian Jacquot : Nov 2014 - Feb 2015, IUT Nice Côte d’Azur, France

Bogdan Sirenko : March - Aug 2015, Master IFI, Ubinet, Univ. of Nice, France

Theodoros Karagkioules : Oct 2015 - March 2016, National and Kapodistrian Univ. of Athens, Greece

Konstantinos Priftis : Oct 2015 - March 2016, Univ. of Patras, Greece

Steven Roumajon : March - Aug 2015, Master RIF, Univ. of Nice, France

Stream Ubinet, Master 2 IFI (http://

Jean-Claude Bermond, member of the scientific committee;

Frédéric Giroire, responsible of the Internships, since October 2011.

International Master 1 (http://

Jean-Claude Bermond, member of the scientific committee of the international track of the M1, responsible of teh recruiting committee and of the winter school.

IUT Nice Côte d'Azur

Christelle Molle-Caillouet, Co-Responsible of QLIO Department, since September 2015;

Joanna Moulierac, Co-Responsible of the DUT Informatique en Alternance, Computer Science Department, since January 2014;

Joanna Moulierac, member of the Conseil de D épartement Informatique at IUT Nice.

PhD : Fatima Zahra Moataz, *Towards Efficient and Fault-Tolerant Optical Networks: Complexity and Algorithms* , Université Nice Sophia Antipolis, October 30, 2015. Supervisor : David Coudert;

PhD : Mohamed Amine Bergach, *Adaptation of the Fast Fourier Transform processing on hybrid integrated CPU/GPU architecture* , Université Nice Sophia Antipolis, October 2, 2015. Supervisors : Robert de Simone (Aoste) and Michel Syska;

PhD in progress : Steven Roumajon, *Regional competitiveness and innovation networks*, since November 2015. Supervisors : Frédéric Giroire and Patrick Musso (GREDEG);

PhD in progress : Nicolas Huin, *Energy-Efficient Software Defined Networks*, since October 2014. Supervisors : Frédéric Giroire and Dino Lopez (I3S);

PhD in progress : Guillaume Ducoffe, *Metric properties of large graphs*, since September 2014. Supervisor : David Coudert;

PhD in progress : William Lochet, *Cliques and independent sets in graph classes, generalisation to the oriented case*, since September 2015, co-supervised by Frédéric Havet and Stéphan Thomassé (ENS Lyon).

Jean-Claude Bermond :

Member of the PhD jury of Fatima Zahra Moataz, Univ. Nice Sophia Antipolis, October 30, 2015.

David Coudert :

Member of the PhD jury of Fatima Zahra Moataz, Univ. Nice Sophia Antipolis, October 30, 2015;

Referee and member of the PhD jury of Benjamin Momège, Univ. Blaise Pascal, Clermont-Ferrand, July 8, 2015.

Frédéric Havet :

Referee and member of the PhD jury of M. Bonamy, Univ. of Montpellier, February 9 2015;

Referee and member of the PhD jury of R. Letourneur, Université of Orléans, July 9 2015;

Member of the PhD jury of Hang Zhou, ENS Paris, July 6 2015.

Michel Syska :

Member of the PhD jury of Mohamed Amine Bergach, Univ. Nice Sophia Antipolis, October 02, 2015.

Vulgarization talk : N. Nisse presented a talk on "Combinatorial Games", Lycée des Remparts (classes de seconde), Marseille (April 17th, 2015).

Fête de la Science : F. Havet presented the stand "Pavage, art et preuves" et "Magie mathématique" at Vinon-sur-Verdon, France (October 12-16, 2015); F. Havet gave the talk "La science du ballon de football" at Vinon-sur-Verdon, France (October 16, 2015).

Semaine des Mathématiques : F. Havet presented the stand "Les maths c'est magique" at Mouans Sartoux (March 18, 2015).

Vendredis de la Science : F. Havet conducted scientific workshops for school children (6-11 year old) on friday afternoon in Rians, France. Once a month in March, April, May, June 2015, and weekly since November 2015.

Jean-Claude Bermond presented a talk on the impact of big data on the telecommunications services and networks for banks investors at Paris, France (April 10 2015).