L'IRIF est une unité mixte de recherche (UMR 8243) entre le CNRS et l'Université Paris Cité, qui héberge une équipe-projet Inria.

Les recherches menées à l'IRIF reposent sur l’étude et la compréhension des fondements de toute l’informatique, afin d’apporter des solutions innovantes aux défis actuels et futurs des sciences numériques.

L'IRIF regroupe près de deux cents personnes. Six de ses membres ont été lauréats de l'European Research Council (ERC), six sont membres de l'Institut Universitaire de France (IUF), deux sont membres de l'Academia Europæa, et un est membre de l'Académie des sciences.

22.6.2022
The 2022 edition of Highlights will happen from June 28th to July 1st, 2022, in Paris, France. The conference will be hosted by Université Paris Cité, and happen on the site of Grands Moulins. To register, please fill in the registration form. If you wish to watch Highlights remotely, please fill in the online registration form. Online attendance is free.

7.6.2022
IRIF is co-organizing a Workshop on Differentiable Programming, June 29-30, Université Paris Cité.

7.6.2022
Four papers coauthored by IRIF members will be presented at the conference TYPES'22, the main conference on type theory, this summer.

7.6.2022
IRIF is co-organizing a Workshop Labyrinth of Combinatorics in memory of Pierre Rosenstiehl, June 15-17, Université Paris Cité

7.6.2022
Four papers coauthored by IRIF members will be presented at the conference PODC'22, the main conference on distributed computing, this summer.

7.6.2022
IRIF is proud to announce that Olivier Carton, professor of Université Paris Cité and researcher at IRIF, was appointed senior member of IUF.

7.6.2022
Two papers coauthored by IRIF members will be presented at the conference ISSAC'22, the main conference on symbolic and algebraic computation , this summer.

(Ces actualités sont présentées selon un classement mêlant priorité et aléatoire.)

Nombre limité d'évènements durant les vacances d'été.

Théorie des types et réalisabilité
Mercredi 6 juillet 2022, 14 heures, Salle 1007
James Lipton (Wesleyan Univ., USA) CUT ELIMINATION in Higher-Order with (HO) constraints

We will present a system of Intensional Higher-Order Intuitionistic Logic with Higher-Order Saraswat Constraints, hoI(C). The Logic and its variants were developed by Artalejo, Nieva, Leach (Madrid), and subsequently by Lipton, Nieva and Hermant, the original aim being to add constraints to a lambda-Prolog style language.

If constraints are unrestricted, cut-elimination is easily shown to fail, because of the way the system handles equality rules. Our work studies conditions on the constraint system C that guarantee cut-elimination. The techniques used are based on Takahashi, Prawitz ande Andrews' work in classical type theory, Lipton and DeMarco for intuitionistic type theory, with ideas developed by Hermant for Logique Modulo, Hermant and Lipton for Logic with sequent axioms, as well as cut-elimination techniques due to Okada and Maehara.

We will briefly discuss Kripke and HA semantics for these calculi, with some remarks on fibrational semantics developed by the speaker with Gianluca Amato (Pescara, Italy) if time permits!

This will be a blackboard talk (with maybe a few slides) and will include work in progress!

Analyse et conception de systèmes
Vendredi 8 juillet 2022, 10 heures 30, Salle 1007
Ada Vienot (IRIF) A reactive operational semantics for a lambda-calculus with time warps

Many computer systems are reactive: they execute in continuous interaction with their environment. From the perspective of functional programming, reactive systems can be modeled and programmed as stream functions. Several lines of research have exploited this point of view. Works based on Nakano’s guarded recursion use type-theoretical modalities to guarantee productivity. Works based on synchronous programming use more specialized methods but guarantee incremental processing of stream fragments. In this paper, we contribute to a recent synthesis between the two approaches by describing how a language with a family of type-theoretical modalities can be given an incremental semantics in the synchronous style. We prove that this semantics coincides with a more usual big-step semantics.

Vérification
Lundi 11 juillet 2022, 11 heures, 3052 and Zoom link
Jaco Van De Pol (Aarhus University) Parallel SCC Detection for Model Checking – Model Checking for Parallel SCC detection

I will introduce a multicore algorithm for the parallel detection of Strongly Connected Components. The algorithm uses a concurrent Union-Find forest to share partial SCCs. As a consequence, we get parallel speedup even if the graph consists of a single SCC. The algorithm works on-the-fly, so it is useful for parallel LTL model checking.

Since parallel graph algorithms are error prone, and this one is used in verification tools, we would like to verify it. We will report a first step, modeling the algorithm in TLA+ and model checking it for instances with a few workers and small graphs.

Algorithmes et complexité
Mardi 12 juillet 2022, 10 heures, Salle 3052
Seeun William Umboh (The University of Sydney) Online Weighted Cardinality Joint Replenishment Problem with Delay

We study a generalization of the classic Online Joint Replenishment Problem (JRP) with Delays that we call the Online Weighted Cardinality JRP with Delays. The JRP is an extensively studied inventory management problem wherein requests for different item types arrive at various points in time. A request is served by ordering its corresponding item type. The cost of serving a set of requests depends on the item types ordered. Furthermore, each request incurs a delay penalty while it is left unserved. The objective is to minimise the total service and delay costs. In the Weighted Cardinality JRP, each item type has a positive weight and the cost of ordering is a non-decreasing, concave function of the total weight of the item types ordered. This problem was first considered in the offline setting by Cheung et al.~(2015) but nothing is known in the online setting. Our main result is a deterministic, constant competitive algorithm for this problem.

Algorithmes et complexité
Mardi 12 juillet 2022, 11 heures, Salle 3052
Kheeran Naidu (University of Bristol) Space Optimal Vertex Cover in Dynamic Streams (with an overview of graph streaming)

With the world as connected as ever and data being created at an unprecedented rate, there has been an increasing need for algorithms that efficiently process massive graphs. Graph streaming is one such memory efficient setting where the edges of a graph are presented as a sequence of edges and an algorithm's goal is to store a sublinear number of edges needed to solve a graph problem exactly or approximately. In particular, this talk discusses the insertion-only, dynamic (or insertion-deletion) and sliding window graph streaming models of computation, highlighting the well-studied maximum matching and sister minimum vertex cover problems, and focusing on a recent space optimal (up to constant factors) algorithm for minimum vertex cover in the dynamic graph streaming model.

One world numeration seminar
Mardi 12 juillet 2022, 14 heures 30, Online
Ruofan Li (South China University of Technology) Rational numbers in ×b-invariant sets

Let $b \ge 2$ be an integer and $S$ be a finite non-empty set of primes not containing divisors of $b$. For any $\times b$-invariant, non-dense subset $A$ of $[0,1)$, we prove the finiteness of rational numbers in $A$ whose denominators can only be divided by primes in $S$. A quantitative result on the largest prime divisors of the denominators of rational numbers in $A$ is also obtained. This is joint work with Bing Li and Yufeng Wu.