IRIF, the Research Institute on the Foundations of Computer Science, is a research laboratory of CNRS and université Paris-Diderot, also hosting two INRIA project-teams.

The research conducted at IRIF is based on the study and understanding of the foundations of all computer science, in order to provide innovative solutions to the current and future challenges of digital sciences.

IRIF hosts about 200 people. Six of its members have been distinguished by the European Research Council (ERC), five are members of the Institut Universitaire de France IUF), and two are members of the Academia Europæa.

IRIF is seeking excellent candidates for about 10 postdoctoral positions in all areas of the Foundations of Computer Science. Deadline for applications: Nov. 3, 2019.


On December 16th, a half-day of talks aimed at a non-specialized audience will take place at IRIF in celebration of Algorithms, the research domain of Claire Mathieu, 2019 recipient of a CNRS Silver Medal. The event will conclude with a discussion of new research directions in Algorithms. Free Registration before November 30th.

Workshop on Gradual Typing

Giuseppe Castagna (IRIF) and Jeremy Siek (Indiana) organize WGT 2020, the first ACM SIGPLAN Workshop on Gradual Typing, colocated with POPL. Submission deadline: Monday, October the 21st.
gradual typing

Gradual typing is a technique that allows the programmer to control which parts of a program check their type correctness (i.e., that apples are added to apples) before execution and which parts check it during their execution instead. It is often used to gradually add the before-execution check to dynamic languages, like JavaScript, which perform the check only at run-time, since it is generally better to find errors before the execution of a program rather than during its execution.
Claire Mathieu

The SODA 2020 conference will include a paper by Vincent Cohen-Addad (LIP6), Frederick Mallmann-Trenn (King's College) and Claire Mathieu (IRIF) about computing with noisy data. The problem: select valuable objects in a setting where each assessment has a probability of error, using redundant assessments.

Sylvain Perifel

From ancient history to quantum, learn about cryptography at “Fête de la science” in an entertaining talk by Sylvain Perifel (IRIF) Friday October 11th, 11am at Amphitheater 4C, Halle aux farines.

Geoffroy Couteau

IRIF has the great pleasure to welcome a new research scientist (CNRS): Geoffroy Couteau, an expert in cryptography, with a focus on secure computation protocols and zero-knowledge proofs.

Hugo Férée

IRIF has the great pleasure to welcome a new associate professor (Université de Paris): Hugo Férée, an expert in various aspects of complexity theory, with interests in programming languages and formal proofs.

Sam Van Gool

IRIF has the great pleasure to welcome a new associate professor (Université de Paris): Sam Van Gool, an expert in algebraic and topological methods for automata, logic, and model theory.

(These news are displayed using a randomized-priority ranking.)

Monday October 21, 2019, 11AM, Salle 1007
Mohamed Faouzi Atig (Uppsala University) On Solving String Constraints

String data types are present in all conventional programming and scripting languages. In fact, it is almost impossible to reason about the correctness and security of such programs without having a decision procedure for string constraints. A typical string constraint consists of word equations over string variables denoting strings of arbitrary lengths, together with constraints on (i) the length of strings, and (ii) the regular languages to which strings belong. Decidability of this general logic is still open. In this talk, we will discuss recent results on the decidability and decision procedures for string constraints. We will focus on decision procedures that are sound and complete for a well-defined fragment of string constraints. We will also cover a technique that uses a Counter-Example Guided Abstraction Refinement (CEGAR) framework which contains both an under- and an over-approximation module. The flow of information between these modules allows increasing the precision in an automatic manner.

Tuesday October 22, 2019, 2PM, Salle 3052
Michael Lampis (Universite Paris Dauphine) Finer Tight Bounds for Coloring on Clique-Width

We revisit the complexity of Coloring with respect to two parameters: the number of given colors k; and the “width” of the input graph w. Here, by width we mean a measure of complexity of the graph. When the notion of width in question is treewidth, the problem is very well-understood: there exists a simple k^w algorithm, and no algorithm can do significantly better under the Strong Exponential Time Hypothesis (SETH), even if we replace treewidth by much more restrictive notions, such distance to linear forest. In this talk we will consider the notion of clique-width, which is the most well-studied generalization of treewidth for dense graphs. We will sketch an algorithm and a matching lower bound (under the SETH) which completely determine the complexity of coloring as a function of clique-width, for any fixed k>=3.

Special talks
Tuesday October 22, 2019, 7PM, 3052
Hao Huang (Emory University) A proof of the Sensitivity Conjecture. (live projection of TCS+ talk)
This is a live video projection of a TCS+ talk. Live questions should be possible.

Thursday October 24, 2019, 5PM, In front of room 3052
Cédric Ho Thanh (IRIF CakeTM) Gâteau de l'IRIF

IRIF CakeTM is an amazing opportunity to meet people while simultaneously eating cakes baked by your fellow colleagues! Join us every Thursday, at 5pm, in front of room 3052 (Sophie Germain 3rd floor) for a weekly feast. You can also express your cooking skills and volunteer to bake a cake by sending an email to

Friday October 25, 2019, 2:30PM, Salle 3052
Luca Reggio (Mathematical Institute, University of Bern) Limits of finite structures: a duality theoretic perspective

A systematic approach to the study of limits of finite structures, motivated by investigations in graph theory, has been developed by Nešetřil and Ossona de Mendez starting in 2012. The basic idea consists in embedding the set of finite structures into a space of measures which is complete, so that every converging sequence of finite structures admits a limit. This limit point can be always realized as a measure.

I will explain how this embedding into a space of measures dually corresponds to enriching First-Order Logic with certain probability operators. Further, I will relate this construction to first-order quantification in logic on words.

This talk is based on joint work with M. Gehrke and T. Jakl.