Seminars

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2021
Fri 10th Dec
11:00 am
12:00 pm
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Séminaire Sebastien Tavenas

Title: Bornes inférieures superpolynomiales pour les circuits de profondeur constante

Abstract:
Tout polynôme multivarié P(X_1,...,X_n) peut être écrit comme une somme de
monômes, i.e., une somme de produits de variables et de constantes du corps.
La taille naturelle d'une telle expression est le nombre de monômes. Mais,
que se passe-t-il si on rajoute un nouveau niveau de complexité en
considérant les expressions de la forme : somme de produits de sommes (de
variables et de constantes) ? Maintenant, il devient moins clair comment
montrer qu'un polynôme donné n'a pas de petite expression. Dans cet exposé
nous résoudrons exactement ce problème. Plus précisément, nous prouvons que
certains polynômes explicites n'ont pas de représentations "somme de
produits de sommes'' (SPS) de taille polynomiale. Nous pouvons aussi obtenir
des résultats similaires pour les SPSP, SPSPS, etc... pour toutes les
expressions de profondeur constante.
"
Thu 25th Nov
2:00 pm
3:00 pm
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Nofar Carmeli in Links' Seminar
Fri 29th Oct
11:00 am
12:00 pm
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Séminaire Antoine Amarilli

Fri 22nd Oct
11:00 am
12:00 pm
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Mikaël Monet in Links' Seminar
Fri 15th Oct
11:00 am
12:00 pm
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Claire Soyez-Martin in Links' seminar
Fri 17th Sep
11:00 am
12:00 pm
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Séminaire Corentin Barloy
Title: Stackless Processing of Streamed Trees
Abstract:
Processing tree-structured data in the streaming model is a chal-lenge: capturing regular properties of streamed trees by means of astack is costly in memory, but falling back to finite-state automata drastically limits the computational power. We propose an intermediate stackless model based on register automata equipped with a single counter, used to maintain the current depth in the tree. We explore the power of this model to validate and query streamed trees. Our main result is an effective characterization of regular path queries (RPQs) that can be evaluated stacklessly—with and without registers. In particular, we confirm the conjectured characterization of tree languages defined by DTDs that are recognizable without registers, by Segoufin and Vianu (2002), in the special case of tree languages defined by means of an RPQ.

Link: paperman.name/data/pub.....0.pdf

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lille-Salle
Fri 10th Sep
10:00 am
11:00 am
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Séminaire de Patrick Baillot
titre: Type-based complexity analysis in a parallel process calculus

Abstract:
Some type systems have been designed to analyse statically the time
coplexity of functional languages. A natural question is whether this approach
can be extended to parallel languages. We address this problem for the
Pi-calculus, a paradigmatic calculus for parallel and concurrent computation.
In Pi-calculus, processes communicate through channels that can carry values
and channel names. We will define notions of sequential and parallel complexity
for Pi-calculus, and present a type system that provides an upper bound on the
time complexity of processes.
This is based on joint work with Alexis Ghyselen (ESOP 2021).

Based on: link.springer.com/chap.....9-3_3
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