Portrait de Pascal Vincent

Pascal Vincent

Membre industriel principal
Professeur agrégé, Université de Montréal, Département d'informatique et de recherche opérationnelle
Chercheur scientifique, Facebook AI Research (FAIR) Montréal
Sujets de recherche
Apprentissage de représentations
Apprentissage profond

Biographie

Pascal Vincent est chercheur à Meta (FAIR, Fundamental IA Research), professeur associé au Département d'informatique et de recherche opérationnelle (DIRO) de l'Université de Montréal, membre fondateur de Mila – Institut québécois d’intelligence artificielle et chercheur associé à l'Institut canadien de recherches avancées (CIFAR, programme Apprentissage automatique, apprentissage biologique).

Ses recherches sur les principes et les algorithmes de l'apprentissage par représentation l'ont amené à développer plusieurs idées fondamentales qui sont devenues des éléments clés du succès des méthodes d'apprentissage profond. Parmi ses travaux les plus influents, il est coauteur de l'article fondateur sur les modèles de langage neuronaux « A Neural Probabilistic Language Model » (Bengio et al., 2013), qui a jeté les bases de tous les modèles de langage fondés sur les réseaux de neurones artificiels. Son travail sur les auto-encodeurs de débruitage (Vincent et al., 2008, 2010) a été le premier à proposer la tâche prétexte de remplir des blancs artificiellement introduits dans le but d'apprendre des représentations utiles dans n'importe quelle modalité, un précurseur de ce que l'on appelle aujourd'hui « l'apprentissage autosupervisé ». En 2011, il a développé le principe du denoising score matching (P. Vincent, « A connection between score matching and denoising autoencoders », Neural Computation, 2011), qui est maintenant couramment utilisé pour former des modèles génératifs basés sur la diffusion. Ses recherches actuelles se concentrent sur de nouvelles théories et de nouveaux algorithmes pour l'apprentissage de la représentation afin de permettre une généralisation robuste en dehors de la distribution.

Publications

Stochastic Neural Network with Kronecker Flow
Recent advances in variational inference enable the modelling of highly structured joint distributions, but are limited in their capacity to… (voir plus) scale to the high-dimensional setting of stochastic neural networks. This limitation motivates a need for scalable parameterizations of the noise generation process, in a manner that adequately captures the dependencies among the various parameters. In this work, we address this need and present the Kronecker Flow, a generalization of the Kronecker product to invertible mappings designed for stochastic neural networks. We apply our method to variational Bayesian neural networks on predictive tasks, PAC-Bayes generalization bound estimation, and approximate Thompson sampling in contextual bandits. In all setups, our methods prove to be competitive with existing methods and better than the baselines.
Implicit Regularization via Neural Feature Alignment
We approach the problem of implicit regularization in deep learning from a geometrical viewpoint. We highlight a regularization effect induc… (voir plus)ed by a dynamical alignment of the neural tangent features introduced by Jacot et al, along a small number of task-relevant directions. This can be interpreted as a combined mechanism of feature selection and compression. By extrapolating a new analysis of Rademacher complexity bounds for linear models, we motivate and study a heuristic complexity measure that captures this phenomenon, in terms of sequences of tangent kernel classes along optimization paths.
An Empirical Study of Batch Normalization and Group Normalization in Conditional Computation
Batch normalization has been widely used to improve optimization in deep neural networks. While the uncertainty in batch statistics can act … (voir plus)as a regularizer, using these dataset statistics specific to the training set impairs generalization in certain tasks. Recently, alternative methods for normalizing feature activations in neural networks have been proposed. Among them, group normalization has been shown to yield similar, in some domains even superior performance to batch normalization. All these methods utilize a learned affine transformation after the normalization operation to increase representational power. Methods used in conditional computation define the parameters of these transformations as learnable functions of conditioning information. In this work, we study whether and where the conditional formulation of group normalization can improve generalization compared to conditional batch normalization. We evaluate performances on the tasks of visual question answering, few-shot learning, and conditional image generation.
Convergent Tree Backup and Retrace with Function Approximation
Off-policy learning is key to scaling up reinforcement learning as it allows to learn about a target policy from the experience generated by… (voir plus) a different behavior policy. Unfortunately, it has been challenging to combine off-policy learning with function approximation and multi-step bootstrapping in a way that leads to both stable and efficient algorithms. In this work, we show that the \textsc{Tree Backup} and \textsc{Retrace} algorithms are unstable with linear function approximation, both in theory and in practice with specific examples. Based on our analysis, we then derive stable and efficient gradient-based algorithms using a quadratic convex-concave saddle-point formulation. By exploiting the problem structure proper to these algorithms, we are able to provide convergence guarantees and finite-sample bounds. The applicability of our new analysis also goes beyond \textsc{Tree Backup} and \textsc{Retrace} and allows us to provide new convergence rates for the GTD and GTD2 algorithms without having recourse to projections or Polyak averaging.
Learning to Compute Word Embeddings on the Fly
Tom Bosc
Stanisław Jastrzębski
Edward Grefenstette
Yoshua Bengios
Words in natural language follow a Zipfian distribution whereby some words are frequent but most are rare. Learning representations for word… (voir plus)s in the "long tail" of this distribution requires enormous amounts of data. Representations of rare words trained directly on end tasks are usually poor, requiring us to pre-train embeddings on external data, or treat all rare words as out-of-vocabulary words with a unique representation. We provide a method for predicting embeddings of rare words on the fly from small amounts of auxiliary data with a network trained end-to-end for the downstream task. We show that this improves results against baselines where embeddings are trained on the end task for reading comprehension, recognizing textual entailment and language modeling.
Theano: A Python framework for fast computation of mathematical expressions
Rami Al-Rfou
Amjad Almahairi
Christof Angermueller
Frédéric Bastien
Justin Bayer
Anatoly Belikov
Alexander Belopolsky
Josh Bleecher Snyder
Pierre-Luc Carrier
Paul Christiano
Myriam Côté
Yann N. Dauphin
Julien Demouth
Sander Dieleman
Ziye Fan
Mathieu Germain
Matt Graham
Balázs Hidasi
Arjun Jain
Kai Jia
Mikhail Korobov
Vivek Kulkarni
Pascal Lamblin
Eric Larsen
Sean Lee
Simon Lefrancois
Jesse A. Livezey
Cory Lorenz
Jeremiah Lowin
Qianli Ma
Robert T. McGibbon
Mehdi Mirza
Alberto Orlandi
Christopher Pal
Colin Raffel
Daniel Renshaw
Matthew Rocklin
Adriana Romero
Markus Roth
Peter Sadowski
John Salvatier
Jan Schlüter
John Schulman
Gabriel Schwartz
Iulian Vlad Serban
Samira Shabanian
Sigurd Spieckermann
S. Ramana Subramanyam
Gijs van Tulder
Sebastian Urban
Dustin J. Webb
Matthew Willson
Lijun Xue
Theano is a Python library that allows to define, optimize, and evaluate mathematical expressions involving multi-dimensional arrays efficie… (voir plus)ntly. Since its introduction, it has been one of the most used CPU and GPU mathematical compilers - especially in the machine learning community - and has shown steady performance improvements. Theano is being actively and continuously developed since 2008, multiple frameworks have been built on top of it and it has been used to produce many state-of-the-art machine learning models. The present article is structured as follows. Section I provides an overview of the Theano software and its community. Section II presents the principal features of Theano and how to use them, and compares them with other similar projects. Section III focuses on recently-introduced functionalities and improvements. Section IV compares the performance of Theano against Torch7 and TensorFlow on several machine learning models. Section V discusses current limitations of Theano and potential ways of improving it.