Simon Lacoste-Julien

Core Academic Member

Canada CIFAR AI Chair

Associate Scientific Director, Mila, Associate Professor, Université de Montréal, Department of Computer Science and Operations Research

Vice President and Lab Director, Samsung Advanced Institute of Technology (SAIT) AI Lab, Montréal

Website

Google Scholar

Biography

Simon Lacoste-Julien is an associate professor at Mila – Quebec Artificial Intelligence Institute and in the Department of Computer Science and Operations Research (DIRO) at Université de Montréal. He is also a Canada CIFAR AI Chair and heads (part time) the SAIT AI Lab Montréal.

Lacoste-Julien‘s research interests are machine learning and applied mathematics, along with their applications to computer vision and natural language processing. He completed a BSc in mathematics, physics and computer science at McGill University, a PhD in computer science at UC Berkeley and a postdoc at the University of Cambridge.

After spending several years as a researcher at INRIA and the École normale supérieure in Paris, he returned to his home city of Montréal in 2016 to answer Yoshua Bengio’s call to help grow the Montréal AI ecosystem.

Current Students

Alexia Jolicoeur-Martineau

Independent visiting researcher - Samsung SAIT

PhD - Université de Montréal

antonio-miguel.gois@mila.quebec

Independent visiting researcher - Samsung SAIT

Independent visiting researcher - Université de Montréal

Independent visiting researcher - Samsung SAIT

PhD - McGill University

Principal supervisor :

Adam M. Oberman

george.orfanides@mila.quebec

Jaewoo Lee

Independent visiting researcher - Pohang University of Science and Technology in Pohang, Korea

jaewoo.lee@mila.quebec

Jose Gallego Posada

PhD - Université de Montréal

PhD - Université de Montréal

juan.ramirez@mila.quebec

Website

Github

Google Scholar

Kiho Cho

Independent visiting researcher - Samsung SAIT

kiho.cho@mila.quebec

Kwon Kisoo

Independent visiting researcher - Seoul National University, Korea

kwon.kisoo@mila.quebec

Lucas Maes

PhD - Université de Montréal

lucas.maes@mila.quebec

Website

Github

Mansi Rankawat

PhD - Université de Montréal

mansi.rankawat@mila.quebec

Independent visiting researcher - Samsung SAIT

marwa.el-halabi@mila.quebec

Collaborating researcher - Université de Montréal

merajhse@mila.quebec

Github

Michelle Liu

Collaborating researcher

liumiche@mila.quebec

Motahareh Sohrabi

Master's Research - Université de Montréal

motahareh.sohrabi@mila.quebec

Website

Pedram Khorsandi

PhD - Université de Montréal

pedram.khorsandi@mila.quebec

Github

Google Scholar

Quentin Bertrand

Postdoctorate - Université de Montréal

Principal supervisor :

Gauthier Gidel

quentin.bertrand@mila.quebec

Website

Github

Google Scholar

Reza Babanezhad Harikandeh

Independent visiting researcher - Samsung SAIT

babanezr@mila.quebec

Rozhin Nobahari

Master's Research - Université de Montréal

rozhin.nobahari@mila.quebec

Sébastien Lachapelle

PhD - Université de Montréal

lachaseb@mila.quebec

Website

Google Scholar

Helen Zhang

PhD - Université de Montréal

tianyue.zhang@mila.quebec

Website

Github

Vitoria Barin Pacela

PhD - Université de Montréal

vitoria.barin-pacela@mila.quebec

Website

Github

Google Scholar

Yan Zhang

Independent visiting researcher - Samsung SAIT

yan.zhang@mila.quebec

Website

Github

Google Scholar

Yash Goyal

Independent visiting researcher - Samsung SAIT

yash.goyal@mila.quebec

Website

Blog Posts

March 18, 2024

Additive Decoders for Latent Variables Identification and Cartesian-Product Extrapolation

Sébastien Lachapelle

Divyat Mahajan

Ioannis Mitliagkas

Simon Lacoste-Julien

Read the article

Publications

Identifiability of Discretized Latent Coordinate Systems via Density Landmarks Detection

Vitória Barin-Pacela

Kartik Ahuja

Simon Lacoste-Julien

Pascal Vincent

2023-06-19

ICML.cc/2023/Workshop/SPIGM (poster)

openreview.net

Can We Scale Transformers to Predict Parameters of Diverse ImageNet Models?

Boris Knyazev

DOHA HWANG

Simon Lacoste-Julien

Pretraining a neural network on a large dataset is becoming a cornerstone in machine learning that is within the reach of only a few communi… (see more)ties with large-resources. We aim at an ambitious goal of democratizing pretraining. Towards that goal, we train and release a single neural network that can predict high quality ImageNet parameters of other neural networks. By using predicted parameters for initialization we are able to boost training of diverse ImageNet models available in PyTorch. When transferred to other datasets, models initialized with predicted parameters also converge faster and reach competitive final performance.

2023-04-24

ICML.cc/2023/Conference (poster)

doi.org

openreview.net

A Survey of Self-Supervised and Few-Shot Object Detection

Gabriel Huang

Issam Hadj Laradji

David Vazquez

Simon Lacoste-Julien

Pau Rodriguez

Labeling data is often expensive and time-consuming, especially for tasks such as object detection and instance segmentation, which require … (see more)dense labeling of the image. While few-shot object detection is about training a model on novel (unseen) object classes with little data, it still requires prior training on many labeled examples of base (seen) classes. On the other hand, self-supervised methods aim at learning representations from unlabeled data which transfer well to downstream tasks such as object detection. Combining few-shot and self-supervised object detection is a promising research direction. In this survey, we review and characterize the most recent approaches on few-shot and self-supervised object detection. Then, we give our main takeaways and discuss future research directions. Project page: https://gabrielhuang.github.io/fsod-survey/.

2023-04-01

IEEE Transactions on Pattern Analysis and Machine Intelligence (published)

doi.org

arxiv.org

Synergies between Disentanglement and Sparsity: Generalization and Identifiability in Multi-Task Learning

Sébastien Lachapelle

Tristan Deleu

Divyat Mahajan

Ioannis Mitliagkas

Yoshua Bengio

Simon Lacoste-Julien

Quentin Bertrand

Although disentangled representations are often said to be beneficial for downstream tasks, current empirical and theoretical understanding … (see more)is limited. In this work, we provide evidence that disentangled representations coupled with sparse task-specific predictors improve generalization. In the context of multi-task learning, we prove a new identifiability result that provides conditions under which maximally sparse predictors yield disentangled representations. Motivated by this theoretical result, we propose a practical approach to learn disentangled representations based on a sparsity-promoting bi-level optimization problem. Finally, we explore a meta-learning version of this algorithm based on group Lasso multiclass SVM predictors, for which we derive a tractable dual formulation. It obtains competitive results on standard few-shot classification benchmarks, while each task is using only a fraction of the learned representations.

2023-01-01

ICML (published)

proceedings.mlr.press

openreview.net

Synergies between Disentanglement and Sparsity: Generalization and Identifiability in Multi-Task Learning

Sébastien Lachapelle

Tristan Deleu

Divyat Mahajan

Ioannis Mitliagkas

Yoshua Bengio

Simon Lacoste-Julien

Quentin Bertrand

Although disentangled representations are often said to be beneficial for downstream tasks, current empirical and theoretical understanding … (see more)is limited. In this work, we provide evidence that disentangled representations coupled with sparse base-predictors improve generalization. In the context of multi-task learning, we prove a new identifiability result that provides conditions under which maximally sparse base-predictors yield disentangled representations. Motivated by this theoretical result, we propose a practical approach to learn disentangled representations based on a sparsity-promoting bi-level optimization problem. Finally, we explore a meta-learning version of this algorithm based on group Lasso multiclass SVM base-predictors, for which we derive a tractable dual formulation. It obtains competitive results on standard few-shot classification benchmarks, while each task is using only a fraction of the learned representations.

2023-01-01

ICML (published)

openreview.net

SVRG meets AdaGrad: painless variance reduction

Benjamin Dubois-Taine

Sharan Vaswani

Reza Babanezhad Harikandeh

Mark Schmidt

Simon Lacoste-Julien

2022-11-10

Machine Learning (published)

doi.org

arxiv.org

Disentanglement via Mechanism Sparsity Regularization: A New Principle for Nonlinear ICA

Sébastien Lachapelle

Pau Rodriguez

Yash Sharma

Katie E Everett

Rémi LE PRIOL

Alexandre Lacoste

Simon Lacoste-Julien

This work introduces a novel principle we call disentanglement via mechanism sparsity regularization, which can be applied when the latent f… (see more)actors of interest depend sparsely on past latent factors and/or observed auxiliary variables. We propose a representation learning method that induces disentanglement by simultaneously learning the latent factors and the sparse causal graphical model that relates them. We develop a rigorous identifiability theory, building on recent nonlinear independent component analysis (ICA) results, that formalizes this principle and shows how the latent variables can be recovered up to permutation if one regularizes the latent mechanisms to be sparse and if some graph connectivity criterion is satisfied by the data generating process. As a special case of our framework, we show how one can leverage unknown-target interventions on the latent factors to disentangle them, thereby drawing further connections between ICA and causality. We propose a VAE-based method in which the latent mechanisms are learned and regularized via binary masks, and validate our theory by showing it learns disentangled representations in simulations.

2022-01-01

CLeaR (published)

proceedings.mlr.press

openreview.net

Predicting Tactical Solutions to Operational Planning Problems under Imperfect Information

Eric Larsen

Sébastien Lachapelle

This paper offers a methodological contribution at the intersection of machine learning and operations research. Namely, we propose a method… (see more)ology to quickly predict expected tactical descriptions of operational solutions (TDOSs). The problem we address occurs in the context of two-stage stochastic programming, where the second stage is demanding computationally. We aim to predict at a high speed the expected TDOS associated with the second-stage problem, conditionally on the first-stage variables. This may be used in support of the solution to the overall two-stage problem by avoiding the online generation of multiple second-stage scenarios and solutions. We formulate the tactical prediction problem as a stochastic optimal prediction program, whose solution we approximate with supervised machine learning. The training data set consists of a large number of deterministic operational problems generated by controlled probabilistic sampling. The labels are computed based on solutions to these problems (solved independently and offline), employing appropriate aggregation and subselection methods to address uncertainty. Results on our motivating application on load planning for rail transportation show that deep learning models produce accurate predictions in very short computing time (milliseconds or less). The predictive accuracy is close to the lower bounds calculated based on sample average approximation of the stochastic prediction programs.

2022-01-01

INFORMS Journal on Computing (published)

doi.org

arxiv.org

Stochastic Gradient Descent-Ascent and Consensus Optimization for Smooth Games: Convergence Analysis under Expected Co-coercivity

Nicolas Loizou

Hugo Berard

Gauthier Gidel

Ioannis Mitliagkas

Simon Lacoste-Julien

Two of the most prominent algorithms for solving unconstrained smooth games are the classical stochastic gradient descent-ascent (SGDA) and … (see more)the recently introduced stochastic consensus optimization (SCO) [Mescheder et al., 2017]. SGDA is known to converge to a stationary point for specific classes of games, but current convergence analyses require a bounded variance assumption. SCO is used successfully for solving large-scale adversarial problems, but its convergence guarantees are limited to its deterministic variant. In this work, we introduce the expected co-coercivity condition, explain its benefits, and provide the first last-iterate convergence guarantees of SGDA and SCO under this condition for solving a class of stochastic variational inequality problems that are potentially non-monotone. We prove linear convergence of both methods to a neighborhood of the solution when they use constant step-size, and we propose insightful stepsize-switching rules to guarantee convergence to the exact solution. In addition, our convergence guarantees hold under the arbitrary sampling paradigm, and as such, we give insights into the complexity of minibatching.

openreview.net

A Survey of Self-Supervised and Few-Shot Object Detection

Gabriel Huang

Issam Hadj Laradji

David Vazquez

Simon Lacoste-Julien

Pau Rodriguez

2021-10-27

ArXiv (preprint)

doi.org

arxiv.org

Stochastic Polyak Step-size for SGD: An Adaptive Learning Rate for Fast Convergence

Nicolas Loizou

Sharan Vaswani

Issam Hadj Laradji

Simon Lacoste-Julien

We propose a stochastic variant of the classical Polyak step-size (Polyak, 1987) commonly used in the subgradient method. Although computing… (see more) the Polyak step-size requires knowledge of the optimal function values, this information is readily available for typical modern machine learning applications. Consequently, the proposed stochastic Polyak step-size (SPS) is an attractive choice for setting the learning rate for stochastic gradient descent (SGD). We provide theoretical convergence guarantees for SGD equipped with SPS in different settings, including strongly convex, convex and non-convex functions. Furthermore, our analysis results in novel convergence guarantees for SGD with a constant step-size. We show that SPS is particularly effective when training over-parameterized models capable of interpolating the training data. In this setting, we prove that SPS enables SGD to converge to the true solution at a fast rate without requiring the knowledge of any problem-dependent constants or additional computational overhead. We experimentally validate our theoretical results via extensive experiments on synthetic and real datasets. We demonstrate the strong performance of SGD with SPS compared to state-of-the-art optimization methods when training over-parameterized models.

2021-03-18

Proceedings of The 24th International Conference on Artificial Intelligence and Statistics (published)

proceedings.mlr.press

arxiv.org

SVRG meets AdaGrad: painless variance reduction

Benjamin Dubois-Taine

Sharan Vaswani

Reza Babanezhad Harikandeh

Mark Schmidt

Simon Lacoste-Julien

2021-02-18

ArXiv (preprint)

doi.org

arxiv.org

AI Research Driven by Real-World Problems

AI Policy Compass

Student Life and Resources

Simon Lacoste-Julien

Biography

Current Students

Blog Posts

Publications

AI Research Driven by Real-World Problems

AI Policy Compass

Student Life and Resources

Popular keywords:

Simon Lacoste-Julien

Biography

Current Students

Blog Posts

Publications