Portrait de Samira Ebrahimi Kahou

Samira Ebrahimi Kahou

Membre affilié
Chaire en IA Canada-CIFAR
Professeure adjointe, University of Calgary, Départment de génie électrique et logiciel
Professeure adjointe, École de technologie suprérieure, Département de génie logiciel et technologies de l'information
Professeure adjointe, McGill University, École d'informatique
Sujets de recherche
Apprentissage automatique médical
Apprentissage de représentations
Apprentissage multimodal
Apprentissage par renforcement
Apprentissage profond
Traitement du langage naturel
Vision par ordinateur

Biographie

Je suis professeure adjointe à l'Université de Calgary, à l'école d'ingénierie Schulich au département de génie électrique et logiciel. Je suis aussi professeure adjointe au département de génie logiciel et technologies de l'information de l'École de technologie supérieure (ÉTS) et professeure adjointe à l'école d'informatique de l’Université McGill. Avant de me joindre à l'ÉTS, j'ai été stagiaire postdoctorale auprès de la professeure Doina Precup à l’Université McGill / Mila – Institut québécois d’intelligence artificielle. Préalablement à mon postdoctorat, j'ai été chercheuse à Microsoft Research, à Montréal. J'ai obtenu mon doctorat à Polytechnique Montréal / Mila en 2016 sous la supervision du professeur Chris Pal. Pendant mes études doctorales, j'ai travaillé sur la vision par ordinateur et l'apprentissage profond appliqués à la reconnaissance des émotions, au suivi d'objets et à la distillation de connaissances.

Étudiants actuels

Maîtrise recherche - École de technologie suprérieure
Doctorat - École de technologie suprérieure
Doctorat - UdeM
Superviseur⋅e principal⋅e :
Collaborateur·rice de recherche - McGill
Co-superviseur⋅e :
Maîtrise professionnelle - UdeM
Maîtrise recherche - École de technologie suprérieure
Superviseur⋅e principal⋅e :
Maîtrise recherche - École de technologie suprérieure
Doctorat - École de technologie suprérieure
Superviseur⋅e principal⋅e :
Doctorat - McGill
Co-superviseur⋅e :
Maîtrise recherche - École de technologie suprérieure
Doctorat - McGill
Superviseur⋅e principal⋅e :
Maîtrise recherche - McGill
Superviseur⋅e principal⋅e :

Publications

A Survey on Fairness Without Demographics
Patrik Joslin Kenfack
Éts Montréal
The issue of bias in Machine Learning (ML) models is a significant challenge for the machine learning community. Real-world biases can be em… (voir plus)bedded in the data used to train models, and prior studies have shown that ML models can learn and even amplify these biases. This can result in unfair treatment of individuals based on their inherent characteristics or sensitive attributes such as gender, race, or age. Ensuring fairness is crucial with the increasing use of ML models in high-stakes scenarios and has gained significant attention from researchers in recent years. However, the challenge of ensuring fairness becomes much greater when the assumption of full access to sensitive attributes does not hold. The settings where the hypothesis does not hold include cases where (1) only limited or noisy demographic information is available or (2) demographic information is entirely unobserved due to privacy restrictions. This survey reviews recent research efforts to enforce fairness when sensitive attributes are missing. We propose a taxonomy of existing works and, more importantly, highlight current challenges and future research directions to stimulate research in ML fairness in the setting of missing sensitive attributes.
On the Limits of Multi-modal Meta-Learning with Auxiliary Task Modulation Using Conditional Batch Normalization
Jordi Armengol-Estap'e
Vincent Michalski
Ramnath Kumar
Pierre-Luc St-Charles
Few-shot learning aims to learn representations that can tackle novel tasks given a small number of examples. Recent studies show that cross… (voir plus)-modal learning can improve representations for few-shot classification. More specifically, language is a rich modality that can be used to guide visual learning. In this work, we experiment with a multi-modal architecture for few-shot learning that consists of three components: a classifier, an auxiliary network, and a bridge network. While the classifier performs the main classification task, the auxiliary network learns to predict language representations from the same input, and the bridge network transforms high-level features of the auxiliary network into modulation parameters for layers of the few-shot classifier using conditional batch normalization. The bridge should encourage a form of lightweight semantic alignment between language and vision which could be useful for the classifier. However, after evaluating the proposed approach on two popular few-shot classification benchmarks we find that a) the improvements do not reproduce across benchmarks, and b) when they do, the improvements are due to the additional compute and parameters introduced by the bridge network. We contribute insights and recommendations for future work in multi-modal meta-learning, especially when using language representations.
Neural semantic tagging for natural language-based search in building information models: Implications for practice
Mehrzad Shahinmoghadam
Ali Motamedi
Spectral Temporal Contrastive Learning
Sacha Morin
Somjit Nath
Learning useful data representations without requiring labels is a cornerstone of modern deep learning. Self-supervised learning methods, pa… (voir plus)rticularly contrastive learning (CL), have proven successful by leveraging data augmentations to define positive pairs. This success has prompted a number of theoretical studies to better understand CL and investigate theoretical bounds for downstream linear probing tasks. This work is concerned with the temporal contrastive learning (TCL) setting where the sequential structure of the data is used instead to define positive pairs, which is more commonly used in RL and robotics contexts. In this paper, we adapt recent work on Spectral CL to formulate Spectral Temporal Contrastive Learning (STCL). We discuss a population loss based on a state graph derived from a time-homogeneous reversible Markov chain with uniform stationary distribution. The STCL loss enables to connect the linear probing performance to the spectral properties of the graph, and can be estimated by considering previously observed data sequences as an ensemble of MCMC chains.
Bridging the Gap Between Offline and Online Reinforcement Learning Evaluation Methodologies
Shiva Kanth Sujit
Pedro Braga
Jorg Bornschein
Reinforcement learning (RL) has shown great promise with algorithms learning in environments with large state and action spaces purely from … (voir plus)scalar reward signals. A crucial challenge for current deep RL algorithms is that they require a tremendous amount of environment interactions for learning. This can be infeasible in situations where such interactions are expensive, such as in robotics. Offline RL algorithms try to address this issue by bootstrapping the learning process from existing logged data without needing to interact with the environment from the very beginning. While online RL algorithms are typically evaluated as a function of the number of environment interactions, there isn't a single established protocol for evaluating offline RL methods. In this paper, we propose a sequential approach to evaluate offline RL algorithms as a function of the training set size and thus by their data efficiency. Sequential evaluation provides valuable insights into the data efficiency of the learning process and the robustness of algorithms to distribution changes in the dataset while also harmonizing the visualization of the offline and online learning phases. Our approach is generally applicable and easy to implement. We compare several existing offline RL algorithms using this approach and present insights from a variety of tasks and offline datasets.
Empowering Clinicians with MeDT: A Framework for Sepsis Treatment
Aamer Abdul Rahman
Pranav Agarwal
Vincent Michalski
Rita Noumeir
RelationalUNet for Image Segmentation
Ivaxi Sheth
Pedro H. M. Braga
Shiva Kanth Sujit
Sahar Dastani
Prioritizing Samples in Reinforcement Learning with Reducible Loss
Shiva Kanth Sujit
Somjit Nath
Pedro Braga
Fairness Under Demographic Scarce Regime
Patrik Joslin Kenfack
Most existing works on fairness assume the model has full access to demographic information. However, there exist scenarios where demographi… (voir plus)c information is partially available because a record was not maintained throughout data collection or due to privacy reasons. This setting is known as demographic scarce regime. Prior research have shown that training an attribute classifier to replace the missing sensitive attributes (proxy) can still improve fairness. However, the use of proxy-sensitive attributes worsens fairness-accuracy trade-offs compared to true sensitive attributes. To address this limitation, we propose a framework to build attribute classifiers that achieve better fairness-accuracy trade-offs. Our method introduces uncertainty awareness in the attribute classifier and enforces fairness on samples with demographic information inferred with the lowest uncertainty. We show empirically that enforcing fairness constraints on samples with uncertain sensitive attributes is detrimental to fairness and accuracy. Our experiments on two datasets showed that the proposed framework yields models with significantly better fairness-accuracy trade-offs compared to classic attribute classifiers. Surprisingly, our framework outperforms models trained with constraints on the true sensitive attributes.
Transformers in Reinforcement Learning: A Survey
Pranav Agarwal
Aamer Abdul Rahman
Pierre-Luc St-Charles
Simon J. D. Prince
Transformers have significantly impacted domains like natural language processing, computer vision, and robotics, where they improve perform… (voir plus)ance compared to other neural networks. This survey explores how transformers are used in reinforcement learning (RL), where they are seen as a promising solution for addressing challenges such as unstable training, credit assignment, lack of interpretability, and partial observability. We begin by providing a brief domain overview of RL, followed by a discussion on the challenges of classical RL algorithms. Next, we delve into the properties of the transformer and its variants and discuss the characteristics that make them well-suited to address the challenges inherent in RL. We examine the application of transformers to various aspects of RL, including representation learning, transition and reward function modeling, and policy optimization. We also discuss recent research that aims to enhance the interpretability and efficiency of transformers in RL, using visualization techniques and efficient training strategies. Often, the transformer architecture must be tailored to the specific needs of a given application. We present a broad overview of how transformers have been adapted for several applications, including robotics, medicine, language modeling, cloud computing, and combinatorial optimization. We conclude by discussing the limitations of using transformers in RL and assess their potential for catalyzing future breakthroughs in this field.
Discovering Object-Centric Generalized Value Functions From Pixels
Somjit Nath
Gopeshh Subbaraj
Deep Reinforcement Learning has shown significant progress in extracting useful representations from high-dimensional inputs albeit using ha… (voir plus)nd-crafted auxiliary tasks and pseudo rewards. Automatically learning such representations in an object-centric manner geared towards control and fast adaptation remains an open research problem. In this paper, we introduce a method that tries to discover meaningful features from objects, translating them to temporally coherent"question"functions and leveraging the subsequent learned general value functions for control. We compare our approach with state-of-the-art techniques alongside other ablations and show competitive performance in both stationary and non-stationary settings. Finally, we also investigate the discovered general value functions and through qualitative analysis show that the learned representations are not only interpretable but also, centered around objects that are invariant to changes across tasks facilitating fast adaptation.
CAMMARL: Conformal Action Modeling in Multi Agent Reinforcement Learning
Nikunj Gupta
Somjit Nath
Before taking actions in an environment with more than one intelligent agent, an autonomous agent may benefit from reasoning about the other… (voir plus) agents and utilizing a notion of a guarantee or confidence about the behavior of the system. In this article, we propose a novel multi-agent reinforcement learning (MARL) algorithm CAMMARL, which involves modeling the actions of other agents in different situations in the form of confident sets, i.e., sets containing their true actions with a high probability. We then use these estimates to inform an agent's decision-making. For estimating such sets, we use the concept of conformal predictions, by means of which, we not only obtain an estimate of the most probable outcome but get to quantify the operable uncertainty as well. For instance, we can predict a set that provably covers the true predictions with high probabilities (e.g., 95%). Through several experiments in two fully cooperative multi-agent tasks, we show that CAMMARL elevates the capabilities of an autonomous agent in MARL by modeling conformal prediction sets over the behavior of other agents in the environment and utilizing such estimates to enhance its policy learning.