Publications

To Each Optimizer a Norm, To Each Norm its Generalization

Sharan Vaswani

Reza Babanezhad Harikandeh

Jose Gallego

Aaron Mishkin

We study the implicit regularization of optimization methods for linear models interpolating the training data in the under-parametrized and… (see more) over-parametrized regimes. Since it is difficult to determine whether an optimizer converges to solutions that minimize a known norm, we flip the problem and investigate what is the corresponding norm minimized by an interpolating solution. Using this reasoning, we prove that for over-parameterized linear regression, projections onto linear spans can be used to move between different interpolating solutions. For under-parameterized linear classification, we prove that for any linear classifier separating the data, there exists a family of quadratic norms ||.||_P such that the classifier's direction is the same as that of the maximum P-margin solution. For linear classification, we argue that analyzing convergence to the standard maximum l2-margin is arbitrary and show that minimizing the norm induced by the data results in better generalization. Furthermore, for over-parameterized linear classification, projections onto the data-span enable us to use techniques from the under-parameterized setting. On the empirical side, we propose techniques to bias optimizers towards better generalizing solutions, improving their test performance. We validate our theoretical results via synthetic experiments, and use the neural tangent kernel to handle non-linear models.

2020-06-11

ArXiv (preprint)

arxiv.org

Glossary for public health surveillance in the age of data science

Arnaud Chiolero

David Buckeridge

Public health surveillance is the ongoing systematic collection, analysis and interpretation of data, closely integrated with the timely dis… (see more)semination of the resulting information to those responsible for preventing and controlling disease and injury. With the rapid development of data science, encompassing big data and artificial intelligence, and with the exponential growth of accessible and highly heterogeneous health-related data, from healthcare providers to user-generated online content, the field of surveillance and health monitoring is changing rapidly. It is, therefore, the right time for a short glossary of key terms in public health surveillance, with an emphasis on new data-science developments in the field.

2020-06-10

Journal of Epidemiology and Community Health (published)

doi.org

A Large-Scale, Open-Domain, Mixed-Interface Dialogue-Based ITS for STEM

Iulian V. Serban

Varun Gupta

Ekaterina Kochmar

Dung D. Vu

Robert Belfer

2020-06-10

Artificial Intelligence in Education (published)

doi.org

arxiv.org

Halting Time is Predictable for Large Models: A Universality Property and Average-Case Analysis

Courtney Paquette

Bart van Merriënboer

Fabian Pedregosa

2020-06-08

ArXiv (preprint)

doi.org

arxiv.org

Multi-agent Assortment Optimization in Sequential Matching Markets

Alfredo Torrico

Margarida Carvalho

Andrea Lodi

2020-06-08

ArXiv (preprint)

arxiv.org

Provable Guarantees for General Two-sided Sequential Matching Markets

Alfredo Torrico

Margarida Carvalho

Andrea Lodi

Two-sided markets have become increasingly more important during the last years, mostly because of their numerous applications in housing, l… (see more)abor and dating. Consumer-supplier matching platforms pose several technical challenges, specially due to the trade-off between recommending suitable suppliers to consumers and avoiding collisions among consumers' preferences. In this work, we study a general version of the two-sided sequential matching model introduced by Ashlagi et al. (2019). The setting is the following: we (the platform) offer a menu of suppliers to each consumer. Then, every consumer selects, simultaneously and independently, to match with a supplier or to remain unmatched. Suppliers observe the subset of consumers that selected them, and choose either to match a consumer or leave the system. Finally, a match takes place if both the consumer and the supplier sequentially select each other. Each agent's behavior is probabilistic and determined by a regular discrete choice model. Our objective is to choose an assortment family that maximizes the expected cardinality of the matching. Given the computational complexity of the problem, we show several provable guarantees for the general model, which in particular, significantly improve the approximation factors previously obtained.

2020-06-08

arXiv.org (preprint)

dblp.uni-trier.de

Dark control: The default mode network as a reinforcement learning agent

Elvis Dohmatob

Guillaume Dumas

Danilo Bzdok

2020-06-05

Human Brain Mapping (published)

doi.org

Prioritization of patients access to outpatient augmentative and alternative communication services in Quebec: a decision tool

Samira Abbasgholizadeh-Rahimi

Julien Dery

Marie‐eve Lamontagne

Ali Jamshidi

Emilie Lacroix

Angel B. Ruiz

Daoud Ait-Kadi

F. Routhier

Abstract Purpose A large number of people living with a chronic disability wait a long time to access publicly funded rehabilitation service… (see more)s such as Augmentative and Alternative Communication (AAC) services, and there is no standardized tool to prioritize these patients. We aimed to develop a prioritization tool to improve the organization and access to the care for this population. Methods In this sequential mixed methods study, we began with a qualitative phase in which we conducted semi-structured interviews with 14 stakeholders including patients, their caregivers, and AAC service providers in Quebec City, Canada to gather their ideas about prioritization criteria. Then, during a half-day consensus group meeting with stakeholders, using a consensus-seeking technique (i.e. Technique for Research of Information by Animation of a Group of Experts), we reached consensus on the most important prioritization criteria. These criteria informed the quantitative phase in which used an electronic questionnaire to collect stakeholders’ views regarding the relative weights for each of the selected criteria. We analyzed these data using a hybrid quantitative method called group based fuzzy analytical hierarchy process, to obtain the importance weights of the selected eight criteria. Results Analyses of the interviews revealed 48 criteria. Collectively, the stakeholders reached consensus on eight criteria, and through the electronic questionnaire they defined the selected criteria’s importance weights. The selected eight prioritization criteria and their importance weights are: person’s safety (weight: 0.274), risks development potential (weight: 0.144), psychological well-being (weight: 0.140), physical well-being (weight: 0.124), life prognosis (weight: 0.106), possible impact on social environment (weight: 0.085), interpersonal relationships (weight: 0.073), and responsibilities and social role (weight: 0.054). Conclusion In this study, we co-developed a prioritization decision tool with the key stakeholders for prioritization of patients who are referred to AAC services in rehabilitation settings. IMPLICATIONS FOR REHABILIATION Studies in Canada have shown that people in Canada with a need for rehabilitation services are not receiving publicly available services in a timely manner. There is no standardized tool for the prioritization of AAC patients. In this mixed methods study, we co-developed a prioritization tool with key stakeholders for prioritization of patients who are referred to AAC services in a rehabilitation center in Quebec, Canada.

2020-06-05

Disability and Rehabilitation: Assistive Technology (published)

doi.org

Prioritization of patients access to outpatient augmentative and alternative communication services in Quebec: a decision tool

Samira Abbasgholizadeh-Rahimi

Julien Dery

Marie-Eve Lamontagne

Afshin Jamshidi

Emilie Lacroix

Angel Ruiz

Daoud Ait-Kadi

François Routhier