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Lam Nguyen

11 accepted papers

2024

Count What You Want: Exemplar Identification and Few-Shot Counting of Human Actions in the Wild

AAAI 2024technical

This paper addresses the task of counting human actions of interest using sensor data from wearable devices. We propose a novel exemplar-based framework, allowing users to provide exemplars of the actions they want to count by vocalizing predefined sounds ``one'', ``two'', and ``three''. Our method…

2021

Hogwild! over Distributed Local Data Sets with Linearly Increasing Mini-Batch Sizes

AISTATS 2021poster

Hogwild! implements asynchronous Stochastic Gradient Descent (SGD) where multiple threads in parallel access a common repository containing training data, perform SGD iterations and update shared state that represents a jointly learned (global) model. We consider big data analysis where training dat…

Cited by 6SourcePDFScholar
2020

A Hybrid Stochastic Policy Gradient Algorithm for Reinforcement Learning

AISTATS 2020poster

We propose a novel hybrid stochastic policy gradient estimator by combining an unbiased policy gradient estimator, the REINFORCE estimator, with another biased one, an adapted SARAH estimator for policy optimization. The hybrid policy gradient estimator is shown to be biased, but has variance reduce…

2020

A Scalable MIP-based Method for Learning Optimal Multivariate Decision Trees

NeurIPS 2020poster

Several recent publications report advances in training optimal decision trees (ODTs) using mixed-integer programs (MIPs), due to algorithmic advances in integer programming and a growing interest in addressing the inherent suboptimality of heuristic approaches such as CART. In this paper, we propos…

Cited by 63SourcePDFScholar
2020

Hybrid Variance-Reduced SGD Algorithms For Minimax Problems with Nonconvex-Linear Function

NeurIPS 2020poster

We develop a novel and single-loop variance-reduced algorithm to solve a class of stochastic nonconvex-convex minimax problems involving a nonconvex-linear objective function, which has various applications in different fields such as ma- chine learning and robust optimization. This problem class ha…

Cited by 29SourcePDFScholar
2020

Stochastic Gauss-Newton Algorithms for Nonconvex Compositional Optimization

ICML 2020poster

We develop two new stochastic Gauss-Newton algorithms for solving a class of non-convex stochastic compositional optimization problems frequently arising in practice. We consider both the expectation and finite-sum settings under standard assumptions, and use both classical stochastic and SARAH esti…

Cited by 35SourcePDFScholar
2019

Characterization of Convex Objective Functions and Optimal Expected Convergence Rates for SGD

ICML 2019oral

We study Stochastic Gradient Descent (SGD) with diminishing step sizes for convex objective functions. We introduce a definitional framework and theory that defines and characterizes a core property, called curvature, of convex objective functions. In terms of curvature we can derive a new inequalit…

Cited by 7SourcePDFScholar
2019

PROVEN: Verifying Robustness of Neural Networks with a Probabilistic Approach

ICML 2019oral

We propose a novel framework PROVEN to \textbf{PRO}babilistically \textbf{VE}rify \textbf{N}eural network’s robustness with statistical guarantees. PROVEN provides probability certificates of neural network robustness when the input perturbation follow distributional characterization. Notably, PROVE…

2019

Tight Dimension Independent Lower Bound on the Expected Convergence Rate for Diminishing Step Sizes in SGD

NeurIPS 2019poster

We study the convergence of Stochastic Gradient Descent (SGD) for strongly convex objective functions. We prove for all $t$ a lower bound on the expected convergence rate after the $t$-th SGD iteration; the lower bound is over all possible sequences of diminishing step sizes. It implies that recent…

Cited by 34SourcePDFScholar
2018

SGD and Hogwild! Convergence Without the Bounded Gradients Assumption

ICML 2018oral

Stochastic gradient descent (SGD) is the optimization algorithm of choice in many machine learning applications such as regularized empirical risk minimization and training deep neural networks. The classical convergence analysis of SGD is carried out under the assumption that the norm of the stocha…

Cited by 266SourcePDFScholar