The theory and practice of stochastic optimization has focused on stochastic gradient descent (SGD) in recent years, retaining the basic first-order stochastic nature of SGD while aiming to improve it via mechanisms such as averaging, momentum, and variance reduction. Improvement can be measured along various dimensions, however, and it has proved difficult to achieve improvements both in terms of nonasymptotic measures of convergence rate and asymptotic measures of distributional tightness. In this work, we consider first-order stochastic optimization from a general statistical point of view, motivating a specific form of recursive averaging of past stochastic gradients. The resulting algorithm, which we refer to as Recursive One-Over-T SGD (ROOT-SGD), matches the state-of-the-art convergence rate among online variance-reduced stochastic approximation methods. Moreover, under slightly stronger distributional assumptions, the rescaled last-iterate of ROOT-SGD converges to a zero-mean Gaussian distribution that achieves near-optimal covariance. This is a joint work with Wenlong Mou, Martin Wainwright, and Michael Jordan.
28 Aug 2020
11:00am - 12:00pm
Where
https://hkust.zoom.us/j/5616960008
Speakers/Performers
Dr. Junchi LI
University of California, Berkeley
Organizer(S)
Department of Mathematics
Contact/Enquiries
mathseminar@ust.hk
Payment Details
Audience
Alumni, Faculty and Staff, PG Students, UG Students
Language(s)
English
Other Events
10 Oct 2025
Seminar, Lecture, Talk
IAS / School of Science Joint Lecture - Use of Large Animal Models to Investigate Brain Diseases
Abstract Genetically modified animal models have been extensively used to investigate the pathogenesis of age-dependent neurodegenerative diseases, such as Alzheimer (AD), Parkinson (PD), Hunti...
14 Jul 2025
Seminar, Lecture, Talk
IAS / School of Science Joint Lecture - Boron Clusters
Abstract The study of carbon clusters led to the discoveries of fullerenes, carbon nanotubes, and graphene. Are there other elements that can form similar nanostructures? To answer this questio...