
CSC@USC/CommNetSMHI Seminar Series
Mon, Aug 27, 2018 @ 02:00 PM  03:30 PM
Ming Hsieh Department of Electrical and Computer Engineering
Conferences, Lectures, & Seminars
Speaker: Jason Lee, University of Southern California
Talk Title: Towards Theoretical Understanding of OverParametrization in Deep Learning
Series: Fall 2018 Joint CSC@USC/CommNetSMHI Seminar Series
Abstract: We provide new theoretical insights on why overparametrization is effective in learning neural networks. For a k hidden node shallow network with quadratic activation and n training data points, we show that as long as k >= sqrt(2n) overparametrization enables local search algorithms to find a globally optimal solution for general smooth and convex loss functions. Further, despite that the number of parameters may exceed the sample size, we show that with weight decay, the solution also generalizes well.
Next, we analyze the implicit regularization effects of various optimization algorithms. In particular we prove that for least squares with mirror descent, the algorithm converges to the closest solution in terms of the Bregman divergence. For linearly separable classification problems, we prove that the steepest descent with respect to a norm solves SVM with respect to the same norm. For overparametrized nonconvex problems such as matrix sensing or neural net with quadratic activation, we prove that gradient descent converges to the minimum nuclear norm solution, which allows for both meaningful optimization and generalization guarantees.
This is a joint work with Suriya Gunasekar, Mor Shpigel, Daniel Soudry, Nati Srebro, and Simon Du.
Biography: Jason Lee is an assistant professor in Data Sciences and Operations at the University of Southern California. Prior to that, he was a postdoctoral researcher at UC Berkeley working with Michael Jordan. Jason received his PhD at Stanford University advised by Trevor Hastie and Jonathan Taylor. His research interests are in statistics, machine learning, and optimization. Lately, he has worked on high dimensional statistical inference, analysis of nonconvex optimization algorithms, and theory for deep learning.
Host: Mihailo Jovanovic, mihailo@usc.edu
Location: Hughes Aircraft Electrical Engineering Center (EEB)  132
Audiences: Everyone Is Invited
Contact: Gerrielyn Ramos