Title:  AsySPA: An Exact Asynchronous Algorithm for Distributed Convex Optimization over Digraphs

Speaker: Keyou You （游科友）, Department of Automation, Tsinghua University

时间：2018年11月7日（星期三） 16:30

地点：数学楼408

Abstract:

This talk focuses on an exact asynchronous subgradient-push algorithm (AsySPA) to solve an additive cost optimization problem over digraphs where each node only has access to a local convex function and updates asynchronously with arbitrarily positive rates. Specifically, each node of a strongly connected digraph does not wait for updates from other nodes but independently starts to update after any bounded time interval. “Exact” means that every node of the AsySPA can converge to the same optimal solution, even under different update rates among nodes with bounded communication delays. To compensate uneven update rates, we design a simple mechanism to adaptively adjust the update stepsize by also using local information, which is substantially different from the existing algorithms. Moreover, we adopt the idea of constructing a delay-free augmented system to address asynchrony and delays. Then, we study the convergence of the AsySPA by examining a generalized incremental subgradient algorithm, which clearly has its own significance, and show that the convergence speed is essentially not affected by the aforementioned asynchrony and delays. Finally, simulation is included to validate our theoretical results.

Bio:

Keyou You received the B.S. degree in Statistical Science from Sun Yat-sen University, Guangzhou, China, in 2007 and the Ph.D. degree in Electrical and Electronic Engineering from Nanyang Technological University (NTU), Singapore, in 2012. After briefly working as a Research Fellow at NTU, he joined Tsinghua University in Beijing, China where he is now an Associate Professor in the Department of Automation. He held visiting positions at Politecnico di Torino, The Hong Kong University of Science and Technology, The University of Melbourne and etc. His current research interests include networked control systems, distributed algorithms and learning, and their applications. Dr. You received the Guan Zhaozhi award at the 29th Chinese Control Conference in 2010 and a CSC-IBM China Faculty Award in 2014. He was selected to the National 1000-Youth Talent Program of China in 2014 and received the National Natural Science Fund for Excellent Young Scholars in 2017.