Title: Power and Scheduling in a Parallel Processing Network

Abstract: We consider a parallel processing network with removable servers. Beginning with the single server model with power and service rate control, we study the importance of a delayed restart when the server is off. In particular, we show that an optimal policy exists (under the average cost criterion) that delays restarting until a “safety stock” of work is in the system. It then behaves similarly to that of the classic service rate control models. With that as the backdrop, we consider scheduling with the ability to remove servers. We introduce “delay-JSQ” (join the shortest queue) policies, show their stability and asymptotic optimality in the two-server case, and conclude with a detailed numerical study that shows they outperform JSQ by up to 80%. This is joint work with Professor Douglas Down from McMaster University and Dr. Pamela Badian-Pessot (now at Proctor and Gamble).

Bio: Professor Lewis received his Ph.D. from Georgia Tech’s ISyE department in 1998 (under the expert tutelage of Hayriye Ayhan and Bob Foley). He spent a year as a postdoctoral researcher in the Centre for Operations Excellence at the University of British Columbia. Mark’s first (tenure track) academic job was at the University of Michigan’s Department of Industrial and Operation Engineering. Professor Lewis joined Cornell’s School of Operations Research and Information Engineering in 2005. His research interest are at the nexus of dynamic decision-making and stochastic processes, where he splits his time studying Markov decision process theory and dynamic queueing control. Before becoming director of the school in 2019, Mark was appointed Senior Associate Dean for Diversity and Faculty Development in the College of Engineering from 2015 to 2020. Some of his accolades include NSF’s Presidential Early Career Award for Science and Engineering (PECASE) and the Sloan Foundation’s Mentor of the Year Award.