Dr. Alejandro Toriello
ISE Assistant Professor
Georgia Institute of Technology
Friday, October 21, 2016 2:20-3:20pm
We study same-day delivery (SDD) systems by formulating the Dynamic Dispatch Waves Problem (DDWP), which models a depot serving geographically dispersed delivery orders that appear dynamically throughout the day. At each decision epoch (wave), the system’s operator chooses whether or not to dispatch a vehicle route loaded with orders ready for service, with the objective of minimizing vehicle travel and penalties for unserved requests. We study both the one-dimensional problem, where orders are on a line with the depot at one end, and the general problem on any network topology. For the 1D case, we propose an efficient dynamic program for the deterministic variant, and leverage this result to derive an optimal a priori solution for the stochastic model. In the general case, we show how to solve the deterministic model with an integer program, extend it to get an a priori policy for the stochastic case, and then design dynamic heuristic policies using the a priori solution. Our computational results suggest that our best dynamic policies can cut the average cost of an a priori policy by 9.1%, achieving a gap of 12.1%. The marginal value of dynamic policies is concentrated in improving order coverage and increases for instances with greater variability and information dynamism. We also analyze the tradeoff between two common SDD objectives: total cost minimization versus maximizing order coverage. Joint work with Alan Erera and Mathias Klapp.
Dr. Alejandro Toriello is Assistant Professor in the Stewart School of Industrial and Systems Engineering (ISyE) at Georgia Tech. Prof. Toriello develops models and methods for decision support in supply chain management, logistics and transportation, and conducts theoretical and computational research in related optimization methodologies. His work has optimized problems as varied as the routing of oil tankers, the shipping of cut flowers and the hiring of health care personnel. He teaches logistics courses in ISyE at the undergraduate and graduate levels, is on the editorial board of various academic journals in operations research and transportation, and is a recipient of an NSF CAREER Award. Toriello received his B.S. and Ph.D. in Industrial Engineering from Georgia Tech in 2003 and 2010, respectively. Prior to joining ISyE, he was Assistant Professor in the Epstein Department of Industrial and Systems Engineering at the University of Southern California.