IE-OPIM Joint Graduate Seminar
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IE-OPIM Joint Graduate Seminar: Deniz Aksen (Koç University)

Battlefield VRP: Clash of Formulations, Valid Inequalities, Commercial Solvers and Solver Options

Date: Wednesday, April 01, 2015
Time: 13:40 – 14:30
Location: FENS G035


Abstract: This study presents an in-depth comparative computational analysis of two well-known and two lesser-known vehicle routing problem (VRP) formulations. We investigate both of their lower and upper bounding performances and their CPU time efficiency using state-of-the-art commercial mixed-integer programming solvers embedded in the optimization software package GAMS. The parallel computing capabilities of these solvers are leveraged by appropriate options—a feature which is sometimes underutilized or yet overlooked in the literature. Incorporated into the tested formulations, we also try a number of valid inequalities (VIs) in our quest for the tightest bounds, best feasible solutions and least CPU times. We report an extensive computational analysis performed on close to 100 test instances retrieved from the VRP Web hosted at the University of Malaga and from the VRPLib hosted at the University of Bologna. The results of our study will be useful not only to practitioners faced with real-world routing problems, but also to researchers who develop novel heuristic or exact algorithms for large-scale VRPs and its extensions.


Bio: Deniz Aksen holds his BS (1994) and MS degrees (1996) from Boğaziçi University Department of Industrial Engineering in İstanbul, Turkey. He received his PhD in Management Information System (MIS) from Krannert School of Management at Purdue University, USA (2003). The same year he joined Koç University (KU) College of Administrative Sciences and Economics (CASE).

Dr. Aksen teaches in the areas of MIS, e-commerce, Internet security, and business spreadsheet applications. Since 2011 he has been also supervising KU student teams participating at the Google Online Marketing Challenge.

His research interests include distribution and collection logistics, vehicle routing, and facility location and interdiction problems. His papers have been published in the European Journal of Operational Research, Computers & Operations Research, International Journal of Production Economics, and Transportation Research Part C, among others.

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