IE-OPIM Joint Seminar Wednesday 5 November 2014 13.40 FENS G035
Finding Robust Timetables for Project Presentations of Student Teams
(joint work with M. Erdem Külünk and Cenk Koçaş)
We describe a methodology developed to find robust solutions to a novel timetabling problem encountered during a course. The problem requires grouping student teams according to diversity/homogeneity criteria and assigning the groups to time--slots for presenting their project results. We develop a mixed integer programming (MIP) formulation of the problem and then solve it with CPLEX. Rather than simply using the optimal solution reported by CPLEX, we obtain a set of solutions provided by the solution pool feature of CPLEX. We then map these solutions to a network, in which each solution is a node and an edge represents the distance between a pair of solutions (as measured by the number of teams assigned to a different time slot in those solutions). Using a scenario--based exact robustness measure, we test a set of metrics to determine which ones can be used to heuristically rank the solutions in terms of their robustness measure. Using seven semesters' worth of actual data, we analyze performances of the solution approach and the metrics. The results show that by using CPLEX's solution pool feature, analysts can quickly obtain a set of Pareto--optimal solutions (with objective function value and the robustness measure as the two criteria). Furthermore, two of the heuristic metrics have strong rank correlation with the robustness measure (mostly above 0.80) making them quite suitable for use in the development of new heuristic search algorithms that can improve the solution pool beyond that given by CPLEX.
Bio: Can Akkan is an Associate Professor of Operations Management at Sabancı School of Management, Sabancı University. He received his B.S. degree in Industrial Engineering from Middle East Technical University and Ph.D. degree in operations research from Cornell University. His main research interests are in production and project scheduling (recently rescheduling and robustness issues in scheduling) and applied discrete optimization. He has published in European Journal of Operations Research, Journal of the Operational Research Society, International Journal of Production Research and Journal of Logic and Algebraic Programming. He has several teaching awards including Outstanding Teaching Assistant Award at Cornell University and Graduating Class Awards at Sabancı University.