Contributed Session Wed.1.H 2013

Wednesday, 10:30 - 12:00 h, Room: H 2013

Cluster 11: Integer & mixed-integer programming [...]

Scheduling I


Chair: Andrea Raith



Wednesday, 10:30 - 10:55 h, Room: H 2013, Talk 1

Hesham Alfares
Integer programming model and optimum solution for a bi-objective days-off scheduling problem

Coauthor: Alfares K. Hesham


An integer programming model and optimal solution procedure are presented for a real-life cyclic day-off scheduling problem. Efficient techniques are used to determine the best assignment of employees to the (10, 14) days-off schedule. This special work schedule, involving ten consecutive workdays in a two-week cycle, is used by a large oil company to schedule employees in remote work locations. The primary objective is to minimize the total number of employees, and the secondary objective is to minimize the total number of active days-off work patterns. Two days-off scheduling rules are enforced: a minimum proportion of weekend days off needs to be given, and a maximum limit on the number of successive work days cannot be exceeded. Primal-dual relationships are used to identify dominant solutions and to determine the minimum workforce size. Utilizing the problem structure and real-life parameter values, simple optimal procedures are developed to determine the minimum number of days-off patterns and the number of employees assigned to each pattern. A rotation scheme is used to ensure sufficient weekend off days are given and work stretch limits are not exceeded.



Wednesday, 11:00 - 11:25 h, Room: H 2013, Talk 2

Andy Felt
MILP model for athletic conference scheduling

Coauthor: Eli Towle


We examine a MILP model used for determining the specific dates and locations for athletic conference match ups given predetermined available dates and teams. The model takes into account home/away game equivalency, the number of consecutive home/away games, as well as any other stipulations requested by the conference. It accommodates multiple sports spanning multiple seasons. Such models have been utilized by the UWSP Center for Athletic Scheduling to generate optimal schedules for NCAA Division-III athletic conferences adhering to the given constraints.



Wednesday, 11:30 - 11:55 h, Room: H 2013, Talk 3

Andrea Raith
Minimising tardiness in parallel machine scheduling with setup times and mould type restrictions

Coauthor: Amelia White


We study a parallel machine scheduling problem with sequence-dependent setup time. The jobs in this machine-scheduling problem have due dates and each job is of a particular job family. Each job family requires a specific mould to be installed on the machine for production. The setup time of the moulds is significant and there is only a small number of each type of mould available. We present preliminary results of our research into this problem. We propose a time-indexed integer programming formulation that minimises overall job tardiness. The formulation has constraints that model both setup times of the moulds and constraints that restrict the number of machines that can produce jobs of the same familiy at the same time due to limited availability of moulds. We show that some of the constraints can be relaxed and that the obtained optimal solutions of the relaxed problem can be post-processed to derive optimal mould-feasible solutions thus speeding up computation time. We give an indication of expected running times for some test problem instances.


  There are three major facts that should be watched out for in all payday loans in the United States. But at the same time, it acts only with sexual arousal. Viagra has a number of advantages in comparison with injections in the sexual organ or other procedures aimed at treatment of impotency.