Examination Timetables and Tabu Search with Longer-Term Memory

Abstract

The examination scheduling problem has been examined and a four-phase system using a tabu search algorithm, OTTABU, has been implemented. This system uses both recency-based short-term memory and move (or frequency)-based longer-term memory to improve the quality of the solutions found. The system was tested using real data obtained from the University of Ottawa registrar’s office and real examination schedules were produced. It was found that the use of longer-term memory produced better schedules that those produced without such memory — typically a 34% improvement was obtained due to this factor alone. The length of the long term memory list was also found to be important. A length that is too small can greatly reduce its effectiveness. A list that is too long only reduces the effectiveness by a small amount. A quantitative analysis method is applied to estimate the appropriate length of the longer-term tabu list and a controlled tabu relaxation technique is used to improve the effectiveness.