Section: New Results

Employee timetabling with time varying demand

We addressed a multi-activity tour scheduling problem with time varying demand. The objective is to compute a schedule for a fixed roster in order to minimize the over-coverage and the under-coverage of different parallel activity demands along a planning horizon. Numerous complicating constraints are present in our problem: all employees are different and can perform several different activities during the same day-shift, lunch breaks and pauses are flexible, demand is given for 15 minutes periods. To the best of our knowledge, the work in [29] is the first attempt to combine days-off scheduling, shift scheduling, shift assignment, activity assignment, pause and lunch break assignment. To solve this problem, we developed several methods: a compact linear Mixed Integer Programming model, a branch-and-price like approach with a nested dynamic program to solve heuristically the subproblems, a diving heuristic, and a greedy heuristic based on our subproblem solver. The computational results, based on both real cases and instances derived from real cases, demonstrate that our methods are able to provide good quality solutions in a short computing time. Our algorithms are now embedded in a commercial software, which is already in use in a mini-mart company.