A simulated annealing approach to the solution of flexible labour scheduling problems

This paper presents a new solution approach to the discontinuous labour tour scheduling problem where the objective is to minimize the number of full-time employees required to satisfy forecast demand. Previous heuristic approaches have often limited the number of allowable tours by restricting labour scheduling flexibility in terms of shift length, shift start-times, days-off, meal-break placement, and other factors. These restrictions were essential to the tractability of the heuristic approaches but often resulted in solutions that contained a substantial amount of excess labour. In this study, the authors relaxed many of the restrictions on scheduling flexibility assumed in previous studies. The resulting problem environment contained more than two billion allowable tours, precluding the use of previous heuristic methods. Consequently, the authors developed a simulated annealing heuristic for solving the problem. An important facet of this new approach is an ‘intelligent’ improvement routine which eliminates the need for long run-times typically associated with simulated annealing algorithms. The simulated annealing framework does not rely on a special problem structure and the present implementation rapidly converged to near-optimal solutions for all problems in the test environment.