Time-Constrained Project Scheduling

T.A. Guldemond, J.L. Hurink, J.J. Paulus and J.M.J. Schutten
Abstract | Instance Description | Weekly Pattern and Costs | Summary of the Results | Details | Contact

Abstract

We study the Time-Constrained Project Scheduling Problem (TCPSP), in which the scheduling of activities is subject to strict deadlines. To be able to meet these deadlines, it is possible to work in overtime or hire additional capacity in regular time or overtime. For this problem, we develop a two stage heuristic. The key of our approach lies in the first stage in which we construct partial schedules with a randomized sampling technique. In these partial schedules, jobs may be scheduled for a shorter duration than required. The second stage uses an ILP formulation of the problem to turn a partial schedule into a feasible schedule, and to perform a neighbourhood search. The developed heuristic is quite flexible and, therefore, suitable for practice. We present experimental results on modified RCPSP benchmark instances. The two stage heuristic solves many instances to optimality, and if we substantially decrease the deadline, the rise in cost is only small.

Details of Computational Experiments

  • Instances:
    • Description of the instance structure.
    • Download the instances from the Project Scheduling Problem Library - PSPlib.
    • Download the weekly pattern of overtime and costs.
    • Download list of deadlines for instances with 30, 60, 90 and 120 jobs. Each row consists of the instance name, follow by the best known makespan and the best known lowerbound on the makespan.
  • Results: