Polyhedral results and valid inequalities for the Continuous Energy-Constrained Scheduling Problem
Résumé
This works deals with event-based mixed integer linear programming formulations for
resource-constrained scheduling problems. In this context, two strongly NP-hard problems
are considered: the Resource-Constrained Project Scheduling Problem (RCPSP)
and the Continuous Energy-Constrained Scheduling Problem (CECSP). Several mixed
integer programs have been developed so far in order to solve them [1, 2, 4].
For the RCPSP, time-indexed formulations have a much better LP relaxation than
the event-based ones. However, time-indexed formulations show their weakness for instances
with large planning horizons and heterogeneous task durations, while eventbased
models proved to be more efficient to provide exact solutions for these types of
instances [1]. For the CECSP, event-based formulations are the only ones that can
provide optimal solutions. Indeed, an instance of the CECSP may have only solutions
containing non-integer values and such a solution can not be reached by a time-indexed
formulation [2]. In this work, we are interested in the strengthening of those event-based
models.