Cumulative Scheduling with Calendars and Overtime

Abstract

Samuel Cloutier, from the University of Laval, in Quebec, tells us that in project scheduling, calendar considerations can increase the duration of a task when its execution overlaps with holidays. On the other hand, the use of overtime may decrease the task’s duration. We introduce the CalendarOvertime constraint which verifies that a task follows a calendar with overtime and holidays. We also introduce the CumulativeOvertime constraint, a variant of the Cumulative constraint, that also reasons with the calendars when propagating according to the resource consumption, the overtime, and the holidays. Experimental results of a RCPSP model on the PSPLIB, BL, and PACK instances augmented with calendars and overtime show that the use of the CalendarOvertime constraint offers a speedup greater than 2.9 on the instances optimally solved and finds better solutions on more than 79% of the remaining instances when compared to a decomposition of the constraint. We also show that the use of our CumulativeOvertime constraint further improves these results