The Multirate Resource Constraint

Alessio Bonfietti, Alessandro Zanarini, Michele Lombardi, Michela Milano

Abstract: Many real world cyclic scheduling problems involve applications that need to be repeated with different periodicity. For example, multirate control systems present multiple control loops that are organized hierarchically: the higher-level loop responds to the slower system dynamics and typically its period can be a few orders of magnitude longer than the lowest level. Cyclic scheduling problems can be cast into classical RCPSP instances via a technique called unfolding [4, 6], which causes graph expansion. In the case of multirate applications, this expansion can be significantly large. In this context, finding a high-quality allocation and schedule could be very challenging. In this paper, we propose a new Multirate Resource Constraint, modeling unary resources, that avoids graph expansion by exploiting the multirate nature of the schedule in its filtering algorithm. In an experimentation on synthetic and real-world instances, we show that our method drastically outperforms approaches based on state-of-the-art unfolding and constraint based scheduling.