Implementing Cumulative Functions with Generalized Cumulative Constraints

TL;DR

This paper introduces a new implementation of generalized cumulative functions for scheduling problems using a global constraint and a novel filtering algorithm, enabling open-source solvers to handle complex conditional and producer-consumer scheduling efficiently.

Contribution

It presents a unified implementation of cumulative functions with conditional intervals and a new filtering algorithm, filling a gap in open-source solver capabilities.

Findings

Competitive performance with existing solvers

Effective scaling to large problems

Enables modeling of producer-consumer scheduling

Abstract

Modeling scheduling problems with conditional time intervals and cumulative functions has become a common approach when using modern commercial constraint programming solvers. This paradigm enables the modeling of a wide range of scheduling problems, including those involving producers and consumers. However, it is unavailable in existing open-source solvers and practical implementation details remain undocumented. In this work, we present an implementation of this modeling approach using a single, generic global constraint called the Generalized Cumulative. We also introduce a novel time-table filtering algorithm specifically designed to handle tasks defined on conditional time-intervals. Experimental results demonstrate that this approach, combined with the new filtering algorithm, performs competitively with existing solvers enabling the modeling of producer and consumer scheduling problems and effectively scales to large-scale problems.