Symbolic Configuration for Interactive Container Ship Stowage Planning

Low-cost containerized shipping requires high-quality stowage plans. Scalable stowage planning optimization algorithms have been developed recently. All of these algorithms, however, produce monolithic solutions that are hard for stowage coordinators to modify, which is necessary in practice owing to exceptions and operational disruptions. This article introduces an approach for modifying a stowage plan interactively without breaking its constraints. We focus on rearranging the containers in a single-bay section and show two approaches for providing complete and backtrack-free decision support using symbolic configuration techniques, one based on binary decision diagrams and one based on DPLL solvers. We show that binary decision diagrams can be used to solve real-world sized instances of a single bay, and that search-based solvers can be used to solve simplified instances going beyond a single bay.