Container Stowage Pre-planning: using search to generate solutions, a case study

Container-ships are vessels possessing an internal structure that facilitates the handling of containerised cargo. At each port along the vessel’s journey, containers destined for those ports are unloaded and additional containers destined for subsequent ports are loaded. Determining a viable arrangement of containers that facilitates this process, in a cost-effective way, constitutes the deep-sea container-ship stowage problem. This paper outlines a computer system that generates good sub-optimal solutions to the stowage pre-planning problem. This is achieved through an intelligent analysis of the domain allowing the problem to be divided into sub-problems: a generalised placement strategy and a specialised placement procedure. This methodology progressively refines the placement of containers within the cargo-space of a container ship until each container is specifically allocated to a stowage location. Heuristic rules are built into objective functions for each stage that enable the combinatorial tree to be explored in an intelligent way, resulting in good, if not optimal, solutions for the problem in a reasonable processing time.