New models and algorithms for the container stack rearrangement problem by yard cranes in maritime ports

Whenever sets of objects are piled up in heaps, columns or stacks, any rearrangement of these objects requires substantial amount of time, effort and cost. In this paper, we study the problem of optimizing such “stack-rearrangement operations” when multiple similar objects or blocks need to be rearranged. We discuss the problem in the context of yard crane operations in maritime ports, where cargo containers are stored and fetched by yard cranes. We intend to minimize the crane operations that are required during container stack rearrangement by yard cranes. This paper defines the underlying abstract mathematical problem and proves its computational complexity. Thereafter, we propose suitable mathematical models for the problem and devise several (exact) approaches to solve it. We provide several families of new problem data instances and the prove the efficacy of our algorithms by doing extensive computational analysis over the data instances.