Worm optimization for the multiple level warehouse layout problem

In this paper, the NP-complete multiple level warehouse layout problem is addressed. The problem consists of assigning items to cells and levels with the objective of minimizing transportation costs. A worm optimization algorithm (WO) is introduced, based on the foraging behaviors of Caenorhabditis elegans (Worms), and its performance was assessed by comparing with a genetic algorithm (GA), ant colony optimization (ACO), and an exact solution (B&B) for small problems. The computational results reflected the superiority of WO in large problems, with a marginally better performance than ACO and GA in smaller ones, while solving the tested problems within a reasonable computational time. Furthermore, WO was able to attain most of the known optimal solutions.