Application of Meta-Tree-Based Distributed Search to the Railway Scheduling Problem∗

Many problems of theoretical and practical interest can be formulated as Constraint Satisfaction Problems (CSPs). Solving a general CSP is known to be NP-complete; however, distributed models may take advantage of dividing the problem into a set of simpler interconnected sub-problems which can be more easily solved. In this work, we present a distributed model for solving large-scale CSPs. Our technique carries out a partition over the constraint network by selection of tree structures; after partitioning, the sub-CSPs are arranged into a meta-tree CSP structure that is used as a hierarchy of communication by our distributed algorithm. We have focused our research on the railway scheduling problem which can be distributed by tree structures. We show that our distributed algorithm outperforms wellknown centralized algorithms. keywords: Distributed Constraint Satisfaction Problems, Tree Partition, Train Scheduling.