Effiziente Algorithmen für ein Fahrplanauskunftsystem

Abstract

Algorithms for timetable information systems are usually based on Dijkstra's algorithm. The concrete scenario that we have in mind is a central information server in the realm of public railroad traffic on wide-area networks. Due to the large size of the underlying timetables the efficiency of a naive implementation is not acceptable in practice, so usually heuristics are used to improve the efficiency. Typically, using such heuristics means that the optimality of the solutions can no longer be guaranteed. In contrast, we investigate optimality-preserving speed-up techniques for Dijkstra's algorithm. The basic question is whether algorithms that compute optimal solutions are competitive on contemporary computer technology. Therefore, we present the results of a computational study based on real-world data: the timetable that contains all German trains, and a snapshot of customer queries to an existing information server.