Adapting a Search Algorithm for the Spanish Railway Network

Abstract

This article describes a search algorithm adapted to the Spanish Railway Network for generating as many traveling options as possible between two railway stations. This algorithm (Warshall's algorithm) uses connecting matrices to find all possible railway journeys. The Spanish Railway Company has imposed severe restrictions: less than 1 second per query in a 600Mhz processor PC with 32Mb RAM and 150Mb hard disk free memory. The final average time for a simple query is around 0.25 seconds and the whole memory consumption is 127Mb. The final implementation has been divided into 3 modules. In the first module, we store additional information in the connecting matrices to accelerate the later search, proposing several strategies for reducing thier size. The journey option calculation module accesses the matrix information and composes the traveling options. Finally, in the filtering module we describe the selection criteria considering the algorithm embedded in a general information service.