A Defensive Strategy Combined with Threat-Space Search in Connect6

Abstract

The study of k-in-a-row games has produced a number of interesting results, and one of its sub-category Connect6 proposed in 2005 has been of particular interest. Since 2006, Connect6 has been included as one of the major competition in the ICGA Computer Olympiad, and is gaining more popularity every year. In this paper, we briefly review current methods applied in Connect6 and related results. A defensive strategy is introduced along with a more strategically sensitive evaluation scheme. Threat-space search is an important algorithm applied in Connect6, some techniques for gaining more efficiency and accuracy will be introduced. The integration of the defensive strategy and threat-space search will also be investigated. The combination of the defensive strategy and threatspace search is proved to be effective, and is able to compete with other top Connect6 programs. The program Kagami, which was implemented with these methods, won the fourth place in the 14th Computer Olympiads.