Bitboard knowledge base system and elegant search architectures for Connect6

Efficiency is critical for game programs. This paper improves the search efficiency of Connect6 program by encoding connection patterns and computing the inherent information in advance. Such information is saved in a bitboard knowledge base system, where special bitwise operations are designed. This paper also proposes efficient methods of generating threat moves and the Multistage Proof Number Search. The methods reduce the time complexity of generating threat moves. The search improves the search performance by developing candidate moves in stages according to their importance. In brief, this paper proposes an efficient knowledge base system and elegant search architectures for Connect6. It is expected that the proposed methods can be applied to all kinds of Connect-k games.