Relative Efficiency of Alpha-Beta Implementations

Most of the data on the relative efficiency of different implementations of the alpha-beta algorithm is neither readily available nor in a form suitable for easy comparisons. In the present study four enhancements to the alpha-beta algorithm—iterative deepening, aspiration search, memory tables and principal variation search—are compared separately and in various combinations to determine the most effective alpha-beta implementation. The rationale for this work is to ensure that new parallel algorithms incorporate the best sequential techniques. Rather than relying on simulation or searches of specially constructed trees, a simple chess program was used to provide a uniform basis for comparisons.