Experiments with the Null-Move Heuristic

The strength of the current generation of chess programs is strongly correlated with their search speed. Thus, any improvement in the efficiency of the tree search usually results in a stronger program. Here we describe a technique, called the null-move heuristic, that can be effectively used to improve search speed with only a small chance of error. Although the technique has been previously used in specialized programs for chess tactics, this chapter describes an implementation suitable for general chess programs.