Experiments in Forward Pruning with Limited Extensions

Abstract

Several heuristics have been developed to reduce the effort needed to select a move in chess. Some of them dynamically change the order in which moves are considered during the search, others assess the opponent’s threats by making a null move. There are many more possibilities including forward-pruning mechanisms recognizing when it is futile to pursue a line of play along the full length of a given path. This paper considers a spectrum of simple heuristics and strategies and applies them to Chinese chess. It also tries to provide quantitative data to support the use of not only these standard techniques but also of some newer ideas involving attack-evading moves and strictly-forced moves. The effect on these methods of the significantly different draw-by-repetition rules for Chinese chess is also considered.