Using knowledge to control tree searching

PARADISE (PAttern Recognition Applied to DIrecting SEarch) uses a knowledge-based analysis and little searching to find the correct move in chess middle game positions. PARADISE's search does not have a depth limit or any other artificial effort limit. This paper describes the methods used to constrain the search. The ideas of using different strategies to show that one move is best and using ranges to express the values of moves (first developed in Berliner's B1 search), are extended and clarified. PARADISE combines these ideas with the use of plans, a threshold, and various measures of possibility. Examples are presented, including one in which PARADISE uses an indirect strategy to prove that one move is best without finding the winning line (a first for a chess program).