CONSPIRACY NUMBERS

McAllester's conspiracy numbers algorithm is an exciting, new minimax search procedure that builds trees to variable depths in an application-independent manner. The algorithm selectively expands nodes in the tree trying to narrow the range of plausible minimax values at the root of the search tree. It does so by computing the conspiracy number for each possible root value; the minimum number of leaf nodes that must change their score to cause the root to change to that value. This paper describes the algorithm and presents an implementation in a computer chess program. Experimental results give rise to optimism about the algorithm's future, although there are still some serious problems to be overcome. © 1990.