Recent progress in understanding minimax search

Abstract

Lookahead search has been known for a long time to be effective in tackling problems which can be cast in minimax form (mainly game playing, but others include maintaining unstable balance against gravity, and business decisions). Recent results have shown that the benefit of lookahead depends on the structure inherent in the problem, and even that there exist some minimax problems for which lookahead search is DIS-advantageous. This paper reviews those results and then discusses algorithms which can be interpreted as recognising the structure of local areas of the search in order to control search expansion. Such algorithms can be orders of magnitude more cost-effective than search using alpha-beta alone.