MTD-f

MTD(f), is a minimax search algorithm, developed in 1994 by Aske Plaat, Jonathan Schaeffer, Wim Pijls, and Arie de Bruin. Experiments with tournament-quality chess, checkers, and Othello programs show it to be the most efficient minimax algorithm. The name MTD(f) is an abbreviation for MTD(n,f) (Memory-enhanced Test Driver with node n and value f). It is an alternative to the alpha-beta pruning algorithm.

Origin

MTD(f) was first described in a University of Alberta Technical Report authored by Aske Plaat, Jonathan Schaeffer, Wim Pijls, and Arie de Bruin, which would later receive the ICCA Novag Best Computer Chess Publication award for 1994/1995. The algorithm MTD(f) was created out of a research effort to understand the SSS* algorithm, a best-first search algorithm invented by George Stockman in 1979. SSS* was found to be equivalent to a series of alpha-beta calls, provided that alpha-beta used storage, such as a well-functioning transposition table.

The name MTD(f) stands for Memory-enhanced Test Driver, referencing Judea Pearl's Test algorithm, which performs Zero-Window Searches. MTD(f) is described in depth in Aske Plaat's 1996 PhD thesis.