DARKTHOUGHT is a bitboard-based chess program developed at the University of Karlsruhe that has successfully participated in all world championships since 1995. On a 500MHz DEC Alpha-21164a with 128MB RAM, DARKTHOUGHT routinely reaches speeds of 200K nps (nodes per second) in the middlegame while peaking at over 650K nps in the endgame.
The article describes the design and inner structure of DARKTHOUGHT. To this end, it presents detailed accounts of the chess engine while elaborating on some of its innovations: rotated bitboards, a fully programmable leaf-node evaluation function, and versatile search parameterization.