How DarkThought Plays Chess

Summary

DarkThought ¹ is a bitboard-based chess program developed at the University of Karlsruhe that has successfully participated in all world championships since 1995. On a 500 MHz Compaq Alpha-21264 XP-1000 workstation with 256 MB RAM, DarkThought routinely reaches speeds of 400 K nps (nodes per second) in the middlegame while peaking at over 1.4 M 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 searchparameterization.

The appendix is an updated reprint of our article “How DarkThought Plays Chess” as published in the ICCA Journal 20(3), pages 166–176, September 1997.