Recognizer Functions

The latest version of DARKTHOUGHT features high-speed recognizers for the following classes of endgame positions with little material on both sides.

• KK, KBK, KNK (always drawn),

• KBKB, KBKN, KNKN (normally drawn but exceptional wins possible for any side by mates in 1 move),

• KBBK, KBNK (normally won for the strong side but exceptional draws possible by stalemate or by conversion to KBK and KNK),

• KNNK, KNNKB, KNNKN (normally drawn but exceptional wins possible for any side by mates in  <= 7 moves),

• KQX*K, KRX*K (normally won for the stronger side but exceptional draws possible by stalemate or by conversion to drawn subgames, X* = arbitrary major and minor pieces),

• KPPP*K (sophisticated detection of draws, P* = one or more Pawns),

• KBP*K, KBP*KB, KBP*KN (sophisticated detection of draws for bishops of wrong colour, P* = one or more Pawns),

• KPK, KQK, KRK (3-piece endgame databases),

• KBKP, KBPK, KNKP, KNPK, KPKP, KPPK, KQKB, KQKN,
  KQKP, KQKQ, KQKR, KRKB, KRKN, KRKP, KRKR
  (4-piece endgame databases).

It goes without saying that we continously search for new classes of positions that allow for their efficient interior-node recognition. We definitely want to add many more recognizer functions in the near future. In this respect, database recognizers for 5-piece endgames are promising candidates. According to our experiences with past versions of DARKTHOUGHT, however, the recognition of and accesses to 5-piece endgame databases require careful fine-tuning until they perform at acceptably high speeds.