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'''[[Main Page|Home]] * [[Knowledge]] * [[Endgame Tablebases]] * Bitbases'''

are compact endgame tablebases with game theoretical values of one or two bits per position stored. They are sufficient for various material configurations to reside inside [[Memory#RAM|RAM]] for short probing access time, intended to use deep inside the [[Search|search]]. The boolean or four valued ranges are either {''won'', ''not_won''} or {''won'', ''draw'', ''loss'', ''invalid''}. While WDL information is sufficient to guide the search into won positions, it lacks any sense of progress in won positions. Therefor, programs either probe full tablebases at the [[Root|root]] to reveal the number of moves until conversion or mate, or combine WDL-scores with heuristic evaluation [[Score|scores]], considering [[Material|material]], ply-distance to the root, pawn closeness to promotion, [[Distance|distance]] of pieces to opponent king, etc.. Endgame Bitbases were described in 1999 by [[Ernst A. Heinz]] in ''Knowledgeable Encoding and Querying of Endgame Databases'', as applied with 4-men in [[DarkThought]] <ref>[[Ernst A. Heinz]] ('''1999'''). ''Knowledgeable Encoding and Querying of Endgame Databases.'' [[ICGA Journal#22_2|ICCA Journal, Vol. 22, No. 2]], [http://people.csail.mit.edu/heinz/ps/know_edb.ps.gz ps]</ref>.