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a WinBoard compliant open source chess engine written by Andrei Fortuna in C++, intended as a test ground for various chess algorithms, first released in February 2000. Freyr is a bitboard engine and uses rotated bitboards to determine sliding piece attacks. The search is PVS [1] with null move pruning inside an aspiration window iterative deepening framework with transposition table, using several move ordering heuristics, such as killer, history and countermove, as well as SEE to order captures. Lazy evaluation considers incremental updated material- and piece-square table scores and cached pawn structure stuff. Evaluation further includes king safety and passed pawns as most dominant terms [2].
Freyr and Gullinbursti[3]

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Chess Engine



  1. ^ A Question on simple Alpha-Beta versus PVS/Negascout by Andrei Fortuna, CCC, March 21, 2000
  2. ^ Planet Source Code™ | Freyr - A Chess Playing Program by Andrei Fortuna
  3. ^ "Freyr" by Johannes Gehrts. The god Freyr stands with his sword and the boar Gullinbursti. Source: Felix Dahn, Therese Dahn (1901). Walhall: Germanische Götter- und Heldensagen. Für Alt und Jung am deutschen Herd. Breitkopf & Härtel, Freyr from Wikipedia

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