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Chess Opening Book: Open-chess 2 101224 (bin and ctg file)

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Open-chess2 - bin opening book.

Book - BIN format ( Used by chess GUIs Arena, Banksia and Droidfish)

Binary books have some important advantages, especially for computer chess engines: space-efficient, fast on accessing and searching, more useful information. 

At the most simple form, they are just a conversion of above text-opening books into binary, in the ready form for software and save text-binary converting steps. However, the major number of top books is built and worked with hash values from transpositions. Often each position is stored as a hash value (8 bytes) and some extra information such as the number of times occurred, number of games won by white/black / drawn with this position, average/maximum Elo of players playing to this opening position, chess program's success with the position. To save space those extra information typically about 2-8 bytes. 

Open-chess 2 101224 (bin file) download

CTG, (ChessBase Opening Tree of Games) an opening book format by ChessBase, supported by their Fritz GUI and ChessBase GUI, and therefore used by all chess engines compatible with these commercial user interfaces. Each Chessbase book consists of four files, the binary CTG file contains the real data, the INI text file provides auxilliary information, the CTB file some kind of bitmap over free pages in the CTG file, and the CTO file, containing a lookup table into the CTG file for fast indexed access. Only White to move positions along with its moves, annotations and engine recommendations, and statistics are stored, probing black positions requires color flipping, of course including en passant square and castling rigths. Further, if the white king is on files a-d, and neither side has any castling rights remaining, the board is mirrored horizontally. The CTG file is organized in 4KiB pages, the first page contains header information such as the number of games, followed by consecutive data pages. Each data page starts with an header specifying the number of positions and bytes per page, followed by a list of a variable length position entries.

Open-chess 2 101224 (ctg file) download


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