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Bitboard
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Bitboard
A bitboard is a specialized bit array data structure commonly used in computer systems that play board games, where each bit corresponds to a game board space or piece.
Bitboards are applicable to any board game whose game state is represented by the presence of pieces on discrete spaces of a gameboard, including chess, checkers, othello and word games. The scheme was first employed in checkers programs in the 1950s, and since the mid-1970s has been the de facto standard for game board representation in computer automatons.
Bitboards are a more space-efficient board representation than the traditional mailbox representation, where each piece or space on the board is an array element.
Bitboards are often also more time-efficient. When the associated bits of related states on the bitboard fit into a single word or double word of the CPU architecture, single bitwise operators like AND and OR can be used to operate on the bitboard. These parallel bitwise operations can be much faster at setting and querying game states, and determining moves and plays in the game, than performing iterative array operations on a mailbox representation would be.
Modern chess engines predominantly utilize magic bitboards, which employ perfect hashing to map a piece's occupancy mask directly to a pre-computed array of attack patterns in a single lookup operation.
A bitboard is a specialized bit field: a format that represents the state of a board game by packing multiple Boolean variables into the same machine word. Each bit represents a space; when the bit is positive, a property of that space is true.
Bitboards allow the computer to answer questions about game state using very few bitwise operations. For example, if a chess program wants to know if the white player has any pawns in the center of the board (center four squares), it can just compare a bitboard for the player's pawns with one for the center of the board using a bitwise AND operation. If there are no center pawns, the result will be all zero bits (i.e. equal to zero). Multiple bitboards may represent different properties of spaces over the board, and special or temporary bitboards (like temporary variables) may represent local properties or hold intermediate collated results.
The efficacy of bitboards is augmented by two other properties of the implementation. First, bitboards are fast to incrementally update; for example flipping the bits at the source and destination positions in a bitboard for piece location when a piece is moved. Second, bitmaps representing static properties like all spaces attacked by each piece type for every position on a chessboard can be pre-collated and stored in a table. This allows a question like "what are the legal moves of a knight on space e4?" to be answered by a single memory fetch.
Hub AI
Bitboard AI simulator
(@Bitboard_simulator)
Bitboard
A bitboard is a specialized bit array data structure commonly used in computer systems that play board games, where each bit corresponds to a game board space or piece.
Bitboards are applicable to any board game whose game state is represented by the presence of pieces on discrete spaces of a gameboard, including chess, checkers, othello and word games. The scheme was first employed in checkers programs in the 1950s, and since the mid-1970s has been the de facto standard for game board representation in computer automatons.
Bitboards are a more space-efficient board representation than the traditional mailbox representation, where each piece or space on the board is an array element.
Bitboards are often also more time-efficient. When the associated bits of related states on the bitboard fit into a single word or double word of the CPU architecture, single bitwise operators like AND and OR can be used to operate on the bitboard. These parallel bitwise operations can be much faster at setting and querying game states, and determining moves and plays in the game, than performing iterative array operations on a mailbox representation would be.
Modern chess engines predominantly utilize magic bitboards, which employ perfect hashing to map a piece's occupancy mask directly to a pre-computed array of attack patterns in a single lookup operation.
A bitboard is a specialized bit field: a format that represents the state of a board game by packing multiple Boolean variables into the same machine word. Each bit represents a space; when the bit is positive, a property of that space is true.
Bitboards allow the computer to answer questions about game state using very few bitwise operations. For example, if a chess program wants to know if the white player has any pawns in the center of the board (center four squares), it can just compare a bitboard for the player's pawns with one for the center of the board using a bitwise AND operation. If there are no center pawns, the result will be all zero bits (i.e. equal to zero). Multiple bitboards may represent different properties of spaces over the board, and special or temporary bitboards (like temporary variables) may represent local properties or hold intermediate collated results.
The efficacy of bitboards is augmented by two other properties of the implementation. First, bitboards are fast to incrementally update; for example flipping the bits at the source and destination positions in a bitboard for piece location when a piece is moved. Second, bitmaps representing static properties like all spaces attacked by each piece type for every position on a chessboard can be pre-collated and stored in a table. This allows a question like "what are the legal moves of a knight on space e4?" to be answered by a single memory fetch.