Module hexe_core::board

Various board types.

Board Representation

There are three chess board representations provided. They each have various advantages and disadvantages, which are outlined below:

Bitboard

Mapping: bit-to-Square

Advantages:

• Throughput—excellent for performing parallel operations on the board:

  • Checking whether a file is empty

  • Generating moves for all pieces

Disadvantages:

• Size—larger overall memory cost:

  • A common compact way of representing all pieces with bitboards is to have 6 × Role bitboards and 2 × Color bitboards. This results in (2 + 6) × 8 = 64 bytes used to represent all pieces.

    This is how MultiBoard works.

  • Using 12 × Piece bitboards is another representation of the entire chess board. This results in 12 × 8 = 96 bytes used to represent all pieces.

  • Operations are often done using 64-bit (8 byte) integers.

MultiBoard

Mapping: Color/Piece/Role to Bitboard

Advantages:

• Lookup—very fast square retrieval:

  let board = MultiBoard::STANDARD;
  
  let king = board.first(Piece::WhiteKing).unwrap();
  println!("White king found at {}", king);
  
  for sq in board.bitboard(Color::White) {
      println!("A white piece at {}", sq);
  }

Disadvantages:

• Checking—slow to find the piece at a square

PieceMap

Mapping: Piece to Square

Advantages:

• Latency—great for performing instantaneous operations on the board

  • Finding whether a square is empty or otherwise what piece sits on it

• Size—lower overall memory cost

  • Operations usually done with a few bytes

Disadvantages:

• Size—larger upfront memory cost

  • Uses exactly 64 bytes for each square on the board and its piece

Modules

bitboard	A bitmap chess board representation.
multi_board	A bitboard-segmented chess board representation.
piece_map	A square to piece mapping for fast square lookups.

Structs

Bitboard	A mapping of sixty-four bits to squares of a chess board.
MultiBoard	A full chess board, represented as multiple bitboard segments.
PieceMap	A mapping of sixty-four squares to pieces.