A visual tool to manipulate 64bit numbers, specially chess bitboards.

Demo

• Code editor (syntax highlight)
• Javascript arithmetic expressions
• Variables Context inspector
• Custom variables/functions: bit scan, bit reverse, byte swap, ...
• Bitboard editor to produce test values easly
• Results displayed as bitboards
• Runs in a browser, no server needed

• Download latest release
• Unzip somwhere
• Launch a local web server (python3 -m http.server for example) where the index.html file is located
• Start using the tool

Each instruction should fit in a single line.

The code is executed sequentially line by line.

If there is an error in a given line, the execution will stop, the global context will not be changed.

Each instruction should be of the form:

    variable_name = arithmetic expression

variable name should be compliant with javascript identifier spec.

The arithmetic expression can contains functions as long as they are accessible in the global scope

Example:

// test rook attacks
occupied = 0b10000000100000000000010000000000001100001n
rook_pos = 0
attacks = BB.sliding_attacks_v(occupied, rook_pos, BB.ROOK_ATTACKS.NORTH[rook_pos])

By default, any variable in the left side of the instruction will be displayed in the result panel. To filter what is displayed, the first line should contain the instruction #observe followed by a comma separated list of variables.

*Example:

Here only y will be visible in the result panel.

#observe y
x = 0xFF00FF17n
y = x << 13

Available via a global variable named BB

• RANKS: an array of 8 bitboards representing each rank (0..7)
• FILES: an array of 8 bitboards representing each file (0..7)
• SQUARES: an array of 64 bitboards representing each square (0..63)
• SQUARE_RANK: an array mapping square index to rank bitboards (0..63)
• SQUARE_FILE: an array mapping square index to file bitboards (0..63)
• ROOK_ATTACKS: rook attacks for each direction and square index
  • ROOK_ATTACKS.NORTH (0..63)
  • ROOK_ATTACKS.EAST (0..63)
  • ROOK_ATTACKS.SOUTH (0..63)
  • ROOK_ATTACKS.WEST (0..63)
• BISHOP_ATTACKS: bishop attacks for each direction and square index
  • BISHOP_ATTACKS.NORTH_EAST (0..63)
  • BISHOP_ATTACKS.SOUTH_EAST (0..63)
  • BISHOP_ATTACKS.NORTH_WEST (0..63)
  • BISHOP_ATTACKS.SOUTH_WEST (0..63)
• KNIGHT_ATTACKS: knight attacks by square index (0..63)
• KING_ATTACKS: king attacks by square index (0..63)

• bsf: (bb: bigint) => number

  Returns the index of the first set bit + 1 if found otherwise 0

• bit_reverse: (bb: bigint) => bigint

  Reverses bitboard (a1 <-> h8, ...)

• byte_swap: (bb: bigint) => bigint

  Swaps bitboard bytes (ranks)

• bit_positions: (bb: bigint) => number[]

  Returns the list bitboard of set bit positions

• sliding_attacks_diag: (occupied: bigint, suqareIndex: number, diagMask: bigint) => bigint

  Returns sliding diagonal attacks of bishop/queen as a bitboard

• sliding_attacks_h: (occupied: bigint, squareIndex: number) => bigint

  Returns sliding horizontal attacks of rook/queen as a bitboard

• sliding_attacks_v: (occupied: bigint, squareIndex: number, verticalMask: bigint) => bigint

  Returns sliding vertical attacks of rook/queen as a bitboard

• from_fen: (fen: string) => bigint

  Creates 'occupied' bitboard from fen string

GNU General Public License v3.0 or later

See LICENCE to see the full text.