Piece Movements

Bitwise Operations

• The use of bitboards enables the use of bit operations for movement generation

>>n    shifts bits n of bits to the right (keeps left most bit as is, use >>> to force 0)
<<n    shifts bits n of bits to the left
n & m    bits in n **AND** m that are both 1 are retained as 1s in result
n | m    bits in n **OR** m that are both 1 are retained as 1s in result
n ^ m    bits in n **OR** m that are 1 **BUT NOT BOTH** are retained as 1s in result (exclusive-or)

Bitboards Required

Pieces

• 6 white: pawn, knights, bishops, rooks, queen, king
• 6 black: pawn, knights, bishops, rooks, queen, king

Board Control

• 2 Files: A & H
  • prevent bad pawn moves (File H -> File A)
  • hold 1's for each bit contained in given file
• 4 Ranks
  • 1 & 8
    • used for pawn promotion
    • hold 1's for each bit contained in given rank
  • 4 & 5
    • used for en passant
    • hold 1's for each bit contained in given rank
• 1 empty spaces
  • hold 1's for each bit that does not have a pc

Captures & Not Captures

• 1 for spaces with black pcs that white can capture
  • bP, bN, bB, bR, bQ
• 1 for spaces with white pcs that black can capture
  • wP, wN, wB, wR, wQ
• 1 for spaces of pcs that white can't capture
  • wP, wN, wB, wR, wQ, wK, bK (because you should never capture the opposing king)
• 1 for spaces of pcs that black can't capture
  • bP, bN, bB, bR, bQ, bK, wK (because you should never capture the opposing king)

Piece moves

• 1 for pawns
  • incl: attack left + attack right + fwd move 1 space + fwd move 2 space
• 1 for knights
• 1 for bishops
• 1 for rooks
• 1 for queen
• 1 for king

Move generation

• concatinate list of all possible moves
• maintain history of moves made
• search can be optimized by only looking between first and last destinations