// polyglot_key() returns the PolyGlot hash key of the given position
public static Key polyglot_key(Position pos)
{
Key key = 0;
Bitboard b = pos.pieces();
while (b != 0)
{
Square s = BitBoard.pop_lsb(ref b);
Piece pc = pos.piece_on(s);
// PolyGlot pieces are: BP = 0, WP = 1, BN = 2, ... BK = 10, WK = 11
int pieceOfs = 2 * (Types.type_of_piece(pc) - 1) + ((Types.color_of(pc) == ColorS.WHITE) ? 1 : 0);
key ^= PG[psq + (64 * pieceOfs + s)];
}
b = (ulong)pos.can_castle_castleright(CastlingRightS.ANY_CASTLING);
while (b != 0)
{
key ^= PG[castle + BitBoard.pop_lsb(ref b)];
}
if (pos.ep_square() != SquareS.SQ_NONE)
{
key ^= PG[enpassant + Types.file_of(pos.ep_square())];
}
if (pos.side_to_move() == ColorS.WHITE)
{
key ^= PG[turn + 0];
}
return(key);
}
