bug and hint (Stockfish)

[lech]

1. bug
The structure of move is changed.
Now it is:

Code: Select all

/// A move needs 16 bits to be stored
///
/// bit  0- 5: destination square (from 0 to 63)
/// bit  6-11: origin square (from 0 to 63)
/// bit 12-13: promotion piece type - 2 (from KNIGHT-2 to QUEEN-2)
/// bit 14-15: special move flag: promotion (1), en passant (2), castle (3)

but the following ugly functions not.
Only fortunately, it works correctly.

Code: Select all

inline bool Position::move_is_capture(Move m) const {

  // Move must not be MOVE_NONE !
  return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
}

inline bool Position::move_is_capture_or_promotion(Move m) const {

  // Move must not be MOVE_NONE !
  return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
}
 

I think it should be made in this way, though:

Code: Select all

inline bool Position::move_is_capture(Move m) const {

  return !square_is_empty(move_to(m)) || move_is_ep(m);
}

inline bool Position::move_is_capture_or_promotion(Move m) const {

  return move_is_capture(m) || move_is_promotion(m);
}

Even if it is a bit slower, this hint is able to get a time bonus.

2. hint
In the perpetual function: Position::pl_move_is_legal() there is a code:

Code: Select all

// Castling moves are checked for legality during move generation.
  if (move_is_castle(m))
      return true;

Castles are very rare moves. It is possible to skip it in the main line and move to the next side lines of this function:

Code: Select all

// If the moving piece is a king, check whether the destination
// square is attacked by the opponent.
if (type_of_piece_on(from) == KING)
  // Castling moves are checked for legality during move generation.
  return move_is_castle(m) ? true : !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us)));

originally it is:

Code: Select all

// If the moving piece is a king, check whether the destination
// square is attacked by the opponent.
if (type_of_piece_on(from) == KING)
  return !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us)));

[mcostalba]

1. bug

Thanks Marek !!

Very useful and nice, both the bug and the hint have been already applied to development branch

[Onno Garms]

Also, SEE returns positive values on castle moves most of the time. Will be fixed in next release. (Marco told me.)