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Code Issues Releases Wiki Activity

Code style and subtle fix in move_is_legal()

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A bunch of trivial code style and comment fixes.

Among them there is a real fix for a subtle case
involving promotion moves.

We currently check that a pawn push to 8/1th rank
must be a promotion, but we don't check the contary,
i.e. that a pawn push on a different rank must NOT be
a promotion. Note that, funny enough, we perform this
control for all the other pieces, but not for the pawns!

This patch fixes this really corner case.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-09-21 18:07:11 +01:00
parent 8487069058
commit 0179a32cf5
1 changed files with 28 additions and 30 deletions
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58
src/movegen.cpp
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@ -55,19 +55,19 @@ namespace {
// Helper templates
template<CastlingSide Side>
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist);
MoveStack* generate_castle_moves(const Position&, MoveStack*);
template<Color Us>
MoveStack* generate_pawn_blocking_evasions(const Position&, Bitboard, Bitboard, MoveStack*);
template<Color Us>
MoveStack* generate_pawn_captures(const Position& pos, MoveStack* mlist);
MoveStack* generate_pawn_captures(const Position&, MoveStack*);
template<Color Us, SquareDelta Diagonal>
MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion);
MoveStack* generate_pawn_captures_diagonal(MoveStack*, Bitboard, Bitboard, bool);
template<Color Us, bool Checks>
MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist, Bitboard dc = EmptyBoardBB, Square ksq = SQ_NONE);
MoveStack* generate_pawn_noncaptures(const Position&, MoveStack*, Bitboard = EmptyBoardBB, Square = SQ_NONE);
template<Color Us, SquareDelta Direction>
inline Bitboard move_pawns(Bitboard p) {
@ -95,7 +95,7 @@ namespace {
// Template generate_piece_moves() with specializations and overloads
template<PieceType>
MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard);
MoveStack* generate_piece_moves(const Position&, MoveStack*, Color, Bitboard);
template<>
MoveStack* generate_piece_moves<KING>(const Position&, MoveStack*, Color, Bitboard);
@ -114,7 +114,7 @@ namespace {
}
template<PieceType>
MoveStack* generate_piece_moves(const Position&, MoveStack*, Color us, Bitboard, Bitboard);
MoveStack* generate_piece_moves(const Position&, MoveStack*, Color, Bitboard, Bitboard);
template<>
inline MoveStack* generate_piece_moves<PAWN>(const Position& p, MoveStack* m,
@ -131,7 +131,7 @@ namespace {
////
/// generate_captures generates() all pseudo-legal captures and queen
/// generate_captures() generates all pseudo-legal captures and queen
/// promotions. Returns a pointer to the end of the move list.
MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
@ -173,8 +173,8 @@ MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
}
/// generate_non_capture_checks() generates all pseudo-legal non-capturing,
/// non-promoting checks. Returns a pointer to the end of the move list.
/// generate_non_capture_checks() generates all pseudo-legal non-captures and
/// underpromotions that give check. Returns a pointer to the end of the move list.
MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
@ -231,8 +231,8 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
Bitboard b_noKing = pos.occupied_squares();
clear_bit(&b_noKing, ksq);
// Find squares attacked by slider checkers, we will
// remove them from king evasions set so to avoid a couple
// Find squares attacked by slider checkers, we will remove
// them from the king evasions set so to avoid a couple
// of cycles in the slow king evasions legality check loop
// and to be able to use attackers_to().
Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
@ -249,14 +249,14 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
sliderAttacks |= rook_attacks_bb(from, b_noKing);
}
// Generate evasions for king, both captures and non captures
Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
// Generate evasions for king, capture and non capture moves
Bitboard enemy = pos.pieces_of_color(them);
Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
while (b1)
{
// Note that we can use attackers_to() only because we have already
// removed from b1 the squares attacked by slider checkers.
to = pop_1st_bit(&b1);
// Note that we can use attackers_to() only because we
// have already removed slider checkers attacked squares.
if (!(pos.attackers_to(to) & enemy))
(*mlist++).move = make_move(ksq, to);
}
@ -345,9 +345,9 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
}
/// generate_moves() computes a complete list of legal or pseudo legal moves in
/// generate_moves() computes a complete list of legal or pseudo-legal moves in
/// the current position. This function is not very fast, and should be used
/// only in situations where performance is unimportant.
/// only in non time-critical paths.
MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLegal) {
@ -377,7 +377,7 @@ MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLega
/// move_is_legal() takes a position and a (not necessarily pseudo-legal)
/// move and tests whether the move is legal. This version is not very fast
/// and should be used only for non time-critical paths.
/// and should be used only in non time-critical paths.
bool move_is_legal(const Position& pos, const Move m) {
@ -391,8 +391,8 @@ bool move_is_legal(const Position& pos, const Move m) {
}
/// Fast version of move_is_legal() that takes a position a move and
/// a pinned pieces bitboard as input, and tests whether the move is legal.
/// Fast version of move_is_legal() that takes a position a move and a
/// bitboard of pinned pieces as input, and tests whether the move is legal.
/// This version must only be used when the side to move is not in check.
bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
@ -407,7 +407,9 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
return move_is_legal(pos, m);
Color us = pos.side_to_move();
Color them = opposite_color(us);
Square from = move_from(m);
Square to = move_to(m);
Piece pc = pos.piece_on(from);
// If the from square is not occupied by a piece belonging to the side to
@ -415,14 +417,11 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
if (color_of_piece(pc) != us)
return false;
Color them = opposite_color(us);
Square to = move_to(m);
// The destination square cannot be occupied by a friendly piece
if (pos.color_of_piece_on(to) == us)
return false;
// Proceed according to the type of the moving piece.
// Handle the special case of a pawn move
if (type_of_piece(pc) == PAWN)
{
// Move direction must be compatible with pawn color
@ -430,14 +429,13 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
if ((us == WHITE) != (direction > 0))
return false;
// If the destination square is on the 8/1th rank, the move must
// be a promotion.
if ( ( (square_rank(to) == RANK_8 && us == WHITE)
||(square_rank(to) == RANK_1 && us != WHITE))
&& !move_is_promotion(m))
// A pawn move is a promotion iff the destination square is
// on the 8/1th rank.
if (( (square_rank(to) == RANK_8 && us == WHITE)
||(square_rank(to) == RANK_1 && us != WHITE)) != bool(move_is_promotion(m)))
return false;
// Proceed according to the square delta between the source and
// Proceed according to the square delta between the origin and
// destionation squares.
switch (direction)
{