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Add generation of castling checks

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When we generate checks one case is missing: generation
of castling moves that give check to the opponent king.

This is a very rare case but anyway it is a case
and we can do this without slowing down the common
case of no castling checks.

So this is the patch.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-05 15:06:41 +01:00
parent cc76951483
commit 03211296f1
1 changed files with 80 additions and 52 deletions
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132
src/movegen.cpp
View file

@ -35,8 +35,14 @@
namespace {
// Function
MoveStack* generate_castle_moves(const Position&, MoveStack*);
enum CastlingSide {
KING_SIDE = 1,
QUEEN_SIDE = 2
};
// Functions
MoveStack* generate_castle_moves(const Position&, MoveStack*, unsigned = (KING_SIDE | QUEEN_SIDE));
bool castling_is_check(const Position& pos, CastlingSide side);
// Template generate_pawn_captures() with specializations
template<Color, Color, Bitboard, SquareDelta, SquareDelta, SquareDelta>
@ -165,8 +171,7 @@ int generate_noncaptures(const Position& pos, MoveStack* mlist) {
/// generate_checks() generates all pseudo-legal non-capturing, non-promoting
/// checks, except castling moves (will add this later). It returns the
/// number of generated moves.
/// checks. It returns the number of generated moves.
int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
@ -207,7 +212,16 @@ int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
// Hopefully we always have a king ;-)
mlist = generate_piece_checks_king(pos, pos.king_square(us), dc, ksq, mlist);
// TODO: Castling moves!
// Castling moves that give check. Very rare but nice to have!
if ( pos.can_castle_queenside(us)
&& (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
&& castling_is_check(pos, QUEEN_SIDE))
mlist = generate_castle_moves(pos, mlist, QUEEN_SIDE);
if ( pos.can_castle_kingside(us)
&& (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
&& castling_is_check(pos, KING_SIDE))
mlist = generate_castle_moves(pos, mlist, KING_SIDE);
return int(mlist - mlist_start);
}
@ -879,70 +893,84 @@ namespace {
return mlist;
}
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, unsigned side) {
Color us = pos.side_to_move();
if (pos.can_castle(us))
if (pos.can_castle_kingside(us) && (side & KING_SIDE))
{
Color them = opposite_color(us);
Square ksq = pos.king_square(us);
assert(pos.piece_on(ksq) == king_of_color(us));
if (pos.can_castle_kingside(us))
{
Square rsq = pos.initial_kr_square(us);
Square g1 = relative_square(us, SQ_G1);
Square f1 = relative_square(us, SQ_F1);
Square s;
bool illegal = false;
Square rsq = pos.initial_kr_square(us);
Square g1 = relative_square(us, SQ_G1);
Square f1 = relative_square(us, SQ_F1);
Square s;
bool illegal = false;
assert(pos.piece_on(rsq) == rook_of_color(us));
assert(pos.piece_on(rsq) == rook_of_color(us));
for (s = Min(ksq, g1); s <= Max(ksq, g1); s++)
if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
|| pos.square_is_attacked(s, them))
illegal = true;
for (s = Min(ksq, g1); s <= Max(ksq, g1); s++)
if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
|| pos.square_is_attacked(s, them))
illegal = true;
for (s = Min(rsq, f1); s <= Max(rsq, f1); s++)
if (s != ksq && s != rsq && pos.square_is_occupied(s))
illegal = true;
if (!illegal)
(*mlist++).move = make_castle_move(ksq, rsq);
}
if (pos.can_castle_queenside(us))
{
Square rsq = pos.initial_qr_square(us);
Square c1 = relative_square(us, SQ_C1);
Square d1 = relative_square(us, SQ_D1);
Square s;
bool illegal = false;
assert(pos.piece_on(rsq) == rook_of_color(us));
for (s = Min(ksq, c1); s <= Max(ksq, c1); s++)
if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
|| pos.square_is_attacked(s, them))
illegal = true;
for (s = Min(rsq, d1); s <= Max(rsq, d1); s++)
if (s != ksq && s != rsq && pos.square_is_occupied(s))
illegal = true;
if ( square_file(rsq) == FILE_B
&& ( pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them)
|| pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
illegal = true;
for (s = Min(rsq, f1); s <= Max(rsq, f1); s++)
if (s != ksq && s != rsq && pos.square_is_occupied(s))
illegal = true;
if (!illegal)
(*mlist++).move = make_castle_move(ksq, rsq);
}
}
if (pos.can_castle_queenside(us) && (side & QUEEN_SIDE))
{
Color them = opposite_color(us);
Square ksq = pos.king_square(us);
assert(pos.piece_on(ksq) == king_of_color(us));
Square rsq = pos.initial_qr_square(us);
Square c1 = relative_square(us, SQ_C1);
Square d1 = relative_square(us, SQ_D1);
Square s;
bool illegal = false;
assert(pos.piece_on(rsq) == rook_of_color(us));
for (s = Min(ksq, c1); s <= Max(ksq, c1); s++)
if ( (s != ksq && s != rsq && pos.square_is_occupied(s))
|| pos.square_is_attacked(s, them))
illegal = true;
for (s = Min(rsq, d1); s <= Max(rsq, d1); s++)
if (s != ksq && s != rsq && pos.square_is_occupied(s))
illegal = true;
if ( square_file(rsq) == FILE_B
&& ( pos.piece_on(relative_square(us, SQ_A1)) == rook_of_color(them)
|| pos.piece_on(relative_square(us, SQ_A1)) == queen_of_color(them)))
illegal = true;
if (!illegal)
(*mlist++).move = make_castle_move(ksq, rsq);
}
return mlist;
}
bool castling_is_check(const Position& pos, CastlingSide side) {
// After castling opponent king is attacked by the castled rook?
File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
Color us = pos.side_to_move();
Square ksq = pos.king_square(us);
Bitboard occ = pos.occupied_squares(), oppKingBB = EmptyBoardBB;
set_bit(&oppKingBB, pos.king_square(opposite_color(us)));
clear_bit(&occ, ksq); // Remove our king from the board
Square rsq = make_square(rookFile, square_rank(ksq));
return (rook_attacks_bb(rsq, occ) & oppKingBB);
}
}