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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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52
src/movegen.cpp
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@ -35,8 +35,14 @@
namespace { namespace {
// Function enum CastlingSide {
MoveStack* generate_castle_moves(const Position&, MoveStack*); 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 generate_pawn_captures() with specializations
template<Color, Color, Bitboard, SquareDelta, SquareDelta, SquareDelta> 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 /// generate_checks() generates all pseudo-legal non-capturing, non-promoting
/// checks, except castling moves (will add this later). It returns the /// checks. It returns the number of generated moves.
/// number of generated moves.
int generate_checks(const Position& pos, MoveStack* mlist, Bitboard dc) { 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 ;-) // Hopefully we always have a king ;-)
mlist = generate_piece_checks_king(pos, pos.king_square(us), dc, ksq, mlist); 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); return int(mlist - mlist_start);
} }
@ -879,20 +893,17 @@ namespace {
return mlist; return mlist;
} }
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist, unsigned side) {
MoveStack* generate_castle_moves(const Position& pos, MoveStack* mlist) {
Color us = pos.side_to_move(); 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); Color them = opposite_color(us);
Square ksq = pos.king_square(us); Square ksq = pos.king_square(us);
assert(pos.piece_on(ksq) == king_of_color(us)); assert(pos.piece_on(ksq) == king_of_color(us));
if (pos.can_castle_kingside(us))
{
Square rsq = pos.initial_kr_square(us); Square rsq = pos.initial_kr_square(us);
Square g1 = relative_square(us, SQ_G1); Square g1 = relative_square(us, SQ_G1);
Square f1 = relative_square(us, SQ_F1); Square f1 = relative_square(us, SQ_F1);
@ -914,8 +925,13 @@ namespace {
(*mlist++).move = make_castle_move(ksq, rsq); (*mlist++).move = make_castle_move(ksq, rsq);
} }
if (pos.can_castle_queenside(us)) 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 rsq = pos.initial_qr_square(us);
Square c1 = relative_square(us, SQ_C1); Square c1 = relative_square(us, SQ_C1);
Square d1 = relative_square(us, SQ_D1); Square d1 = relative_square(us, SQ_D1);
@ -941,8 +957,20 @@ namespace {
if (!illegal) if (!illegal)
(*mlist++).move = make_castle_move(ksq, rsq); (*mlist++).move = make_castle_move(ksq, rsq);
} }
}
return mlist; 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);
}
} }