From: Marco Costalba Date: Thu, 5 Feb 2009 14:06:41 +0000 (+0100) Subject: Add generation of castling checks X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=03211296f1b99da5a0117094b3865fa7612791d3 Add generation of castling checks 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 --- diff --git a/src/movegen.cpp b/src/movegen.cpp index 7273ca9a..aeb0d598 100644 --- a/src/movegen.cpp +++ b/src/movegen.cpp @@ -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 @@ -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; + 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 (!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; + if (pos.can_castle_queenside(us) && (side & QUEEN_SIDE)) + { + Color them = opposite_color(us); + Square ksq = pos.king_square(us); - assert(pos.piece_on(rsq) == rook_of_color(us)); + assert(pos.piece_on(ksq) == king_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; + 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; - for (s = Min(rsq, d1); s <= Max(rsq, d1); s++) - if (s != ksq && s != rsq && pos.square_is_occupied(s)) - illegal = true; + assert(pos.piece_on(rsq) == rook_of_color(us)); - 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(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; - if (!illegal) - (*mlist++).move = make_castle_move(ksq, rsq); - } + 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); + } }