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https://github.com/sockspls/badfish
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Let check_is_useless() follow SF coding style
No functional change Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Joona Kiiski
Marco Costalba
parent
cf85ffbb97
commit
47f5560e2d
1 changed files with 93 additions and 87 deletions
180
src/search.cpp
180
src/search.cpp
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@ -297,6 +297,8 @@ namespace {
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template <NodeType PvNode>
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Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
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bool check_is_useless(Position &pos, Move move, Value eval, Value futilityBase, Value beta, Value *bValue);
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Bitboard attacks(const Piece P, const Square sq, const Bitboard occ);
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bool connected_moves(const Position& pos, Move m1, Move m2);
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bool value_is_mate(Value value);
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Value value_to_tt(Value v, int ply);
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@ -1448,90 +1450,6 @@ split_point_start: // At split points actual search starts from here
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return bestValue;
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}
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Bitboard attacks(const Piece P, const Square sq, const Bitboard occ)
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{
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switch(P)
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{
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case WP:
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case BP:
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case WN:
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case BN:
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case WK:
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case BK:
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return StepAttackBB[P][sq];
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case WB:
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case BB:
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return bishop_attacks_bb(sq, occ);
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case WR:
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case BR:
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return rook_attacks_bb(sq, occ);
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case WQ:
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case BQ:
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return bishop_attacks_bb(sq, occ) | rook_attacks_bb(sq, occ);
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default:
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assert(false);
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return 0ULL;
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}
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}
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bool check_is_useless(Position &pos, Move move, Value eval, Value futilityBase, Value beta, Value *bValue)
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{
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Value bestValue = *bValue;
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/// Rule 1. Using checks to reposition pieces when close to beta
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if (eval + PawnValueMidgame / 4 < beta)
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{
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if (eval + PawnValueMidgame / 4 > bestValue)
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bestValue = eval + PawnValueMidgame / 4;
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}
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else
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return false;
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Square from = move_from(move);
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Square to = move_to(move);
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Color oppColor = opposite_color(pos.side_to_move());
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Square oppKing = pos.king_square(oppColor);
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Bitboard occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL <<oppKing);
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Bitboard oppOcc = pos.pieces_of_color(oppColor) & ~(1ULL <<oppKing);
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Bitboard oldAtt = attacks(pos.piece_on(from), from, occ);
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Bitboard newAtt = attacks(pos.piece_on(from), to, occ);
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// Rule 2. Checks which give opponent's king at most one escape square are dangerous
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Bitboard escapeBB = attacks(WK, oppKing, 0) & ~oppOcc & ~newAtt & ~(1ULL << to);
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if (!escapeBB)
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return false;
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if (!(escapeBB & (escapeBB - 1)))
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return false;
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/// Rule 3. Queen contact check is very dangerous
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if ( pos.type_of_piece_on(from) == QUEEN
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&& bit_is_set(attacks(WK, oppKing, 0), to))
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return false;
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/// Rule 4. Creating new double threats with checks
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Bitboard newVictims = oppOcc & ~oldAtt & newAtt;
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while(newVictims)
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{
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Square victimSq = pop_1st_bit(&newVictims);
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Value futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
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// Note that here we generate illegal "double move"!
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if (futilityValue >= beta && pos.see_sign(make_move(from, victimSq)) >= 0)
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return false;
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if (futilityValue > bestValue)
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bestValue = futilityValue;
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}
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*bValue = bestValue;
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return true;
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}
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// qsearch() is the quiescence search function, which is called by the main
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// search function when the remaining depth is zero (or, to be more precise,
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// less than ONE_PLY).
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@ -1670,10 +1588,10 @@ split_point_start: // At split points actual search starts from here
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// Don't search useless checks
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if ( !PvNode
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&& !isCheck
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&& move != ttMove
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&& !move_is_promotion(move)
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&& !pos.move_is_capture(move)
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&& moveIsCheck
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&& move != ttMove
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&& !pos.move_is_capture(move)
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&& !move_is_promotion(move)
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&& check_is_useless(pos, move, ss->eval, futilityBase, beta, &bestValue))
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continue;
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@ -1713,6 +1631,94 @@ split_point_start: // At split points actual search starts from here
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return bestValue;
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}
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// check_is_useless() tests if a checking move can be pruned in qsearch().
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// bestValue is updated when necesary.
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bool check_is_useless(Position &pos, Move move, Value eval, Value futilityBase, Value beta, Value *bValue)
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{
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Value bestValue = *bValue;
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/// Rule 1. Using checks to reposition pieces when close to beta
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if (eval + PawnValueMidgame / 4 < beta)
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{
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if (eval + PawnValueMidgame / 4 > bestValue)
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bestValue = eval + PawnValueMidgame / 4;
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}
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else
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return false;
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Square from = move_from(move);
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Square to = move_to(move);
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Color oppColor = opposite_color(pos.side_to_move());
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Square oppKing = pos.king_square(oppColor);
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Bitboard occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL <<oppKing);
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Bitboard oppOcc = pos.pieces_of_color(oppColor) & ~(1ULL <<oppKing);
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Bitboard oldAtt = attacks(pos.piece_on(from), from, occ);
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Bitboard newAtt = attacks(pos.piece_on(from), to, occ);
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// Rule 2. Checks which give opponent's king at most one escape square are dangerous
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Bitboard escapeBB = attacks(WK, oppKing, 0) & ~oppOcc & ~newAtt & ~(1ULL << to);
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if (!escapeBB)
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return false;
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if (!(escapeBB & (escapeBB - 1)))
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return false;
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/// Rule 3. Queen contact check is very dangerous
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if ( pos.type_of_piece_on(from) == QUEEN
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&& bit_is_set(attacks(WK, oppKing, 0), to))
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return false;
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/// Rule 4. Creating new double threats with checks
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Bitboard newVictims = oppOcc & ~oldAtt & newAtt;
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while(newVictims)
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{
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Square victimSq = pop_1st_bit(&newVictims);
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Value futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
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// Note that here we generate illegal "double move"!
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if (futilityValue >= beta && pos.see_sign(make_move(from, victimSq)) >= 0)
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return false;
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if (futilityValue > bestValue)
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bestValue = futilityValue;
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}
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*bValue = bestValue;
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return true;
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}
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// attacks() returns attacked squares.
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Bitboard attacks(const Piece P, const Square sq, const Bitboard occ)
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{
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switch(P)
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{
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case WP:
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case BP:
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case WN:
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case BN:
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case WK:
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case BK:
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return StepAttackBB[P][sq];
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case WB:
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case BB:
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return bishop_attacks_bb(sq, occ);
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case WR:
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case BR:
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return rook_attacks_bb(sq, occ);
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case WQ:
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case BQ:
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return bishop_attacks_bb(sq, occ) | rook_attacks_bb(sq, occ);
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default:
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assert(false);
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return 0ULL;
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}
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}
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// connected_moves() tests whether two moves are 'connected' in the sense
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// that the first move somehow made the second move possible (for instance
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