- // Bonus for restricting their piece moves
- b = attackedBy[Them][ALL_PIECES]
- & ~stronglyProtected
- & attackedBy[Us][ALL_PIECES];
- score += RestrictedPiece * popcount(b);
-
- // Protected or unattacked squares
- safe = ~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES];
-
- // Bonus for attacking enemy pieces with our relatively safe pawns
- b = pos.pieces(Us, PAWN) & safe;
- b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
- score += ThreatBySafePawn * popcount(b);
-
- // Find squares where our pawns can push on the next move
- b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
- b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
-
- // Keep only the squares which are relatively safe
- b &= ~attackedBy[Them][PAWN] & safe;
-
- // Bonus for safe pawn threats on the next move
- b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
- score += ThreatByPawnPush * popcount(b);
-
- // Bonus for threats on the next moves against enemy queen
- if (pos.count<QUEEN>(Them) == 1)
- {
- bool queenImbalance = pos.count<QUEEN>() == 1;
-
- Square s = pos.square<QUEEN>(Them);
- safe = mobilityArea[Us]
- & ~pos.pieces(Us, PAWN)
- & ~stronglyProtected;
-
- b = attackedBy[Us][KNIGHT] & attacks_bb<KNIGHT>(s);
-
- score += KnightOnQueen * popcount(b & safe) * (1 + queenImbalance);
-
- b = (attackedBy[Us][BISHOP] & attacks_bb<BISHOP>(s, pos.pieces()))
- | (attackedBy[Us][ROOK ] & attacks_bb<ROOK >(s, pos.pieces()));
-
- score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]) * (1 + queenImbalance);
- }
-
- if constexpr (T)
- Trace::add(THREAT, Us, score);
-
- return score;
- }
-
- // Evaluation::passed() evaluates the passed pawns and candidate passed
- // pawns of the given color.
-
- template<Tracing T> template<Color Us>
- Score Evaluation<T>::passed() const {
-
- constexpr Color Them = ~Us;
- constexpr Direction Up = pawn_push(Us);
- constexpr Direction Down = -Up;
-
- auto king_proximity = [&](Color c, Square s) {
- return std::min(distance(pos.square<KING>(c), s), 5);
- };
-
- Bitboard b, bb, squaresToQueen, unsafeSquares, blockedPassers, helpers;
- Score score = SCORE_ZERO;
-
- b = pe->passed_pawns(Us);
-
- blockedPassers = b & shift<Down>(pos.pieces(Them, PAWN));
- if (blockedPassers)
- {
- helpers = shift<Up>(pos.pieces(Us, PAWN))
- & ~pos.pieces(Them)
- & (~attackedBy2[Them] | attackedBy[Us][ALL_PIECES]);
-
- // Remove blocked candidate passers that don't have help to pass
- b &= ~blockedPassers
- | shift<WEST>(helpers)
- | shift<EAST>(helpers);
- }
-
- while (b)
- {
- Square s = pop_lsb(b);
-
- assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
-
- int r = relative_rank(Us, s);
-
- Score bonus = PassedRank[r];
-
- if (r > RANK_3)
- {
- int w = 5 * r - 13;
- Square blockSq = s + Up;
-
- // Adjust bonus based on the king's proximity
- bonus += make_score(0, ( king_proximity(Them, blockSq) * 19 / 4
- - king_proximity(Us, blockSq) * 2) * w);
-
- // If blockSq is not the queening square then consider also a second push
- if (r != RANK_7)
- bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
-
- // If the pawn is free to advance, then increase the bonus
- if (pos.empty(blockSq))
- {
- squaresToQueen = forward_file_bb(Us, s);
- unsafeSquares = passed_pawn_span(Us, s);
-
- bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN);
-
- if (!(pos.pieces(Them) & bb))
- unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
-
- // If there are no enemy pieces or attacks on passed pawn span, assign a big bonus.
- // Or if there is some, but they are all attacked by our pawns, assign a bit smaller bonus.
- // Otherwise assign a smaller bonus if the path to queen is not attacked
- // and even smaller bonus if it is attacked but block square is not.
- int k = !unsafeSquares ? 36 :
- !(unsafeSquares & ~attackedBy[Us][PAWN]) ? 30 :
- !(unsafeSquares & squaresToQueen) ? 17 :
- !(unsafeSquares & blockSq) ? 7 :
- 0 ;
-
- // Assign a larger bonus if the block square is defended
- if ((pos.pieces(Us) & bb) || (attackedBy[Us][ALL_PIECES] & blockSq))
- k += 5;
-
- bonus += make_score(k * w, k * w);
- }
- } // r > RANK_3
-
- score += bonus - PassedFile * edge_distance(file_of(s));
- }
-
- if constexpr (T)
- Trace::add(PASSED, Us, score);
-
- return score;
- }
-
-
- // Evaluation::space() computes a space evaluation for a given side, aiming to improve game
- // play in the opening. It is based on the number of safe squares on the four central files
- // on ranks 2 to 4. Completely safe squares behind a friendly pawn are counted twice.
- // Finally, the space bonus is multiplied by a weight which decreases according to occupancy.
-
- template<Tracing T> template<Color Us>
- Score Evaluation<T>::space() const {
-
- // Early exit if, for example, both queens or 6 minor pieces have been exchanged
- if (pos.non_pawn_material() < SpaceThreshold)
- return SCORE_ZERO;
-
- constexpr Color Them = ~Us;
- constexpr Direction Down = -pawn_push(Us);
- constexpr Bitboard SpaceMask =
- Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
- : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
-
- // Find the available squares for our pieces inside the area defined by SpaceMask
- Bitboard safe = SpaceMask
- & ~pos.pieces(Us, PAWN)
- & ~attackedBy[Them][PAWN];
-
- // Find all squares which are at most three squares behind some friendly pawn
- Bitboard behind = pos.pieces(Us, PAWN);
- behind |= shift<Down>(behind);
- behind |= shift<Down+Down>(behind);
-
- // Compute space score based on the number of safe squares and number of our pieces
- // increased with number of total blocked pawns in position.
- int bonus = popcount(safe) + popcount(behind & safe & ~attackedBy[Them][ALL_PIECES]);
- int weight = pos.count<ALL_PIECES>(Us) - 3 + std::min(pe->blocked_count(), 9);
- Score score = make_score(bonus * weight * weight / 16, 0);
-
- if constexpr (T)
- Trace::add(SPACE, Us, score);
-
- return score;
- }
-
-
- // Evaluation::winnable() adjusts the midgame and endgame score components, based on
- // the known attacking/defending status of the players. The final value is derived
- // by interpolation from the midgame and endgame values.
-
- template<Tracing T>
- Value Evaluation<T>::winnable(Score score) const {
-
- int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
- + int(rank_of(pos.square<KING>(WHITE)) - rank_of(pos.square<KING>(BLACK)));
-
- bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
- && (pos.pieces(PAWN) & KingSide);
-
- bool almostUnwinnable = outflanking < 0
- && !pawnsOnBothFlanks;
-
- bool infiltration = rank_of(pos.square<KING>(WHITE)) > RANK_4
- || rank_of(pos.square<KING>(BLACK)) < RANK_5;
-
- // Compute the initiative bonus for the attacking side
- int complexity = 9 * pe->passed_count()
- + 12 * pos.count<PAWN>()
- + 9 * outflanking
- + 21 * pawnsOnBothFlanks
- + 24 * infiltration
- + 51 * !pos.non_pawn_material()
- - 43 * almostUnwinnable
- -110 ;
-
- Value mg = mg_value(score);
- Value eg = eg_value(score);
-
- // Now apply the bonus: note that we find the attacking side by extracting the
- // sign of the midgame or endgame values, and that we carefully cap the bonus
- // so that the midgame and endgame scores do not change sign after the bonus.
- int u = ((mg > 0) - (mg < 0)) * std::clamp(complexity + 50, -abs(mg), 0);
- int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
-
- mg += u;
- eg += v;
-
- // Compute the scale factor for the winning side
- Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
- int sf = me->scale_factor(pos, strongSide);
-
- // If scale factor is not already specific, scale up/down via general heuristics
- if (sf == SCALE_FACTOR_NORMAL)
- {
- if (pos.opposite_bishops())
- {
- // For pure opposite colored bishops endgames use scale factor
- // based on the number of passed pawns of the strong side.
- if ( pos.non_pawn_material(WHITE) == BishopValueMg
- && pos.non_pawn_material(BLACK) == BishopValueMg)
- sf = 18 + 4 * popcount(pe->passed_pawns(strongSide));
- // For every other opposite colored bishops endgames use scale factor
- // based on the number of all pieces of the strong side.
- else
- sf = 22 + 3 * pos.count<ALL_PIECES>(strongSide);
- }
- // For rook endgames with strong side not having overwhelming pawn number advantage
- // and its pawns being on one flank and weak side protecting its pieces with a king
- // use lower scale factor.
- else if ( pos.non_pawn_material(WHITE) == RookValueMg
- && pos.non_pawn_material(BLACK) == RookValueMg
- && pos.count<PAWN>(strongSide) - pos.count<PAWN>(~strongSide) <= 1
- && bool(KingSide & pos.pieces(strongSide, PAWN)) != bool(QueenSide & pos.pieces(strongSide, PAWN))
- && (attacks_bb<KING>(pos.square<KING>(~strongSide)) & pos.pieces(~strongSide, PAWN)))
- sf = 36;
- // For queen vs no queen endgames use scale factor
- // based on number of minors of side that doesn't have queen.
- else if (pos.count<QUEEN>() == 1)
- sf = 37 + 3 * (pos.count<QUEEN>(WHITE) == 1 ? pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK)
- : pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE));
- // In every other case use scale factor based on
- // the number of pawns of the strong side reduced if pawns are on a single flank.
- else
- sf = std::min(sf, 36 + 7 * pos.count<PAWN>(strongSide)) - 4 * !pawnsOnBothFlanks;
-
- // Reduce scale factor in case of pawns being on a single flank
- sf -= 4 * !pawnsOnBothFlanks;
- }
-
- // Interpolate between the middlegame and (scaled by 'sf') endgame score
- v = mg * int(me->game_phase())
- + eg * int(PHASE_MIDGAME - me->game_phase()) * ScaleFactor(sf) / SCALE_FACTOR_NORMAL;
- v /= PHASE_MIDGAME;
-
- if constexpr (T)
- {
- Trace::add(WINNABLE, make_score(u, eg * ScaleFactor(sf) / SCALE_FACTOR_NORMAL - eg_value(score)));
- Trace::add(TOTAL, make_score(mg, eg * ScaleFactor(sf) / SCALE_FACTOR_NORMAL));
- }
-
- return Value(v);
- }
-
-
- // Evaluation::value() is the main function of the class. It computes the various
- // parts of the evaluation and returns the value of the position from the point
- // of view of the side to move.
-
- template<Tracing T>
- Value Evaluation<T>::value() {
-
- assert(!pos.checkers());
-
- // Probe the material hash table
- me = Material::probe(pos);
-
- // If we have a specialized evaluation function for the current material
- // configuration, call it and return.
- if (me->specialized_eval_exists())
- return me->evaluate(pos);
-
- // Initialize score by reading the incrementally updated scores included in
- // the position object (material + piece square tables) and the material
- // imbalance. Score is computed internally from the white point of view.
- Score score = pos.psq_score() + me->imbalance() + pos.this_thread()->trend;
-
- // Probe the pawn hash table
- pe = Pawns::probe(pos);
- score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
-
- // Early exit if score is high
- auto lazy_skip = [&](Value lazyThreshold) {
- return abs(mg_value(score) + eg_value(score)) > lazyThreshold
- + std::abs(pos.this_thread()->bestValue) * 5 / 4
- + pos.non_pawn_material() / 32;
- };
-
- if (lazy_skip(LazyThreshold1))
- goto make_v;
-
- // Main evaluation begins here
- initialize<WHITE>();
- initialize<BLACK>();
-
- // Pieces evaluated first (also populates attackedBy, attackedBy2).
- // Note that the order of evaluation of the terms is left unspecified.
- score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
- + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
- + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
- + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
-
- score += mobility[WHITE] - mobility[BLACK];
-
- // More complex interactions that require fully populated attack bitboards
- score += king< WHITE>() - king< BLACK>()
- + passed< WHITE>() - passed< BLACK>();
-
- if (lazy_skip(LazyThreshold2))
- goto make_v;
-
- score += threats<WHITE>() - threats<BLACK>()
- + space< WHITE>() - space< BLACK>();
-
-make_v:
- // Derive single value from mg and eg parts of score
- Value v = winnable(score);
-
- // In case of tracing add all remaining individual evaluation terms
- if constexpr (T)
- {
- Trace::add(MATERIAL, pos.psq_score());
- Trace::add(IMBALANCE, me->imbalance());
- Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
- Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
- }
-
- // Evaluation grain
- v = (v / 16) * 16;
-
- // Side to move point of view
- v = (pos.side_to_move() == WHITE ? v : -v);
-
- return v;
- }
-
-
- /// Fisher Random Chess: correction for cornered bishops, to fix chess960 play with NNUE
-
- Value fix_FRC(const Position& pos) {
-
- constexpr Bitboard Corners = 1ULL << SQ_A1 | 1ULL << SQ_H1 | 1ULL << SQ_A8 | 1ULL << SQ_H8;
-
- if (!(pos.pieces(BISHOP) & Corners))
- return VALUE_ZERO;
-
- int correction = 0;
-
- if ( pos.piece_on(SQ_A1) == W_BISHOP
- && pos.piece_on(SQ_B2) == W_PAWN)
- correction -= CorneredBishop;
-
- if ( pos.piece_on(SQ_H1) == W_BISHOP
- && pos.piece_on(SQ_G2) == W_PAWN)
- correction -= CorneredBishop;
-
- if ( pos.piece_on(SQ_A8) == B_BISHOP
- && pos.piece_on(SQ_B7) == B_PAWN)
- correction += CorneredBishop;
-
- if ( pos.piece_on(SQ_H8) == B_BISHOP
- && pos.piece_on(SQ_G7) == B_PAWN)
- correction += CorneredBishop;
-
- return pos.side_to_move() == WHITE ? Value(3 * correction)
- : -Value(3 * correction);
- }
-
-} // namespace Eval
-
-
-/// evaluate() is the evaluator for the outer world. It returns a static
-/// evaluation of the position from the point of view of the side to move.
-
-Value Eval::evaluate(const Position& pos, int* complexity) {