2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <cstring> // For std::memset
35 enum Tracing { NO_TRACE, TRACE };
37 enum Term { // The first 8 entries are reserved for PieceType
38 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, INITIATIVE, TOTAL, TERM_NB
41 Score scores[TERM_NB][COLOR_NB];
43 double to_cp(Value v) { return double(v) / PawnValueEg; }
45 void add(int idx, Color c, Score s) {
49 void add(int idx, Score w, Score b = SCORE_ZERO) {
50 scores[idx][WHITE] = w;
51 scores[idx][BLACK] = b;
54 std::ostream& operator<<(std::ostream& os, Score s) {
55 os << std::setw(5) << to_cp(mg_value(s)) << " "
56 << std::setw(5) << to_cp(eg_value(s));
60 std::ostream& operator<<(std::ostream& os, Term t) {
62 if (t == MATERIAL || t == IMBALANCE || t == INITIATIVE || t == TOTAL)
63 os << " ---- ----" << " | " << " ---- ----";
65 os << scores[t][WHITE] << " | " << scores[t][BLACK];
67 os << " | " << scores[t][WHITE] - scores[t][BLACK] << "\n";
72 using namespace Trace;
76 constexpr Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
77 constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
78 constexpr Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
79 constexpr Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
81 constexpr Bitboard KingFlank[FILE_NB] = {
82 QueenSide ^ FileDBB, QueenSide, QueenSide,
83 CenterFiles, CenterFiles,
84 KingSide, KingSide, KingSide ^ FileEBB
87 // Threshold for lazy and space evaluation
88 constexpr Value LazyThreshold = Value(1500);
89 constexpr Value SpaceThreshold = Value(12222);
91 // KingAttackWeights[PieceType] contains king attack weights by piece type
92 constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 77, 55, 44, 10 };
94 // Penalties for enemy's safe checks
95 constexpr int QueenSafeCheck = 780;
96 constexpr int RookSafeCheck = 1080;
97 constexpr int BishopSafeCheck = 635;
98 constexpr int KnightSafeCheck = 790;
100 #define S(mg, eg) make_score(mg, eg)
102 // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
103 // indexed by piece type and number of attacked squares in the mobility area.
104 constexpr Score MobilityBonus[][32] = {
105 { S(-62,-81), S(-53,-56), S(-12,-30), S( -4,-14), S( 3, 8), S( 13, 15), // Knights
106 S( 22, 23), S( 28, 27), S( 33, 33) },
107 { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
108 S( 55, 54), S( 63, 57), S( 63, 65), S( 68, 73), S( 81, 78), S( 81, 86),
109 S( 91, 88), S( 98, 97) },
110 { S(-58,-76), S(-27,-18), S(-15, 28), S(-10, 55), S( -5, 69), S( -2, 82), // Rooks
111 S( 9,112), S( 16,118), S( 30,132), S( 29,142), S( 32,155), S( 38,165),
112 S( 46,166), S( 48,169), S( 58,171) },
113 { S(-39,-36), S(-21,-15), S( 3, 8), S( 3, 18), S( 14, 34), S( 22, 54), // Queens
114 S( 28, 61), S( 41, 73), S( 43, 79), S( 48, 92), S( 56, 94), S( 60,104),
115 S( 60,113), S( 66,120), S( 67,123), S( 70,126), S( 71,133), S( 73,136),
116 S( 79,140), S( 88,143), S( 88,148), S( 99,166), S(102,170), S(102,175),
117 S(106,184), S(109,191), S(113,206), S(116,212) }
120 // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
121 // pieces if they occupy or can reach an outpost square, bigger if that
122 // square is supported by a pawn.
123 constexpr Score Outpost[][2] = {
124 { S(22, 6), S(36,12) }, // Knight
125 { S( 9, 2), S(15, 5) } // Bishop
128 // RookOnFile[semiopen/open] contains bonuses for each rook when there is
129 // no (friendly) pawn on the rook file.
130 constexpr Score RookOnFile[] = { S(18, 7), S(44, 20) };
132 // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
133 // which piece type attacks which one. Attacks on lesser pieces which are
134 // pawn-defended are not considered.
135 constexpr Score ThreatByMinor[PIECE_TYPE_NB] = {
136 S(0, 0), S(0, 31), S(39, 42), S(57, 44), S(68, 112), S(62, 120)
139 constexpr Score ThreatByRook[PIECE_TYPE_NB] = {
140 S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(51, 38)
143 // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
144 constexpr Score PassedRank[RANK_NB] = {
145 S(0, 0), S(5, 18), S(12, 23), S(10, 31), S(57, 62), S(163, 167), S(271, 250)
148 // PassedFile[File] contains a bonus according to the file of a passed pawn
149 constexpr Score PassedFile[FILE_NB] = {
150 S( -1, 7), S( 0, 9), S(-9, -8), S(-30,-14),
151 S(-30,-14), S(-9, -8), S( 0, 9), S( -1, 7)
154 // Assorted bonuses and penalties
155 constexpr Score BishopPawns = S( 3, 7);
156 constexpr Score CloseEnemies = S( 8, 0);
157 constexpr Score CorneredBishop = S( 50, 50);
158 constexpr Score Hanging = S( 69, 36);
159 constexpr Score KingProtector = S( 7, 8);
160 constexpr Score KnightOnQueen = S( 16, 12);
161 constexpr Score LongDiagonalBishop = S( 45, 0);
162 constexpr Score MinorBehindPawn = S( 18, 3);
163 constexpr Score PawnlessFlank = S( 17, 95);
164 constexpr Score RestrictedPiece = S( 7, 7);
165 constexpr Score RookOnPawn = S( 10, 32);
166 constexpr Score SliderOnQueen = S( 59, 18);
167 constexpr Score ThreatByKing = S( 24, 89);
168 constexpr Score ThreatByPawnPush = S( 48, 39);
169 constexpr Score ThreatByRank = S( 13, 0);
170 constexpr Score ThreatBySafePawn = S(173, 94);
171 constexpr Score TrappedRook = S( 47, 4);
172 constexpr Score WeakQueen = S( 49, 15);
173 constexpr Score WeakUnopposedPawn = S( 12, 23);
177 // Evaluation class computes and stores attacks tables and other working data
182 Evaluation() = delete;
183 explicit Evaluation(const Position& p) : pos(p) {}
184 Evaluation& operator=(const Evaluation&) = delete;
188 template<Color Us> void initialize();
189 template<Color Us, PieceType Pt> Score pieces();
190 template<Color Us> Score king() const;
191 template<Color Us> Score threats() const;
192 template<Color Us> Score passed() const;
193 template<Color Us> Score space() const;
194 ScaleFactor scale_factor(Value eg) const;
195 Score initiative(Value eg) const;
200 Bitboard mobilityArea[COLOR_NB];
201 Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
203 // attackedBy[color][piece type] is a bitboard representing all squares
204 // attacked by a given color and piece type. Special "piece types" which
205 // is also calculated is ALL_PIECES.
206 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
208 // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
209 // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
210 // pawn or squares attacked by 2 pawns are not explicitly added.
211 Bitboard attackedBy2[COLOR_NB];
213 // kingRing[color] are the squares adjacent to the king, plus (only for a
214 // king on its first rank) the squares two ranks in front. For instance,
215 // if black's king is on g8, kingRing[BLACK] is f8, h8, f7, g7, h7, f6, g6
217 Bitboard kingRing[COLOR_NB];
219 // kingAttackersCount[color] is the number of pieces of the given color
220 // which attack a square in the kingRing of the enemy king.
221 int kingAttackersCount[COLOR_NB];
223 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of
224 // the given color which attack a square in the kingRing of the enemy king.
225 // The weights of the individual piece types are given by the elements in
226 // the KingAttackWeights array.
227 int kingAttackersWeight[COLOR_NB];
229 // kingAttacksCount[color] is the number of attacks by the given color to
230 // squares directly adjacent to the enemy king. Pieces which attack more
231 // than one square are counted multiple times. For instance, if there is
232 // a white knight on g5 and black's king is on g8, this white knight adds 2
233 // to kingAttacksCount[WHITE].
234 int kingAttacksCount[COLOR_NB];
238 // Evaluation::initialize() computes king and pawn attacks, and the king ring
239 // bitboard for a given color. This is done at the beginning of the evaluation.
240 template<Tracing T> template<Color Us>
241 void Evaluation<T>::initialize() {
243 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
244 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
245 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
246 constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
248 // Find our pawns that are blocked or on the first two ranks
249 Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
251 // Squares occupied by those pawns, by our king or queen, or controlled by enemy pawns
252 // are excluded from the mobility area.
253 mobilityArea[Us] = ~(b | pos.pieces(Us, KING, QUEEN) | pe->pawn_attacks(Them));
255 // Initialise attackedBy bitboards for kings and pawns
256 attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
257 attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
258 attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];
259 attackedBy2[Us] = attackedBy[Us][KING] & attackedBy[Us][PAWN];
261 // Init our king safety tables
262 kingRing[Us] = attackedBy[Us][KING];
263 if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
264 kingRing[Us] |= shift<Up>(kingRing[Us]);
266 if (file_of(pos.square<KING>(Us)) == FILE_H)
267 kingRing[Us] |= shift<WEST>(kingRing[Us]);
269 else if (file_of(pos.square<KING>(Us)) == FILE_A)
270 kingRing[Us] |= shift<EAST>(kingRing[Us]);
272 kingAttackersCount[Them] = popcount(kingRing[Us] & pe->pawn_attacks(Them));
273 kingRing[Us] &= ~double_pawn_attacks_bb<Us>(pos.pieces(Us, PAWN));
274 kingAttacksCount[Them] = kingAttackersWeight[Them] = 0;
278 // Evaluation::pieces() scores pieces of a given color and type
279 template<Tracing T> template<Color Us, PieceType Pt>
280 Score Evaluation<T>::pieces() {
282 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
283 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
284 constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
285 : Rank5BB | Rank4BB | Rank3BB);
286 const Square* pl = pos.squares<Pt>(Us);
290 Score score = SCORE_ZERO;
292 attackedBy[Us][Pt] = 0;
294 while ((s = *pl++) != SQ_NONE)
296 // Find attacked squares, including x-ray attacks for bishops and rooks
297 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
298 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
299 : pos.attacks_from<Pt>(s);
301 if (pos.blockers_for_king(Us) & s)
302 b &= LineBB[pos.square<KING>(Us)][s];
304 attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
305 attackedBy[Us][Pt] |= b;
306 attackedBy[Us][ALL_PIECES] |= b;
308 if (b & kingRing[Them])
310 kingAttackersCount[Us]++;
311 kingAttackersWeight[Us] += KingAttackWeights[Pt];
312 kingAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
315 int mob = popcount(b & mobilityArea[Us]);
317 mobility[Us] += MobilityBonus[Pt - 2][mob];
319 if (Pt == BISHOP || Pt == KNIGHT)
321 // Bonus if piece is on an outpost square or can reach one
322 bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
324 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;
326 else if (bb &= b & ~pos.pieces(Us))
327 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
329 // Knight and Bishop bonus for being right behind a pawn
330 if (shift<Down>(pos.pieces(PAWN)) & s)
331 score += MinorBehindPawn;
333 // Penalty if the piece is far from the king
334 score -= KingProtector * distance(s, pos.square<KING>(Us));
338 // Penalty according to number of pawns on the same color square as the
339 // bishop, bigger when the center files are blocked with pawns.
340 Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());
342 score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s)
343 * (1 + popcount(blocked & CenterFiles));
345 // Bonus for bishop on a long diagonal which can "see" both center squares
346 if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))
347 score += LongDiagonalBishop;
350 // An important Chess960 pattern: A cornered bishop blocked by a friendly
351 // pawn diagonally in front of it is a very serious problem, especially
352 // when that pawn is also blocked.
355 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
357 Direction d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
358 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
359 score -= !pos.empty(s + d + pawn_push(Us)) ? CorneredBishop * 4
360 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? CorneredBishop * 2
367 // Bonus for aligning rook with enemy pawns on the same rank/file
368 if (relative_rank(Us, s) >= RANK_5)
369 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
371 // Bonus for rook on an open or semi-open file
372 if (pe->semiopen_file(Us, file_of(s)))
373 score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];
375 // Penalty when trapped by the king, even more if the king cannot castle
378 File kf = file_of(pos.square<KING>(Us));
379 if ((kf < FILE_E) == (file_of(s) < kf))
380 score -= TrappedRook * (1 + !pos.castling_rights(Us));
386 // Penalty if any relative pin or discovered attack against the queen
387 Bitboard queenPinners;
388 if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
393 Trace::add(Pt, Us, score);
399 // Evaluation::king() assigns bonuses and penalties to a king of a given color
400 template<Tracing T> template<Color Us>
401 Score Evaluation<T>::king() const {
403 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
404 constexpr Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
405 : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
407 const Square ksq = pos.square<KING>(Us);
408 Bitboard kingFlank, weak, b, b1, b2, safe, unsafeChecks;
410 // King shelter and enemy pawns storm
411 Score score = pe->king_safety<Us>(pos);
413 // Find the squares that opponent attacks in our king flank, and the squares
414 // which are attacked twice in that flank.
415 kingFlank = KingFlank[file_of(ksq)];
416 b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;
417 b2 = b1 & attackedBy2[Them];
419 int tropism = popcount(b1) + popcount(b2);
421 // Main king safety evaluation
425 // Attacked squares defended at most once by our queen or king
426 weak = attackedBy[Them][ALL_PIECES]
428 & (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);
430 // Analyse the safe enemy's checks which are possible on next move
431 safe = ~pos.pieces(Them);
432 safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
434 b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
435 b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
437 // Enemy rooks checks
438 Bitboard RookCheck = b1
440 & attackedBy[Them][ROOK];
443 kingDanger += RookSafeCheck;
445 unsafeChecks |= b1 & attackedBy[Them][ROOK];
447 // Enemy queen safe checks: we count them only if they are from squares from
448 // which we can't give a rook check, because rook checks are more valuable.
449 Bitboard QueenCheck = (b1 | b2)
450 & attackedBy[Them][QUEEN]
452 & ~attackedBy[Us][QUEEN]
456 kingDanger += QueenSafeCheck;
458 // Enemy bishops checks: we count them only if they are from squares from
459 // which we can't give a queen check, because queen checks are more valuable.
460 Bitboard BishopCheck = b2
461 & attackedBy[Them][BISHOP]
466 kingDanger += BishopSafeCheck;
468 unsafeChecks |= b2 & attackedBy[Them][BISHOP];
470 // Enemy knights checks
471 b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
474 kingDanger += KnightSafeCheck;
478 // Unsafe or occupied checking squares will also be considered, as long as
479 // the square is in the attacker's mobility area.
480 unsafeChecks &= mobilityArea[Them];
482 kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]
483 + 69 * kingAttacksCount[Them]
484 + 185 * popcount(kingRing[Us] & weak)
485 - 100 * bool(attackedBy[Us][KNIGHT] & attackedBy[Us][KING])
486 + 150 * popcount(pos.blockers_for_king(Us) | unsafeChecks)
487 + 5 * tropism * tropism / 16
488 - 873 * !pos.count<QUEEN>(Them)
489 - 6 * mg_value(score) / 8
490 + mg_value(mobility[Them] - mobility[Us])
493 // Transform the kingDanger units into a Score, and subtract it from the evaluation
495 score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
497 // Penalty when our king is on a pawnless flank
498 if (!(pos.pieces(PAWN) & kingFlank))
499 score -= PawnlessFlank;
501 // King tropism bonus, to anticipate slow motion attacks on our king
502 score -= CloseEnemies * tropism;
505 Trace::add(KING, Us, score);
511 // Evaluation::threats() assigns bonuses according to the types of the
512 // attacking and the attacked pieces.
513 template<Tracing T> template<Color Us>
514 Score Evaluation<T>::threats() const {
516 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
517 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
518 constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
520 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safe, restricted;
521 Score score = SCORE_ZERO;
524 nonPawnEnemies = pos.pieces(Them) & ~pos.pieces(PAWN);
526 // Squares strongly protected by the enemy, either because they defend the
527 // square with a pawn, or because they defend the square twice and we don't.
528 stronglyProtected = attackedBy[Them][PAWN]
529 | (attackedBy2[Them] & ~attackedBy2[Us]);
531 // Non-pawn enemies, strongly protected
532 defended = nonPawnEnemies & stronglyProtected;
534 // Enemies not strongly protected and under our attack
535 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
537 // Safe or protected squares
538 safe = ~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES];
540 // Bonus according to the kind of attacking pieces
543 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
546 Square s = pop_lsb(&b);
547 score += ThreatByMinor[type_of(pos.piece_on(s))];
548 if (type_of(pos.piece_on(s)) != PAWN)
549 score += ThreatByRank * (int)relative_rank(Them, s);
552 b = weak & attackedBy[Us][ROOK];
555 Square s = pop_lsb(&b);
556 score += ThreatByRook[type_of(pos.piece_on(s))];
557 if (type_of(pos.piece_on(s)) != PAWN)
558 score += ThreatByRank * (int)relative_rank(Them, s);
561 if (weak & attackedBy[Us][KING])
562 score += ThreatByKing;
564 b = ~attackedBy[Them][ALL_PIECES]
565 | (nonPawnEnemies & attackedBy2[Us]);
566 score += Hanging * popcount(weak & b);
569 // Bonus for restricting their piece moves
570 restricted = attackedBy[Them][ALL_PIECES]
572 & attackedBy[Us][ALL_PIECES];
573 score += RestrictedPiece * popcount(restricted);
575 // Bonus for enemy unopposed weak pawns
576 if (pos.pieces(Us, ROOK, QUEEN))
577 score += WeakUnopposedPawn * pe->weak_unopposed(Them);
579 // Find squares where our pawns can push on the next move
580 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
581 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
583 // Keep only the squares which are relatively safe
584 b &= ~attackedBy[Them][PAWN] & safe;
586 // Bonus for safe pawn threats on the next move
587 b = pawn_attacks_bb<Us>(b) & pos.pieces(Them);
588 score += ThreatByPawnPush * popcount(b);
590 // Our safe or protected pawns
591 b = pos.pieces(Us, PAWN) & safe;
593 b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
594 score += ThreatBySafePawn * popcount(b);
596 // Bonus for threats on the next moves against enemy queen
597 if (pos.count<QUEEN>(Them) == 1)
599 Square s = pos.square<QUEEN>(Them);
600 safe = mobilityArea[Us] & ~stronglyProtected;
602 b = attackedBy[Us][KNIGHT] & pos.attacks_from<KNIGHT>(s);
604 score += KnightOnQueen * popcount(b & safe);
606 b = (attackedBy[Us][BISHOP] & pos.attacks_from<BISHOP>(s))
607 | (attackedBy[Us][ROOK ] & pos.attacks_from<ROOK >(s));
609 score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]);
613 Trace::add(THREAT, Us, score);
618 // Evaluation::passed() evaluates the passed pawns and candidate passed
619 // pawns of the given color.
621 template<Tracing T> template<Color Us>
622 Score Evaluation<T>::passed() const {
624 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
625 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
627 auto king_proximity = [&](Color c, Square s) {
628 return std::min(distance(pos.square<KING>(c), s), 5);
631 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
632 Score score = SCORE_ZERO;
634 b = pe->passed_pawns(Us);
638 Square s = pop_lsb(&b);
640 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
642 int r = relative_rank(Us, s);
644 Score bonus = PassedRank[r];
648 int w = (r-2) * (r-2) + 2;
649 Square blockSq = s + Up;
651 // Adjust bonus based on the king's proximity
652 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
653 - king_proximity(Us, blockSq) * 2) * w);
655 // If blockSq is not the queening square then consider also a second push
657 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
659 // If the pawn is free to advance, then increase the bonus
660 if (pos.empty(blockSq))
662 // If there is a rook or queen attacking/defending the pawn from behind,
663 // consider all the squaresToQueen. Otherwise consider only the squares
664 // in the pawn's path attacked or occupied by the enemy.
665 defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
667 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
669 if (!(pos.pieces(Us) & bb))
670 defendedSquares &= attackedBy[Us][ALL_PIECES];
672 if (!(pos.pieces(Them) & bb))
673 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
675 // If there aren't any enemy attacks, assign a big bonus. Otherwise
676 // assign a smaller bonus if the block square isn't attacked.
677 int k = !unsafeSquares ? 20 : !(unsafeSquares & blockSq) ? 9 : 0;
679 // If the path to the queen is fully defended, assign a big bonus.
680 // Otherwise assign a smaller bonus if the block square is defended.
681 if (defendedSquares == squaresToQueen)
684 else if (defendedSquares & blockSq)
687 bonus += make_score(k * w, k * w);
691 // Scale down bonus for candidate passers which need more than one
692 // pawn push to become passed, or have a pawn in front of them.
693 if ( !pos.pawn_passed(Us, s + Up)
694 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
697 score += bonus + PassedFile[file_of(s)];
701 Trace::add(PASSED, Us, score);
707 // Evaluation::space() computes the space evaluation for a given side. The
708 // space evaluation is a simple bonus based on the number of safe squares
709 // available for minor pieces on the central four files on ranks 2--4. Safe
710 // squares one, two or three squares behind a friendly pawn are counted
711 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
712 // improve play on game opening.
714 template<Tracing T> template<Color Us>
715 Score Evaluation<T>::space() const {
717 if (pos.non_pawn_material() < SpaceThreshold)
720 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
721 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
722 constexpr Bitboard SpaceMask =
723 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
724 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
726 // Find the available squares for our pieces inside the area defined by SpaceMask
727 Bitboard safe = SpaceMask
728 & ~pos.pieces(Us, PAWN)
729 & ~attackedBy[Them][PAWN];
731 // Find all squares which are at most three squares behind some friendly pawn
732 Bitboard behind = pos.pieces(Us, PAWN);
733 behind |= shift<Down>(behind);
734 behind |= shift<Down>(shift<Down>(behind));
736 int bonus = popcount(safe) + popcount(behind & safe);
737 int weight = pos.count<ALL_PIECES>(Us)
738 - 2 * popcount(pe->semiopenFiles[WHITE] & pe->semiopenFiles[BLACK]);
740 Score score = make_score(bonus * weight * weight / 16, 0);
743 Trace::add(SPACE, Us, score);
749 // Evaluation::initiative() computes the initiative correction value
750 // for the position. It is a second order bonus/malus based on the
751 // known attacking/defending status of the players.
754 Score Evaluation<T>::initiative(Value eg) const {
756 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
757 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
759 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
760 && (pos.pieces(PAWN) & KingSide);
762 // Compute the initiative bonus for the attacking side
763 int complexity = 9 * pe->pawn_asymmetry()
764 + 11 * pos.count<PAWN>()
766 + 18 * pawnsOnBothFlanks
767 + 49 * !pos.non_pawn_material()
770 // Now apply the bonus: note that we find the attacking side by extracting
771 // the sign of the endgame value, and that we carefully cap the bonus so
772 // that the endgame score will never change sign after the bonus.
773 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
776 Trace::add(INITIATIVE, make_score(0, v));
778 return make_score(0, v);
782 // Evaluation::scale_factor() computes the scale factor for the winning side
785 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
787 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
788 int sf = me->scale_factor(pos, strongSide);
790 // If scale is not already specific, scale down the endgame via general heuristics
791 if (sf == SCALE_FACTOR_NORMAL)
793 if ( pos.opposite_bishops()
794 && pos.non_pawn_material(WHITE) == BishopValueMg
795 && pos.non_pawn_material(BLACK) == BishopValueMg)
796 sf = 8 + 4 * pe->pawn_asymmetry();
798 sf = std::min(40 + (pos.opposite_bishops() ? 2 : 7) * pos.count<PAWN>(strongSide), sf);
802 return ScaleFactor(sf);
806 // Evaluation::value() is the main function of the class. It computes the various
807 // parts of the evaluation and returns the value of the position from the point
808 // of view of the side to move.
811 Value Evaluation<T>::value() {
813 assert(!pos.checkers());
815 // Probe the material hash table
816 me = Material::probe(pos);
818 // If we have a specialized evaluation function for the current material
819 // configuration, call it and return.
820 if (me->specialized_eval_exists())
821 return me->evaluate(pos);
823 // Initialize score by reading the incrementally updated scores included in
824 // the position object (material + piece square tables) and the material
825 // imbalance. Score is computed internally from the white point of view.
826 Score score = pos.psq_score() + me->imbalance() + pos.this_thread()->contempt;
828 // Probe the pawn hash table
829 pe = Pawns::probe(pos);
830 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
832 // Early exit if score is high
833 Value v = (mg_value(score) + eg_value(score)) / 2;
834 if (abs(v) > LazyThreshold)
835 return pos.side_to_move() == WHITE ? v : -v;
837 // Main evaluation begins here
842 // Pieces should be evaluated first (populate attack tables)
843 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
844 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
845 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
846 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
848 score += mobility[WHITE] - mobility[BLACK];
850 score += king< WHITE>() - king< BLACK>()
851 + threats<WHITE>() - threats<BLACK>()
852 + passed< WHITE>() - passed< BLACK>()
853 + space< WHITE>() - space< BLACK>();
855 score += initiative(eg_value(score));
857 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
858 ScaleFactor sf = scale_factor(eg_value(score));
859 v = mg_value(score) * int(me->game_phase())
860 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
862 v /= int(PHASE_MIDGAME);
864 // In case of tracing add all remaining individual evaluation terms
867 Trace::add(MATERIAL, pos.psq_score());
868 Trace::add(IMBALANCE, me->imbalance());
869 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
870 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
871 Trace::add(TOTAL, score);
874 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
881 /// evaluate() is the evaluator for the outer world. It returns a static
882 /// evaluation of the position from the point of view of the side to move.
884 Value Eval::evaluate(const Position& pos) {
885 return Evaluation<NO_TRACE>(pos).value();
889 /// trace() is like evaluate(), but instead of returning a value, it returns
890 /// a string (suitable for outputting to stdout) that contains the detailed
891 /// descriptions and values of each evaluation term. Useful for debugging.
893 std::string Eval::trace(const Position& pos) {
895 std::memset(scores, 0, sizeof(scores));
897 pos.this_thread()->contempt = SCORE_ZERO; // Reset any dynamic contempt
899 Value v = Evaluation<TRACE>(pos).value();
901 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
903 std::stringstream ss;
904 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
905 << " Term | White | Black | Total \n"
906 << " | MG EG | MG EG | MG EG \n"
907 << " ------------+-------------+-------------+------------\n"
908 << " Material | " << Term(MATERIAL)
909 << " Imbalance | " << Term(IMBALANCE)
910 << " Initiative | " << Term(INITIATIVE)
911 << " Pawns | " << Term(PAWN)
912 << " Knights | " << Term(KNIGHT)
913 << " Bishops | " << Term(BISHOP)
914 << " Rooks | " << Term(ROOK)
915 << " Queens | " << Term(QUEEN)
916 << " Mobility | " << Term(MOBILITY)
917 << " King safety | " << Term(KING)
918 << " Threats | " << Term(THREAT)
919 << " Passed | " << Term(PASSED)
920 << " Space | " << Term(SPACE)
921 << " ------------+-------------+-------------+------------\n"
922 << " Total | " << Term(TOTAL);
924 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";