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) 2015-2018 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
32 std::atomic<Score> Eval::Contempt;
36 enum Tracing { NO_TRACE, TRACE };
38 enum Term { // The first 8 entries are reserved for PieceType
39 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, INITIATIVE, TOTAL, TERM_NB
42 Score scores[TERM_NB][COLOR_NB];
44 double to_cp(Value v) { return double(v) / PawnValueEg; }
46 void add(int idx, Color c, Score s) {
50 void add(int idx, Score w, Score b = SCORE_ZERO) {
51 scores[idx][WHITE] = w;
52 scores[idx][BLACK] = b;
55 std::ostream& operator<<(std::ostream& os, Score s) {
56 os << std::setw(5) << to_cp(mg_value(s)) << " "
57 << std::setw(5) << to_cp(eg_value(s));
61 std::ostream& operator<<(std::ostream& os, Term t) {
63 if (t == MATERIAL || t == IMBALANCE || t == INITIATIVE || t == TOTAL)
64 os << " ---- ----" << " | " << " ---- ----";
66 os << scores[t][WHITE] << " | " << scores[t][BLACK];
68 os << " | " << scores[t][WHITE] - scores[t][BLACK] << "\n";
73 using namespace Trace;
77 const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
78 const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
79 const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
80 const Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
82 const Bitboard KingFlank[FILE_NB] = {
83 QueenSide, QueenSide, QueenSide,
84 CenterFiles, CenterFiles,
85 KingSide, KingSide, KingSide
88 // Threshold for lazy and space evaluation
89 const Value LazyThreshold = Value(1500);
90 const Value SpaceThreshold = Value(12222);
92 // KingAttackWeights[PieceType] contains king attack weights by piece type
93 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
95 // Penalties for enemy's safe checks
96 const int QueenSafeCheck = 780;
97 const int RookSafeCheck = 880;
98 const int BishopSafeCheck = 435;
99 const int KnightSafeCheck = 790;
101 #define S(mg, eg) make_score(mg, eg)
103 // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
104 // indexed by piece type and number of attacked squares in the mobility area.
105 const Score MobilityBonus[][32] = {
106 { S(-75,-76), S(-57,-54), S( -9,-28), S( -2,-10), S( 6, 5), S( 14, 12), // Knights
107 S( 22, 26), S( 29, 29), S( 36, 29) },
108 { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
109 S( 55, 54), S( 63, 57), S( 63, 65), S( 68, 73), S( 81, 78), S( 81, 86),
110 S( 91, 88), S( 98, 97) },
111 { S(-58,-76), S(-27,-18), S(-15, 28), S(-10, 55), S( -5, 69), S( -2, 82), // Rooks
112 S( 9,112), S( 16,118), S( 30,132), S( 29,142), S( 32,155), S( 38,165),
113 S( 46,166), S( 48,169), S( 58,171) },
114 { S(-39,-36), S(-21,-15), S( 3, 8), S( 3, 18), S( 14, 34), S( 22, 54), // Queens
115 S( 28, 61), S( 41, 73), S( 43, 79), S( 48, 92), S( 56, 94), S( 60,104),
116 S( 60,113), S( 66,120), S( 67,123), S( 70,126), S( 71,133), S( 73,136),
117 S( 79,140), S( 88,143), S( 88,148), S( 99,166), S(102,170), S(102,175),
118 S(106,184), S(109,191), S(113,206), S(116,212) }
121 // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
122 // pieces if they occupy or can reach an outpost square, bigger if that
123 // square is supported by a pawn.
124 const Score Outpost[][2] = {
125 { S(22, 6), S(36,12) }, // Knight
126 { S( 9, 2), S(15, 5) } // Bishop
129 // RookOnFile[semiopen/open] contains bonuses for each rook when there is
130 // no (friendly) pawn on the rook file.
131 const Score RookOnFile[] = { S(20, 7), S(45, 20) };
133 // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
134 // which piece type attacks which one. Attacks on lesser pieces which are
135 // pawn-defended are not considered.
136 const Score ThreatByMinor[PIECE_TYPE_NB] = {
137 S(0, 0), S(0, 31), S(39, 42), S(57, 44), S(68, 112), S(47, 120)
140 const Score ThreatByRook[PIECE_TYPE_NB] = {
141 S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(36, 38)
144 // ThreatByKing[on one/on many] contains bonuses for king attacks on
145 // pawns or pieces which are not pawn-defended.
146 const Score ThreatByKing[] = { S(3, 65), S(9, 145) };
148 // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
149 const Score PassedRank[RANK_NB] = {
150 S(0, 0), S(5, 7), S(5, 13), S(32, 42), S(70, 70), S(172, 170), S(217, 269)
153 // PassedFile[File] contains a bonus according to the file of a passed pawn
154 const Score PassedFile[FILE_NB] = {
155 S( 9, 10), S(2, 10), S(1, -8), S(-20,-12),
156 S(-20,-12), S(1, -8), S(2, 10), S( 9, 10)
159 // PassedDanger[Rank] contains a term to weight the passed score
160 const int PassedDanger[RANK_NB] = { 0, 0, 0, 2, 7, 12, 19 };
162 // KingProtector[PieceType-2] contains a penalty according to distance from king
163 const Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
165 // Assorted bonuses and penalties
166 const Score BishopPawns = S( 8, 12);
167 const Score CloseEnemies = S( 7, 0);
168 const Score Hanging = S( 52, 30);
169 const Score HinderPassedPawn = S( 8, 1);
170 const Score KnightOnQueen = S( 21, 11);
171 const Score LongRangedBishop = S( 22, 0);
172 const Score MinorBehindPawn = S( 16, 0);
173 const Score PawnlessFlank = S( 20, 80);
174 const Score RookOnPawn = S( 8, 24);
175 const Score SliderOnQueen = S( 42, 21);
176 const Score ThreatByPawnPush = S( 47, 26);
177 const Score ThreatByRank = S( 16, 3);
178 const Score ThreatBySafePawn = S(175,168);
179 const Score TrappedBishopA1H1 = S( 50, 50);
180 const Score TrappedRook = S( 92, 0);
181 const Score WeakQueen = S( 50, 10);
182 const Score WeakUnopposedPawn = S( 5, 25);
186 // Evaluation class computes and stores attacks tables and other working data
191 Evaluation() = delete;
192 explicit Evaluation(const Position& p) : pos(p) {}
193 Evaluation& operator=(const Evaluation&) = delete;
197 template<Color Us> void initialize();
198 template<Color Us, PieceType Pt> Score pieces();
199 template<Color Us> Score king() const;
200 template<Color Us> Score threats() const;
201 template<Color Us> Score passed() const;
202 template<Color Us> Score space() const;
203 ScaleFactor scale_factor(Value eg) const;
204 Score initiative(Value eg) const;
209 Bitboard mobilityArea[COLOR_NB];
210 Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
212 // attackedBy[color][piece type] is a bitboard representing all squares
213 // attacked by a given color and piece type. Special "piece types" which
214 // is also calculated is ALL_PIECES.
215 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
217 // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
218 // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
219 // pawn or squares attacked by 2 pawns are not explicitly added.
220 Bitboard attackedBy2[COLOR_NB];
222 // kingRing[color] are the squares adjacent to the king, plus (only for a
223 // king on its first rank) the squares two ranks in front. For instance,
224 // if black's king is on g8, kingRing[BLACK] is f8, h8, f7, g7, h7, f6, g6
225 // and h6. It is set to 0 when king safety evaluation is skipped.
226 Bitboard kingRing[COLOR_NB];
228 // kingAttackersCount[color] is the number of pieces of the given color
229 // which attack a square in the kingRing of the enemy king.
230 int kingAttackersCount[COLOR_NB];
232 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
233 // given color which attack a square in the kingRing of the enemy king. The
234 // weights of the individual piece types are given by the elements in the
235 // KingAttackWeights array.
236 int kingAttackersWeight[COLOR_NB];
238 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
239 // color to squares directly adjacent to the enemy king. Pieces which attack
240 // more than one square are counted multiple times. For instance, if there is
241 // a white knight on g5 and black's king is on g8, this white knight adds 2
242 // to kingAdjacentZoneAttacksCount[WHITE].
243 int kingAdjacentZoneAttacksCount[COLOR_NB];
247 // Evaluation::initialize() computes king and pawn attacks, and the king ring
248 // bitboard for a given color. This is done at the beginning of the evaluation.
249 template<Tracing T> template<Color Us>
250 void Evaluation<T>::initialize() {
252 const Color Them = (Us == WHITE ? BLACK : WHITE);
253 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
254 const Direction Down = (Us == WHITE ? SOUTH : NORTH);
255 const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
257 // Find our pawns that are blocked or on the first two ranks
258 Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
260 // Squares occupied by those pawns, by our king, or controlled by enemy pawns
261 // are excluded from the mobility area.
262 mobilityArea[Us] = ~(b | pos.square<KING>(Us) | pe->pawn_attacks(Them));
264 // Initialise attackedBy bitboards for kings and pawns
265 attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
266 attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
267 attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];
268 attackedBy2[Us] = attackedBy[Us][KING] & attackedBy[Us][PAWN];
270 // Init our king safety tables only if we are going to use them
271 if (pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)
273 kingRing[Us] = attackedBy[Us][KING];
274 if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
275 kingRing[Us] |= shift<Up>(kingRing[Us]);
277 kingAttackersCount[Them] = popcount(attackedBy[Us][KING] & pe->pawn_attacks(Them));
278 kingAdjacentZoneAttacksCount[Them] = kingAttackersWeight[Them] = 0;
281 kingRing[Us] = kingAttackersCount[Them] = 0;
285 // Evaluation::pieces() scores pieces of a given color and type
286 template<Tracing T> template<Color Us, PieceType Pt>
287 Score Evaluation<T>::pieces() {
289 const Color Them = (Us == WHITE ? BLACK : WHITE);
290 const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
291 : Rank5BB | Rank4BB | Rank3BB);
292 const Square* pl = pos.squares<Pt>(Us);
296 Score score = SCORE_ZERO;
298 attackedBy[Us][Pt] = 0;
300 while ((s = *pl++) != SQ_NONE)
302 // Find attacked squares, including x-ray attacks for bishops and rooks
303 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
304 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
305 : pos.attacks_from<Pt>(s);
307 if (pos.blockers_for_king(Us) & s)
308 b &= LineBB[pos.square<KING>(Us)][s];
310 attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
311 attackedBy[Us][Pt] |= b;
312 attackedBy[Us][ALL_PIECES] |= b;
314 if (b & kingRing[Them])
316 kingAttackersCount[Us]++;
317 kingAttackersWeight[Us] += KingAttackWeights[Pt];
318 kingAdjacentZoneAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
321 int mob = popcount(b & mobilityArea[Us]);
323 mobility[Us] += MobilityBonus[Pt - 2][mob];
325 // Penalty if the piece is far from the king
326 score -= KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));
328 if (Pt == BISHOP || Pt == KNIGHT)
330 // Bonus if piece is on an outpost square or can reach one
331 bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
333 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;
335 else if (bb &= b & ~pos.pieces(Us))
336 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
338 // Bonus when behind a pawn
339 if ( relative_rank(Us, s) < RANK_5
340 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
341 score += MinorBehindPawn;
345 // Penalty according to number of pawns on the same color square as the bishop
346 score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
348 // Bonus for bishop on a long diagonal which can "see" both center squares
349 if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
350 score += LongRangedBishop;
353 // An important Chess960 pattern: A cornered bishop blocked by a friendly
354 // pawn diagonally in front of it is a very serious problem, especially
355 // when that pawn is also blocked.
358 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
360 Direction d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
361 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
362 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
363 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
370 // Bonus for aligning rook with with enemy pawns on the same rank/file
371 if (relative_rank(Us, s) >= RANK_5)
372 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
374 // Bonus for rook on an open or semi-open file
375 if (pe->semiopen_file(Us, file_of(s)))
376 score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];
378 // Penalty when trapped by the king, even more if the king cannot castle
381 File kf = file_of(pos.square<KING>(Us));
382 if ((kf < FILE_E) == (file_of(s) < kf))
383 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
389 // Penalty if any relative pin or discovered attack against the queen
390 Bitboard queenPinners;
391 if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
396 Trace::add(Pt, Us, score);
402 // Evaluation::king() assigns bonuses and penalties to a king of a given color
403 template<Tracing T> template<Color Us>
404 Score Evaluation<T>::king() const {
406 const Color Them = (Us == WHITE ? BLACK : WHITE);
407 const Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
408 : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
410 const Square ksq = pos.square<KING>(Us);
411 Bitboard weak, b, b1, b2, safe, unsafeChecks, pinned;
413 // King shelter and enemy pawns storm
414 Score score = pe->king_safety<Us>(pos, ksq);
416 // Main king safety evaluation
417 if (kingAttackersCount[Them] > 1 - pos.count<QUEEN>(Them))
419 int kingDanger = unsafeChecks = 0;
421 // Attacked squares defended at most once by our queen or king
422 weak = attackedBy[Them][ALL_PIECES]
424 & (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);
426 // Analyse the safe enemy's checks which are possible on next move
427 safe = ~pos.pieces(Them);
428 safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
430 b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
431 b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
433 // Enemy queen safe checks
434 if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])
435 kingDanger += QueenSafeCheck;
437 b1 &= attackedBy[Them][ROOK];
438 b2 &= attackedBy[Them][BISHOP];
440 // Enemy rooks checks
442 kingDanger += RookSafeCheck;
446 // Enemy bishops checks
448 kingDanger += BishopSafeCheck;
452 // Enemy knights checks
453 b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
455 kingDanger += KnightSafeCheck;
459 // Unsafe or occupied checking squares will also be considered, as long as
460 // the square is in the attacker's mobility area.
461 unsafeChecks &= mobilityArea[Them];
462 pinned = pos.blockers_for_king(Us) & pos.pieces(Us);
464 kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]
465 + 102 * kingAdjacentZoneAttacksCount[Them]
466 + 191 * popcount(kingRing[Us] & weak)
467 + 143 * popcount(pinned | unsafeChecks)
468 - 848 * !pos.count<QUEEN>(Them)
469 - 9 * mg_value(score) / 8
472 // Transform the kingDanger units into a Score, and subtract it from the evaluation
475 int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
476 kingDanger = std::max(0, kingDanger + mobilityDanger);
477 score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
481 Bitboard kf = KingFlank[file_of(ksq)];
483 // Penalty when our king is on a pawnless flank
484 if (!(pos.pieces(PAWN) & kf))
485 score -= PawnlessFlank;
487 // Find the squares that opponent attacks in our king flank, and the squares
488 // which are attacked twice in that flank but not defended by our pawns.
489 b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
490 b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
492 // King tropism, to anticipate slow motion attacks on our king
493 score -= CloseEnemies * (popcount(b1) + popcount(b2));
496 Trace::add(KING, Us, score);
502 // Evaluation::threats() assigns bonuses according to the types of the
503 // attacking and the attacked pieces.
504 template<Tracing T> template<Color Us>
505 Score Evaluation<T>::threats() const {
507 const Color Them = (Us == WHITE ? BLACK : WHITE);
508 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
509 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
511 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
512 Score score = SCORE_ZERO;
514 // Non-pawn enemies attacked by a pawn
515 nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
516 weak = nonPawnEnemies & attackedBy[Us][PAWN];
520 // Our safe or protected pawns
521 b = pos.pieces(Us, PAWN)
522 & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
524 safeThreats = pawn_attacks_bb<Us>(b) & weak;
525 score += ThreatBySafePawn * popcount(safeThreats);
528 // Squares strongly protected by the enemy, either because they defend the
529 // square with a pawn, or because they defend the square twice and we don't.
530 stronglyProtected = attackedBy[Them][PAWN]
531 | (attackedBy2[Them] & ~attackedBy2[Us]);
533 // Non-pawn enemies, strongly protected
534 defended = nonPawnEnemies & stronglyProtected;
536 // Enemies not strongly protected and under our attack
537 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
539 // Bonus according to the kind of attacking pieces
542 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
545 Square s = pop_lsb(&b);
546 score += ThreatByMinor[type_of(pos.piece_on(s))];
547 if (type_of(pos.piece_on(s)) != PAWN)
548 score += ThreatByRank * (int)relative_rank(Them, s);
551 b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
554 Square s = pop_lsb(&b);
555 score += ThreatByRook[type_of(pos.piece_on(s))];
556 if (type_of(pos.piece_on(s)) != PAWN)
557 score += ThreatByRank * (int)relative_rank(Them, s);
560 score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
562 b = weak & attackedBy[Us][KING];
564 score += ThreatByKing[more_than_one(b)];
567 // Bonus for enemy unopposed weak pawns
568 if (pos.pieces(Us, ROOK, QUEEN))
569 score += WeakUnopposedPawn * pe->weak_unopposed(Them);
571 // Find squares where our pawns can push on the next move
572 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
573 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
575 // Keep only the squares which are not completely unsafe
576 b &= ~attackedBy[Them][PAWN]
577 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
579 // Bonus for safe pawn threats on the next move
580 b = pawn_attacks_bb<Us>(b)
582 & ~attackedBy[Us][PAWN];
584 score += ThreatByPawnPush * popcount(b);
586 // Bonus for threats on the next moves against enemy queen
587 if (pos.count<QUEEN>(Them) == 1)
589 Square s = pos.square<QUEEN>(Them);
590 safeThreats = mobilityArea[Us] & ~stronglyProtected;
592 b = attackedBy[Us][KNIGHT] & pos.attacks_from<KNIGHT>(s);
594 score += KnightOnQueen * popcount(b & safeThreats);
596 b = (attackedBy[Us][BISHOP] & pos.attacks_from<BISHOP>(s))
597 | (attackedBy[Us][ROOK ] & pos.attacks_from<ROOK >(s));
599 score += SliderOnQueen * popcount(b & safeThreats & attackedBy2[Us]);
603 Trace::add(THREAT, Us, score);
608 // Evaluation::passed() evaluates the passed pawns and candidate passed
609 // pawns of the given color.
611 template<Tracing T> template<Color Us>
612 Score Evaluation<T>::passed() const {
614 const Color Them = (Us == WHITE ? BLACK : WHITE);
615 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
617 auto king_proximity = [&](Color c, Square s) {
618 return std::min(distance(pos.square<KING>(c), s), 5);
621 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
622 Score score = SCORE_ZERO;
624 b = pe->passed_pawns(Us);
628 Square s = pop_lsb(&b);
630 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
632 bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
633 score -= HinderPassedPawn * popcount(bb);
635 int r = relative_rank(Us, s);
636 int w = PassedDanger[r];
638 Score bonus = PassedRank[r];
642 Square blockSq = s + Up;
644 // Adjust bonus based on the king's proximity
645 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
646 - king_proximity(Us, blockSq) * 2) * w);
648 // If blockSq is not the queening square then consider also a second push
650 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
652 // If the pawn is free to advance, then increase the bonus
653 if (pos.empty(blockSq))
655 // If there is a rook or queen attacking/defending the pawn from behind,
656 // consider all the squaresToQueen. Otherwise consider only the squares
657 // in the pawn's path attacked or occupied by the enemy.
658 defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
660 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
662 if (!(pos.pieces(Us) & bb))
663 defendedSquares &= attackedBy[Us][ALL_PIECES];
665 if (!(pos.pieces(Them) & bb))
666 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
668 // If there aren't any enemy attacks, assign a big bonus. Otherwise
669 // assign a smaller bonus if the block square isn't attacked.
670 int k = !unsafeSquares ? 20 : !(unsafeSquares & blockSq) ? 9 : 0;
672 // If the path to the queen is fully defended, assign a big bonus.
673 // Otherwise assign a smaller bonus if the block square is defended.
674 if (defendedSquares == squaresToQueen)
677 else if (defendedSquares & blockSq)
680 bonus += make_score(k * w, k * w);
682 else if (pos.pieces(Us) & blockSq)
683 bonus += make_score(w + r * 2, w + r * 2);
686 // Scale down bonus for candidate passers which need more than one
687 // pawn push to become passed or have a pawn in front of them.
688 if ( !pos.pawn_passed(Us, s + Up)
689 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
692 score += bonus + PassedFile[file_of(s)];
696 Trace::add(PASSED, Us, score);
702 // Evaluation::space() computes the space evaluation for a given side. The
703 // space evaluation is a simple bonus based on the number of safe squares
704 // available for minor pieces on the central four files on ranks 2--4. Safe
705 // squares one, two or three squares behind a friendly pawn are counted
706 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
707 // improve play on game opening.
709 template<Tracing T> template<Color Us>
710 Score Evaluation<T>::space() const {
712 const Color Them = (Us == WHITE ? BLACK : WHITE);
713 const Bitboard SpaceMask =
714 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
715 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
717 if (pos.non_pawn_material() < SpaceThreshold)
720 // Find the safe squares for our pieces inside the area defined by
721 // SpaceMask. A square is unsafe if it is attacked by an enemy
722 // pawn, or if it is undefended and attacked by an enemy piece.
723 Bitboard safe = SpaceMask
724 & ~pos.pieces(Us, PAWN)
725 & ~attackedBy[Them][PAWN]
726 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
728 // Find all squares which are at most three squares behind some friendly pawn
729 Bitboard behind = pos.pieces(Us, PAWN);
730 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
731 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
733 int bonus = popcount(safe) + popcount(behind & safe);
734 int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
736 Score score = make_score(bonus * weight * weight / 16, 0);
739 Trace::add(SPACE, Us, score);
745 // Evaluation::initiative() computes the initiative correction value
746 // for the position. It is a second order bonus/malus based on the
747 // known attacking/defending status of the players.
750 Score Evaluation<T>::initiative(Value eg) const {
752 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
753 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
755 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
756 && (pos.pieces(PAWN) & KingSide);
758 // Compute the initiative bonus for the attacking side
759 int complexity = 8 * outflanking
760 + 8 * pe->pawn_asymmetry()
761 + 12 * pos.count<PAWN>()
762 + 16 * pawnsOnBothFlanks
765 // Now apply the bonus: note that we find the attacking side by extracting
766 // the sign of the endgame value, and that we carefully cap the bonus so
767 // that the endgame score will never change sign after the bonus.
768 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
771 Trace::add(INITIATIVE, make_score(0, v));
773 return make_score(0, v);
777 // Evaluation::scale_factor() computes the scale factor for the winning side
780 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
782 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
783 int sf = me->scale_factor(pos, strongSide);
785 // If we don't already have an unusual scale factor, check for certain
786 // types of endgames, and use a lower scale for those.
787 if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
789 if (pos.opposite_bishops())
791 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
792 // is almost a draw, in case of KBP vs KB, it is even more a draw.
793 if ( pos.non_pawn_material(WHITE) == BishopValueMg
794 && pos.non_pawn_material(BLACK) == BishopValueMg)
795 sf = more_than_one(pos.pieces(PAWN)) ? 31 : 9;
797 // Endgame with opposite-colored bishops, but also other pieces. Still
798 // a bit drawish, but not as drawish as with only the two bishops.
802 // Endings where weaker side can place his king in front of the enemy's
803 // pawns are drawish.
804 else if ( abs(eg) <= BishopValueEg
805 && pos.count<PAWN>(strongSide) <= 2
806 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
807 sf = 37 + 7 * pos.count<PAWN>(strongSide);
810 return ScaleFactor(sf);
814 // Evaluation::value() is the main function of the class. It computes the various
815 // parts of the evaluation and returns the value of the position from the point
816 // of view of the side to move.
819 Value Evaluation<T>::value() {
821 assert(!pos.checkers());
823 // Probe the material hash table
824 me = Material::probe(pos);
826 // If we have a specialized evaluation function for the current material
827 // configuration, call it and return.
828 if (me->specialized_eval_exists())
829 return me->evaluate(pos);
831 // Initialize score by reading the incrementally updated scores included in
832 // the position object (material + piece square tables) and the material
833 // imbalance. Score is computed internally from the white point of view.
834 Score score = pos.psq_score() + me->imbalance() + Eval::Contempt;
836 // Probe the pawn hash table
837 pe = Pawns::probe(pos);
838 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
840 // Early exit if score is high
841 Value v = (mg_value(score) + eg_value(score)) / 2;
842 if (abs(v) > LazyThreshold)
843 return pos.side_to_move() == WHITE ? v : -v;
845 // Main evaluation begins here
850 // Pieces should be evaluated first (populate attack tables)
851 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
852 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
853 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
854 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
856 score += mobility[WHITE] - mobility[BLACK];
858 score += king< WHITE>() - king< BLACK>()
859 + threats<WHITE>() - threats<BLACK>()
860 + passed< WHITE>() - passed< BLACK>()
861 + space< WHITE>() - space< BLACK>();
863 score += initiative(eg_value(score));
865 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
866 ScaleFactor sf = scale_factor(eg_value(score));
867 v = mg_value(score) * int(me->game_phase())
868 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
870 v /= int(PHASE_MIDGAME);
872 // In case of tracing add all remaining individual evaluation terms
875 Trace::add(MATERIAL, pos.psq_score());
876 Trace::add(IMBALANCE, me->imbalance());
877 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
878 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
879 Trace::add(TOTAL, score);
882 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
889 /// evaluate() is the evaluator for the outer world. It returns a static
890 /// evaluation of the position from the point of view of the side to move.
892 Value Eval::evaluate(const Position& pos) {
893 return Evaluation<NO_TRACE>(pos).value();
897 /// trace() is like evaluate(), but instead of returning a value, it returns
898 /// a string (suitable for outputting to stdout) that contains the detailed
899 /// descriptions and values of each evaluation term. Useful for debugging.
901 std::string Eval::trace(const Position& pos) {
903 std::memset(scores, 0, sizeof(scores));
905 Eval::Contempt = SCORE_ZERO; // Reset any dynamic contempt
907 Value v = Evaluation<TRACE>(pos).value();
909 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
911 std::stringstream ss;
912 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
913 << " Term | White | Black | Total \n"
914 << " | MG EG | MG EG | MG EG \n"
915 << " ------------+-------------+-------------+------------\n"
916 << " Material | " << Term(MATERIAL)
917 << " Imbalance | " << Term(IMBALANCE)
918 << " Initiative | " << Term(INITIATIVE)
919 << " Pawns | " << Term(PAWN)
920 << " Knights | " << Term(KNIGHT)
921 << " Bishops | " << Term(BISHOP)
922 << " Rooks | " << Term(ROOK)
923 << " Queens | " << Term(QUEEN)
924 << " Mobility | " << Term(MOBILITY)
925 << " King safety | " << Term(KING)
926 << " Threats | " << Term(THREAT)
927 << " Passed | " << Term(PASSED)
928 << " Space | " << Term(SPACE)
929 << " ------------+-------------+-------------+------------\n"
930 << " Total | " << Term(TOTAL);
932 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";