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 LongRangedBishop = S( 22, 0);
171 const Score MinorBehindPawn = S( 16, 0);
172 const Score PawnlessFlank = S( 20, 80);
173 const Score RookOnPawn = S( 8, 24);
174 const Score ThreatByPawnPush = S( 47, 26);
175 const Score ThreatByRank = S( 16, 3);
176 const Score ThreatBySafePawn = S(175,168);
177 const Score ThreatOnQueen = S( 42, 21);
178 const Score TrappedBishopA1H1 = S( 50, 50);
179 const Score TrappedRook = S( 92, 0);
180 const Score WeakQueen = S( 50, 10);
181 const Score WeakUnopposedPawn = S( 5, 25);
185 // Evaluation class computes and stores attacks tables and other working data
190 Evaluation() = delete;
191 explicit Evaluation(const Position& p) : pos(p) {}
192 Evaluation& operator=(const Evaluation&) = delete;
196 template<Color Us> void initialize();
197 template<Color Us, PieceType Pt> Score pieces();
198 template<Color Us> Score king() const;
199 template<Color Us> Score threats() const;
200 template<Color Us> Score passed() const;
201 template<Color Us> Score space() const;
202 ScaleFactor scale_factor(Value eg) const;
203 Score initiative(Value eg) const;
208 Bitboard mobilityArea[COLOR_NB];
209 Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
211 // attackedBy[color][piece type] is a bitboard representing all squares
212 // attacked by a given color and piece type. Special "piece types" which
213 // are also calculated are QUEEN_DIAGONAL and ALL_PIECES.
214 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
216 // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
217 // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
218 // pawn or squares attacked by 2 pawns are not explicitly added.
219 Bitboard attackedBy2[COLOR_NB];
221 // kingRing[color] are the squares adjacent to the king, plus (only for a
222 // king on its first rank) the squares two ranks in front. For instance,
223 // if black's king is on g8, kingRing[BLACK] is f8, h8, f7, g7, h7, f6, g6
224 // and h6. It is set to 0 when king safety evaluation is skipped.
225 Bitboard kingRing[COLOR_NB];
227 // kingAttackersCount[color] is the number of pieces of the given color
228 // which attack a square in the kingRing of the enemy king.
229 int kingAttackersCount[COLOR_NB];
231 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
232 // given color which attack a square in the kingRing of the enemy king. The
233 // weights of the individual piece types are given by the elements in the
234 // KingAttackWeights array.
235 int kingAttackersWeight[COLOR_NB];
237 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
238 // color to squares directly adjacent to the enemy king. Pieces which attack
239 // more than one square are counted multiple times. For instance, if there is
240 // a white knight on g5 and black's king is on g8, this white knight adds 2
241 // to kingAdjacentZoneAttacksCount[WHITE].
242 int kingAdjacentZoneAttacksCount[COLOR_NB];
246 // Evaluation::initialize() computes king and pawn attacks, and the king ring
247 // bitboard for a given color. This is done at the beginning of the evaluation.
248 template<Tracing T> template<Color Us>
249 void Evaluation<T>::initialize() {
251 const Color Them = (Us == WHITE ? BLACK : WHITE);
252 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
253 const Direction Down = (Us == WHITE ? SOUTH : NORTH);
254 const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
256 // Find our pawns that are blocked or on the first two ranks
257 Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
259 // Squares occupied by those pawns, by our king, or controlled by enemy pawns
260 // are excluded from the mobility area.
261 mobilityArea[Us] = ~(b | pos.square<KING>(Us) | pe->pawn_attacks(Them));
263 // Initialise attackedBy bitboards for kings and pawns
264 attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
265 attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
266 attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];
267 attackedBy2[Us] = attackedBy[Us][KING] & attackedBy[Us][PAWN];
269 // Init our king safety tables only if we are going to use them
270 if (pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)
272 kingRing[Us] = attackedBy[Us][KING];
273 if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
274 kingRing[Us] |= shift<Up>(kingRing[Us]);
276 kingAttackersCount[Them] = popcount(attackedBy[Us][KING] & pe->pawn_attacks(Them));
277 kingAdjacentZoneAttacksCount[Them] = kingAttackersWeight[Them] = 0;
280 kingRing[Us] = kingAttackersCount[Them] = 0;
284 // Evaluation::pieces() scores pieces of a given color and type
285 template<Tracing T> template<Color Us, PieceType Pt>
286 Score Evaluation<T>::pieces() {
288 const Color Them = (Us == WHITE ? BLACK : WHITE);
289 const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
290 : Rank5BB | Rank4BB | Rank3BB);
291 const Square* pl = pos.squares<Pt>(Us);
295 Score score = SCORE_ZERO;
297 attackedBy[Us][Pt] = 0;
300 attackedBy[Us][QUEEN_DIAGONAL] = 0;
302 while ((s = *pl++) != SQ_NONE)
304 // Find attacked squares, including x-ray attacks for bishops and rooks
305 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
306 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
307 : pos.attacks_from<Pt>(s);
309 if (pos.blockers_for_king(Us) & s)
310 b &= LineBB[pos.square<KING>(Us)][s];
312 attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
313 attackedBy[Us][Pt] |= b;
314 attackedBy[Us][ALL_PIECES] |= b;
317 attackedBy[Us][QUEEN_DIAGONAL] |= b & PseudoAttacks[BISHOP][s];
319 if (b & kingRing[Them])
321 kingAttackersCount[Us]++;
322 kingAttackersWeight[Us] += KingAttackWeights[Pt];
323 kingAdjacentZoneAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
326 int mob = popcount(b & mobilityArea[Us]);
328 mobility[Us] += MobilityBonus[Pt - 2][mob];
330 // Penalty if the piece is far from the king
331 score -= KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));
333 if (Pt == BISHOP || Pt == KNIGHT)
335 // Bonus if piece is on an outpost square or can reach one
336 bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
338 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;
340 else if (bb &= b & ~pos.pieces(Us))
341 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
343 // Bonus when behind a pawn
344 if ( relative_rank(Us, s) < RANK_5
345 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
346 score += MinorBehindPawn;
350 // Penalty according to number of pawns on the same color square as the bishop
351 score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
353 // Bonus for bishop on a long diagonal which can "see" both center squares
354 if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
355 score += LongRangedBishop;
358 // An important Chess960 pattern: A cornered bishop blocked by a friendly
359 // pawn diagonally in front of it is a very serious problem, especially
360 // when that pawn is also blocked.
363 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
365 Direction d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
366 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
367 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
368 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
375 // Bonus for aligning rook with with enemy pawns on the same rank/file
376 if (relative_rank(Us, s) >= RANK_5)
377 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
379 // Bonus for rook on an open or semi-open file
380 if (pe->semiopen_file(Us, file_of(s)))
381 score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];
383 // Penalty when trapped by the king, even more if the king cannot castle
386 File kf = file_of(pos.square<KING>(Us));
387 if ((kf < FILE_E) == (file_of(s) < kf))
388 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
394 // Penalty if any relative pin or discovered attack against the queen
395 Bitboard queenPinners;
396 if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
401 Trace::add(Pt, Us, score);
407 // Evaluation::king() assigns bonuses and penalties to a king of a given color
408 template<Tracing T> template<Color Us>
409 Score Evaluation<T>::king() const {
411 const Color Them = (Us == WHITE ? BLACK : WHITE);
412 const Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
413 : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
415 const Square ksq = pos.square<KING>(Us);
416 Bitboard weak, b, b1, b2, safe, unsafeChecks, pinned;
418 // King shelter and enemy pawns storm
419 Score score = pe->king_safety<Us>(pos, ksq);
421 // Main king safety evaluation
422 if (kingAttackersCount[Them] > 1 - pos.count<QUEEN>(Them))
424 int kingDanger = unsafeChecks = 0;
426 // Attacked squares defended at most once by our queen or king
427 weak = attackedBy[Them][ALL_PIECES]
429 & (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);
431 // Analyse the safe enemy's checks which are possible on next move
432 safe = ~pos.pieces(Them);
433 safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
435 b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
436 b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
438 // Enemy queen safe checks
439 if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])
440 kingDanger += QueenSafeCheck;
442 b1 &= attackedBy[Them][ROOK];
443 b2 &= attackedBy[Them][BISHOP];
445 // Enemy rooks checks
447 kingDanger += RookSafeCheck;
451 // Enemy bishops checks
453 kingDanger += BishopSafeCheck;
457 // Enemy knights checks
458 b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
460 kingDanger += KnightSafeCheck;
464 // Unsafe or occupied checking squares will also be considered, as long as
465 // the square is in the attacker's mobility area.
466 unsafeChecks &= mobilityArea[Them];
467 pinned = pos.blockers_for_king(Us) & pos.pieces(Us);
469 kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]
470 + 102 * kingAdjacentZoneAttacksCount[Them]
471 + 191 * popcount(kingRing[Us] & weak)
472 + 143 * popcount(pinned | unsafeChecks)
473 - 848 * !pos.count<QUEEN>(Them)
474 - 9 * mg_value(score) / 8
477 // Transform the kingDanger units into a Score, and subtract it from the evaluation
480 int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
481 kingDanger = std::max(0, kingDanger + mobilityDanger);
482 score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
485 // Penalty when our king is on a pawnless flank
486 if (!(pos.pieces(PAWN) & KingFlank[file_of(ksq)]))
487 score -= PawnlessFlank;
489 // King tropism: firstly, find attacked squares in our king flank
490 b = attackedBy[Them][ALL_PIECES] & KingFlank[file_of(ksq)] & Camp;
492 assert(((Us == WHITE ? b << 4 : b >> 4) & b) == 0);
493 assert(popcount(Us == WHITE ? b << 4 : b >> 4) == popcount(b));
495 // Secondly, add the squares which are attacked twice in that flank and
496 // which are not defended by our pawns.
497 b = (Us == WHITE ? b << 4 : b >> 4)
498 | (b & attackedBy2[Them] & ~attackedBy[Us][PAWN]);
500 score -= CloseEnemies * popcount(b);
503 Trace::add(KING, Us, score);
509 // Evaluation::threats() assigns bonuses according to the types of the
510 // attacking and the attacked pieces.
511 template<Tracing T> template<Color Us>
512 Score Evaluation<T>::threats() const {
514 const Color Them = (Us == WHITE ? BLACK : WHITE);
515 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
516 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
518 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
519 Score score = SCORE_ZERO;
521 // Non-pawn enemies attacked by a pawn
522 nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
523 weak = nonPawnEnemies & attackedBy[Us][PAWN];
527 // Our safe or protected pawns
528 b = pos.pieces(Us, PAWN)
529 & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
531 safeThreats = pawn_attacks_bb<Us>(b) & weak;
532 score += ThreatBySafePawn * popcount(safeThreats);
535 // Squares strongly protected by the enemy, either because they defend the
536 // square with a pawn, or because they defend the square twice and we don't.
537 stronglyProtected = attackedBy[Them][PAWN]
538 | (attackedBy2[Them] & ~attackedBy2[Us]);
540 // Non-pawn enemies, strongly protected
541 defended = nonPawnEnemies & stronglyProtected;
543 // Enemies not strongly protected and under our attack
544 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
546 // Bonus according to the kind of attacking pieces
549 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
552 Square s = pop_lsb(&b);
553 score += ThreatByMinor[type_of(pos.piece_on(s))];
554 if (type_of(pos.piece_on(s)) != PAWN)
555 score += ThreatByRank * (int)relative_rank(Them, s);
558 b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
561 Square s = pop_lsb(&b);
562 score += ThreatByRook[type_of(pos.piece_on(s))];
563 if (type_of(pos.piece_on(s)) != PAWN)
564 score += ThreatByRank * (int)relative_rank(Them, s);
567 score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
569 b = weak & attackedBy[Us][KING];
571 score += ThreatByKing[more_than_one(b)];
574 // Bonus for enemy unopposed weak pawns
575 if (pos.pieces(Us, ROOK, QUEEN))
576 score += WeakUnopposedPawn * pe->weak_unopposed(Them);
578 // Find squares where our pawns can push on the next move
579 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
580 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
582 // Keep only the squares which are not completely unsafe
583 b &= ~attackedBy[Them][PAWN]
584 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
586 // Bonus for safe pawn threats on the next move
587 b = pawn_attacks_bb<Us>(b)
589 & ~attackedBy[Us][PAWN];
591 score += ThreatByPawnPush * popcount(b);
593 // Bonus for safe slider threats on the next move toward enemy queen
594 safeThreats = ~pos.pieces(Us) & ~attackedBy2[Them] & attackedBy2[Us];
595 b = (attackedBy[Us][BISHOP] & attackedBy[Them][QUEEN_DIAGONAL])
596 | (attackedBy[Us][ROOK ] & attackedBy[Them][QUEEN] & ~attackedBy[Them][QUEEN_DIAGONAL]);
598 score += ThreatOnQueen * popcount(b & safeThreats);
601 Trace::add(THREAT, Us, score);
606 // Evaluation::passed() evaluates the passed pawns and candidate passed
607 // pawns of the given color.
609 template<Tracing T> template<Color Us>
610 Score Evaluation<T>::passed() const {
612 const Color Them = (Us == WHITE ? BLACK : WHITE);
613 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
615 auto king_proximity = [&](Color c, Square s) {
616 return std::min(distance(pos.square<KING>(c), s), 5);
619 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
620 Score score = SCORE_ZERO;
622 b = pe->passed_pawns(Us);
626 Square s = pop_lsb(&b);
628 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
630 bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
631 score -= HinderPassedPawn * popcount(bb);
633 int r = relative_rank(Us, s);
634 int w = PassedDanger[r];
636 Score bonus = PassedRank[r];
640 Square blockSq = s + Up;
642 // Adjust bonus based on the king's proximity
643 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
644 - king_proximity(Us, blockSq) * 2) * w);
646 // If blockSq is not the queening square then consider also a second push
648 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
650 // If the pawn is free to advance, then increase the bonus
651 if (pos.empty(blockSq))
653 // If there is a rook or queen attacking/defending the pawn from behind,
654 // consider all the squaresToQueen. Otherwise consider only the squares
655 // in the pawn's path attacked or occupied by the enemy.
656 defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
658 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
660 if (!(pos.pieces(Us) & bb))
661 defendedSquares &= attackedBy[Us][ALL_PIECES];
663 if (!(pos.pieces(Them) & bb))
664 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
666 // If there aren't any enemy attacks, assign a big bonus. Otherwise
667 // assign a smaller bonus if the block square isn't attacked.
668 int k = !unsafeSquares ? 20 : !(unsafeSquares & blockSq) ? 9 : 0;
670 // If the path to the queen is fully defended, assign a big bonus.
671 // Otherwise assign a smaller bonus if the block square is defended.
672 if (defendedSquares == squaresToQueen)
675 else if (defendedSquares & blockSq)
678 bonus += make_score(k * w, k * w);
680 else if (pos.pieces(Us) & blockSq)
681 bonus += make_score(w + r * 2, w + r * 2);
684 // Scale down bonus for candidate passers which need more than one
685 // pawn push to become passed or have a pawn in front of them.
686 if ( !pos.pawn_passed(Us, s + Up)
687 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
690 score += bonus + PassedFile[file_of(s)];
694 Trace::add(PASSED, Us, score);
700 // Evaluation::space() computes the space evaluation for a given side. The
701 // space evaluation is a simple bonus based on the number of safe squares
702 // available for minor pieces on the central four files on ranks 2--4. Safe
703 // squares one, two or three squares behind a friendly pawn are counted
704 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
705 // improve play on game opening.
707 template<Tracing T> template<Color Us>
708 Score Evaluation<T>::space() const {
710 const Color Them = (Us == WHITE ? BLACK : WHITE);
711 const Bitboard SpaceMask =
712 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
713 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
715 if (pos.non_pawn_material() < SpaceThreshold)
718 // Find the safe squares for our pieces inside the area defined by
719 // SpaceMask. A square is unsafe if it is attacked by an enemy
720 // pawn, or if it is undefended and attacked by an enemy piece.
721 Bitboard safe = SpaceMask
722 & ~pos.pieces(Us, PAWN)
723 & ~attackedBy[Them][PAWN]
724 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
726 // Find all squares which are at most three squares behind some friendly pawn
727 Bitboard behind = pos.pieces(Us, PAWN);
728 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
729 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
731 // Since SpaceMask[Us] is fully on our half of the board...
732 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
734 // ...count safe + (behind & safe) with a single popcount.
735 int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
736 int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
737 Score score = make_score(bonus * weight * weight / 16, 0);
740 Trace::add(SPACE, Us, score);
746 // Evaluation::initiative() computes the initiative correction value
747 // for the position. It is a second order bonus/malus based on the
748 // known attacking/defending status of the players.
751 Score Evaluation<T>::initiative(Value eg) const {
753 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
754 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
756 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
757 && (pos.pieces(PAWN) & KingSide);
759 // Compute the initiative bonus for the attacking side
760 int complexity = 8 * outflanking
761 + 8 * pe->pawn_asymmetry()
762 + 12 * pos.count<PAWN>()
763 + 16 * pawnsOnBothFlanks
766 // Now apply the bonus: note that we find the attacking side by extracting
767 // the sign of the endgame value, and that we carefully cap the bonus so
768 // that the endgame score will never change sign after the bonus.
769 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
772 Trace::add(INITIATIVE, make_score(0, v));
774 return make_score(0, v);
778 // Evaluation::scale_factor() computes the scale factor for the winning side
781 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
783 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
784 int sf = me->scale_factor(pos, strongSide);
786 // If we don't already have an unusual scale factor, check for certain
787 // types of endgames, and use a lower scale for those.
788 if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
790 if (pos.opposite_bishops())
792 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
793 // is almost a draw, in case of KBP vs KB, it is even more a draw.
794 if ( pos.non_pawn_material(WHITE) == BishopValueMg
795 && pos.non_pawn_material(BLACK) == BishopValueMg)
796 sf = more_than_one(pos.pieces(PAWN)) ? 31 : 9;
798 // Endgame with opposite-colored bishops, but also other pieces. Still
799 // a bit drawish, but not as drawish as with only the two bishops.
803 // Endings where weaker side can place his king in front of the enemy's
804 // pawns are drawish.
805 else if ( abs(eg) <= BishopValueEg
806 && pos.count<PAWN>(strongSide) <= 2
807 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
808 sf = 37 + 7 * pos.count<PAWN>(strongSide);
811 return ScaleFactor(sf);
815 // Evaluation::value() is the main function of the class. It computes the various
816 // parts of the evaluation and returns the value of the position from the point
817 // of view of the side to move.
820 Value Evaluation<T>::value() {
822 assert(!pos.checkers());
824 // Probe the material hash table
825 me = Material::probe(pos);
827 // If we have a specialized evaluation function for the current material
828 // configuration, call it and return.
829 if (me->specialized_eval_exists())
830 return me->evaluate(pos);
832 // Initialize score by reading the incrementally updated scores included in
833 // the position object (material + piece square tables) and the material
834 // imbalance. Score is computed internally from the white point of view.
835 Score score = pos.psq_score() + me->imbalance() + Eval::Contempt;
837 // Probe the pawn hash table
838 pe = Pawns::probe(pos);
839 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
841 // Early exit if score is high
842 Value v = (mg_value(score) + eg_value(score)) / 2;
843 if (abs(v) > LazyThreshold)
844 return pos.side_to_move() == WHITE ? v : -v;
846 // Main evaluation begins here
851 // Pieces should be evaluated first (populate attack tables)
852 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
853 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
854 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
855 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
857 score += mobility[WHITE] - mobility[BLACK];
859 score += king< WHITE>() - king< BLACK>()
860 + threats<WHITE>() - threats<BLACK>()
861 + passed< WHITE>() - passed< BLACK>()
862 + space< WHITE>() - space< BLACK>();
864 score += initiative(eg_value(score));
866 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
867 ScaleFactor sf = scale_factor(eg_value(score));
868 v = mg_value(score) * int(me->game_phase())
869 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
871 v /= int(PHASE_MIDGAME);
873 // In case of tracing add all remaining individual evaluation terms
876 Trace::add(MATERIAL, pos.psq_score());
877 Trace::add(IMBALANCE, me->imbalance());
878 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
879 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
880 Trace::add(TOTAL, score);
883 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
890 /// evaluate() is the evaluator for the outer world. It returns a static
891 /// evaluation of the position from the point of view of the side to move.
893 Value Eval::evaluate(const Position& pos) {
894 return Evaluation<NO_TRACE>(pos).value();
898 /// trace() is like evaluate(), but instead of returning a value, it returns
899 /// a string (suitable for outputting to stdout) that contains the detailed
900 /// descriptions and values of each evaluation term. Useful for debugging.
902 std::string Eval::trace(const Position& pos) {
904 std::memset(scores, 0, sizeof(scores));
906 Eval::Contempt = SCORE_ZERO; // Reset any dynamic contempt
908 Value v = Evaluation<TRACE>(pos).value();
910 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
912 std::stringstream ss;
913 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
914 << " Term | White | Black | Total \n"
915 << " | MG EG | MG EG | MG EG \n"
916 << " ------------+-------------+-------------+------------\n"
917 << " Material | " << Term(MATERIAL)
918 << " Imbalance | " << Term(IMBALANCE)
919 << " Initiative | " << Term(INITIATIVE)
920 << " Pawns | " << Term(PAWN)
921 << " Knights | " << Term(KNIGHT)
922 << " Bishops | " << Term(BISHOP)
923 << " Rooks | " << Term(ROOK)
924 << " Queens | " << Term(QUEEN)
925 << " Mobility | " << Term(MOBILITY)
926 << " King safety | " << Term(KING)
927 << " Threats | " << Term(THREAT)
928 << " Passed | " << Term(PASSED)
929 << " Space | " << Term(SPACE)
930 << " ------------+-------------+-------------+------------\n"
931 << " Total | " << Term(TOTAL);
933 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";