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);
486 Bitboard kf = KingFlank[file_of(ksq)];
488 // Penalty when our king is on a pawnless flank
489 if (!(pos.pieces(PAWN) & kf))
490 score -= PawnlessFlank;
492 // Find the squares that opponent attacks in our king flank, and the squares
493 // which are attacked twice in that flank but not defended by our pawns.
494 b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
495 b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
497 // King tropism, to anticipate slow motion attacks on our king
498 score -= CloseEnemies * (popcount(b1) + popcount(b2));
501 Trace::add(KING, Us, score);
507 // Evaluation::threats() assigns bonuses according to the types of the
508 // attacking and the attacked pieces.
509 template<Tracing T> template<Color Us>
510 Score Evaluation<T>::threats() const {
512 const Color Them = (Us == WHITE ? BLACK : WHITE);
513 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
514 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
516 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
517 Score score = SCORE_ZERO;
519 // Non-pawn enemies attacked by a pawn
520 nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
521 weak = nonPawnEnemies & attackedBy[Us][PAWN];
525 // Our safe or protected pawns
526 b = pos.pieces(Us, PAWN)
527 & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
529 safeThreats = pawn_attacks_bb<Us>(b) & weak;
530 score += ThreatBySafePawn * popcount(safeThreats);
533 // Squares strongly protected by the enemy, either because they defend the
534 // square with a pawn, or because they defend the square twice and we don't.
535 stronglyProtected = attackedBy[Them][PAWN]
536 | (attackedBy2[Them] & ~attackedBy2[Us]);
538 // Non-pawn enemies, strongly protected
539 defended = nonPawnEnemies & stronglyProtected;
541 // Enemies not strongly protected and under our attack
542 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
544 // Bonus according to the kind of attacking pieces
547 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
550 Square s = pop_lsb(&b);
551 score += ThreatByMinor[type_of(pos.piece_on(s))];
552 if (type_of(pos.piece_on(s)) != PAWN)
553 score += ThreatByRank * (int)relative_rank(Them, s);
556 b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
559 Square s = pop_lsb(&b);
560 score += ThreatByRook[type_of(pos.piece_on(s))];
561 if (type_of(pos.piece_on(s)) != PAWN)
562 score += ThreatByRank * (int)relative_rank(Them, s);
565 score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
567 b = weak & attackedBy[Us][KING];
569 score += ThreatByKing[more_than_one(b)];
572 // Bonus for enemy unopposed weak pawns
573 if (pos.pieces(Us, ROOK, QUEEN))
574 score += WeakUnopposedPawn * pe->weak_unopposed(Them);
576 // Find squares where our pawns can push on the next move
577 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
578 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
580 // Keep only the squares which are not completely unsafe
581 b &= ~attackedBy[Them][PAWN]
582 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
584 // Bonus for safe pawn threats on the next move
585 b = pawn_attacks_bb<Us>(b)
587 & ~attackedBy[Us][PAWN];
589 score += ThreatByPawnPush * popcount(b);
591 // Bonus for safe slider threats on the next move toward enemy queen
592 safeThreats = ~pos.pieces(Us) & ~attackedBy2[Them] & attackedBy2[Us];
593 b = (attackedBy[Us][BISHOP] & attackedBy[Them][QUEEN_DIAGONAL])
594 | (attackedBy[Us][ROOK ] & attackedBy[Them][QUEEN] & ~attackedBy[Them][QUEEN_DIAGONAL]);
596 score += ThreatOnQueen * popcount(b & safeThreats);
599 Trace::add(THREAT, Us, score);
604 // Evaluation::passed() evaluates the passed pawns and candidate passed
605 // pawns of the given color.
607 template<Tracing T> template<Color Us>
608 Score Evaluation<T>::passed() const {
610 const Color Them = (Us == WHITE ? BLACK : WHITE);
611 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
613 auto king_proximity = [&](Color c, Square s) {
614 return std::min(distance(pos.square<KING>(c), s), 5);
617 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
618 Score score = SCORE_ZERO;
620 b = pe->passed_pawns(Us);
624 Square s = pop_lsb(&b);
626 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
628 bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
629 score -= HinderPassedPawn * popcount(bb);
631 int r = relative_rank(Us, s);
632 int w = PassedDanger[r];
634 Score bonus = PassedRank[r];
638 Square blockSq = s + Up;
640 // Adjust bonus based on the king's proximity
641 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
642 - king_proximity(Us, blockSq) * 2) * w);
644 // If blockSq is not the queening square then consider also a second push
646 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
648 // If the pawn is free to advance, then increase the bonus
649 if (pos.empty(blockSq))
651 // If there is a rook or queen attacking/defending the pawn from behind,
652 // consider all the squaresToQueen. Otherwise consider only the squares
653 // in the pawn's path attacked or occupied by the enemy.
654 defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
656 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
658 if (!(pos.pieces(Us) & bb))
659 defendedSquares &= attackedBy[Us][ALL_PIECES];
661 if (!(pos.pieces(Them) & bb))
662 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
664 // If there aren't any enemy attacks, assign a big bonus. Otherwise
665 // assign a smaller bonus if the block square isn't attacked.
666 int k = !unsafeSquares ? 20 : !(unsafeSquares & blockSq) ? 9 : 0;
668 // If the path to the queen is fully defended, assign a big bonus.
669 // Otherwise assign a smaller bonus if the block square is defended.
670 if (defendedSquares == squaresToQueen)
673 else if (defendedSquares & blockSq)
676 bonus += make_score(k * w, k * w);
678 else if (pos.pieces(Us) & blockSq)
679 bonus += make_score(w + r * 2, w + r * 2);
682 // Scale down bonus for candidate passers which need more than one
683 // pawn push to become passed or have a pawn in front of them.
684 if ( !pos.pawn_passed(Us, s + Up)
685 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
688 score += bonus + PassedFile[file_of(s)];
692 Trace::add(PASSED, Us, score);
698 // Evaluation::space() computes the space evaluation for a given side. The
699 // space evaluation is a simple bonus based on the number of safe squares
700 // available for minor pieces on the central four files on ranks 2--4. Safe
701 // squares one, two or three squares behind a friendly pawn are counted
702 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
703 // improve play on game opening.
705 template<Tracing T> template<Color Us>
706 Score Evaluation<T>::space() const {
708 const Color Them = (Us == WHITE ? BLACK : WHITE);
709 const Bitboard SpaceMask =
710 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
711 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
713 if (pos.non_pawn_material() < SpaceThreshold)
716 // Find the safe squares for our pieces inside the area defined by
717 // SpaceMask. A square is unsafe if it is attacked by an enemy
718 // pawn, or if it is undefended and attacked by an enemy piece.
719 Bitboard safe = SpaceMask
720 & ~pos.pieces(Us, PAWN)
721 & ~attackedBy[Them][PAWN]
722 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
724 // Find all squares which are at most three squares behind some friendly pawn
725 Bitboard behind = pos.pieces(Us, PAWN);
726 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
727 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
729 // Since SpaceMask[Us] is fully on our half of the board...
730 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
732 // ...count safe + (behind & safe) with a single popcount.
733 int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
734 int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
735 Score score = make_score(bonus * weight * weight / 16, 0);
738 Trace::add(SPACE, Us, score);
744 // Evaluation::initiative() computes the initiative correction value
745 // for the position. It is a second order bonus/malus based on the
746 // known attacking/defending status of the players.
749 Score Evaluation<T>::initiative(Value eg) const {
751 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
752 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
754 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
755 && (pos.pieces(PAWN) & KingSide);
757 // Compute the initiative bonus for the attacking side
758 int complexity = 8 * outflanking
759 + 8 * pe->pawn_asymmetry()
760 + 12 * pos.count<PAWN>()
761 + 16 * pawnsOnBothFlanks
764 // Now apply the bonus: note that we find the attacking side by extracting
765 // the sign of the endgame value, and that we carefully cap the bonus so
766 // that the endgame score will never change sign after the bonus.
767 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
770 Trace::add(INITIATIVE, make_score(0, v));
772 return make_score(0, v);
776 // Evaluation::scale_factor() computes the scale factor for the winning side
779 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
781 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
782 int sf = me->scale_factor(pos, strongSide);
784 // If we don't already have an unusual scale factor, check for certain
785 // types of endgames, and use a lower scale for those.
786 if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
788 if (pos.opposite_bishops())
790 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
791 // is almost a draw, in case of KBP vs KB, it is even more a draw.
792 if ( pos.non_pawn_material(WHITE) == BishopValueMg
793 && pos.non_pawn_material(BLACK) == BishopValueMg)
794 sf = more_than_one(pos.pieces(PAWN)) ? 31 : 9;
796 // Endgame with opposite-colored bishops, but also other pieces. Still
797 // a bit drawish, but not as drawish as with only the two bishops.
801 // Endings where weaker side can place his king in front of the enemy's
802 // pawns are drawish.
803 else if ( abs(eg) <= BishopValueEg
804 && pos.count<PAWN>(strongSide) <= 2
805 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
806 sf = 37 + 7 * pos.count<PAWN>(strongSide);
809 return ScaleFactor(sf);
813 // Evaluation::value() is the main function of the class. It computes the various
814 // parts of the evaluation and returns the value of the position from the point
815 // of view of the side to move.
818 Value Evaluation<T>::value() {
820 assert(!pos.checkers());
822 // Probe the material hash table
823 me = Material::probe(pos);
825 // If we have a specialized evaluation function for the current material
826 // configuration, call it and return.
827 if (me->specialized_eval_exists())
828 return me->evaluate(pos);
830 // Initialize score by reading the incrementally updated scores included in
831 // the position object (material + piece square tables) and the material
832 // imbalance. Score is computed internally from the white point of view.
833 Score score = pos.psq_score() + me->imbalance() + Eval::Contempt;
835 // Probe the pawn hash table
836 pe = Pawns::probe(pos);
837 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
839 // Early exit if score is high
840 Value v = (mg_value(score) + eg_value(score)) / 2;
841 if (abs(v) > LazyThreshold)
842 return pos.side_to_move() == WHITE ? v : -v;
844 // Main evaluation begins here
849 // Pieces should be evaluated first (populate attack tables)
850 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
851 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
852 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
853 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
855 score += mobility[WHITE] - mobility[BLACK];
857 score += king< WHITE>() - king< BLACK>()
858 + threats<WHITE>() - threats<BLACK>()
859 + passed< WHITE>() - passed< BLACK>()
860 + space< WHITE>() - space< BLACK>();
862 score += initiative(eg_value(score));
864 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
865 ScaleFactor sf = scale_factor(eg_value(score));
866 v = mg_value(score) * int(me->game_phase())
867 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
869 v /= int(PHASE_MIDGAME);
871 // In case of tracing add all remaining individual evaluation terms
874 Trace::add(MATERIAL, pos.psq_score());
875 Trace::add(IMBALANCE, me->imbalance());
876 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
877 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
878 Trace::add(TOTAL, score);
881 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
888 /// evaluate() is the evaluator for the outer world. It returns a static
889 /// evaluation of the position from the point of view of the side to move.
891 Value Eval::evaluate(const Position& pos) {
892 return Evaluation<NO_TRACE>(pos).value();
896 /// trace() is like evaluate(), but instead of returning a value, it returns
897 /// a string (suitable for outputting to stdout) that contains the detailed
898 /// descriptions and values of each evaluation term. Useful for debugging.
900 std::string Eval::trace(const Position& pos) {
902 std::memset(scores, 0, sizeof(scores));
904 Eval::Contempt = SCORE_ZERO; // Reset any dynamic contempt
906 Value v = Evaluation<TRACE>(pos).value();
908 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
910 std::stringstream ss;
911 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
912 << " Term | White | Black | Total \n"
913 << " | MG EG | MG EG | MG EG \n"
914 << " ------------+-------------+-------------+------------\n"
915 << " Material | " << Term(MATERIAL)
916 << " Imbalance | " << Term(IMBALANCE)
917 << " Initiative | " << Term(INITIATIVE)
918 << " Pawns | " << Term(PAWN)
919 << " Knights | " << Term(KNIGHT)
920 << " Bishops | " << Term(BISHOP)
921 << " Rooks | " << Term(ROOK)
922 << " Queens | " << Term(QUEEN)
923 << " Mobility | " << Term(MOBILITY)
924 << " King safety | " << Term(KING)
925 << " Threats | " << Term(THREAT)
926 << " Passed | " << Term(PASSED)
927 << " Space | " << Term(SPACE)
928 << " ------------+-------------+-------------+------------\n"
929 << " Total | " << Term(TOTAL);
931 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";