2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <cstring> // For std::memset
35 enum Tracing { NO_TRACE, TRACE };
37 enum Term { // The first 8 entries are reserved for PieceType
38 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, INITIATIVE, TOTAL, TERM_NB
41 Score scores[TERM_NB][COLOR_NB];
43 double to_cp(Value v) { return double(v) / PawnValueEg; }
45 void add(int idx, Color c, Score s) {
49 void add(int idx, Score w, Score b = SCORE_ZERO) {
50 scores[idx][WHITE] = w;
51 scores[idx][BLACK] = b;
54 std::ostream& operator<<(std::ostream& os, Score s) {
55 os << std::setw(5) << to_cp(mg_value(s)) << " "
56 << std::setw(5) << to_cp(eg_value(s));
60 std::ostream& operator<<(std::ostream& os, Term t) {
62 if (t == MATERIAL || t == IMBALANCE || t == INITIATIVE || t == TOTAL)
63 os << " ---- ----" << " | " << " ---- ----";
65 os << scores[t][WHITE] << " | " << scores[t][BLACK];
67 os << " | " << scores[t][WHITE] - scores[t][BLACK] << "\n";
72 using namespace Trace;
76 // Threshold for lazy and space evaluation
77 constexpr Value LazyThreshold = Value(1400);
78 constexpr Value SpaceThreshold = Value(12222);
80 // KingAttackWeights[PieceType] contains king attack weights by piece type
81 constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 77, 55, 44, 10 };
83 // Penalties for enemy's safe checks
84 constexpr int QueenSafeCheck = 780;
85 constexpr int RookSafeCheck = 1080;
86 constexpr int BishopSafeCheck = 635;
87 constexpr int KnightSafeCheck = 790;
89 #define S(mg, eg) make_score(mg, eg)
91 // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
92 // indexed by piece type and number of attacked squares in the mobility area.
93 constexpr Score MobilityBonus[][32] = {
94 { S(-62,-81), S(-53,-56), S(-12,-30), S( -4,-14), S( 3, 8), S( 13, 15), // Knights
95 S( 22, 23), S( 28, 27), S( 33, 33) },
96 { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
97 S( 55, 54), S( 63, 57), S( 63, 65), S( 68, 73), S( 81, 78), S( 81, 86),
98 S( 91, 88), S( 98, 97) },
99 { S(-58,-76), S(-27,-18), S(-15, 28), S(-10, 55), S( -5, 69), S( -2, 82), // Rooks
100 S( 9,112), S( 16,118), S( 30,132), S( 29,142), S( 32,155), S( 38,165),
101 S( 46,166), S( 48,169), S( 58,171) },
102 { S(-39,-36), S(-21,-15), S( 3, 8), S( 3, 18), S( 14, 34), S( 22, 54), // Queens
103 S( 28, 61), S( 41, 73), S( 43, 79), S( 48, 92), S( 56, 94), S( 60,104),
104 S( 60,113), S( 66,120), S( 67,123), S( 70,126), S( 71,133), S( 73,136),
105 S( 79,140), S( 88,143), S( 88,148), S( 99,166), S(102,170), S(102,175),
106 S(106,184), S(109,191), S(113,206), S(116,212) }
109 // RookOnFile[semiopen/open] contains bonuses for each rook when there is
110 // no (friendly) pawn on the rook file.
111 constexpr Score RookOnFile[] = { S(18, 7), S(44, 20) };
113 // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
114 // which piece type attacks which one. Attacks on lesser pieces which are
115 // pawn-defended are not considered.
116 constexpr Score ThreatByMinor[PIECE_TYPE_NB] = {
117 S(0, 0), S(0, 31), S(39, 42), S(57, 44), S(68, 112), S(62, 120)
120 constexpr Score ThreatByRook[PIECE_TYPE_NB] = {
121 S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(51, 38)
124 // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
125 constexpr Score PassedRank[RANK_NB] = {
126 S(0, 0), S(5, 18), S(12, 23), S(10, 31), S(57, 62), S(163, 167), S(271, 250)
129 // PassedFile[File] contains a bonus according to the file of a passed pawn
130 constexpr Score PassedFile[FILE_NB] = {
131 S( -1, 7), S( 0, 9), S(-9, -8), S(-30,-14),
132 S(-30,-14), S(-9, -8), S( 0, 9), S( -1, 7)
135 // Assorted bonuses and penalties
136 constexpr Score AttacksOnSpaceArea = S( 4, 0);
137 constexpr Score BishopPawns = S( 3, 7);
138 constexpr Score CorneredBishop = S( 50, 50);
139 constexpr Score FlankAttacks = S( 8, 0);
140 constexpr Score Hanging = S( 69, 36);
141 constexpr Score KingProtector = S( 7, 8);
142 constexpr Score KnightOnQueen = S( 16, 12);
143 constexpr Score LongDiagonalBishop = S( 45, 0);
144 constexpr Score MinorBehindPawn = S( 18, 3);
145 constexpr Score Outpost = S( 36, 12);
146 constexpr Score PawnlessFlank = S( 17, 95);
147 constexpr Score RestrictedPiece = S( 7, 7);
148 constexpr Score RookOnPawn = S( 10, 32);
149 constexpr Score SliderOnQueen = S( 59, 18);
150 constexpr Score ThreatByKing = S( 24, 89);
151 constexpr Score ThreatByPawnPush = S( 48, 39);
152 constexpr Score ThreatByRank = S( 13, 0);
153 constexpr Score ThreatBySafePawn = S(173, 94);
154 constexpr Score TrappedRook = S( 47, 4);
155 constexpr Score WeakQueen = S( 49, 15);
159 // Evaluation class computes and stores attacks tables and other working data
164 Evaluation() = delete;
165 explicit Evaluation(const Position& p) : pos(p) {}
166 Evaluation& operator=(const Evaluation&) = delete;
170 template<Color Us> void initialize();
171 template<Color Us, PieceType Pt> Score pieces();
172 template<Color Us> Score king() const;
173 template<Color Us> Score threats() const;
174 template<Color Us> Score passed() const;
175 template<Color Us> Score space() const;
176 ScaleFactor scale_factor(Value eg) const;
177 Score initiative(Value eg) const;
182 Bitboard mobilityArea[COLOR_NB];
183 Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
185 // attackedBy[color][piece type] is a bitboard representing all squares
186 // attacked by a given color and piece type. Special "piece types" which
187 // is also calculated is ALL_PIECES.
188 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
190 // attackedBy2[color] are the squares attacked by at least 2 units of a given
191 // color, including x-rays. But diagonal x-rays through pawns are not computed.
192 Bitboard attackedBy2[COLOR_NB];
194 // kingRing[color] are the squares adjacent to the king plus some other
195 // very near squares, depending on king position.
196 Bitboard kingRing[COLOR_NB];
198 // kingAttackersCount[color] is the number of pieces of the given color
199 // which attack a square in the kingRing of the enemy king.
200 int kingAttackersCount[COLOR_NB];
202 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of
203 // the given color which attack a square in the kingRing of the enemy king.
204 // The weights of the individual piece types are given by the elements in
205 // the KingAttackWeights array.
206 int kingAttackersWeight[COLOR_NB];
208 // kingAttacksCount[color] is the number of attacks by the given color to
209 // squares directly adjacent to the enemy king. Pieces which attack more
210 // than one square are counted multiple times. For instance, if there is
211 // a white knight on g5 and black's king is on g8, this white knight adds 2
212 // to kingAttacksCount[WHITE].
213 int kingAttacksCount[COLOR_NB];
217 // Evaluation::initialize() computes king and pawn attacks, and the king ring
218 // bitboard for a given color. This is done at the beginning of the evaluation.
219 template<Tracing T> template<Color Us>
220 void Evaluation<T>::initialize() {
222 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
223 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
224 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
225 constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
227 const Square ksq = pos.square<KING>(Us);
229 Bitboard dblAttackByPawn = pawn_double_attacks_bb<Us>(pos.pieces(Us, PAWN));
231 // Find our pawns that are blocked or on the first two ranks
232 Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
234 // Squares occupied by those pawns, by our king or queen or controlled by
235 // enemy pawns are excluded from the mobility area.
236 mobilityArea[Us] = ~(b | pos.pieces(Us, KING, QUEEN) | pe->pawn_attacks(Them));
238 // Initialize attackedBy[] for king and pawns
239 attackedBy[Us][KING] = pos.attacks_from<KING>(ksq);
240 attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
241 attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];
242 attackedBy2[Us] = dblAttackByPawn | (attackedBy[Us][KING] & attackedBy[Us][PAWN]);
244 // Init our king safety tables
245 kingRing[Us] = attackedBy[Us][KING];
246 if (relative_rank(Us, ksq) == RANK_1)
247 kingRing[Us] |= shift<Up>(kingRing[Us]);
249 if (file_of(ksq) == FILE_H)
250 kingRing[Us] |= shift<WEST>(kingRing[Us]);
252 else if (file_of(ksq) == FILE_A)
253 kingRing[Us] |= shift<EAST>(kingRing[Us]);
255 kingAttackersCount[Them] = popcount(kingRing[Us] & pe->pawn_attacks(Them));
256 kingAttacksCount[Them] = kingAttackersWeight[Them] = 0;
258 // Remove from kingRing[] the squares defended by two pawns
259 kingRing[Us] &= ~dblAttackByPawn;
263 // Evaluation::pieces() scores pieces of a given color and type
264 template<Tracing T> template<Color Us, PieceType Pt>
265 Score Evaluation<T>::pieces() {
267 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
268 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
269 constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
270 : Rank5BB | Rank4BB | Rank3BB);
271 const Square* pl = pos.squares<Pt>(Us);
274 Score score = SCORE_ZERO;
276 attackedBy[Us][Pt] = 0;
278 for (Square s = *pl; s != SQ_NONE; s = *++pl)
280 // Find attacked squares, including x-ray attacks for bishops and rooks
281 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
282 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
283 : pos.attacks_from<Pt>(s);
285 if (pos.blockers_for_king(Us) & s)
286 b &= LineBB[pos.square<KING>(Us)][s];
288 attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
289 attackedBy[Us][Pt] |= b;
290 attackedBy[Us][ALL_PIECES] |= b;
292 if (b & kingRing[Them])
294 kingAttackersCount[Us]++;
295 kingAttackersWeight[Us] += KingAttackWeights[Pt];
296 kingAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
299 int mob = popcount(b & mobilityArea[Us]);
301 mobility[Us] += MobilityBonus[Pt - 2][mob];
303 if (Pt == BISHOP || Pt == KNIGHT)
305 // Bonus if piece is on an outpost square or can reach one
306 bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them);
308 score += Outpost * (Pt == KNIGHT ? 2 : 1);
310 else if (bb & b & ~pos.pieces(Us))
311 score += Outpost / (Pt == KNIGHT ? 1 : 2);
313 // Knight and Bishop bonus for being right behind a pawn
314 if (shift<Down>(pos.pieces(PAWN)) & s)
315 score += MinorBehindPawn;
317 // Penalty if the piece is far from the king
318 score -= KingProtector * distance(s, pos.square<KING>(Us));
322 // Penalty according to number of pawns on the same color square as the
323 // bishop, bigger when the center files are blocked with pawns.
324 Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());
326 score -= BishopPawns * pos.pawns_on_same_color_squares(Us, s)
327 * (1 + popcount(blocked & CenterFiles));
329 // Bonus for bishop on a long diagonal which can "see" both center squares
330 if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))
331 score += LongDiagonalBishop;
334 // An important Chess960 pattern: A cornered bishop blocked by a friendly
335 // pawn diagonally in front of it is a very serious problem, especially
336 // when that pawn is also blocked.
339 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
341 Direction d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
342 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
343 score -= !pos.empty(s + d + pawn_push(Us)) ? CorneredBishop * 4
344 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? CorneredBishop * 2
351 // Bonus for aligning rook with enemy pawns on the same rank/file
352 if (relative_rank(Us, s) >= RANK_5)
353 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
355 // Bonus for rook on an open or semi-open file
356 if (pos.is_on_semiopen_file(Us, s))
357 score += RookOnFile[bool(pos.is_on_semiopen_file(Them, s))];
359 // Penalty when trapped by the king, even more if the king cannot castle
362 File kf = file_of(pos.square<KING>(Us));
363 if ((kf < FILE_E) == (file_of(s) < kf))
364 score -= TrappedRook * (1 + !pos.castling_rights(Us));
370 // Penalty if any relative pin or discovered attack against the queen
371 Bitboard queenPinners;
372 if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
377 Trace::add(Pt, Us, score);
383 // Evaluation::king() assigns bonuses and penalties to a king of a given color
384 template<Tracing T> template<Color Us>
385 Score Evaluation<T>::king() const {
387 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
388 constexpr Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
389 : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
391 Bitboard weak, b1, b2, safe, unsafeChecks = 0;
392 Bitboard rookChecks, queenChecks, bishopChecks, knightChecks;
394 const Square ksq = pos.square<KING>(Us);
396 // Init the score with king shelter and enemy pawns storm
397 Score score = pe->king_safety<Us>(pos);
399 // Attacked squares defended at most once by our queen or king
400 weak = attackedBy[Them][ALL_PIECES]
402 & (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);
404 // Analyse the safe enemy's checks which are possible on next move
405 safe = ~pos.pieces(Them);
406 safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
408 b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
409 b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
411 // Enemy rooks checks
412 rookChecks = b1 & safe & attackedBy[Them][ROOK];
415 kingDanger += RookSafeCheck;
417 unsafeChecks |= b1 & attackedBy[Them][ROOK];
419 // Enemy queen safe checks: we count them only if they are from squares from
420 // which we can't give a rook check, because rook checks are more valuable.
421 queenChecks = (b1 | b2)
422 & attackedBy[Them][QUEEN]
424 & ~attackedBy[Us][QUEEN]
428 kingDanger += QueenSafeCheck;
430 // Enemy bishops checks: we count them only if they are from squares from
431 // which we can't give a queen check, because queen checks are more valuable.
433 & attackedBy[Them][BISHOP]
438 kingDanger += BishopSafeCheck;
440 unsafeChecks |= b2 & attackedBy[Them][BISHOP];
442 // Enemy knights checks
443 knightChecks = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
445 if (knightChecks & safe)
446 kingDanger += KnightSafeCheck;
448 unsafeChecks |= knightChecks;
450 // Unsafe or occupied checking squares will also be considered, as long as
451 // the square is in the attacker's mobility area.
452 unsafeChecks &= mobilityArea[Them];
454 // Find the squares that opponent attacks in our king flank, and the squares
455 // which are attacked twice in that flank.
456 b1 = attackedBy[Them][ALL_PIECES] & KingFlank[file_of(ksq)] & Camp;
457 b2 = b1 & attackedBy2[Them];
459 int kingFlankAttacks = popcount(b1) + popcount(b2);
461 kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]
462 + 69 * kingAttacksCount[Them]
463 + 185 * popcount(kingRing[Us] & weak)
464 - 100 * bool(attackedBy[Us][KNIGHT] & attackedBy[Us][KING])
465 - 35 * bool(attackedBy[Us][BISHOP] & attackedBy[Us][KING])
466 + 150 * popcount(pos.blockers_for_king(Us) | unsafeChecks)
467 - 873 * !pos.count<QUEEN>(Them)
468 - 6 * mg_value(score) / 8
469 + mg_value(mobility[Them] - mobility[Us])
470 + 5 * kingFlankAttacks * kingFlankAttacks / 16
473 // Transform the kingDanger units into a Score, and subtract it from the evaluation
474 if (kingDanger > 100)
475 score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
477 // Penalty when our king is on a pawnless flank
478 if (!(pos.pieces(PAWN) & KingFlank[file_of(ksq)]))
479 score -= PawnlessFlank;
481 // Penalty if king flank is under attack, potentially moving toward the king
482 score -= FlankAttacks * kingFlankAttacks;
485 Trace::add(KING, Us, score);
491 // Evaluation::threats() assigns bonuses according to the types of the
492 // attacking and the attacked pieces.
493 template<Tracing T> template<Color Us>
494 Score Evaluation<T>::threats() const {
496 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
497 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
498 constexpr Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
500 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safe;
501 Score score = SCORE_ZERO;
504 nonPawnEnemies = pos.pieces(Them) & ~pos.pieces(PAWN);
506 // Squares strongly protected by the enemy, either because they defend the
507 // square with a pawn, or because they defend the square twice and we don't.
508 stronglyProtected = attackedBy[Them][PAWN]
509 | (attackedBy2[Them] & ~attackedBy2[Us]);
511 // Non-pawn enemies, strongly protected
512 defended = nonPawnEnemies & stronglyProtected;
514 // Enemies not strongly protected and under our attack
515 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
517 // Safe or protected squares
518 safe = ~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES];
520 // Bonus according to the kind of attacking pieces
523 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
526 Square s = pop_lsb(&b);
527 score += ThreatByMinor[type_of(pos.piece_on(s))];
528 if (type_of(pos.piece_on(s)) != PAWN)
529 score += ThreatByRank * (int)relative_rank(Them, s);
532 b = weak & attackedBy[Us][ROOK];
535 Square s = pop_lsb(&b);
536 score += ThreatByRook[type_of(pos.piece_on(s))];
537 if (type_of(pos.piece_on(s)) != PAWN)
538 score += ThreatByRank * (int)relative_rank(Them, s);
541 if (weak & attackedBy[Us][KING])
542 score += ThreatByKing;
544 b = ~attackedBy[Them][ALL_PIECES]
545 | (nonPawnEnemies & attackedBy2[Us]);
546 score += Hanging * popcount(weak & b);
549 // Bonus for restricting their piece moves
550 b = attackedBy[Them][ALL_PIECES]
552 & attackedBy[Us][ALL_PIECES];
554 score += RestrictedPiece * popcount(b);
556 // Find squares where our pawns can push on the next move
557 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
558 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
560 // Keep only the squares which are relatively safe
561 b &= ~attackedBy[Them][PAWN] & safe;
563 // Bonus for safe pawn threats on the next move
564 b = pawn_attacks_bb<Us>(b) & pos.pieces(Them);
565 score += ThreatByPawnPush * popcount(b);
567 // Our safe or protected pawns
568 b = pos.pieces(Us, PAWN) & safe;
570 b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
571 score += ThreatBySafePawn * popcount(b);
573 // Bonus for threats on the next moves against enemy queen
574 if (pos.count<QUEEN>(Them) == 1)
576 Square s = pos.square<QUEEN>(Them);
577 safe = mobilityArea[Us] & ~stronglyProtected;
579 b = attackedBy[Us][KNIGHT] & pos.attacks_from<KNIGHT>(s);
581 score += KnightOnQueen * popcount(b & safe);
583 b = (attackedBy[Us][BISHOP] & pos.attacks_from<BISHOP>(s))
584 | (attackedBy[Us][ROOK ] & pos.attacks_from<ROOK >(s));
586 score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]);
590 Trace::add(THREAT, Us, score);
595 // Evaluation::passed() evaluates the passed pawns and candidate passed
596 // pawns of the given color.
598 template<Tracing T> template<Color Us>
599 Score Evaluation<T>::passed() const {
601 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
602 constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
604 auto king_proximity = [&](Color c, Square s) {
605 return std::min(distance(pos.square<KING>(c), s), 5);
608 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
609 Score score = SCORE_ZERO;
611 b = pe->passed_pawns(Us);
615 Square s = pop_lsb(&b);
617 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
619 int r = relative_rank(Us, s);
621 Score bonus = PassedRank[r];
625 int w = (r-2) * (r-2) + 2;
626 Square blockSq = s + Up;
628 // Adjust bonus based on the king's proximity
629 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
630 - king_proximity(Us, blockSq) * 2) * w);
632 // If blockSq is not the queening square then consider also a second push
634 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
636 // If the pawn is free to advance, then increase the bonus
637 if (pos.empty(blockSq))
639 defendedSquares = squaresToQueen = forward_file_bb(Us, s);
640 unsafeSquares = passed_pawn_span(Us, s);
642 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN);
644 if (!(pos.pieces(Us) & bb))
645 defendedSquares &= attackedBy[Us][ALL_PIECES];
647 if (!(pos.pieces(Them) & bb))
648 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
650 // If there are no enemy attacks on passed pawn span, assign a big bonus.
651 // Otherwise assign a smaller bonus if the path to queen is not attacked
652 // and even smaller bonus if it is attacked but block square is not.
653 int k = !unsafeSquares ? 35 :
654 !(unsafeSquares & squaresToQueen) ? 20 :
655 !(unsafeSquares & blockSq) ? 9 :
658 // Assign a larger bonus if the block square is defended.
659 if (defendedSquares & blockSq)
662 bonus += make_score(k * w, k * w);
666 // Scale down bonus for candidate passers which need more than one
667 // pawn push to become passed, or have a pawn in front of them.
668 if ( !pos.pawn_passed(Us, s + Up)
669 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
672 score += bonus + PassedFile[file_of(s)];
676 Trace::add(PASSED, Us, score);
682 // Evaluation::space() computes the space evaluation for a given side. The
683 // space evaluation is a simple bonus based on the number of safe squares
684 // available for minor pieces on the central four files on ranks 2--4. Safe
685 // squares one, two or three squares behind a friendly pawn are counted
686 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
687 // improve play on game opening.
689 template<Tracing T> template<Color Us>
690 Score Evaluation<T>::space() const {
692 if (pos.non_pawn_material() < SpaceThreshold)
695 constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
696 constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
697 constexpr Bitboard SpaceMask =
698 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
699 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
701 // Find the available squares for our pieces inside the area defined by SpaceMask
702 Bitboard safe = SpaceMask
703 & ~pos.pieces(Us, PAWN)
704 & ~attackedBy[Them][PAWN];
706 // Find all squares which are at most three squares behind some friendly pawn
707 Bitboard behind = pos.pieces(Us, PAWN);
708 behind |= shift<Down>(behind);
709 behind |= shift<Down+Down>(behind);
711 int bonus = popcount(safe) + popcount(behind & safe);
712 int weight = pos.count<ALL_PIECES>(Us) - 1;
713 Score score = make_score(bonus * weight * weight / 16, 0);
715 score -= AttacksOnSpaceArea * popcount(attackedBy[Them][ALL_PIECES] & behind & safe);
718 Trace::add(SPACE, Us, score);
724 // Evaluation::initiative() computes the initiative correction value
725 // for the position. It is a second order bonus/malus based on the
726 // known attacking/defending status of the players.
729 Score Evaluation<T>::initiative(Value eg) const {
731 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
732 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
734 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
735 && (pos.pieces(PAWN) & KingSide);
737 // Compute the initiative bonus for the attacking side
738 int complexity = 9 * pe->passed_count()
739 + 11 * pos.count<PAWN>()
741 + 18 * pawnsOnBothFlanks
742 + 49 * !pos.non_pawn_material()
745 // Now apply the bonus: note that we find the attacking side by extracting
746 // the sign of the endgame value, and that we carefully cap the bonus so
747 // that the endgame score will never change sign after the bonus.
748 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
751 Trace::add(INITIATIVE, make_score(0, v));
753 return make_score(0, v);
757 // Evaluation::scale_factor() computes the scale factor for the winning side
760 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
762 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
763 int sf = me->scale_factor(pos, strongSide);
765 // If scale is not already specific, scale down the endgame via general heuristics
766 if (sf == SCALE_FACTOR_NORMAL)
768 if ( pos.opposite_bishops()
769 && pos.non_pawn_material() == 2 * BishopValueMg)
770 sf = 16 + 4 * pe->passed_count();
772 sf = std::min(40 + (pos.opposite_bishops() ? 2 : 7) * pos.count<PAWN>(strongSide), sf);
776 return ScaleFactor(sf);
780 // Evaluation::value() is the main function of the class. It computes the various
781 // parts of the evaluation and returns the value of the position from the point
782 // of view of the side to move.
785 Value Evaluation<T>::value() {
787 assert(!pos.checkers());
789 // Probe the material hash table
790 me = Material::probe(pos);
792 // If we have a specialized evaluation function for the current material
793 // configuration, call it and return.
794 if (me->specialized_eval_exists())
795 return me->evaluate(pos);
797 // Initialize score by reading the incrementally updated scores included in
798 // the position object (material + piece square tables) and the material
799 // imbalance. Score is computed internally from the white point of view.
800 Score score = pos.psq_score() + me->imbalance() + pos.this_thread()->contempt;
802 // Probe the pawn hash table
803 pe = Pawns::probe(pos);
804 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
806 // Early exit if score is high
807 Value v = (mg_value(score) + eg_value(score)) / 2;
808 if (abs(v) > LazyThreshold + pos.non_pawn_material() / 64)
809 return pos.side_to_move() == WHITE ? v : -v;
811 // Main evaluation begins here
816 // Pieces should be evaluated first (populate attack tables)
817 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
818 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
819 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
820 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
822 score += mobility[WHITE] - mobility[BLACK];
824 score += king< WHITE>() - king< BLACK>()
825 + threats<WHITE>() - threats<BLACK>()
826 + passed< WHITE>() - passed< BLACK>()
827 + space< WHITE>() - space< BLACK>();
829 score += initiative(eg_value(score));
831 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
832 ScaleFactor sf = scale_factor(eg_value(score));
833 v = mg_value(score) * int(me->game_phase())
834 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
838 // In case of tracing add all remaining individual evaluation terms
841 Trace::add(MATERIAL, pos.psq_score());
842 Trace::add(IMBALANCE, me->imbalance());
843 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
844 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
845 Trace::add(TOTAL, score);
848 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
855 /// evaluate() is the evaluator for the outer world. It returns a static
856 /// evaluation of the position from the point of view of the side to move.
858 Value Eval::evaluate(const Position& pos) {
859 return Evaluation<NO_TRACE>(pos).value();
863 /// trace() is like evaluate(), but instead of returning a value, it returns
864 /// a string (suitable for outputting to stdout) that contains the detailed
865 /// descriptions and values of each evaluation term. Useful for debugging.
867 std::string Eval::trace(const Position& pos) {
869 std::memset(scores, 0, sizeof(scores));
871 pos.this_thread()->contempt = SCORE_ZERO; // Reset any dynamic contempt
873 Value v = Evaluation<TRACE>(pos).value();
875 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
877 std::stringstream ss;
878 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
879 << " Term | White | Black | Total \n"
880 << " | MG EG | MG EG | MG EG \n"
881 << " ------------+-------------+-------------+------------\n"
882 << " Material | " << Term(MATERIAL)
883 << " Imbalance | " << Term(IMBALANCE)
884 << " Pawns | " << Term(PAWN)
885 << " Knights | " << Term(KNIGHT)
886 << " Bishops | " << Term(BISHOP)
887 << " Rooks | " << Term(ROOK)
888 << " Queens | " << Term(QUEEN)
889 << " Mobility | " << Term(MOBILITY)
890 << " King safety | " << Term(KING)
891 << " Threats | " << Term(THREAT)
892 << " Passed | " << Term(PASSED)
893 << " Space | " << Term(SPACE)
894 << " Initiative | " << Term(INITIATIVE)
895 << " ------------+-------------+-------------+------------\n"
896 << " Total | " << Term(TOTAL);
898 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";