2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <cstring> // For std::memset
32 std::atomic<Score> Eval::Contempt;
36 enum Tracing { NO_TRACE, TRACE };
38 enum Term { // The first 8 entries are reserved for PieceType
39 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, INITIATIVE, TOTAL, TERM_NB
42 Score scores[TERM_NB][COLOR_NB];
44 double to_cp(Value v) { return double(v) / PawnValueEg; }
46 void add(int idx, Color c, Score s) {
50 void add(int idx, Score w, Score b = SCORE_ZERO) {
51 scores[idx][WHITE] = w;
52 scores[idx][BLACK] = b;
55 std::ostream& operator<<(std::ostream& os, Score s) {
56 os << std::setw(5) << to_cp(mg_value(s)) << " "
57 << std::setw(5) << to_cp(eg_value(s));
61 std::ostream& operator<<(std::ostream& os, Term t) {
63 if (t == MATERIAL || t == IMBALANCE || t == INITIATIVE || t == TOTAL)
64 os << " ---- ----" << " | " << " ---- ----";
66 os << scores[t][WHITE] << " | " << scores[t][BLACK];
68 os << " | " << scores[t][WHITE] - scores[t][BLACK] << "\n";
73 using namespace Trace;
77 const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
78 const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
79 const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
80 const Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
82 const Bitboard KingFlank[FILE_NB] = {
83 QueenSide, QueenSide, QueenSide,
84 CenterFiles, CenterFiles,
85 KingSide, KingSide, KingSide
88 // Threshold for lazy and space evaluation
89 const Value LazyThreshold = Value(1500);
90 const Value SpaceThreshold = Value(12222);
92 // KingAttackWeights[PieceType] contains king attack weights by piece type
93 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
95 // Penalties for enemy's safe checks
96 const int QueenSafeCheck = 780;
97 const int RookSafeCheck = 880;
98 const int BishopSafeCheck = 435;
99 const int KnightSafeCheck = 790;
101 #define S(mg, eg) make_score(mg, eg)
103 // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
104 // indexed by piece type and number of attacked squares in the mobility area.
105 const Score MobilityBonus[][32] = {
106 { S(-75,-76), S(-57,-54), S( -9,-28), S( -2,-10), S( 6, 5), S( 14, 12), // Knights
107 S( 22, 26), S( 29, 29), S( 36, 29) },
108 { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
109 S( 55, 54), S( 63, 57), S( 63, 65), S( 68, 73), S( 81, 78), S( 81, 86),
110 S( 91, 88), S( 98, 97) },
111 { S(-58,-76), S(-27,-18), S(-15, 28), S(-10, 55), S( -5, 69), S( -2, 82), // Rooks
112 S( 9,112), S( 16,118), S( 30,132), S( 29,142), S( 32,155), S( 38,165),
113 S( 46,166), S( 48,169), S( 58,171) },
114 { S(-39,-36), S(-21,-15), S( 3, 8), S( 3, 18), S( 14, 34), S( 22, 54), // Queens
115 S( 28, 61), S( 41, 73), S( 43, 79), S( 48, 92), S( 56, 94), S( 60,104),
116 S( 60,113), S( 66,120), S( 67,123), S( 70,126), S( 71,133), S( 73,136),
117 S( 79,140), S( 88,143), S( 88,148), S( 99,166), S(102,170), S(102,175),
118 S(106,184), S(109,191), S(113,206), S(116,212) }
121 // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
122 // pieces if they occupy or can reach an outpost square, bigger if that
123 // square is supported by a pawn.
124 const Score Outpost[][2] = {
125 { S(22, 6), S(36,12) }, // Knight
126 { S( 9, 2), S(15, 5) } // Bishop
129 // RookOnFile[semiopen/open] contains bonuses for each rook when there is
130 // no (friendly) pawn on the rook file.
131 const Score RookOnFile[] = { S(20, 7), S(45, 20) };
133 // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
134 // which piece type attacks which one. Attacks on lesser pieces which are
135 // pawn-defended are not considered.
136 const Score ThreatByMinor[PIECE_TYPE_NB] = {
137 S(0, 0), S(0, 31), S(39, 42), S(57, 44), S(68, 112), S(47, 120)
140 const Score ThreatByRook[PIECE_TYPE_NB] = {
141 S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(36, 38)
144 // ThreatByKing[on one/on many] contains bonuses for king attacks on
145 // pawns or pieces which are not pawn-defended.
146 const Score ThreatByKing[] = { S(3, 65), S(9, 145) };
148 // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
149 const Score PassedRank[RANK_NB] = {
150 S(0, 0), S(5, 7), S(5, 13), S(32, 42), S(70, 70), S(172, 170), S(217, 269)
153 // PassedFile[File] contains a bonus according to the file of a passed pawn
154 const Score PassedFile[FILE_NB] = {
155 S( 9, 10), S(2, 10), S(1, -8), S(-20,-12),
156 S(-20,-12), S(1, -8), S(2, 10), S( 9, 10)
159 // PassedDanger[Rank] contains a term to weight the passed score
160 const int PassedDanger[RANK_NB] = { 0, 0, 0, 2, 7, 12, 19 };
162 // KingProtector[PieceType-2] contains a penalty according to distance from king
163 const Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
165 // Assorted bonuses and penalties
166 const Score BishopPawns = S( 8, 12);
167 const Score CloseEnemies = S( 7, 0);
168 const Score Hanging = S( 52, 30);
169 const Score HinderPassedPawn = S( 8, 1);
170 const Score KnightOnQueen = S( 21, 11);
171 const Score LongRangedBishop = S( 22, 0);
172 const Score MinorBehindPawn = S( 16, 0);
173 const Score PawnlessFlank = S( 20, 80);
174 const Score RookOnPawn = S( 8, 24);
175 const Score ThreatByPawnPush = S( 47, 26);
176 const Score ThreatByRank = S( 16, 3);
177 const Score ThreatBySafePawn = S(175,168);
178 const Score ThreatOnQueen = S( 42, 21);
179 const Score TrappedBishopA1H1 = S( 50, 50);
180 const Score TrappedRook = S( 92, 0);
181 const Score WeakQueen = S( 50, 10);
182 const Score WeakUnopposedPawn = S( 5, 25);
186 // Evaluation class computes and stores attacks tables and other working data
191 Evaluation() = delete;
192 explicit Evaluation(const Position& p) : pos(p) {}
193 Evaluation& operator=(const Evaluation&) = delete;
197 template<Color Us> void initialize();
198 template<Color Us, PieceType Pt> Score pieces();
199 template<Color Us> Score king() const;
200 template<Color Us> Score threats() const;
201 template<Color Us> Score passed() const;
202 template<Color Us> Score space() const;
203 ScaleFactor scale_factor(Value eg) const;
204 Score initiative(Value eg) const;
209 Bitboard mobilityArea[COLOR_NB];
210 Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
212 // attackedBy[color][piece type] is a bitboard representing all squares
213 // attacked by a given color and piece type. Special "piece types" which
214 // are also calculated are QUEEN_DIAGONAL and ALL_PIECES.
215 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
217 // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
218 // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
219 // pawn or squares attacked by 2 pawns are not explicitly added.
220 Bitboard attackedBy2[COLOR_NB];
222 // kingRing[color] are the squares adjacent to the king, plus (only for a
223 // king on its first rank) the squares two ranks in front. For instance,
224 // if black's king is on g8, kingRing[BLACK] is f8, h8, f7, g7, h7, f6, g6
225 // and h6. It is set to 0 when king safety evaluation is skipped.
226 Bitboard kingRing[COLOR_NB];
228 // kingAttackersCount[color] is the number of pieces of the given color
229 // which attack a square in the kingRing of the enemy king.
230 int kingAttackersCount[COLOR_NB];
232 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
233 // given color which attack a square in the kingRing of the enemy king. The
234 // weights of the individual piece types are given by the elements in the
235 // KingAttackWeights array.
236 int kingAttackersWeight[COLOR_NB];
238 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
239 // color to squares directly adjacent to the enemy king. Pieces which attack
240 // more than one square are counted multiple times. For instance, if there is
241 // a white knight on g5 and black's king is on g8, this white knight adds 2
242 // to kingAdjacentZoneAttacksCount[WHITE].
243 int kingAdjacentZoneAttacksCount[COLOR_NB];
247 // Evaluation::initialize() computes king and pawn attacks, and the king ring
248 // bitboard for a given color. This is done at the beginning of the evaluation.
249 template<Tracing T> template<Color Us>
250 void Evaluation<T>::initialize() {
252 const Color Them = (Us == WHITE ? BLACK : WHITE);
253 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
254 const Direction Down = (Us == WHITE ? SOUTH : NORTH);
255 const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
257 // Find our pawns that are blocked or on the first two ranks
258 Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
260 // Squares occupied by those pawns, by our king, or controlled by enemy pawns
261 // are excluded from the mobility area.
262 mobilityArea[Us] = ~(b | pos.square<KING>(Us) | pe->pawn_attacks(Them));
264 // Initialise attackedBy bitboards for kings and pawns
265 attackedBy[Us][KING] = pos.attacks_from<KING>(pos.square<KING>(Us));
266 attackedBy[Us][PAWN] = pe->pawn_attacks(Us);
267 attackedBy[Us][ALL_PIECES] = attackedBy[Us][KING] | attackedBy[Us][PAWN];
268 attackedBy2[Us] = attackedBy[Us][KING] & attackedBy[Us][PAWN];
270 // Init our king safety tables only if we are going to use them
271 if (pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)
273 kingRing[Us] = attackedBy[Us][KING];
274 if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
275 kingRing[Us] |= shift<Up>(kingRing[Us]);
277 kingAttackersCount[Them] = popcount(attackedBy[Us][KING] & pe->pawn_attacks(Them));
278 kingAdjacentZoneAttacksCount[Them] = kingAttackersWeight[Them] = 0;
281 kingRing[Us] = kingAttackersCount[Them] = 0;
285 // Evaluation::pieces() scores pieces of a given color and type
286 template<Tracing T> template<Color Us, PieceType Pt>
287 Score Evaluation<T>::pieces() {
289 const Color Them = (Us == WHITE ? BLACK : WHITE);
290 const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
291 : Rank5BB | Rank4BB | Rank3BB);
292 const Square* pl = pos.squares<Pt>(Us);
296 Score score = SCORE_ZERO;
298 attackedBy[Us][Pt] = 0;
301 attackedBy[Us][QUEEN_DIAGONAL] = 0;
303 while ((s = *pl++) != SQ_NONE)
305 // Find attacked squares, including x-ray attacks for bishops and rooks
306 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
307 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
308 : pos.attacks_from<Pt>(s);
310 if (pos.blockers_for_king(Us) & s)
311 b &= LineBB[pos.square<KING>(Us)][s];
313 attackedBy2[Us] |= attackedBy[Us][ALL_PIECES] & b;
314 attackedBy[Us][Pt] |= b;
315 attackedBy[Us][ALL_PIECES] |= b;
318 attackedBy[Us][QUEEN_DIAGONAL] |= b & PseudoAttacks[BISHOP][s];
320 if (b & kingRing[Them])
322 kingAttackersCount[Us]++;
323 kingAttackersWeight[Us] += KingAttackWeights[Pt];
324 kingAdjacentZoneAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
327 int mob = popcount(b & mobilityArea[Us]);
329 mobility[Us] += MobilityBonus[Pt - 2][mob];
331 // Penalty if the piece is far from the king
332 score -= KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));
334 if (Pt == BISHOP || Pt == KNIGHT)
336 // Bonus if piece is on an outpost square or can reach one
337 bb = OutpostRanks & ~pe->pawn_attacks_span(Them);
339 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & s)] * 2;
341 else if (bb &= b & ~pos.pieces(Us))
342 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
344 // Bonus when behind a pawn
345 if ( relative_rank(Us, s) < RANK_5
346 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
347 score += MinorBehindPawn;
351 // Penalty according to number of pawns on the same color square as the bishop
352 score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
354 // Bonus for bishop on a long diagonal which can "see" both center squares
355 if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
356 score += LongRangedBishop;
359 // An important Chess960 pattern: A cornered bishop blocked by a friendly
360 // pawn diagonally in front of it is a very serious problem, especially
361 // when that pawn is also blocked.
364 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
366 Direction d = pawn_push(Us) + (file_of(s) == FILE_A ? EAST : WEST);
367 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
368 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
369 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
376 // Bonus for aligning rook with with enemy pawns on the same rank/file
377 if (relative_rank(Us, s) >= RANK_5)
378 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
380 // Bonus for rook on an open or semi-open file
381 if (pe->semiopen_file(Us, file_of(s)))
382 score += RookOnFile[bool(pe->semiopen_file(Them, file_of(s)))];
384 // Penalty when trapped by the king, even more if the king cannot castle
387 File kf = file_of(pos.square<KING>(Us));
388 if ((kf < FILE_E) == (file_of(s) < kf))
389 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
395 // Penalty if any relative pin or discovered attack against the queen
396 Bitboard queenPinners;
397 if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
402 Trace::add(Pt, Us, score);
408 // Evaluation::king() assigns bonuses and penalties to a king of a given color
409 template<Tracing T> template<Color Us>
410 Score Evaluation<T>::king() const {
412 const Color Them = (Us == WHITE ? BLACK : WHITE);
413 const Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
414 : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
416 const Square ksq = pos.square<KING>(Us);
417 Bitboard weak, b, b1, b2, safe, unsafeChecks, pinned;
419 // King shelter and enemy pawns storm
420 Score score = pe->king_safety<Us>(pos, ksq);
422 // Main king safety evaluation
423 if (kingAttackersCount[Them] > 1 - pos.count<QUEEN>(Them))
425 int kingDanger = unsafeChecks = 0;
427 // Attacked squares defended at most once by our queen or king
428 weak = attackedBy[Them][ALL_PIECES]
430 & (~attackedBy[Us][ALL_PIECES] | attackedBy[Us][KING] | attackedBy[Us][QUEEN]);
432 // Analyse the safe enemy's checks which are possible on next move
433 safe = ~pos.pieces(Them);
434 safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
436 b1 = attacks_bb<ROOK >(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
437 b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
439 // Enemy queen safe checks
440 if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])
441 kingDanger += QueenSafeCheck;
443 b1 &= attackedBy[Them][ROOK];
444 b2 &= attackedBy[Them][BISHOP];
446 // Enemy rooks checks
448 kingDanger += RookSafeCheck;
452 // Enemy bishops checks
454 kingDanger += BishopSafeCheck;
458 // Enemy knights checks
459 b = pos.attacks_from<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
461 kingDanger += KnightSafeCheck;
465 // Unsafe or occupied checking squares will also be considered, as long as
466 // the square is in the attacker's mobility area.
467 unsafeChecks &= mobilityArea[Them];
468 pinned = pos.blockers_for_king(Us) & pos.pieces(Us);
470 kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them]
471 + 102 * kingAdjacentZoneAttacksCount[Them]
472 + 191 * popcount(kingRing[Us] & weak)
473 + 143 * popcount(pinned | unsafeChecks)
474 - 848 * !pos.count<QUEEN>(Them)
475 - 9 * mg_value(score) / 8
478 // Transform the kingDanger units into a Score, and subtract it from the evaluation
481 int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
482 kingDanger = std::max(0, kingDanger + mobilityDanger);
483 score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
487 Bitboard kf = KingFlank[file_of(ksq)];
489 // Penalty when our king is on a pawnless flank
490 if (!(pos.pieces(PAWN) & kf))
491 score -= PawnlessFlank;
493 // Find the squares that opponent attacks in our king flank, and the squares
494 // which are attacked twice in that flank but not defended by our pawns.
495 b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
496 b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
498 // King tropism, to anticipate slow motion attacks on our king
499 score -= CloseEnemies * (popcount(b1) + popcount(b2));
502 Trace::add(KING, Us, score);
508 // Evaluation::threats() assigns bonuses according to the types of the
509 // attacking and the attacked pieces.
510 template<Tracing T> template<Color Us>
511 Score Evaluation<T>::threats() const {
513 const Color Them = (Us == WHITE ? BLACK : WHITE);
514 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
515 const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
517 Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
518 Score score = SCORE_ZERO;
520 // Non-pawn enemies attacked by a pawn
521 nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
522 weak = nonPawnEnemies & attackedBy[Us][PAWN];
526 // Our safe or protected pawns
527 b = pos.pieces(Us, PAWN)
528 & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
530 safeThreats = pawn_attacks_bb<Us>(b) & weak;
531 score += ThreatBySafePawn * popcount(safeThreats);
534 // Squares strongly protected by the enemy, either because they defend the
535 // square with a pawn, or because they defend the square twice and we don't.
536 stronglyProtected = attackedBy[Them][PAWN]
537 | (attackedBy2[Them] & ~attackedBy2[Us]);
539 // Non-pawn enemies, strongly protected
540 defended = nonPawnEnemies & stronglyProtected;
542 // Enemies not strongly protected and under our attack
543 weak = pos.pieces(Them) & ~stronglyProtected & attackedBy[Us][ALL_PIECES];
545 // Bonus according to the kind of attacking pieces
548 b = (defended | weak) & (attackedBy[Us][KNIGHT] | attackedBy[Us][BISHOP]);
551 Square s = pop_lsb(&b);
552 score += ThreatByMinor[type_of(pos.piece_on(s))];
553 if (type_of(pos.piece_on(s)) != PAWN)
554 score += ThreatByRank * (int)relative_rank(Them, s);
557 b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
560 Square s = pop_lsb(&b);
561 score += ThreatByRook[type_of(pos.piece_on(s))];
562 if (type_of(pos.piece_on(s)) != PAWN)
563 score += ThreatByRank * (int)relative_rank(Them, s);
566 score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
568 b = weak & attackedBy[Us][KING];
570 score += ThreatByKing[more_than_one(b)];
573 // Bonus for enemy unopposed weak pawns
574 if (pos.pieces(Us, ROOK, QUEEN))
575 score += WeakUnopposedPawn * pe->weak_unopposed(Them);
577 // Find squares where our pawns can push on the next move
578 b = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
579 b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
581 // Keep only the squares which are not completely unsafe
582 b &= ~attackedBy[Them][PAWN]
583 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
585 // Bonus for safe pawn threats on the next move
586 b = pawn_attacks_bb<Us>(b)
588 & ~attackedBy[Us][PAWN];
590 score += ThreatByPawnPush * popcount(b);
592 // Bonus for safe slider threats on the next move toward enemy queen
593 safeThreats = ~pos.pieces(Us) & ~attackedBy2[Them] & attackedBy2[Us];
594 b = (attackedBy[Us][BISHOP] & attackedBy[Them][QUEEN_DIAGONAL])
595 | (attackedBy[Us][ROOK ] & attackedBy[Them][QUEEN] & ~attackedBy[Them][QUEEN_DIAGONAL]);
597 score += ThreatOnQueen * popcount(b & safeThreats);
599 // Bonus for knight threats on the next moves against enemy queen
600 if (pos.count<QUEEN>(Them) == 1)
602 b = pos.attacks_from<KNIGHT>(pos.square<QUEEN>(Them))
603 & attackedBy[Us][KNIGHT]
604 & ~pos.pieces(Us, PAWN, KING)
605 & ~stronglyProtected;
607 score += KnightOnQueen * popcount(b);
611 Trace::add(THREAT, Us, score);
616 // Evaluation::passed() evaluates the passed pawns and candidate passed
617 // pawns of the given color.
619 template<Tracing T> template<Color Us>
620 Score Evaluation<T>::passed() const {
622 const Color Them = (Us == WHITE ? BLACK : WHITE);
623 const Direction Up = (Us == WHITE ? NORTH : SOUTH);
625 auto king_proximity = [&](Color c, Square s) {
626 return std::min(distance(pos.square<KING>(c), s), 5);
629 Bitboard b, bb, squaresToQueen, defendedSquares, unsafeSquares;
630 Score score = SCORE_ZERO;
632 b = pe->passed_pawns(Us);
636 Square s = pop_lsb(&b);
638 assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
640 bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
641 score -= HinderPassedPawn * popcount(bb);
643 int r = relative_rank(Us, s);
644 int w = PassedDanger[r];
646 Score bonus = PassedRank[r];
650 Square blockSq = s + Up;
652 // Adjust bonus based on the king's proximity
653 bonus += make_score(0, ( king_proximity(Them, blockSq) * 5
654 - king_proximity(Us, blockSq) * 2) * w);
656 // If blockSq is not the queening square then consider also a second push
658 bonus -= make_score(0, king_proximity(Us, blockSq + Up) * w);
660 // If the pawn is free to advance, then increase the bonus
661 if (pos.empty(blockSq))
663 // If there is a rook or queen attacking/defending the pawn from behind,
664 // consider all the squaresToQueen. Otherwise consider only the squares
665 // in the pawn's path attacked or occupied by the enemy.
666 defendedSquares = unsafeSquares = squaresToQueen = forward_file_bb(Us, s);
668 bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
670 if (!(pos.pieces(Us) & bb))
671 defendedSquares &= attackedBy[Us][ALL_PIECES];
673 if (!(pos.pieces(Them) & bb))
674 unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
676 // If there aren't any enemy attacks, assign a big bonus. Otherwise
677 // assign a smaller bonus if the block square isn't attacked.
678 int k = !unsafeSquares ? 20 : !(unsafeSquares & blockSq) ? 9 : 0;
680 // If the path to the queen is fully defended, assign a big bonus.
681 // Otherwise assign a smaller bonus if the block square is defended.
682 if (defendedSquares == squaresToQueen)
685 else if (defendedSquares & blockSq)
688 bonus += make_score(k * w, k * w);
690 else if (pos.pieces(Us) & blockSq)
691 bonus += make_score(w + r * 2, w + r * 2);
694 // Scale down bonus for candidate passers which need more than one
695 // pawn push to become passed or have a pawn in front of them.
696 if ( !pos.pawn_passed(Us, s + Up)
697 || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
700 score += bonus + PassedFile[file_of(s)];
704 Trace::add(PASSED, Us, score);
710 // Evaluation::space() computes the space evaluation for a given side. The
711 // space evaluation is a simple bonus based on the number of safe squares
712 // available for minor pieces on the central four files on ranks 2--4. Safe
713 // squares one, two or three squares behind a friendly pawn are counted
714 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
715 // improve play on game opening.
717 template<Tracing T> template<Color Us>
718 Score Evaluation<T>::space() const {
720 const Color Them = (Us == WHITE ? BLACK : WHITE);
721 const Bitboard SpaceMask =
722 Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
723 : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
725 if (pos.non_pawn_material() < SpaceThreshold)
728 // Find the safe squares for our pieces inside the area defined by
729 // SpaceMask. A square is unsafe if it is attacked by an enemy
730 // pawn, or if it is undefended and attacked by an enemy piece.
731 Bitboard safe = SpaceMask
732 & ~pos.pieces(Us, PAWN)
733 & ~attackedBy[Them][PAWN]
734 & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
736 // Find all squares which are at most three squares behind some friendly pawn
737 Bitboard behind = pos.pieces(Us, PAWN);
738 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
739 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
741 int bonus = popcount(safe) + popcount(behind & safe);
742 int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
744 Score score = make_score(bonus * weight * weight / 16, 0);
747 Trace::add(SPACE, Us, score);
753 // Evaluation::initiative() computes the initiative correction value
754 // for the position. It is a second order bonus/malus based on the
755 // known attacking/defending status of the players.
758 Score Evaluation<T>::initiative(Value eg) const {
760 int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
761 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
763 bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
764 && (pos.pieces(PAWN) & KingSide);
766 // Compute the initiative bonus for the attacking side
767 int complexity = 8 * outflanking
768 + 8 * pe->pawn_asymmetry()
769 + 12 * pos.count<PAWN>()
770 + 16 * pawnsOnBothFlanks
773 // Now apply the bonus: note that we find the attacking side by extracting
774 // the sign of the endgame value, and that we carefully cap the bonus so
775 // that the endgame score will never change sign after the bonus.
776 int v = ((eg > 0) - (eg < 0)) * std::max(complexity, -abs(eg));
779 Trace::add(INITIATIVE, make_score(0, v));
781 return make_score(0, v);
785 // Evaluation::scale_factor() computes the scale factor for the winning side
788 ScaleFactor Evaluation<T>::scale_factor(Value eg) const {
790 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
791 int sf = me->scale_factor(pos, strongSide);
793 // If we don't already have an unusual scale factor, check for certain
794 // types of endgames, and use a lower scale for those.
795 if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
797 if (pos.opposite_bishops())
799 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
800 // is almost a draw, in case of KBP vs KB, it is even more a draw.
801 if ( pos.non_pawn_material(WHITE) == BishopValueMg
802 && pos.non_pawn_material(BLACK) == BishopValueMg)
803 sf = more_than_one(pos.pieces(PAWN)) ? 31 : 9;
805 // Endgame with opposite-colored bishops, but also other pieces. Still
806 // a bit drawish, but not as drawish as with only the two bishops.
810 // Endings where weaker side can place his king in front of the enemy's
811 // pawns are drawish.
812 else if ( abs(eg) <= BishopValueEg
813 && pos.count<PAWN>(strongSide) <= 2
814 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
815 sf = 37 + 7 * pos.count<PAWN>(strongSide);
818 return ScaleFactor(sf);
822 // Evaluation::value() is the main function of the class. It computes the various
823 // parts of the evaluation and returns the value of the position from the point
824 // of view of the side to move.
827 Value Evaluation<T>::value() {
829 assert(!pos.checkers());
831 // Probe the material hash table
832 me = Material::probe(pos);
834 // If we have a specialized evaluation function for the current material
835 // configuration, call it and return.
836 if (me->specialized_eval_exists())
837 return me->evaluate(pos);
839 // Initialize score by reading the incrementally updated scores included in
840 // the position object (material + piece square tables) and the material
841 // imbalance. Score is computed internally from the white point of view.
842 Score score = pos.psq_score() + me->imbalance() + Eval::Contempt;
844 // Probe the pawn hash table
845 pe = Pawns::probe(pos);
846 score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
848 // Early exit if score is high
849 Value v = (mg_value(score) + eg_value(score)) / 2;
850 if (abs(v) > LazyThreshold)
851 return pos.side_to_move() == WHITE ? v : -v;
853 // Main evaluation begins here
858 // Pieces should be evaluated first (populate attack tables)
859 score += pieces<WHITE, KNIGHT>() - pieces<BLACK, KNIGHT>()
860 + pieces<WHITE, BISHOP>() - pieces<BLACK, BISHOP>()
861 + pieces<WHITE, ROOK >() - pieces<BLACK, ROOK >()
862 + pieces<WHITE, QUEEN >() - pieces<BLACK, QUEEN >();
864 score += mobility[WHITE] - mobility[BLACK];
866 score += king< WHITE>() - king< BLACK>()
867 + threats<WHITE>() - threats<BLACK>()
868 + passed< WHITE>() - passed< BLACK>()
869 + space< WHITE>() - space< BLACK>();
871 score += initiative(eg_value(score));
873 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
874 ScaleFactor sf = scale_factor(eg_value(score));
875 v = mg_value(score) * int(me->game_phase())
876 + eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
878 v /= int(PHASE_MIDGAME);
880 // In case of tracing add all remaining individual evaluation terms
883 Trace::add(MATERIAL, pos.psq_score());
884 Trace::add(IMBALANCE, me->imbalance());
885 Trace::add(PAWN, pe->pawn_score(WHITE), pe->pawn_score(BLACK));
886 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
887 Trace::add(TOTAL, score);
890 return (pos.side_to_move() == WHITE ? v : -v) // Side to move point of view
897 /// evaluate() is the evaluator for the outer world. It returns a static
898 /// evaluation of the position from the point of view of the side to move.
900 Value Eval::evaluate(const Position& pos) {
901 return Evaluation<NO_TRACE>(pos).value();
905 /// trace() is like evaluate(), but instead of returning a value, it returns
906 /// a string (suitable for outputting to stdout) that contains the detailed
907 /// descriptions and values of each evaluation term. Useful for debugging.
909 std::string Eval::trace(const Position& pos) {
911 std::memset(scores, 0, sizeof(scores));
913 Eval::Contempt = SCORE_ZERO; // Reset any dynamic contempt
915 Value v = Evaluation<TRACE>(pos).value();
917 v = pos.side_to_move() == WHITE ? v : -v; // Trace scores are from white's point of view
919 std::stringstream ss;
920 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
921 << " Term | White | Black | Total \n"
922 << " | MG EG | MG EG | MG EG \n"
923 << " ------------+-------------+-------------+------------\n"
924 << " Material | " << Term(MATERIAL)
925 << " Imbalance | " << Term(IMBALANCE)
926 << " Initiative | " << Term(INITIATIVE)
927 << " Pawns | " << Term(PAWN)
928 << " Knights | " << Term(KNIGHT)
929 << " Bishops | " << Term(BISHOP)
930 << " Rooks | " << Term(ROOK)
931 << " Queens | " << Term(QUEEN)
932 << " Mobility | " << Term(MOBILITY)
933 << " King safety | " << Term(KING)
934 << " Threats | " << Term(THREAT)
935 << " Passed | " << Term(PASSED)
936 << " Space | " << Term(SPACE)
937 << " ------------+-------------+-------------+------------\n"
938 << " Total | " << Term(TOTAL);
940 ss << "\nTotal evaluation: " << to_cp(v) << " (white side)\n";