2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 // Struct EvalInfo contains various information computed and collected
35 // by the evaluation functions.
38 // Pointers to material and pawn hash table entries
42 // attackedBy[color][piece type] is a bitboard representing all squares
43 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
44 // contains all squares attacked by the given color.
45 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
47 // kingRing[color] is the zone around the king which is considered
48 // by the king safety evaluation. This consists of the squares directly
49 // adjacent to the king, and the three (or two, for a king on an edge file)
50 // squares two ranks in front of the king. For instance, if black's king
51 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
52 // f7, g7, h7, f6, g6 and h6.
53 Bitboard kingRing[COLOR_NB];
55 // kingAttackersCount[color] is the number of pieces of the given color
56 // which attack a square in the kingRing of the enemy king.
57 int kingAttackersCount[COLOR_NB];
59 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
60 // given color which attack a square in the kingRing of the enemy king. The
61 // weights of the individual piece types are given by the variables
62 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
63 // KnightAttackWeight in evaluate.cpp
64 int kingAttackersWeight[COLOR_NB];
66 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
67 // directly adjacent to the king of the given color. Pieces which attack
68 // more than one square are counted multiple times. For instance, if black's
69 // king is on g8 and there's a white knight on g5, this knight adds
70 // 2 to kingAdjacentZoneAttacksCount[BLACK].
71 int kingAdjacentZoneAttacksCount[COLOR_NB];
73 Bitboard pinnedPieces[COLOR_NB];
78 enum Terms { // First 8 entries are for PieceType
79 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
82 Score terms[COLOR_NB][TERMS_NB];
86 double to_cp(Value v);
87 void add_term(int idx, Score term_w, Score term_b = SCORE_ZERO);
88 void format_row(std::stringstream& ss, const char* name, int idx);
89 std::string do_trace(const Position& pos);
92 // Evaluation weights, initialized from UCI options
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
94 struct Weight { int mg, eg; } Weights[6];
97 #define S(mg, eg) make_score(mg, eg)
99 // Internal evaluation weights. These are applied on top of the evaluation
100 // weights read from UCI parameters. The purpose is to be able to change
101 // the evaluation weights while keeping the default values of the UCI
102 // parameters at 100, which looks prettier.
104 // Values modified by Joona Kiiski
105 const Score WeightsInternal[] = {
106 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
109 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
110 // game, indexed by piece type and number of attacked squares not occupied by
112 const Score MobilityBonus[][32] = {
114 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
115 S( 37, 28), S( 42, 31), S(44, 33) },
116 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
117 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
118 S( 84, 79), S( 86, 81) },
119 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
120 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
121 S( 35,122), S( 36,123), S(37,124) },
122 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
123 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
124 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
129 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
130 // indexed by piece type and square (from white's point of view).
131 const Value Outpost[][SQUARE_NB] = {
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
134 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
135 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
136 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
137 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
138 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
140 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
141 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
142 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
143 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
144 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
145 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
148 // Threat[attacking][attacked] contains bonuses according to which piece
149 // type attacks which one.
150 const Score Threat[][PIECE_TYPE_NB] = {
151 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
152 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[] = {
158 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
163 const Score Tempo = make_score(24, 11);
164 const Score RookOnPawn = make_score(10, 28);
165 const Score RookOpenFile = make_score(43, 21);
166 const Score RookSemiopenFile = make_score(19, 10);
167 const Score BishopPawns = make_score( 8, 12);
168 const Score MinorBehindPawn = make_score(16, 0);
169 const Score UndefendedMinor = make_score(25, 10);
170 const Score TrappedRook = make_score(90, 0);
171 const Score Unstoppable = make_score( 0, 20);
173 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
174 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
175 // happen in Chess960 games.
176 const Score TrappedBishopA1H1 = make_score(50, 50);
178 // SpaceMask[Color] contains the area of the board which is considered
179 // by the space evaluation. In the middlegame, each side is given a bonus
180 // based on how many squares inside this area are safe and available for
181 // friendly minor pieces.
182 const Bitboard SpaceMask[] = {
183 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
184 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
187 // King danger constants and variables. The king danger scores are taken
188 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
189 // of the enemy attack are added up into an integer, which is used as an
190 // index to KingDanger[].
192 // KingAttackWeights[PieceType] contains king attack weights by piece type
193 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
195 // Bonuses for enemy's safe checks
196 const int QueenContactCheck = 24;
197 const int RookContactCheck = 16;
198 const int QueenCheck = 12;
199 const int RookCheck = 8;
200 const int BishopCheck = 2;
201 const int KnightCheck = 3;
203 // KingDanger[Color][attackUnits] contains the actual king danger weighted
204 // scores, indexed by color and by a calculated integer number.
205 Score KingDanger[COLOR_NB][128];
208 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
209 Score apply_weight(Score v, const Weight& w) {
210 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
214 // weight_option() computes the value of an evaluation weight, by combining
215 // two UCI-configurable weights (midgame and endgame) with an internal weight.
217 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
219 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
220 Options[egOpt] * eg_value(internalWeight) / 100 };
225 // interpolate() interpolates between a middlegame and an endgame score,
226 // based on game phase. It also scales the return value by a ScaleFactor array.
228 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
230 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
231 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
232 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
234 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
235 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
239 // init_eval_info() initializes king bitboards for given color adding
240 // pawn attacks. To be done at the beginning of the evaluation.
243 void init_eval_info(const Position& pos, EvalInfo& ei) {
245 const Color Them = (Us == WHITE ? BLACK : WHITE);
246 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
248 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
250 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
251 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
253 // Init king safety tables only if we are going to use them
254 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
256 ei.kingRing[Them] = b | shift_bb<Down>(b);
257 b &= ei.attackedBy[Us][PAWN];
258 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
259 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
262 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
266 // evaluate_outposts() evaluates bishop and knight outpost squares
268 template<PieceType Pt, Color Us>
269 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
271 const Color Them = (Us == WHITE ? BLACK : WHITE);
273 assert (Pt == BISHOP || Pt == KNIGHT);
275 // Initial bonus based on square
276 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
278 // Increase bonus if supported by pawn, especially if the opponent has
279 // no minor piece which can trade with the outpost piece.
280 if (bonus && (ei.attackedBy[Us][PAWN] & s))
282 if ( !pos.pieces(Them, KNIGHT)
283 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
284 bonus += bonus + bonus / 2;
289 return make_score(bonus, bonus);
293 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
295 template<PieceType Pt, Color Us, bool Trace>
296 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
300 Score score = SCORE_ZERO;
302 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
303 const Color Them = (Us == WHITE ? BLACK : WHITE);
304 const Square* pl = pos.list<Pt>(Us);
306 ei.attackedBy[Us][Pt] = 0;
308 while ((s = *pl++) != SQ_NONE)
310 // Find attacked squares, including x-ray attacks for bishops and rooks
311 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
312 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
313 : pos.attacks_from<Pt>(s);
315 if (ei.pinnedPieces[Us] & s)
316 b &= LineBB[pos.king_square(Us)][s];
318 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
320 if (b & ei.kingRing[Them])
322 ei.kingAttackersCount[Us]++;
323 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
324 Bitboard bb = b & ei.attackedBy[Them][KING];
326 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
330 b &= ~( ei.attackedBy[Them][KNIGHT]
331 | ei.attackedBy[Them][BISHOP]
332 | ei.attackedBy[Them][ROOK]);
334 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
335 : popcount<Full >(b & mobilityArea[Us]);
337 mobility[Us] += MobilityBonus[Pt][mob];
339 // Decrease score if we are attacked by an enemy pawn. The remaining part
340 // of threat evaluation must be done later when we have full attack info.
341 if (ei.attackedBy[Them][PAWN] & s)
342 score -= ThreatenedByPawn[Pt];
344 if (Pt == BISHOP || Pt == KNIGHT)
346 // Penalty for bishop with same colored pawns
348 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
350 // Bishop and knight outposts squares
351 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
352 score += evaluate_outposts<Pt, Us>(pos, ei, s);
354 // Bishop or knight behind a pawn
355 if ( relative_rank(Us, s) < RANK_5
356 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
357 score += MinorBehindPawn;
362 // Rook piece attacking enemy pawns on the same rank/file
363 if (relative_rank(Us, s) >= RANK_5)
365 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
367 score += popcount<Max15>(pawns) * RookOnPawn;
370 // Give a bonus for a rook on a open or semi-open file
371 if (ei.pi->semiopen_file(Us, file_of(s)))
372 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
374 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
377 Square ksq = pos.king_square(Us);
379 // Penalize rooks which are trapped by a king. Penalize more if the
380 // king has lost its castling capability.
381 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
382 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
383 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
384 score -= (TrappedRook - make_score(mob * 8, 0)) * (1 + !pos.can_castle(Us));
387 // An important Chess960 pattern: A cornered bishop blocked by a friendly
388 // pawn diagonally in front of it is a very serious problem, especially
389 // when that pawn is also blocked.
392 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
394 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
395 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
396 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
397 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
403 Tracing::terms[Us][Pt] = score;
405 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
409 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
411 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
414 // evaluate_king() assigns bonuses and penalties to a king of a given color
416 template<Color Us, bool Trace>
417 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
419 const Color Them = (Us == WHITE ? BLACK : WHITE);
421 Bitboard undefended, b, b1, b2, safe;
423 const Square ksq = pos.king_square(Us);
425 // King shelter and enemy pawns storm
426 Score score = ei.pi->king_safety<Us>(pos, ksq);
428 // Main king safety evaluation
429 if (ei.kingAttackersCount[Them])
431 // Find the attacked squares around the king which have no defenders
432 // apart from the king itself
433 undefended = ei.attackedBy[Them][ALL_PIECES]
434 & ei.attackedBy[Us][KING]
435 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
436 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
437 | ei.attackedBy[Us][QUEEN]);
439 // Initialize the 'attackUnits' variable, which is used later on as an
440 // index to the KingDanger[] array. The initial value is based on the
441 // number and types of the enemy's attacking pieces, the number of
442 // attacked and undefended squares around our king and the quality of
443 // the pawn shelter (current 'score' value).
444 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
445 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
446 + 2 * (ei.pinnedPieces[Us] != 0)
447 - mg_value(score) / 32;
449 // Analyse the enemy's safe queen contact checks. Firstly, find the
450 // undefended squares around the king that are attacked by the enemy's
452 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
455 // ...and then remove squares not supported by another enemy piece
456 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
457 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
460 attackUnits += QueenContactCheck
462 * (Them == pos.side_to_move() ? 2 : 1);
465 // Analyse the enemy's safe rook contact checks. Firstly, find the
466 // undefended squares around the king that are attacked by the enemy's
468 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
470 // Consider only squares where the enemy's rook gives check
471 b &= PseudoAttacks[ROOK][ksq];
475 // ...and then remove squares not supported by another enemy piece
476 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
477 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
480 attackUnits += RookContactCheck
482 * (Them == pos.side_to_move() ? 2 : 1);
485 // Analyse the enemy's safe distance checks for sliders and knights
486 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
488 b1 = pos.attacks_from<ROOK>(ksq) & safe;
489 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
491 // Enemy queen safe checks
492 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
494 attackUnits += QueenCheck * popcount<Max15>(b);
496 // Enemy rooks safe checks
497 b = b1 & ei.attackedBy[Them][ROOK];
499 attackUnits += RookCheck * popcount<Max15>(b);
501 // Enemy bishops safe checks
502 b = b2 & ei.attackedBy[Them][BISHOP];
504 attackUnits += BishopCheck * popcount<Max15>(b);
506 // Enemy knights safe checks
507 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
509 attackUnits += KnightCheck * popcount<Max15>(b);
511 // To index KingDanger[] attackUnits must be in [0, 99] range
512 attackUnits = std::min(99, std::max(0, attackUnits));
514 // Finally, extract the king danger score from the KingDanger[]
515 // array and subtract the score from evaluation.
516 score -= KingDanger[Us == Search::RootColor][attackUnits];
520 Tracing::terms[Us][KING] = score;
526 // evaluate_threats() assigns bonuses according to the type of attacking piece
527 // and the type of attacked one.
529 template<Color Us, bool Trace>
530 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
532 const Color Them = (Us == WHITE ? BLACK : WHITE);
534 Bitboard b, undefendedMinors, weakEnemies;
535 Score score = SCORE_ZERO;
537 // Undefended minors get penalized even if they are not under attack
538 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
539 & ~ei.attackedBy[Them][ALL_PIECES];
541 if (undefendedMinors)
542 score += UndefendedMinor;
544 // Enemy pieces not defended by a pawn and under our attack
545 weakEnemies = pos.pieces(Them)
546 & ~ei.attackedBy[Them][PAWN]
547 & ei.attackedBy[Us][ALL_PIECES];
549 // Add a bonus according if the attacking pieces are minor or major
552 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
554 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
556 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
558 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
562 Tracing::terms[Us][Tracing::THREAT] = score;
568 // evaluate_passed_pawns() evaluates the passed pawns of the given color
570 template<Color Us, bool Trace>
571 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
573 const Color Them = (Us == WHITE ? BLACK : WHITE);
575 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
576 Score score = SCORE_ZERO;
578 b = ei.pi->passed_pawns(Us);
582 Square s = pop_lsb(&b);
584 assert(pos.pawn_passed(Us, s));
586 Rank r = relative_rank(Us, s) - RANK_2;
587 Rank rr = r * (r - 1);
589 // Base bonus based on rank
590 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
594 Square blockSq = s + pawn_push(Us);
596 // Adjust bonus based on the king's proximity
597 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
598 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
600 // If blockSq is not the queening square then consider also a second push
601 if (relative_rank(Us, blockSq) != RANK_8)
602 ebonus -= rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us));
604 // If the pawn is free to advance, then increase the bonus
605 if (pos.empty(blockSq))
607 squaresToQueen = forward_bb(Us, s);
609 // If there is an enemy rook or queen attacking the pawn from behind,
610 // add all X-ray attacks by the rook or queen. Otherwise consider only
611 // the squares in the pawn's path attacked or occupied by the enemy.
612 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
613 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
614 unsafeSquares = squaresToQueen;
616 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
618 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
619 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
620 defendedSquares = squaresToQueen;
622 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
624 // If there aren't any enemy attacks, assign a big bonus. Otherwise
625 // assign a smaller bonus if the block square isn't attacked.
626 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
628 // If the path to queen is fully defended, assign a big bonus.
629 // Otherwise assign a smaller bonus if the block square is defended.
630 if (defendedSquares == squaresToQueen)
633 else if (defendedSquares & blockSq)
636 mbonus += k * rr, ebonus += k * rr;
640 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
641 ebonus += ebonus / 4;
643 score += make_score(mbonus, ebonus);
647 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
649 // Add the scores to the middlegame and endgame eval
650 return apply_weight(score, Weights[PassedPawns]);
654 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
655 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
656 // related to the possibility that pawns are unstoppable.
658 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
660 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
662 if (!b || pos.non_pawn_material(~us))
665 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
669 // evaluate_space() computes the space evaluation for a given side. The
670 // space evaluation is a simple bonus based on the number of safe squares
671 // available for minor pieces on the central four files on ranks 2--4. Safe
672 // squares one, two or three squares behind a friendly pawn are counted
673 // twice. Finally, the space bonus is scaled by a weight taken from the
674 // material hash table. The aim is to improve play on game opening.
676 int evaluate_space(const Position& pos, const EvalInfo& ei) {
678 const Color Them = (Us == WHITE ? BLACK : WHITE);
680 // Find the safe squares for our pieces inside the area defined by
681 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
682 // pawn, or if it is undefended and attacked by an enemy piece.
683 Bitboard safe = SpaceMask[Us]
684 & ~pos.pieces(Us, PAWN)
685 & ~ei.attackedBy[Them][PAWN]
686 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
688 // Find all squares which are at most three squares behind some friendly pawn
689 Bitboard behind = pos.pieces(Us, PAWN);
690 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
691 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
693 // Since SpaceMask[Us] is fully on our half of the board
694 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
696 // Count safe + (behind & safe) with a single popcount
697 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
701 // do_evaluate() is the evaluation entry point, called directly from evaluate()
704 Value do_evaluate(const Position& pos) {
706 assert(!pos.checkers());
709 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
710 Thread* thisThread = pos.this_thread();
712 // Initialize score by reading the incrementally updated scores included
713 // in the position object (material + piece square tables) and adding a
714 // Tempo bonus. Score is computed from the point of view of white.
715 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
717 // Probe the material hash table
718 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
719 score += ei.mi->material_value();
721 // If we have a specialized evaluation function for the current material
722 // configuration, call it and return.
723 if (ei.mi->specialized_eval_exists())
724 return ei.mi->evaluate(pos);
726 // Probe the pawn hash table
727 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
728 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
730 // Initialize attack and king safety bitboards
731 init_eval_info<WHITE>(pos, ei);
732 init_eval_info<BLACK>(pos, ei);
734 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
735 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
737 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
738 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
739 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
741 // Evaluate pieces and mobility
742 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
743 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
745 // Evaluate kings after all other pieces because we need complete attack
746 // information when computing the king safety evaluation.
747 score += evaluate_king<WHITE, Trace>(pos, ei)
748 - evaluate_king<BLACK, Trace>(pos, ei);
750 // Evaluate tactical threats, we need full attack information including king
751 score += evaluate_threats<WHITE, Trace>(pos, ei)
752 - evaluate_threats<BLACK, Trace>(pos, ei);
754 // Evaluate passed pawns, we need full attack information including king
755 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
756 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
758 // If one side has only a king, score for potential unstoppable pawns
759 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
760 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
761 - evaluate_unstoppable_pawns(pos, BLACK, ei);
763 // Evaluate space for both sides, only in middlegame
764 if (ei.mi->space_weight())
766 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
767 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
770 // Scale winning side if position is more drawish than it appears
771 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
772 : ei.mi->scale_factor(pos, BLACK);
774 // If we don't already have an unusual scale factor, check for opposite
775 // colored bishop endgames, and use a lower scale for those.
776 if ( ei.mi->game_phase() < PHASE_MIDGAME
777 && pos.opposite_bishops()
778 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
780 // Ignoring any pawns, do both sides only have a single bishop and no
782 if ( pos.non_pawn_material(WHITE) == BishopValueMg
783 && pos.non_pawn_material(BLACK) == BishopValueMg)
785 // Check for KBP vs KB with only a single pawn that is almost
786 // certainly a draw or at least two pawns.
787 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
788 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
791 // Endgame with opposite-colored bishops, but also other pieces. Still
792 // a bit drawish, but not as drawish as with only the two bishops.
793 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
796 Value v = interpolate(score, ei.mi->game_phase(), sf);
798 // In case of tracing add all single evaluation contributions for both white and black
801 Tracing::add_term(Tracing::PST, pos.psq_score());
802 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
803 Tracing::add_term(PAWN, ei.pi->pawns_value());
804 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
805 , apply_weight(mobility[BLACK], Weights[Mobility]));
806 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
807 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
808 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
809 Tracing::add_term(Tracing::TOTAL, score);
814 return pos.side_to_move() == WHITE ? v : -v;
818 // Tracing function definitions
820 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
822 void Tracing::add_term(int idx, Score wScore, Score bScore) {
824 terms[WHITE][idx] = wScore;
825 terms[BLACK][idx] = bScore;
828 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
830 Score wScore = terms[WHITE][idx];
831 Score bScore = terms[BLACK][idx];
834 case PST: case IMBALANCE: case PAWN: case TOTAL:
835 ss << std::setw(20) << name << " | --- --- | --- --- | "
836 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
837 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
840 ss << std::setw(20) << name << " | " << std::noshowpos
841 << std::setw(5) << to_cp(mg_value(wScore)) << " "
842 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
843 << std::setw(5) << to_cp(mg_value(bScore)) << " "
844 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
845 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
846 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
850 std::string Tracing::do_trace(const Position& pos) {
852 std::memset(terms, 0, sizeof(terms));
854 Value v = do_evaluate<true>(pos);
855 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
857 std::stringstream ss;
858 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
859 << " Eval term | White | Black | Total \n"
860 << " | MG EG | MG EG | MG EG \n"
861 << "---------------------+-------------+-------------+-------------\n";
863 format_row(ss, "Material, PST, Tempo", PST);
864 format_row(ss, "Material imbalance", IMBALANCE);
865 format_row(ss, "Pawns", PAWN);
866 format_row(ss, "Knights", KNIGHT);
867 format_row(ss, "Bishops", BISHOP);
868 format_row(ss, "Rooks", ROOK);
869 format_row(ss, "Queens", QUEEN);
870 format_row(ss, "Mobility", MOBILITY);
871 format_row(ss, "King safety", KING);
872 format_row(ss, "Threats", THREAT);
873 format_row(ss, "Passed pawns", PASSED);
874 format_row(ss, "Space", SPACE);
876 ss << "---------------------+-------------+-------------+-------------\n";
877 format_row(ss, "Total", TOTAL);
879 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
889 /// evaluate() is the main evaluation function. It returns a static evaluation
890 /// of the position always from the point of view of the side to move.
892 Value evaluate(const Position& pos) {
893 return do_evaluate<false>(pos);
897 /// trace() is like evaluate(), but instead of returning a value, it returns
898 /// a string (suitable for outputting to stdout) that contains the detailed
899 /// descriptions and values of each evaluation term. It's mainly used for
901 std::string trace(const Position& pos) {
902 return Tracing::do_trace(pos);
906 /// init() computes evaluation weights from the corresponding UCI parameters
907 /// and setup king tables.
911 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
912 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
913 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
914 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
915 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
916 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
918 const double MaxSlope = 30;
919 const double Peak = 1280;
921 for (int t = 0, i = 1; i < 100; ++i)
923 t = std::min(Peak, std::min(0.4 * i * i, t + MaxSlope));
925 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
926 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);