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 // init_eval_info() initializes king bitboards for given color adding
226 // pawn attacks. To be done at the beginning of the evaluation.
229 void init_eval_info(const Position& pos, EvalInfo& ei) {
231 const Color Them = (Us == WHITE ? BLACK : WHITE);
232 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
234 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
236 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
237 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
239 // Init king safety tables only if we are going to use them
240 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
242 ei.kingRing[Them] = b | shift_bb<Down>(b);
243 b &= ei.attackedBy[Us][PAWN];
244 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
245 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
248 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
252 // evaluate_outposts() evaluates bishop and knight outpost squares
254 template<PieceType Pt, Color Us>
255 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
257 const Color Them = (Us == WHITE ? BLACK : WHITE);
259 assert (Pt == BISHOP || Pt == KNIGHT);
261 // Initial bonus based on square
262 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
264 // Increase bonus if supported by pawn, especially if the opponent has
265 // no minor piece which can trade with the outpost piece.
266 if (bonus && (ei.attackedBy[Us][PAWN] & s))
268 if ( !pos.pieces(Them, KNIGHT)
269 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
270 bonus += bonus + bonus / 2;
275 return make_score(bonus, bonus);
279 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
281 template<PieceType Pt, Color Us, bool Trace>
282 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
286 Score score = SCORE_ZERO;
288 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
289 const Color Them = (Us == WHITE ? BLACK : WHITE);
290 const Square* pl = pos.list<Pt>(Us);
292 ei.attackedBy[Us][Pt] = 0;
294 while ((s = *pl++) != SQ_NONE)
296 // Find attacked squares, including x-ray attacks for bishops and rooks
297 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
298 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
299 : pos.attacks_from<Pt>(s);
301 if (ei.pinnedPieces[Us] & s)
302 b &= LineBB[pos.king_square(Us)][s];
304 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
306 if (b & ei.kingRing[Them])
308 ei.kingAttackersCount[Us]++;
309 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
310 Bitboard bb = b & ei.attackedBy[Them][KING];
312 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
316 b &= ~( ei.attackedBy[Them][KNIGHT]
317 | ei.attackedBy[Them][BISHOP]
318 | ei.attackedBy[Them][ROOK]);
320 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
321 : popcount<Full >(b & mobilityArea[Us]);
323 mobility[Us] += MobilityBonus[Pt][mob];
325 // Decrease score if we are attacked by an enemy pawn. The remaining part
326 // of threat evaluation must be done later when we have full attack info.
327 if (ei.attackedBy[Them][PAWN] & s)
328 score -= ThreatenedByPawn[Pt];
330 if (Pt == BISHOP || Pt == KNIGHT)
332 // Penalty for bishop with same colored pawns
334 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
336 // Bishop and knight outposts squares
337 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
338 score += evaluate_outposts<Pt, Us>(pos, ei, s);
340 // Bishop or knight behind a pawn
341 if ( relative_rank(Us, s) < RANK_5
342 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
343 score += MinorBehindPawn;
348 // Rook piece attacking enemy pawns on the same rank/file
349 if (relative_rank(Us, s) >= RANK_5)
351 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
353 score += popcount<Max15>(pawns) * RookOnPawn;
356 // Give a bonus for a rook on a open or semi-open file
357 if (ei.pi->semiopen_file(Us, file_of(s)))
358 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
360 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
363 Square ksq = pos.king_square(Us);
365 // Penalize rooks which are trapped by a king. Penalize more if the
366 // king has lost its castling capability.
367 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
368 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
369 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
370 score -= (TrappedRook - make_score(mob * 8, 0)) * (1 + !pos.can_castle(Us));
373 // An important Chess960 pattern: A cornered bishop blocked by a friendly
374 // pawn diagonally in front of it is a very serious problem, especially
375 // when that pawn is also blocked.
378 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
380 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
381 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
382 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
383 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
389 Tracing::terms[Us][Pt] = score;
391 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
395 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
397 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
400 // evaluate_king() assigns bonuses and penalties to a king of a given color
402 template<Color Us, bool Trace>
403 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
405 const Color Them = (Us == WHITE ? BLACK : WHITE);
407 Bitboard undefended, b, b1, b2, safe;
409 const Square ksq = pos.king_square(Us);
411 // King shelter and enemy pawns storm
412 Score score = ei.pi->king_safety<Us>(pos, ksq);
414 // Main king safety evaluation
415 if (ei.kingAttackersCount[Them])
417 // Find the attacked squares around the king which have no defenders
418 // apart from the king itself
419 undefended = ei.attackedBy[Them][ALL_PIECES]
420 & ei.attackedBy[Us][KING]
421 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
422 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
423 | ei.attackedBy[Us][QUEEN]);
425 // Initialize the 'attackUnits' variable, which is used later on as an
426 // index to the KingDanger[] array. The initial value is based on the
427 // number and types of the enemy's attacking pieces, the number of
428 // attacked and undefended squares around our king and the quality of
429 // the pawn shelter (current 'score' value).
430 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
431 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
432 + 2 * (ei.pinnedPieces[Us] != 0)
433 - mg_value(score) / 32;
435 // Analyse the enemy's safe queen contact checks. Firstly, find the
436 // undefended squares around the king that are attacked by the enemy's
438 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
441 // ...and then remove squares not supported by another enemy piece
442 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
443 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
446 attackUnits += QueenContactCheck
448 * (Them == pos.side_to_move() ? 2 : 1);
451 // Analyse the enemy's safe rook contact checks. Firstly, find the
452 // undefended squares around the king that are attacked by the enemy's
454 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
456 // Consider only squares where the enemy's rook gives check
457 b &= PseudoAttacks[ROOK][ksq];
461 // ...and then remove squares not supported by another enemy piece
462 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
463 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
466 attackUnits += RookContactCheck
468 * (Them == pos.side_to_move() ? 2 : 1);
471 // Analyse the enemy's safe distance checks for sliders and knights
472 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
474 b1 = pos.attacks_from<ROOK>(ksq) & safe;
475 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
477 // Enemy queen safe checks
478 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
480 attackUnits += QueenCheck * popcount<Max15>(b);
482 // Enemy rooks safe checks
483 b = b1 & ei.attackedBy[Them][ROOK];
485 attackUnits += RookCheck * popcount<Max15>(b);
487 // Enemy bishops safe checks
488 b = b2 & ei.attackedBy[Them][BISHOP];
490 attackUnits += BishopCheck * popcount<Max15>(b);
492 // Enemy knights safe checks
493 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
495 attackUnits += KnightCheck * popcount<Max15>(b);
497 // To index KingDanger[] attackUnits must be in [0, 99] range
498 attackUnits = std::min(99, std::max(0, attackUnits));
500 // Finally, extract the king danger score from the KingDanger[]
501 // array and subtract the score from evaluation.
502 score -= KingDanger[Us == Search::RootColor][attackUnits];
506 Tracing::terms[Us][KING] = score;
512 // evaluate_threats() assigns bonuses according to the type of attacking piece
513 // and the type of attacked one.
515 template<Color Us, bool Trace>
516 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
518 const Color Them = (Us == WHITE ? BLACK : WHITE);
520 Bitboard b, undefendedMinors, weakEnemies;
521 Score score = SCORE_ZERO;
523 // Undefended minors get penalized even if they are not under attack
524 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
525 & ~ei.attackedBy[Them][ALL_PIECES];
527 if (undefendedMinors)
528 score += UndefendedMinor;
530 // Enemy pieces not defended by a pawn and under our attack
531 weakEnemies = pos.pieces(Them)
532 & ~ei.attackedBy[Them][PAWN]
533 & ei.attackedBy[Us][ALL_PIECES];
535 // Add a bonus according if the attacking pieces are minor or major
538 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
540 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
542 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
544 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
548 Tracing::terms[Us][Tracing::THREAT] = score;
554 // evaluate_passed_pawns() evaluates the passed pawns of the given color
556 template<Color Us, bool Trace>
557 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
559 const Color Them = (Us == WHITE ? BLACK : WHITE);
561 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
562 Score score = SCORE_ZERO;
564 b = ei.pi->passed_pawns(Us);
568 Square s = pop_lsb(&b);
570 assert(pos.pawn_passed(Us, s));
572 int r = relative_rank(Us, s) - RANK_2;
573 int rr = r * (r - 1);
575 // Base bonus based on rank
576 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
580 Square blockSq = s + pawn_push(Us);
582 // Adjust bonus based on the king's proximity
583 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
584 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
586 // If blockSq is not the queening square then consider also a second push
587 if (relative_rank(Us, blockSq) != RANK_8)
588 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
590 // If the pawn is free to advance, then increase the bonus
591 if (pos.empty(blockSq))
593 squaresToQueen = forward_bb(Us, s);
595 // If there is an enemy rook or queen attacking the pawn from behind,
596 // add all X-ray attacks by the rook or queen. Otherwise consider only
597 // the squares in the pawn's path attacked or occupied by the enemy.
598 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
599 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
600 unsafeSquares = squaresToQueen;
602 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
604 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
605 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
606 defendedSquares = squaresToQueen;
608 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
610 // If there aren't any enemy attacks, assign a big bonus. Otherwise
611 // assign a smaller bonus if the block square isn't attacked.
612 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
614 // If the path to queen is fully defended, assign a big bonus.
615 // Otherwise assign a smaller bonus if the block square is defended.
616 if (defendedSquares == squaresToQueen)
619 else if (defendedSquares & blockSq)
622 mbonus += k * rr, ebonus += k * rr;
626 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
627 ebonus += ebonus / 4;
629 score += make_score(mbonus, ebonus);
633 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
635 // Add the scores to the middlegame and endgame eval
636 return apply_weight(score, Weights[PassedPawns]);
640 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
641 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
642 // related to the possibility that pawns are unstoppable.
644 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
646 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
648 if (!b || pos.non_pawn_material(~us))
651 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
655 // evaluate_space() computes the space evaluation for a given side. The
656 // space evaluation is a simple bonus based on the number of safe squares
657 // available for minor pieces on the central four files on ranks 2--4. Safe
658 // squares one, two or three squares behind a friendly pawn are counted
659 // twice. Finally, the space bonus is scaled by a weight taken from the
660 // material hash table. The aim is to improve play on game opening.
662 int evaluate_space(const Position& pos, const EvalInfo& ei) {
664 const Color Them = (Us == WHITE ? BLACK : WHITE);
666 // Find the safe squares for our pieces inside the area defined by
667 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
668 // pawn, or if it is undefended and attacked by an enemy piece.
669 Bitboard safe = SpaceMask[Us]
670 & ~pos.pieces(Us, PAWN)
671 & ~ei.attackedBy[Them][PAWN]
672 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
674 // Find all squares which are at most three squares behind some friendly pawn
675 Bitboard behind = pos.pieces(Us, PAWN);
676 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
677 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
679 // Since SpaceMask[Us] is fully on our half of the board
680 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
682 // Count safe + (behind & safe) with a single popcount
683 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
687 // do_evaluate() is the evaluation entry point, called directly from evaluate()
690 Value do_evaluate(const Position& pos) {
692 assert(!pos.checkers());
695 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
696 Thread* thisThread = pos.this_thread();
698 // Initialize score by reading the incrementally updated scores included
699 // in the position object (material + piece square tables) and adding a
700 // Tempo bonus. Score is computed from the point of view of white.
701 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
703 // Probe the material hash table
704 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
705 score += ei.mi->material_value();
707 // If we have a specialized evaluation function for the current material
708 // configuration, call it and return.
709 if (ei.mi->specialized_eval_exists())
710 return ei.mi->evaluate(pos);
712 // Probe the pawn hash table
713 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
714 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
716 // Initialize attack and king safety bitboards
717 init_eval_info<WHITE>(pos, ei);
718 init_eval_info<BLACK>(pos, ei);
720 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
721 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
723 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
724 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
725 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
727 // Evaluate pieces and mobility
728 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
729 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
731 // Evaluate kings after all other pieces because we need complete attack
732 // information when computing the king safety evaluation.
733 score += evaluate_king<WHITE, Trace>(pos, ei)
734 - evaluate_king<BLACK, Trace>(pos, ei);
736 // Evaluate tactical threats, we need full attack information including king
737 score += evaluate_threats<WHITE, Trace>(pos, ei)
738 - evaluate_threats<BLACK, Trace>(pos, ei);
740 // Evaluate passed pawns, we need full attack information including king
741 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
742 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
744 // If one side has only a king, score for potential unstoppable pawns
745 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
746 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
747 - evaluate_unstoppable_pawns(pos, BLACK, ei);
749 // Evaluate space for both sides, only in middlegame
750 if (ei.mi->space_weight())
752 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
753 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
756 // Scale winning side if position is more drawish than it appears
757 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
758 : ei.mi->scale_factor(pos, BLACK);
760 // If we don't already have an unusual scale factor, check for opposite
761 // colored bishop endgames, and use a lower scale for those.
762 if ( ei.mi->game_phase() < PHASE_MIDGAME
763 && pos.opposite_bishops()
764 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
766 // Ignoring any pawns, do both sides only have a single bishop and no
768 if ( pos.non_pawn_material(WHITE) == BishopValueMg
769 && pos.non_pawn_material(BLACK) == BishopValueMg)
771 // Check for KBP vs KB with only a single pawn that is almost
772 // certainly a draw or at least two pawns.
773 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
774 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
777 // Endgame with opposite-colored bishops, but also other pieces. Still
778 // a bit drawish, but not as drawish as with only the two bishops.
779 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
782 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
783 Value v = mg_value(score) * int(ei.mi->game_phase())
784 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
788 // In case of tracing add all single evaluation contributions for both white and black
791 Tracing::add_term(Tracing::PST, pos.psq_score());
792 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
793 Tracing::add_term(PAWN, ei.pi->pawns_value());
794 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
795 , apply_weight(mobility[BLACK], Weights[Mobility]));
796 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
797 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
798 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
799 Tracing::add_term(Tracing::TOTAL, score);
804 return pos.side_to_move() == WHITE ? v : -v;
808 // Tracing function definitions
810 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
812 void Tracing::add_term(int idx, Score wScore, Score bScore) {
814 terms[WHITE][idx] = wScore;
815 terms[BLACK][idx] = bScore;
818 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
820 Score wScore = terms[WHITE][idx];
821 Score bScore = terms[BLACK][idx];
824 case PST: case IMBALANCE: case PAWN: case TOTAL:
825 ss << std::setw(20) << name << " | --- --- | --- --- | "
826 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
827 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
830 ss << std::setw(20) << name << " | " << std::noshowpos
831 << std::setw(5) << to_cp(mg_value(wScore)) << " "
832 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
833 << std::setw(5) << to_cp(mg_value(bScore)) << " "
834 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
835 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
836 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
840 std::string Tracing::do_trace(const Position& pos) {
842 std::memset(terms, 0, sizeof(terms));
844 Value v = do_evaluate<true>(pos);
845 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
847 std::stringstream ss;
848 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
849 << " Eval term | White | Black | Total \n"
850 << " | MG EG | MG EG | MG EG \n"
851 << "---------------------+-------------+-------------+-------------\n";
853 format_row(ss, "Material, PST, Tempo", PST);
854 format_row(ss, "Material imbalance", IMBALANCE);
855 format_row(ss, "Pawns", PAWN);
856 format_row(ss, "Knights", KNIGHT);
857 format_row(ss, "Bishops", BISHOP);
858 format_row(ss, "Rooks", ROOK);
859 format_row(ss, "Queens", QUEEN);
860 format_row(ss, "Mobility", MOBILITY);
861 format_row(ss, "King safety", KING);
862 format_row(ss, "Threats", THREAT);
863 format_row(ss, "Passed pawns", PASSED);
864 format_row(ss, "Space", SPACE);
866 ss << "---------------------+-------------+-------------+-------------\n";
867 format_row(ss, "Total", TOTAL);
869 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
879 /// evaluate() is the main evaluation function. It returns a static evaluation
880 /// of the position always from the point of view of the side to move.
882 Value evaluate(const Position& pos) {
883 return do_evaluate<false>(pos);
887 /// trace() is like evaluate(), but instead of returning a value, it returns
888 /// a string (suitable for outputting to stdout) that contains the detailed
889 /// descriptions and values of each evaluation term. It's mainly used for
891 std::string trace(const Position& pos) {
892 return Tracing::do_trace(pos);
896 /// init() computes evaluation weights from the corresponding UCI parameters
897 /// and setup king tables.
901 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
902 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
903 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
904 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
905 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
906 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
908 const double MaxSlope = 30;
909 const double Peak = 1280;
911 for (int t = 0, i = 1; i < 100; ++i)
913 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
915 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
916 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);