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(-35,-30), S(-22,-20), 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(-22,-27), S( -8,-13), 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(-17,-33), S(-11,-16), 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(-12,-20), S( -8,-13), 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 RookOn7th = make_score(11, 20);
165 const Score RookOnPawn = make_score(10, 28);
166 const Score RookOpenFile = make_score(43, 21);
167 const Score RookSemiopenFile = make_score(19, 10);
168 const Score BishopPawns = make_score( 8, 12);
169 const Score KnightPawns = make_score( 8, 4);
170 const Score MinorBehindPawn = make_score(16, 0);
171 const Score UndefendedMinor = make_score(25, 10);
172 const Score TrappedRook = make_score(90, 0);
173 const Score Unstoppable = make_score( 0, 20);
174 const Score LowMobPenalty = make_score(40, 20);
176 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
177 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
178 // happen in Chess960 games.
179 const Score TrappedBishopA1H1 = make_score(50, 50);
181 // SpaceMask[Color] contains the area of the board which is considered
182 // by the space evaluation. In the middlegame, each side is given a bonus
183 // based on how many squares inside this area are safe and available for
184 // friendly minor pieces.
185 const Bitboard SpaceMask[] = {
186 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
187 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
190 const Bitboard EdgeBB = Rank1BB | Rank8BB | FileABB | FileHBB;
192 // King danger constants and variables. The king danger scores are taken
193 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
194 // of the enemy attack are added up into an integer, which is used as an
195 // index to KingDanger[].
197 // KingAttackWeights[PieceType] contains king attack weights by piece type
198 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
200 // Bonuses for enemy's safe checks
201 const int QueenContactCheck = 24;
202 const int RookContactCheck = 16;
203 const int QueenCheck = 12;
204 const int RookCheck = 8;
205 const int BishopCheck = 2;
206 const int KnightCheck = 3;
208 // KingDanger[Color][attackUnits] contains the actual king danger weighted
209 // scores, indexed by color and by a calculated integer number.
210 Score KingDanger[COLOR_NB][128];
212 // Function prototypes
214 Value do_evaluate(const Position& pos);
217 void init_eval_info(const Position& pos, EvalInfo& ei);
220 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility);
222 template<Color Us, bool Trace>
223 Score evaluate_king(const Position& pos, const EvalInfo& ei);
225 template<Color Us, bool Trace>
226 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
228 template<Color Us, bool Trace>
229 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
232 int evaluate_space(const Position& pos, const EvalInfo& ei);
234 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
236 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
237 Score apply_weight(Score v, const Weight& w);
238 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
244 /// evaluate() is the main evaluation function. It always computes two
245 /// values, an endgame score and a middlegame score, and interpolates
246 /// between them based on the remaining material.
248 Value evaluate(const Position& pos) {
249 return do_evaluate<false>(pos);
253 /// trace() is like evaluate(), but instead of returning a value, it returns
254 /// a string (suitable for outputting to stdout) that contains the detailed
255 /// descriptions and values of each evaluation term. It's mainly used for
257 std::string trace(const Position& pos) {
258 return Tracing::do_trace(pos);
262 /// init() computes evaluation weights from the corresponding UCI parameters
263 /// and setup king tables.
267 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
268 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
269 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
270 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
271 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
272 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
274 const int MaxSlope = 30;
275 const int Peak = 1280;
277 for (int t = 0, i = 1; i < 100; ++i)
279 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
281 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
282 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
292 Value do_evaluate(const Position& pos) {
294 assert(!pos.checkers());
297 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
298 Thread* thisThread = pos.this_thread();
300 // Initialize score by reading the incrementally updated scores included
301 // in the position object (material + piece square tables) and adding a
302 // Tempo bonus. Score is computed from the point of view of white.
303 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
305 // Probe the material hash table
306 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
307 score += ei.mi->material_value();
309 // If we have a specialized evaluation function for the current material
310 // configuration, call it and return.
311 if (ei.mi->specialized_eval_exists())
312 return ei.mi->evaluate(pos);
314 // Probe the pawn hash table
315 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
316 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
318 // Initialize attack and king safety bitboards
319 init_eval_info<WHITE>(pos, ei);
320 init_eval_info<BLACK>(pos, ei);
322 // Evaluate pieces and mobility
323 score += evaluate_pieces<Trace>(pos, ei, mobility);
325 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
327 // Evaluate kings after all other pieces because we need complete attack
328 // information when computing the king safety evaluation.
329 score += evaluate_king<WHITE, Trace>(pos, ei)
330 - evaluate_king<BLACK, Trace>(pos, ei);
332 // Evaluate tactical threats, we need full attack information including king
333 score += evaluate_threats<WHITE, Trace>(pos, ei)
334 - evaluate_threats<BLACK, Trace>(pos, ei);
336 // Evaluate passed pawns, we need full attack information including king
337 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
338 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
340 // If one side has only a king, score for potential unstoppable pawns
341 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
342 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
343 - evaluate_unstoppable_pawns(pos, BLACK, ei);
345 // Evaluate space for both sides, only in middlegame
346 if (ei.mi->space_weight())
348 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
349 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
352 // Scale winning side if position is more drawish than it appears
353 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
354 : ei.mi->scale_factor(pos, BLACK);
356 // If we don't already have an unusual scale factor, check for opposite
357 // colored bishop endgames, and use a lower scale for those.
358 if ( ei.mi->game_phase() < PHASE_MIDGAME
359 && pos.opposite_bishops()
360 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
362 // Ignoring any pawns, do both sides only have a single bishop and no
364 if ( pos.non_pawn_material(WHITE) == BishopValueMg
365 && pos.non_pawn_material(BLACK) == BishopValueMg)
367 // Check for KBP vs KB with only a single pawn that is almost
368 // certainly a draw or at least two pawns.
369 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
370 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
373 // Endgame with opposite-colored bishops, but also other pieces. Still
374 // a bit drawish, but not as drawish as with only the two bishops.
375 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
378 Value v = interpolate(score, ei.mi->game_phase(), sf);
380 // In case of tracing add all single evaluation contributions for both white and black
383 Tracing::add_term(Tracing::PST, pos.psq_score());
384 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
385 Tracing::add_term(PAWN, ei.pi->pawns_value());
386 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
387 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
388 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
389 Tracing::add_term(Tracing::TOTAL, score);
394 return pos.side_to_move() == WHITE ? v : -v;
398 // init_eval_info() initializes king bitboards for given color adding
399 // pawn attacks. To be done at the beginning of the evaluation.
402 void init_eval_info(const Position& pos, EvalInfo& ei) {
404 const Color Them = (Us == WHITE ? BLACK : WHITE);
405 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
407 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
409 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
410 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
412 // Init king safety tables only if we are going to use them
413 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
415 ei.kingRing[Them] = b | shift_bb<Down>(b);
416 b &= ei.attackedBy[Us][PAWN];
417 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
418 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
421 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
425 // evaluate_outposts() evaluates bishop and knight outpost squares
427 template<PieceType Pt, Color Us>
428 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
430 const Color Them = (Us == WHITE ? BLACK : WHITE);
432 assert (Pt == BISHOP || Pt == KNIGHT);
434 // Initial bonus based on square
435 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
437 // Increase bonus if supported by pawn, especially if the opponent has
438 // no minor piece which can trade with the outpost piece.
439 if (bonus && (ei.attackedBy[Us][PAWN] & s))
441 if ( !pos.pieces(Them, KNIGHT)
442 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
443 bonus += bonus + bonus / 2;
448 return make_score(bonus, bonus);
452 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
454 template<PieceType Pt, Color Us, bool Trace>
455 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
459 Score score = SCORE_ZERO;
461 const Color Them = (Us == WHITE ? BLACK : WHITE);
462 const Square* pl = pos.list<Pt>(Us);
464 ei.attackedBy[Us][Pt] = 0;
466 while ((s = *pl++) != SQ_NONE)
468 // Find attacked squares, including x-ray attacks for bishops and rooks
469 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
470 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
471 : pos.attacks_from<Pt>(s);
473 if (ei.pinnedPieces[Us] & s)
474 b &= LineBB[pos.king_square(Us)][s];
476 ei.attackedBy[Us][Pt] |= b;
478 if (b & ei.kingRing[Them])
480 ei.kingAttackersCount[Us]++;
481 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
482 Bitboard bb = b & ei.attackedBy[Them][KING];
484 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
488 b &= ~( ei.attackedBy[Them][KNIGHT]
489 | ei.attackedBy[Them][BISHOP]
490 | ei.attackedBy[Them][ROOK]);
492 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea)
493 : popcount<Full >(b & mobilityArea);
495 mobility[Us] += MobilityBonus[Pt][mob];
497 if (mob <= 1 && (EdgeBB & s))
498 score -= LowMobPenalty;
500 // Decrease score if we are attacked by an enemy pawn. The remaining part
501 // of threat evaluation must be done later when we have full attack info.
502 if (ei.attackedBy[Them][PAWN] & s)
503 score -= ThreatenedByPawn[Pt];
505 if (Pt == BISHOP || Pt == KNIGHT)
507 // Penalty for bishop with same colored pawns
509 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
511 // Penalty for knight when there are few enemy pawns
513 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
515 // Bishop and knight outposts squares
516 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
517 score += evaluate_outposts<Pt, Us>(pos, ei, s);
519 // Bishop or knight behind a pawn
520 if ( relative_rank(Us, s) < RANK_5
521 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
522 score += MinorBehindPawn;
527 // Rook on 7th rank and enemy king trapped on 8th
528 if ( relative_rank(Us, s) == RANK_7
529 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
532 // Rook piece attacking enemy pawns on the same rank/file
533 if (relative_rank(Us, s) >= RANK_5)
535 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
537 score += popcount<Max15>(pawns) * RookOnPawn;
540 // Give a bonus for a rook on a open or semi-open file
541 if (ei.pi->semiopen(Us, file_of(s)))
542 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
544 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
547 Square ksq = pos.king_square(Us);
549 // Penalize rooks which are trapped by a king. Penalize more if the
550 // king has lost its castling capability.
551 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
552 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
553 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
554 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
557 // An important Chess960 pattern: A cornered bishop blocked by a friendly
558 // pawn diagonally in front of it is a very serious problem, especially
559 // when that pawn is also blocked.
562 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
564 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
565 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
566 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
567 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
573 Tracing::terms[Us][Pt] = score;
579 // evaluate_pieces() assigns bonuses and penalties to all the pieces of both colors
582 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
584 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
585 const Bitboard whiteMobilityArea = ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING));
586 const Bitboard blackMobilityArea = ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING));
590 score = evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
591 - evaluate_pieces<KNIGHT, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
592 score += evaluate_pieces<BISHOP, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
593 - evaluate_pieces<BISHOP, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
594 score += evaluate_pieces< ROOK, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
595 - evaluate_pieces< ROOK, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
596 score += evaluate_pieces< QUEEN, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
597 - evaluate_pieces< QUEEN, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
599 // Sum up all attacked squares (updated in evaluate_pieces)
600 ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[WHITE][PAWN] | ei.attackedBy[WHITE][KNIGHT]
601 | ei.attackedBy[WHITE][BISHOP] | ei.attackedBy[WHITE][ROOK]
602 | ei.attackedBy[WHITE][QUEEN] | ei.attackedBy[WHITE][KING];
604 ei.attackedBy[BLACK][ALL_PIECES] = ei.attackedBy[BLACK][PAWN] | ei.attackedBy[BLACK][KNIGHT]
605 | ei.attackedBy[BLACK][BISHOP] | ei.attackedBy[BLACK][ROOK]
606 | ei.attackedBy[BLACK][QUEEN] | ei.attackedBy[BLACK][KING];
609 Tracing::terms[WHITE][Tracing::MOBILITY] = apply_weight(mobility[WHITE], Weights[Mobility]);
610 Tracing::terms[BLACK][Tracing::MOBILITY] = apply_weight(mobility[BLACK], Weights[Mobility]);
617 // evaluate_king() assigns bonuses and penalties to a king of a given color
619 template<Color Us, bool Trace>
620 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
622 const Color Them = (Us == WHITE ? BLACK : WHITE);
624 Bitboard undefended, b, b1, b2, safe;
626 const Square ksq = pos.king_square(Us);
628 // King shelter and enemy pawns storm
629 Score score = ei.pi->king_safety<Us>(pos, ksq);
631 // Main king safety evaluation
632 if (ei.kingAttackersCount[Them])
634 // Find the attacked squares around the king which have no defenders
635 // apart from the king itself
636 undefended = ei.attackedBy[Them][ALL_PIECES]
637 & ei.attackedBy[Us][KING]
638 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
639 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
640 | ei.attackedBy[Us][QUEEN]);
642 // Initialize the 'attackUnits' variable, which is used later on as an
643 // index to the KingDanger[] array. The initial value is based on the
644 // number and types of the enemy's attacking pieces, the number of
645 // attacked and undefended squares around our king and the quality of
646 // the pawn shelter (current 'score' value).
647 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
648 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
649 + 2 * (ei.pinnedPieces[Us] != 0)
650 - mg_value(score) / 32;
652 // Analyse the enemy's safe queen contact checks. Firstly, find the
653 // undefended squares around the king that are attacked by the enemy's
655 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
658 // ...and then remove squares not supported by another enemy piece
659 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
660 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
663 attackUnits += QueenContactCheck
665 * (Them == pos.side_to_move() ? 2 : 1);
668 // Analyse the enemy's safe rook contact checks. Firstly, find the
669 // undefended squares around the king that are attacked by the enemy's
671 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
673 // Consider only squares where the enemy's rook gives check
674 b &= PseudoAttacks[ROOK][ksq];
678 // ...and then remove squares not supported by another enemy piece
679 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
680 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
683 attackUnits += RookContactCheck
685 * (Them == pos.side_to_move() ? 2 : 1);
688 // Analyse the enemy's safe distance checks for sliders and knights
689 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
691 b1 = pos.attacks_from<ROOK>(ksq) & safe;
692 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
694 // Enemy queen safe checks
695 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
697 attackUnits += QueenCheck * popcount<Max15>(b);
699 // Enemy rooks safe checks
700 b = b1 & ei.attackedBy[Them][ROOK];
702 attackUnits += RookCheck * popcount<Max15>(b);
704 // Enemy bishops safe checks
705 b = b2 & ei.attackedBy[Them][BISHOP];
707 attackUnits += BishopCheck * popcount<Max15>(b);
709 // Enemy knights safe checks
710 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
712 attackUnits += KnightCheck * popcount<Max15>(b);
714 // To index KingDanger[] attackUnits must be in [0, 99] range
715 attackUnits = std::min(99, std::max(0, attackUnits));
717 // Finally, extract the king danger score from the KingDanger[]
718 // array and subtract the score from evaluation.
719 score -= KingDanger[Us == Search::RootColor][attackUnits];
723 Tracing::terms[Us][KING] = score;
729 // evaluate_threats() assigns bonuses according to the type of attacking piece
730 // and the type of attacked one.
732 template<Color Us, bool Trace>
733 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
735 const Color Them = (Us == WHITE ? BLACK : WHITE);
737 Bitboard b, undefendedMinors, weakEnemies;
738 Score score = SCORE_ZERO;
740 // Undefended minors get penalized even if they are not under attack
741 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
742 & ~ei.attackedBy[Them][ALL_PIECES];
744 if (undefendedMinors)
745 score += UndefendedMinor;
747 // Enemy pieces not defended by a pawn and under our attack
748 weakEnemies = pos.pieces(Them)
749 & ~ei.attackedBy[Them][PAWN]
750 & ei.attackedBy[Us][ALL_PIECES];
752 // Add a bonus according if the attacking pieces are minor or major
755 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
757 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
759 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
761 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
765 Tracing::terms[Us][Tracing::THREAT] = score;
771 // evaluate_passed_pawns() evaluates the passed pawns of the given color
773 template<Color Us, bool Trace>
774 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
776 const Color Them = (Us == WHITE ? BLACK : WHITE);
778 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
779 Score score = SCORE_ZERO;
781 b = ei.pi->passed_pawns(Us);
785 Square s = pop_lsb(&b);
787 assert(pos.pawn_passed(Us, s));
789 int r = int(relative_rank(Us, s) - RANK_2);
790 int rr = r * (r - 1);
792 // Base bonus based on rank
793 Value mbonus = Value(17 * rr);
794 Value ebonus = Value(7 * (rr + r + 1));
798 Square blockSq = s + pawn_push(Us);
800 // Adjust bonus based on the king's proximity
801 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
802 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
804 // If blockSq is not the queening square then consider also a second push
805 if (relative_rank(Us, blockSq) != RANK_8)
806 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
808 // If the pawn is free to advance, then increase the bonus
809 if (pos.empty(blockSq))
811 squaresToQueen = forward_bb(Us, s);
813 // If there is an enemy rook or queen attacking the pawn from behind,
814 // add all X-ray attacks by the rook or queen. Otherwise consider only
815 // the squares in the pawn's path attacked or occupied by the enemy.
816 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
817 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
818 unsafeSquares = squaresToQueen;
820 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
822 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
823 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
824 defendedSquares = squaresToQueen;
826 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
828 // If there aren't any enemy attacks, then assign a huge bonus.
829 // The bonus will be a bit smaller if at least the block square
830 // isn't attacked, otherwise assign the smallest possible bonus.
831 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
833 // Assign a big bonus if the path to the queen is fully defended,
834 // otherwise assign a bit less of a bonus if at least the block
835 // square is defended.
836 if (defendedSquares == squaresToQueen)
839 else if (defendedSquares & blockSq)
840 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
842 mbonus += Value(k * rr), ebonus += Value(k * rr);
846 // Increase the bonus if the passed pawn is supported by a friendly pawn
847 // on the same rank and a bit smaller if it's on the previous rank.
848 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
849 if (supportingPawns & rank_bb(s))
850 ebonus += Value(r * 20);
852 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
853 ebonus += Value(r * 12);
855 // Rook pawns are a special case: They are sometimes worse, and
856 // sometimes better than other passed pawns. It is difficult to find
857 // good rules for determining whether they are good or bad. For now,
858 // we try the following: Increase the value for rook pawns if the
859 // other side has no pieces apart from a knight, and decrease the
860 // value if the other side has a rook or queen.
861 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
863 if (pos.non_pawn_material(Them) <= KnightValueMg)
864 ebonus += ebonus / 4;
866 else if (pos.pieces(Them, ROOK, QUEEN))
867 ebonus -= ebonus / 4;
870 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
871 ebonus += ebonus / 4;
873 score += make_score(mbonus, ebonus);
877 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
879 // Add the scores to the middlegame and endgame eval
880 return apply_weight(score, Weights[PassedPawns]);
884 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
885 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
886 // related to the possibility that pawns are unstoppable.
888 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
890 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
892 if (!b || pos.non_pawn_material(~us))
895 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
899 // evaluate_space() computes the space evaluation for a given side. The
900 // space evaluation is a simple bonus based on the number of safe squares
901 // available for minor pieces on the central four files on ranks 2--4. Safe
902 // squares one, two or three squares behind a friendly pawn are counted
903 // twice. Finally, the space bonus is scaled by a weight taken from the
904 // material hash table. The aim is to improve play on game opening.
906 int evaluate_space(const Position& pos, const EvalInfo& ei) {
908 const Color Them = (Us == WHITE ? BLACK : WHITE);
910 // Find the safe squares for our pieces inside the area defined by
911 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
912 // pawn, or if it is undefended and attacked by an enemy piece.
913 Bitboard safe = SpaceMask[Us]
914 & ~pos.pieces(Us, PAWN)
915 & ~ei.attackedBy[Them][PAWN]
916 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
918 // Find all squares which are at most three squares behind some friendly pawn
919 Bitboard behind = pos.pieces(Us, PAWN);
920 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
921 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
923 // Since SpaceMask[Us] is fully on our half of the board
924 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
926 // Count safe + (behind & safe) with a single popcount
927 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
931 // interpolate() interpolates between a middlegame and an endgame score,
932 // based on game phase. It also scales the return value by a ScaleFactor array.
934 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
936 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
937 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
938 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
940 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
941 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
944 // apply_weight() weights score v by score w trying to prevent overflow
945 Score apply_weight(Score v, const Weight& w) {
947 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
950 // weight_option() computes the value of an evaluation weight, by combining
951 // two UCI-configurable weights (midgame and endgame) with an internal weight.
953 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
955 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
956 Options[egOpt] * eg_value(internalWeight) / 100 };
961 // Tracing function definitions
963 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
965 void Tracing::add_term(int idx, Score wScore, Score bScore) {
967 terms[WHITE][idx] = wScore;
968 terms[BLACK][idx] = bScore;
971 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
973 Score wScore = terms[WHITE][idx];
974 Score bScore = terms[BLACK][idx];
977 case PST: case IMBALANCE: case PAWN: case TOTAL:
978 ss << std::setw(20) << name << " | --- --- | --- --- | "
979 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
980 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
983 ss << std::setw(20) << name << " | " << std::noshowpos
984 << std::setw(5) << to_cp(mg_value(wScore)) << " "
985 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
986 << std::setw(5) << to_cp(mg_value(bScore)) << " "
987 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
988 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
989 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
993 std::string Tracing::do_trace(const Position& pos) {
995 std::memset(terms, 0, sizeof(terms));
997 Value v = do_evaluate<true>(pos);
998 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
1000 std::stringstream ss;
1001 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
1002 << " Eval term | White | Black | Total \n"
1003 << " | MG EG | MG EG | MG EG \n"
1004 << "---------------------+-------------+-------------+-------------\n";
1006 format_row(ss, "Material, PST, Tempo", PST);
1007 format_row(ss, "Material imbalance", IMBALANCE);
1008 format_row(ss, "Pawns", PAWN);
1009 format_row(ss, "Knights", KNIGHT);
1010 format_row(ss, "Bishops", BISHOP);
1011 format_row(ss, "Rooks", ROOK);
1012 format_row(ss, "Queens", QUEEN);
1013 format_row(ss, "Mobility", MOBILITY);
1014 format_row(ss, "King safety", KING);
1015 format_row(ss, "Threats", THREAT);
1016 format_row(ss, "Passed pawns", PASSED);
1017 format_row(ss, "Space", SPACE);
1019 ss << "---------------------+-------------+-------------+-------------\n";
1020 format_row(ss, "Total", TOTAL);
1022 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";