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 };
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(-2, -1), S( 1, 5), S( 4, 11), // Queens
123 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
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 QueenOn7th = make_score( 3, 8);
166 const Score RookOnPawn = make_score(10, 28);
167 const Score QueenOnPawn = make_score( 4, 20);
168 const Score RookOpenFile = make_score(43, 21);
169 const Score RookSemiopenFile = make_score(19, 10);
170 const Score BishopPawns = make_score( 8, 12);
171 const Score KnightPawns = make_score( 8, 4);
172 const Score MinorBehindPawn = make_score(16, 0);
173 const Score UndefendedMinor = make_score(25, 10);
174 const Score TrappedRook = make_score(90, 0);
175 const Score Unstoppable = make_score( 0, 20);
177 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
178 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
179 // happen in Chess960 games.
180 const Score TrappedBishopA1H1 = make_score(50, 50);
182 // SpaceMask[Color] contains the area of the board which is considered
183 // by the space evaluation. In the middlegame, each side is given a bonus
184 // based on how many squares inside this area are safe and available for
185 // friendly minor pieces.
186 const Bitboard SpaceMask[] = {
187 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
188 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
191 // King danger constants and variables. The king danger scores are taken
192 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
193 // of the enemy attack are added up into an integer, which is used as an
194 // index to KingDanger[].
196 // KingAttackWeights[PieceType] contains king attack weights by piece type
197 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
199 // Bonuses for enemy's safe checks
200 const int QueenContactCheck = 24;
201 const int RookContactCheck = 16;
202 const int QueenCheck = 12;
203 const int RookCheck = 8;
204 const int BishopCheck = 2;
205 const int KnightCheck = 3;
207 // KingDanger[Color][attackUnits] contains the actual king danger weighted
208 // scores, indexed by color and by a calculated integer number.
209 Score KingDanger[COLOR_NB][128];
211 // Function prototypes
213 Value do_evaluate(const Position& pos);
216 void init_eval_info(const Position& pos, EvalInfo& ei);
218 template<Color Us, bool Trace>
219 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility);
221 template<Color Us, bool Trace>
222 Score evaluate_king(const Position& pos, const EvalInfo& ei);
224 template<Color Us, bool Trace>
225 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
227 template<Color Us, bool Trace>
228 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
231 int evaluate_space(const Position& pos, const EvalInfo& ei);
233 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
235 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
236 Score apply_weight(Score v, Score w);
237 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
243 /// evaluate() is the main evaluation function. It always computes two
244 /// values, an endgame score and a middlegame score, and interpolates
245 /// between them based on the remaining material.
247 Value evaluate(const Position& pos) {
248 return do_evaluate<false>(pos);
252 /// trace() is like evaluate(), but instead of returning a value, it returns
253 /// a string (suitable for outputting to stdout) that contains the detailed
254 /// descriptions and values of each evaluation term. It's mainly used for
256 std::string trace(const Position& pos) {
257 return Tracing::do_trace(pos);
261 /// init() computes evaluation weights from the corresponding UCI parameters
262 /// and setup king tables.
266 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
267 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
268 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
269 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
270 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
271 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
273 const int MaxSlope = 30;
274 const int Peak = 1280;
276 for (int t = 0, i = 1; i < 100; ++i)
278 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
280 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
281 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
291 Value do_evaluate(const Position& pos) {
293 assert(!pos.checkers());
296 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
297 Thread* thisThread = pos.this_thread();
299 // Initialize score by reading the incrementally updated scores included
300 // in the position object (material + piece square tables) and adding a
301 // Tempo bonus. Score is computed from the point of view of white.
302 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
304 // Probe the material hash table
305 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
306 score += ei.mi->material_value();
308 // If we have a specialized evaluation function for the current material
309 // configuration, call it and return.
310 if (ei.mi->specialized_eval_exists())
311 return ei.mi->evaluate(pos);
313 // Probe the pawn hash table
314 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
315 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
317 // Initialize attack and king safety bitboards
318 init_eval_info<WHITE>(pos, ei);
319 init_eval_info<BLACK>(pos, ei);
321 // Evaluate pieces and mobility
322 score += evaluate_pieces<WHITE, Trace>(pos, ei, mobility)
323 - evaluate_pieces<BLACK, 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);
487 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea)
488 : popcount<Full >(b & mobilityArea);
490 mobility[Us] += MobilityBonus[Pt][mob];
492 // Decrease score if we are attacked by an enemy pawn. The remaining part
493 // of threat evaluation must be done later when we have full attack info.
494 if (ei.attackedBy[Them][PAWN] & s)
495 score -= ThreatenedByPawn[Pt];
497 if (Pt == BISHOP || Pt == KNIGHT)
499 // Penalty for bishop with same colored pawns
501 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
503 // Penalty for knight when there are few enemy pawns
505 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
507 // Bishop and knight outposts squares
508 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
509 score += evaluate_outposts<Pt, Us>(pos, ei, s);
511 // Bishop or knight behind a pawn
512 if ( relative_rank(Us, s) < RANK_5
513 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
514 score += MinorBehindPawn;
517 if ( (Pt == ROOK || Pt == QUEEN)
518 && relative_rank(Us, s) >= RANK_5)
520 // Major piece on 7th rank and enemy king trapped on 8th
521 if ( relative_rank(Us, s) == RANK_7
522 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
523 score += Pt == ROOK ? RookOn7th : QueenOn7th;
525 // Major piece attacking enemy pawns on the same rank/file
526 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
528 score += popcount<Max15>(pawns) * (Pt == ROOK ? RookOnPawn : QueenOnPawn);
531 // Special extra evaluation for rooks
534 // Give a bonus for a rook on a open or semi-open file
535 if (ei.pi->semiopen(Us, file_of(s)))
536 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
538 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
541 Square ksq = pos.king_square(Us);
543 // Penalize rooks which are trapped by a king. Penalize more if the
544 // king has lost its castling capability.
545 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
546 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
547 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
548 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
551 // An important Chess960 pattern: A cornered bishop blocked by a friendly
552 // pawn diagonally in front of it is a very serious problem, especially
553 // when that pawn is also blocked.
556 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
558 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
559 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
560 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
561 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
567 Tracing::terms[Us][Pt] = score;
573 // evaluate_pieces() assigns bonuses and penalties to all the
574 // pieces of a given color.
576 template<Color Us, bool Trace>
577 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
579 const Color Them = (Us == WHITE ? BLACK : WHITE);
581 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
582 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
584 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
585 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
586 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
587 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
589 // Sum up all attacked squares (updated in evaluate_pieces)
590 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
591 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
592 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
594 Tracing::terms[Us][Tracing::MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
600 // evaluate_king() assigns bonuses and penalties to a king of a given color
602 template<Color Us, bool Trace>
603 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
605 const Color Them = (Us == WHITE ? BLACK : WHITE);
607 Bitboard undefended, b, b1, b2, safe;
609 const Square ksq = pos.king_square(Us);
611 // King shelter and enemy pawns storm
612 Score score = ei.pi->king_safety<Us>(pos, ksq);
614 // Main king safety evaluation
615 if (ei.kingAttackersCount[Them])
617 // Find the attacked squares around the king which have no defenders
618 // apart from the king itself
619 undefended = ei.attackedBy[Them][ALL_PIECES]
620 & ei.attackedBy[Us][KING]
621 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
622 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
623 | ei.attackedBy[Us][QUEEN]);
625 // Initialize the 'attackUnits' variable, which is used later on as an
626 // index to the KingDanger[] array. The initial value is based on the
627 // number and types of the enemy's attacking pieces, the number of
628 // attacked and undefended squares around our king and the quality of
629 // the pawn shelter (current 'score' value).
630 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
631 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
632 - mg_value(score) / 32;
634 // Analyse the enemy's safe queen contact checks. Firstly, find the
635 // undefended squares around the king that are attacked by the enemy's
637 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
640 // ...and then remove squares not supported by another enemy piece
641 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
642 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
645 attackUnits += QueenContactCheck
647 * (Them == pos.side_to_move() ? 2 : 1);
650 // Analyse the enemy's safe rook contact checks. Firstly, find the
651 // undefended squares around the king that are attacked by the enemy's
653 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
655 // Consider only squares where the enemy's rook gives check
656 b &= PseudoAttacks[ROOK][ksq];
660 // ...and then remove squares not supported by another enemy piece
661 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
662 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
665 attackUnits += RookContactCheck
667 * (Them == pos.side_to_move() ? 2 : 1);
670 // Analyse the enemy's safe distance checks for sliders and knights
671 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
673 b1 = pos.attacks_from<ROOK>(ksq) & safe;
674 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
676 // Enemy queen safe checks
677 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
679 attackUnits += QueenCheck * popcount<Max15>(b);
681 // Enemy rooks safe checks
682 b = b1 & ei.attackedBy[Them][ROOK];
684 attackUnits += RookCheck * popcount<Max15>(b);
686 // Enemy bishops safe checks
687 b = b2 & ei.attackedBy[Them][BISHOP];
689 attackUnits += BishopCheck * popcount<Max15>(b);
691 // Enemy knights safe checks
692 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
694 attackUnits += KnightCheck * popcount<Max15>(b);
696 // To index KingDanger[] attackUnits must be in [0, 99] range
697 attackUnits = std::min(99, std::max(0, attackUnits));
699 // Finally, extract the king danger score from the KingDanger[]
700 // array and subtract the score from evaluation.
701 score -= KingDanger[Us == Search::RootColor][attackUnits];
705 Tracing::terms[Us][KING] = score;
711 // evaluate_threats() assigns bonuses according to the type of attacking piece
712 // and the type of attacked one.
714 template<Color Us, bool Trace>
715 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
717 const Color Them = (Us == WHITE ? BLACK : WHITE);
719 Bitboard b, undefendedMinors, weakEnemies;
720 Score score = SCORE_ZERO;
722 // Undefended minors get penalized even if they are not under attack
723 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
724 & ~ei.attackedBy[Them][ALL_PIECES];
726 if (undefendedMinors)
727 score += UndefendedMinor;
729 // Enemy pieces not defended by a pawn and under our attack
730 weakEnemies = pos.pieces(Them)
731 & ~ei.attackedBy[Them][PAWN]
732 & ei.attackedBy[Us][ALL_PIECES];
734 // Add a bonus according if the attacking pieces are minor or major
737 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
739 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
741 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
743 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
747 Tracing::terms[Us][Tracing::THREAT] = score;
753 // evaluate_passed_pawns() evaluates the passed pawns of the given color
755 template<Color Us, bool Trace>
756 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
758 const Color Them = (Us == WHITE ? BLACK : WHITE);
760 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
761 Score score = SCORE_ZERO;
763 b = ei.pi->passed_pawns(Us);
767 Square s = pop_lsb(&b);
769 assert(pos.pawn_passed(Us, s));
771 int r = int(relative_rank(Us, s) - RANK_2);
772 int rr = r * (r - 1);
774 // Base bonus based on rank
775 Value mbonus = Value(17 * rr);
776 Value ebonus = Value(7 * (rr + r + 1));
780 Square blockSq = s + pawn_push(Us);
782 // Adjust bonus based on the king's proximity
783 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
784 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
786 // If blockSq is not the queening square then consider also a second push
787 if (relative_rank(Us, blockSq) != RANK_8)
788 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
790 // If the pawn is free to advance, then increase the bonus
791 if (pos.empty(blockSq))
793 squaresToQueen = forward_bb(Us, s);
795 // If there is an enemy rook or queen attacking the pawn from behind,
796 // add all X-ray attacks by the rook or queen. Otherwise consider only
797 // the squares in the pawn's path attacked or occupied by the enemy.
798 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
799 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
800 unsafeSquares = squaresToQueen;
802 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
804 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
805 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
806 defendedSquares = squaresToQueen;
808 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
810 // If there aren't any enemy attacks, then assign a huge bonus.
811 // The bonus will be a bit smaller if at least the block square
812 // isn't attacked, otherwise assign the smallest possible bonus.
813 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
815 // Assign a big bonus if the path to the queen is fully defended,
816 // otherwise assign a bit less of a bonus if at least the block
817 // square is defended.
818 if (defendedSquares == squaresToQueen)
821 else if (defendedSquares & blockSq)
822 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
824 mbonus += Value(k * rr), ebonus += Value(k * rr);
828 // Increase the bonus if the passed pawn is supported by a friendly pawn
829 // on the same rank and a bit smaller if it's on the previous rank.
830 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
831 if (supportingPawns & rank_bb(s))
832 ebonus += Value(r * 20);
834 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
835 ebonus += Value(r * 12);
837 // Rook pawns are a special case: They are sometimes worse, and
838 // sometimes better than other passed pawns. It is difficult to find
839 // good rules for determining whether they are good or bad. For now,
840 // we try the following: Increase the value for rook pawns if the
841 // other side has no pieces apart from a knight, and decrease the
842 // value if the other side has a rook or queen.
843 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
845 if (pos.non_pawn_material(Them) <= KnightValueMg)
846 ebonus += ebonus / 4;
848 else if (pos.pieces(Them, ROOK, QUEEN))
849 ebonus -= ebonus / 4;
852 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
853 ebonus += ebonus / 4;
855 score += make_score(mbonus, ebonus);
859 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
861 // Add the scores to the middlegame and endgame eval
862 return apply_weight(score, Weights[PassedPawns]);
866 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
867 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
868 // related to the possibility that pawns are unstoppable.
870 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
872 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
874 if (!b || pos.non_pawn_material(~us))
877 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
881 // evaluate_space() computes the space evaluation for a given side. The
882 // space evaluation is a simple bonus based on the number of safe squares
883 // available for minor pieces on the central four files on ranks 2--4. Safe
884 // squares one, two or three squares behind a friendly pawn are counted
885 // twice. Finally, the space bonus is scaled by a weight taken from the
886 // material hash table. The aim is to improve play on game opening.
888 int evaluate_space(const Position& pos, const EvalInfo& ei) {
890 const Color Them = (Us == WHITE ? BLACK : WHITE);
892 // Find the safe squares for our pieces inside the area defined by
893 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
894 // pawn, or if it is undefended and attacked by an enemy piece.
895 Bitboard safe = SpaceMask[Us]
896 & ~pos.pieces(Us, PAWN)
897 & ~ei.attackedBy[Them][PAWN]
898 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
900 // Find all squares which are at most three squares behind some friendly pawn
901 Bitboard behind = pos.pieces(Us, PAWN);
902 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
903 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
905 // Since SpaceMask[Us] is fully on our half of the board
906 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
908 // Count safe + (behind & safe) with a single popcount
909 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
913 // interpolate() interpolates between a middlegame and an endgame score,
914 // based on game phase. It also scales the return value by a ScaleFactor array.
916 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
918 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
919 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
920 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
922 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
923 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
926 // apply_weight() weights score v by score w trying to prevent overflow
927 Score apply_weight(Score v, Score w) {
929 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
930 (int(eg_value(v)) * eg_value(w)) / 0x100);
933 // weight_option() computes the value of an evaluation weight, by combining
934 // two UCI-configurable weights (midgame and endgame) with an internal weight.
936 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
938 // Scale option value from 100 to 256
939 int mg = Options[mgOpt] * 256 / 100;
940 int eg = Options[egOpt] * 256 / 100;
942 return apply_weight(make_score(mg, eg), internalWeight);
946 // Tracing function definitions
948 double Tracing::to_cp(Value v) { return double(v) / PawnValueMg; }
950 void Tracing::add_term(int idx, Score wScore, Score bScore) {
952 terms[WHITE][idx] = wScore;
953 terms[BLACK][idx] = bScore;
956 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
958 Score wScore = terms[WHITE][idx];
959 Score bScore = terms[BLACK][idx];
962 case PST: case IMBALANCE: case PAWN: case TOTAL:
963 ss << std::setw(20) << name << " | --- --- | --- --- | "
964 << std::setw(6) << to_cp(mg_value(wScore)) << " "
965 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
968 ss << std::setw(20) << name << " | " << std::noshowpos
969 << std::setw(5) << to_cp(mg_value(wScore)) << " "
970 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
971 << std::setw(5) << to_cp(mg_value(bScore)) << " "
972 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
974 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
975 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
979 std::string Tracing::do_trace(const Position& pos) {
981 std::memset(terms, 0, sizeof(terms));
983 Value v = do_evaluate<true>(pos);
985 std::stringstream ss;
986 ss << std::showpoint << std::showpos << std::fixed << std::setprecision(2)
987 << " Eval term | White | Black | Total \n"
988 << " | MG EG | MG EG | MG EG \n"
989 << "---------------------+-------------+-------------+---------------\n";
991 format_row(ss, "Material, PST, Tempo", PST);
992 format_row(ss, "Material imbalance", IMBALANCE);
993 format_row(ss, "Pawns", PAWN);
994 format_row(ss, "Knights", KNIGHT);
995 format_row(ss, "Bishops", BISHOP);
996 format_row(ss, "Rooks", ROOK);
997 format_row(ss, "Queens", QUEEN);
998 format_row(ss, "Mobility", MOBILITY);
999 format_row(ss, "King safety", KING);
1000 format_row(ss, "Threats", THREAT);
1001 format_row(ss, "Passed pawns", PASSED);
1002 format_row(ss, "Space", SPACE);
1004 ss << "---------------------+-------------+-------------+---------------\n";
1005 format_row(ss, "Total", TOTAL);
1007 ss << "\nScaling: " << std::noshowpos
1008 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
1009 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
1010 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
1011 << "Total evaluation: " << to_cp(v);