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 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);
175 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
176 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
177 // happen in Chess960 games.
178 const Score TrappedBishopA1H1 = make_score(50, 50);
180 // SpaceMask[Color] contains the area of the board which is considered
181 // by the space evaluation. In the middlegame, each side is given a bonus
182 // based on how many squares inside this area are safe and available for
183 // friendly minor pieces.
184 const Bitboard SpaceMask[] = {
185 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
186 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
189 // King danger constants and variables. The king danger scores are taken
190 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
191 // of the enemy attack are added up into an integer, which is used as an
192 // index to KingDanger[].
194 // KingAttackWeights[PieceType] contains king attack weights by piece type
195 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
197 // Bonuses for enemy's safe checks
198 const int QueenContactCheck = 24;
199 const int RookContactCheck = 16;
200 const int QueenCheck = 12;
201 const int RookCheck = 8;
202 const int BishopCheck = 2;
203 const int KnightCheck = 3;
205 // KingDanger[Color][attackUnits] contains the actual king danger weighted
206 // scores, indexed by color and by a calculated integer number.
207 Score KingDanger[COLOR_NB][128];
209 // Function prototypes
211 Value do_evaluate(const Position& pos);
214 void init_eval_info(const Position& pos, EvalInfo& ei);
216 template<PieceType Pt, Color Us, bool Trace>
217 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea);
219 template<Color Us, bool Trace>
220 Score evaluate_king(const Position& pos, const EvalInfo& ei);
222 template<Color Us, bool Trace>
223 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
225 template<Color Us, bool Trace>
226 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
229 int evaluate_space(const Position& pos, const EvalInfo& ei);
231 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
233 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
234 Score apply_weight(Score v, const Weight& w);
235 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
241 /// evaluate() is the main evaluation function. It always computes two
242 /// values, an endgame score and a middlegame score, and interpolates
243 /// between them based on the remaining material.
245 Value evaluate(const Position& pos) {
246 return do_evaluate<false>(pos);
250 /// trace() is like evaluate(), but instead of returning a value, it returns
251 /// a string (suitable for outputting to stdout) that contains the detailed
252 /// descriptions and values of each evaluation term. It's mainly used for
254 std::string trace(const Position& pos) {
255 return Tracing::do_trace(pos);
259 /// init() computes evaluation weights from the corresponding UCI parameters
260 /// and setup king tables.
264 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
265 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
266 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
267 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
268 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
269 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
271 const int MaxSlope = 30;
272 const int Peak = 1280;
274 for (int t = 0, i = 1; i < 100; ++i)
276 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
278 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
279 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
289 Value do_evaluate(const Position& pos) {
291 assert(!pos.checkers());
294 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
295 Thread* thisThread = pos.this_thread();
297 // Initialize score by reading the incrementally updated scores included
298 // in the position object (material + piece square tables) and adding a
299 // Tempo bonus. Score is computed from the point of view of white.
300 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
302 // Probe the material hash table
303 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
304 score += ei.mi->material_value();
306 // If we have a specialized evaluation function for the current material
307 // configuration, call it and return.
308 if (ei.mi->specialized_eval_exists())
309 return ei.mi->evaluate(pos);
311 // Probe the pawn hash table
312 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
313 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
315 // Initialize attack and king safety bitboards
316 init_eval_info<WHITE>(pos, ei);
317 init_eval_info<BLACK>(pos, ei);
319 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
320 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
322 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
323 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
324 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
326 // Evaluate pieces and mobility
327 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
328 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
330 // Evaluate kings after all other pieces because we need complete attack
331 // information when computing the king safety evaluation.
332 score += evaluate_king<WHITE, Trace>(pos, ei)
333 - evaluate_king<BLACK, Trace>(pos, ei);
335 // Evaluate tactical threats, we need full attack information including king
336 score += evaluate_threats<WHITE, Trace>(pos, ei)
337 - evaluate_threats<BLACK, Trace>(pos, ei);
339 // Evaluate passed pawns, we need full attack information including king
340 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
341 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
343 // If one side has only a king, score for potential unstoppable pawns
344 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
345 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
346 - evaluate_unstoppable_pawns(pos, BLACK, ei);
348 // Evaluate space for both sides, only in middlegame
349 if (ei.mi->space_weight())
351 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
352 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
355 // Scale winning side if position is more drawish than it appears
356 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
357 : ei.mi->scale_factor(pos, BLACK);
359 // If we don't already have an unusual scale factor, check for opposite
360 // colored bishop endgames, and use a lower scale for those.
361 if ( ei.mi->game_phase() < PHASE_MIDGAME
362 && pos.opposite_bishops()
363 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
365 // Ignoring any pawns, do both sides only have a single bishop and no
367 if ( pos.non_pawn_material(WHITE) == BishopValueMg
368 && pos.non_pawn_material(BLACK) == BishopValueMg)
370 // Check for KBP vs KB with only a single pawn that is almost
371 // certainly a draw or at least two pawns.
372 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
373 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
376 // Endgame with opposite-colored bishops, but also other pieces. Still
377 // a bit drawish, but not as drawish as with only the two bishops.
378 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
381 Value v = interpolate(score, ei.mi->game_phase(), sf);
383 // In case of tracing add all single evaluation contributions for both white and black
386 Tracing::add_term(Tracing::PST, pos.psq_score());
387 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
388 Tracing::add_term(PAWN, ei.pi->pawns_value());
389 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
390 , apply_weight(mobility[BLACK], Weights[Mobility]));
391 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
392 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
393 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
394 Tracing::add_term(Tracing::TOTAL, score);
399 return pos.side_to_move() == WHITE ? v : -v;
403 // init_eval_info() initializes king bitboards for given color adding
404 // pawn attacks. To be done at the beginning of the evaluation.
407 void init_eval_info(const Position& pos, EvalInfo& ei) {
409 const Color Them = (Us == WHITE ? BLACK : WHITE);
410 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
412 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
414 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
415 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
417 // Init king safety tables only if we are going to use them
418 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
420 ei.kingRing[Them] = b | shift_bb<Down>(b);
421 b &= ei.attackedBy[Us][PAWN];
422 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
423 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
426 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
430 // evaluate_outposts() evaluates bishop and knight outpost squares
432 template<PieceType Pt, Color Us>
433 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
435 const Color Them = (Us == WHITE ? BLACK : WHITE);
437 assert (Pt == BISHOP || Pt == KNIGHT);
439 // Initial bonus based on square
440 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
442 // Increase bonus if supported by pawn, especially if the opponent has
443 // no minor piece which can trade with the outpost piece.
444 if (bonus && (ei.attackedBy[Us][PAWN] & s))
446 if ( !pos.pieces(Them, KNIGHT)
447 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
448 bonus += bonus + bonus / 2;
453 return make_score(bonus, bonus);
457 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
459 template<PieceType Pt, Color Us, bool Trace>
460 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
464 Score score = SCORE_ZERO;
466 const Color Them = (Us == WHITE ? BLACK : WHITE);
467 const Square* pl = pos.list<Pt>(Us);
469 ei.attackedBy[Us][Pt] = 0;
471 while ((s = *pl++) != SQ_NONE)
473 // Find attacked squares, including x-ray attacks for bishops and rooks
474 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
475 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
476 : pos.attacks_from<Pt>(s);
478 if (ei.pinnedPieces[Us] & s)
479 b &= LineBB[pos.king_square(Us)][s];
481 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
483 if (b & ei.kingRing[Them])
485 ei.kingAttackersCount[Us]++;
486 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
487 Bitboard bb = b & ei.attackedBy[Them][KING];
489 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
493 b &= ~( ei.attackedBy[Them][KNIGHT]
494 | ei.attackedBy[Them][BISHOP]
495 | ei.attackedBy[Them][ROOK]);
497 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
498 : popcount<Full >(b & mobilityArea[Us]);
500 mobility[Us] += MobilityBonus[Pt][mob];
502 // Decrease score if we are attacked by an enemy pawn. The remaining part
503 // of threat evaluation must be done later when we have full attack info.
504 if (ei.attackedBy[Them][PAWN] & s)
505 score -= ThreatenedByPawn[Pt];
507 if (Pt == BISHOP || Pt == KNIGHT)
509 // Penalty for bishop with same colored pawns
511 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
513 // Penalty for knight when there are few enemy pawns
515 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
517 // Bishop and knight outposts squares
518 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
519 score += evaluate_outposts<Pt, Us>(pos, ei, s);
521 // Bishop or knight behind a pawn
522 if ( relative_rank(Us, s) < RANK_5
523 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
524 score += MinorBehindPawn;
529 // Rook on 7th rank and enemy king trapped on 8th
530 if ( relative_rank(Us, s) == RANK_7
531 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
534 // Rook piece attacking enemy pawns on the same rank/file
535 if (relative_rank(Us, s) >= RANK_5)
537 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
539 score += popcount<Max15>(pawns) * RookOnPawn;
542 // Give a bonus for a rook on a open or semi-open file
543 if (ei.pi->semiopen(Us, file_of(s)))
544 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
546 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
549 Square ksq = pos.king_square(Us);
551 // Penalize rooks which are trapped by a king. Penalize more if the
552 // king has lost its castling capability.
553 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
554 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
555 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
556 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
559 // An important Chess960 pattern: A cornered bishop blocked by a friendly
560 // pawn diagonally in front of it is a very serious problem, especially
561 // when that pawn is also blocked.
564 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
566 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
567 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
568 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
569 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
575 Tracing::terms[Us][Pt] = score;
577 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
579 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
583 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
585 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
588 // evaluate_king() assigns bonuses and penalties to a king of a given color
590 template<Color Us, bool Trace>
591 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
593 const Color Them = (Us == WHITE ? BLACK : WHITE);
595 Bitboard undefended, b, b1, b2, safe;
597 const Square ksq = pos.king_square(Us);
599 // King shelter and enemy pawns storm
600 Score score = ei.pi->king_safety<Us>(pos, ksq);
602 // Main king safety evaluation
603 if (ei.kingAttackersCount[Them])
605 // Find the attacked squares around the king which have no defenders
606 // apart from the king itself
607 undefended = ei.attackedBy[Them][ALL_PIECES]
608 & ei.attackedBy[Us][KING]
609 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
610 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
611 | ei.attackedBy[Us][QUEEN]);
613 // Initialize the 'attackUnits' variable, which is used later on as an
614 // index to the KingDanger[] array. The initial value is based on the
615 // number and types of the enemy's attacking pieces, the number of
616 // attacked and undefended squares around our king and the quality of
617 // the pawn shelter (current 'score' value).
618 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
619 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
620 + 2 * (ei.pinnedPieces[Us] != 0)
621 - mg_value(score) / 32;
623 // Analyse the enemy's safe queen contact checks. Firstly, find the
624 // undefended squares around the king that are attacked by the enemy's
626 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
629 // ...and then remove squares not supported by another enemy piece
630 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
631 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
634 attackUnits += QueenContactCheck
636 * (Them == pos.side_to_move() ? 2 : 1);
639 // Analyse the enemy's safe rook contact checks. Firstly, find the
640 // undefended squares around the king that are attacked by the enemy's
642 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
644 // Consider only squares where the enemy's rook gives check
645 b &= PseudoAttacks[ROOK][ksq];
649 // ...and then remove squares not supported by another enemy piece
650 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
651 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
654 attackUnits += RookContactCheck
656 * (Them == pos.side_to_move() ? 2 : 1);
659 // Analyse the enemy's safe distance checks for sliders and knights
660 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
662 b1 = pos.attacks_from<ROOK>(ksq) & safe;
663 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
665 // Enemy queen safe checks
666 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
668 attackUnits += QueenCheck * popcount<Max15>(b);
670 // Enemy rooks safe checks
671 b = b1 & ei.attackedBy[Them][ROOK];
673 attackUnits += RookCheck * popcount<Max15>(b);
675 // Enemy bishops safe checks
676 b = b2 & ei.attackedBy[Them][BISHOP];
678 attackUnits += BishopCheck * popcount<Max15>(b);
680 // Enemy knights safe checks
681 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
683 attackUnits += KnightCheck * popcount<Max15>(b);
685 // To index KingDanger[] attackUnits must be in [0, 99] range
686 attackUnits = std::min(99, std::max(0, attackUnits));
688 // Finally, extract the king danger score from the KingDanger[]
689 // array and subtract the score from evaluation.
690 score -= KingDanger[Us == Search::RootColor][attackUnits];
694 Tracing::terms[Us][KING] = score;
700 // evaluate_threats() assigns bonuses according to the type of attacking piece
701 // and the type of attacked one.
703 template<Color Us, bool Trace>
704 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
706 const Color Them = (Us == WHITE ? BLACK : WHITE);
708 Bitboard b, undefendedMinors, weakEnemies;
709 Score score = SCORE_ZERO;
711 // Undefended minors get penalized even if they are not under attack
712 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
713 & ~ei.attackedBy[Them][ALL_PIECES];
715 if (undefendedMinors)
716 score += UndefendedMinor;
718 // Enemy pieces not defended by a pawn and under our attack
719 weakEnemies = pos.pieces(Them)
720 & ~ei.attackedBy[Them][PAWN]
721 & ei.attackedBy[Us][ALL_PIECES];
723 // Add a bonus according if the attacking pieces are minor or major
726 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
728 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
730 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
732 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
736 Tracing::terms[Us][Tracing::THREAT] = score;
742 // evaluate_passed_pawns() evaluates the passed pawns of the given color
744 template<Color Us, bool Trace>
745 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
747 const Color Them = (Us == WHITE ? BLACK : WHITE);
749 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
750 Score score = SCORE_ZERO;
752 b = ei.pi->passed_pawns(Us);
756 Square s = pop_lsb(&b);
758 assert(pos.pawn_passed(Us, s));
760 int r = int(relative_rank(Us, s) - RANK_2);
761 int rr = r * (r - 1);
763 // Base bonus based on rank
764 Value mbonus = Value(17 * rr);
765 Value ebonus = Value(7 * (rr + r + 1));
769 Square blockSq = s + pawn_push(Us);
771 // Adjust bonus based on the king's proximity
772 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
773 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
775 // If blockSq is not the queening square then consider also a second push
776 if (relative_rank(Us, blockSq) != RANK_8)
777 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
779 // If the pawn is free to advance, then increase the bonus
780 if (pos.empty(blockSq))
782 squaresToQueen = forward_bb(Us, s);
784 // If there is an enemy rook or queen attacking the pawn from behind,
785 // add all X-ray attacks by the rook or queen. Otherwise consider only
786 // the squares in the pawn's path attacked or occupied by the enemy.
787 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
788 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
789 unsafeSquares = squaresToQueen;
791 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
793 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
794 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
795 defendedSquares = squaresToQueen;
797 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
799 // If there aren't any enemy attacks, then assign a huge bonus.
800 // The bonus will be a bit smaller if at least the block square
801 // isn't attacked, otherwise assign the smallest possible bonus.
802 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
804 // Assign a big bonus if the path to the queen is fully defended,
805 // otherwise assign a bit less of a bonus if at least the block
806 // square is defended.
807 if (defendedSquares == squaresToQueen)
810 else if (defendedSquares & blockSq)
811 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
813 mbonus += Value(k * rr), ebonus += Value(k * rr);
817 // Increase the bonus if the passed pawn is supported by a friendly pawn
818 // on the same rank and a bit smaller if it's on the previous rank.
819 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
820 if (supportingPawns & rank_bb(s))
821 ebonus += Value(r * 20);
823 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
824 ebonus += Value(r * 12);
826 // Rook pawns are a special case: They are sometimes worse, and
827 // sometimes better than other passed pawns. It is difficult to find
828 // good rules for determining whether they are good or bad. For now,
829 // we try the following: Increase the value for rook pawns if the
830 // other side has no pieces apart from a knight, and decrease the
831 // value if the other side has a rook or queen.
832 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
834 if (pos.non_pawn_material(Them) <= KnightValueMg)
835 ebonus += ebonus / 4;
837 else if (pos.pieces(Them, ROOK, QUEEN))
838 ebonus -= ebonus / 4;
841 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
842 ebonus += ebonus / 4;
844 score += make_score(mbonus, ebonus);
848 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
850 // Add the scores to the middlegame and endgame eval
851 return apply_weight(score, Weights[PassedPawns]);
855 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
856 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
857 // related to the possibility that pawns are unstoppable.
859 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
861 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
863 if (!b || pos.non_pawn_material(~us))
866 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
870 // evaluate_space() computes the space evaluation for a given side. The
871 // space evaluation is a simple bonus based on the number of safe squares
872 // available for minor pieces on the central four files on ranks 2--4. Safe
873 // squares one, two or three squares behind a friendly pawn are counted
874 // twice. Finally, the space bonus is scaled by a weight taken from the
875 // material hash table. The aim is to improve play on game opening.
877 int evaluate_space(const Position& pos, const EvalInfo& ei) {
879 const Color Them = (Us == WHITE ? BLACK : WHITE);
881 // Find the safe squares for our pieces inside the area defined by
882 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
883 // pawn, or if it is undefended and attacked by an enemy piece.
884 Bitboard safe = SpaceMask[Us]
885 & ~pos.pieces(Us, PAWN)
886 & ~ei.attackedBy[Them][PAWN]
887 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
889 // Find all squares which are at most three squares behind some friendly pawn
890 Bitboard behind = pos.pieces(Us, PAWN);
891 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
892 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
894 // Since SpaceMask[Us] is fully on our half of the board
895 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
897 // Count safe + (behind & safe) with a single popcount
898 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
902 // interpolate() interpolates between a middlegame and an endgame score,
903 // based on game phase. It also scales the return value by a ScaleFactor array.
905 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
907 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
908 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
909 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
911 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
912 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
915 // apply_weight() weights score v by score w trying to prevent overflow
916 Score apply_weight(Score v, const Weight& w) {
918 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
921 // weight_option() computes the value of an evaluation weight, by combining
922 // two UCI-configurable weights (midgame and endgame) with an internal weight.
924 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
926 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
927 Options[egOpt] * eg_value(internalWeight) / 100 };
932 // Tracing function definitions
934 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
936 void Tracing::add_term(int idx, Score wScore, Score bScore) {
938 terms[WHITE][idx] = wScore;
939 terms[BLACK][idx] = bScore;
942 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
944 Score wScore = terms[WHITE][idx];
945 Score bScore = terms[BLACK][idx];
948 case PST: case IMBALANCE: case PAWN: case TOTAL:
949 ss << std::setw(20) << name << " | --- --- | --- --- | "
950 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
951 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
954 ss << std::setw(20) << name << " | " << std::noshowpos
955 << std::setw(5) << to_cp(mg_value(wScore)) << " "
956 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
957 << std::setw(5) << to_cp(mg_value(bScore)) << " "
958 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
959 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
960 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
964 std::string Tracing::do_trace(const Position& pos) {
966 std::memset(terms, 0, sizeof(terms));
968 Value v = do_evaluate<true>(pos);
969 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
971 std::stringstream ss;
972 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
973 << " Eval term | White | Black | Total \n"
974 << " | MG EG | MG EG | MG EG \n"
975 << "---------------------+-------------+-------------+-------------\n";
977 format_row(ss, "Material, PST, Tempo", PST);
978 format_row(ss, "Material imbalance", IMBALANCE);
979 format_row(ss, "Pawns", PAWN);
980 format_row(ss, "Knights", KNIGHT);
981 format_row(ss, "Bishops", BISHOP);
982 format_row(ss, "Rooks", ROOK);
983 format_row(ss, "Queens", QUEEN);
984 format_row(ss, "Mobility", MOBILITY);
985 format_row(ss, "King safety", KING);
986 format_row(ss, "Threats", THREAT);
987 format_row(ss, "Passed pawns", PASSED);
988 format_row(ss, "Space", SPACE);
990 ss << "---------------------+-------------+-------------+-------------\n";
991 format_row(ss, "Total", TOTAL);
993 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";