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);
219 template<PieceType Pt, Color Us, bool Trace>
220 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea);
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 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
323 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
325 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
326 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
327 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
329 // Evaluate pieces and mobility
330 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
331 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
333 // Evaluate kings after all other pieces because we need complete attack
334 // information when computing the king safety evaluation.
335 score += evaluate_king<WHITE, Trace>(pos, ei)
336 - evaluate_king<BLACK, Trace>(pos, ei);
338 // Evaluate tactical threats, we need full attack information including king
339 score += evaluate_threats<WHITE, Trace>(pos, ei)
340 - evaluate_threats<BLACK, Trace>(pos, ei);
342 // Evaluate passed pawns, we need full attack information including king
343 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
344 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
346 // If one side has only a king, score for potential unstoppable pawns
347 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
348 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
349 - evaluate_unstoppable_pawns(pos, BLACK, ei);
351 // Evaluate space for both sides, only in middlegame
352 if (ei.mi->space_weight())
354 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
355 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
358 // Scale winning side if position is more drawish than it appears
359 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
360 : ei.mi->scale_factor(pos, BLACK);
362 // If we don't already have an unusual scale factor, check for opposite
363 // colored bishop endgames, and use a lower scale for those.
364 if ( ei.mi->game_phase() < PHASE_MIDGAME
365 && pos.opposite_bishops()
366 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
368 // Ignoring any pawns, do both sides only have a single bishop and no
370 if ( pos.non_pawn_material(WHITE) == BishopValueMg
371 && pos.non_pawn_material(BLACK) == BishopValueMg)
373 // Check for KBP vs KB with only a single pawn that is almost
374 // certainly a draw or at least two pawns.
375 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
376 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
379 // Endgame with opposite-colored bishops, but also other pieces. Still
380 // a bit drawish, but not as drawish as with only the two bishops.
381 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
384 Value v = interpolate(score, ei.mi->game_phase(), sf);
386 // In case of tracing add all single evaluation contributions for both white and black
389 Tracing::add_term(Tracing::PST, pos.psq_score());
390 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
391 Tracing::add_term(PAWN, ei.pi->pawns_value());
392 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
393 , apply_weight(mobility[BLACK], Weights[Mobility]));
394 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
395 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
396 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
397 Tracing::add_term(Tracing::TOTAL, score);
402 return pos.side_to_move() == WHITE ? v : -v;
406 // init_eval_info() initializes king bitboards for given color adding
407 // pawn attacks. To be done at the beginning of the evaluation.
410 void init_eval_info(const Position& pos, EvalInfo& ei) {
412 const Color Them = (Us == WHITE ? BLACK : WHITE);
413 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
415 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
417 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
418 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
420 // Init king safety tables only if we are going to use them
421 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
423 ei.kingRing[Them] = b | shift_bb<Down>(b);
424 b &= ei.attackedBy[Us][PAWN];
425 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
426 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
429 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
433 // evaluate_outposts() evaluates bishop and knight outpost squares
435 template<PieceType Pt, Color Us>
436 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
438 const Color Them = (Us == WHITE ? BLACK : WHITE);
440 assert (Pt == BISHOP || Pt == KNIGHT);
442 // Initial bonus based on square
443 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
445 // Increase bonus if supported by pawn, especially if the opponent has
446 // no minor piece which can trade with the outpost piece.
447 if (bonus && (ei.attackedBy[Us][PAWN] & s))
449 if ( !pos.pieces(Them, KNIGHT)
450 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
451 bonus += bonus + bonus / 2;
456 return make_score(bonus, bonus);
460 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
462 template<PieceType Pt, Color Us, bool Trace>
463 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
467 Score score = SCORE_ZERO;
469 const Color Them = (Us == WHITE ? BLACK : WHITE);
470 const Square* pl = pos.list<Pt>(Us);
472 ei.attackedBy[Us][Pt] = 0;
474 while ((s = *pl++) != SQ_NONE)
476 // Find attacked squares, including x-ray attacks for bishops and rooks
477 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
478 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
479 : pos.attacks_from<Pt>(s);
481 if (ei.pinnedPieces[Us] & s)
482 b &= LineBB[pos.king_square(Us)][s];
484 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
486 if (b & ei.kingRing[Them])
488 ei.kingAttackersCount[Us]++;
489 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
490 Bitboard bb = b & ei.attackedBy[Them][KING];
492 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
496 b &= ~( ei.attackedBy[Them][KNIGHT]
497 | ei.attackedBy[Them][BISHOP]
498 | ei.attackedBy[Them][ROOK]);
500 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
501 : popcount<Full >(b & mobilityArea[Us]);
503 mobility[Us] += MobilityBonus[Pt][mob];
505 if (mob <= 1 && (EdgeBB & s))
506 score -= LowMobPenalty;
508 // Decrease score if we are attacked by an enemy pawn. The remaining part
509 // of threat evaluation must be done later when we have full attack info.
510 if (ei.attackedBy[Them][PAWN] & s)
511 score -= ThreatenedByPawn[Pt];
513 if (Pt == BISHOP || Pt == KNIGHT)
515 // Penalty for bishop with same colored pawns
517 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
519 // Penalty for knight when there are few enemy pawns
521 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
523 // Bishop and knight outposts squares
524 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
525 score += evaluate_outposts<Pt, Us>(pos, ei, s);
527 // Bishop or knight behind a pawn
528 if ( relative_rank(Us, s) < RANK_5
529 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
530 score += MinorBehindPawn;
535 // Rook on 7th rank and enemy king trapped on 8th
536 if ( relative_rank(Us, s) == RANK_7
537 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
540 // Rook piece attacking enemy pawns on the same rank/file
541 if (relative_rank(Us, s) >= RANK_5)
543 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
545 score += popcount<Max15>(pawns) * RookOnPawn;
548 // Give a bonus for a rook on a open or semi-open file
549 if (ei.pi->semiopen(Us, file_of(s)))
550 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
552 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
555 Square ksq = pos.king_square(Us);
557 // Penalize rooks which are trapped by a king. Penalize more if the
558 // king has lost its castling capability.
559 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
560 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
561 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
562 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
565 // An important Chess960 pattern: A cornered bishop blocked by a friendly
566 // pawn diagonally in front of it is a very serious problem, especially
567 // when that pawn is also blocked.
570 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
572 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
573 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
574 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
575 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
581 Tracing::terms[Us][Pt] = score;
583 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
585 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
589 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
591 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
594 // evaluate_king() assigns bonuses and penalties to a king of a given color
596 template<Color Us, bool Trace>
597 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
599 const Color Them = (Us == WHITE ? BLACK : WHITE);
601 Bitboard undefended, b, b1, b2, safe;
603 const Square ksq = pos.king_square(Us);
605 // King shelter and enemy pawns storm
606 Score score = ei.pi->king_safety<Us>(pos, ksq);
608 // Main king safety evaluation
609 if (ei.kingAttackersCount[Them])
611 // Find the attacked squares around the king which have no defenders
612 // apart from the king itself
613 undefended = ei.attackedBy[Them][ALL_PIECES]
614 & ei.attackedBy[Us][KING]
615 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
616 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
617 | ei.attackedBy[Us][QUEEN]);
619 // Initialize the 'attackUnits' variable, which is used later on as an
620 // index to the KingDanger[] array. The initial value is based on the
621 // number and types of the enemy's attacking pieces, the number of
622 // attacked and undefended squares around our king and the quality of
623 // the pawn shelter (current 'score' value).
624 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
625 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
626 + 2 * (ei.pinnedPieces[Us] != 0)
627 - mg_value(score) / 32;
629 // Analyse the enemy's safe queen contact checks. Firstly, find the
630 // undefended squares around the king that are attacked by the enemy's
632 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
635 // ...and then remove squares not supported by another enemy piece
636 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
637 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
640 attackUnits += QueenContactCheck
642 * (Them == pos.side_to_move() ? 2 : 1);
645 // Analyse the enemy's safe rook contact checks. Firstly, find the
646 // undefended squares around the king that are attacked by the enemy's
648 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
650 // Consider only squares where the enemy's rook gives check
651 b &= PseudoAttacks[ROOK][ksq];
655 // ...and then remove squares not supported by another enemy piece
656 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
657 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
660 attackUnits += RookContactCheck
662 * (Them == pos.side_to_move() ? 2 : 1);
665 // Analyse the enemy's safe distance checks for sliders and knights
666 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
668 b1 = pos.attacks_from<ROOK>(ksq) & safe;
669 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
671 // Enemy queen safe checks
672 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
674 attackUnits += QueenCheck * popcount<Max15>(b);
676 // Enemy rooks safe checks
677 b = b1 & ei.attackedBy[Them][ROOK];
679 attackUnits += RookCheck * popcount<Max15>(b);
681 // Enemy bishops safe checks
682 b = b2 & ei.attackedBy[Them][BISHOP];
684 attackUnits += BishopCheck * popcount<Max15>(b);
686 // Enemy knights safe checks
687 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
689 attackUnits += KnightCheck * popcount<Max15>(b);
691 // To index KingDanger[] attackUnits must be in [0, 99] range
692 attackUnits = std::min(99, std::max(0, attackUnits));
694 // Finally, extract the king danger score from the KingDanger[]
695 // array and subtract the score from evaluation.
696 score -= KingDanger[Us == Search::RootColor][attackUnits];
700 Tracing::terms[Us][KING] = score;
706 // evaluate_threats() assigns bonuses according to the type of attacking piece
707 // and the type of attacked one.
709 template<Color Us, bool Trace>
710 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
712 const Color Them = (Us == WHITE ? BLACK : WHITE);
714 Bitboard b, undefendedMinors, weakEnemies;
715 Score score = SCORE_ZERO;
717 // Undefended minors get penalized even if they are not under attack
718 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
719 & ~ei.attackedBy[Them][ALL_PIECES];
721 if (undefendedMinors)
722 score += UndefendedMinor;
724 // Enemy pieces not defended by a pawn and under our attack
725 weakEnemies = pos.pieces(Them)
726 & ~ei.attackedBy[Them][PAWN]
727 & ei.attackedBy[Us][ALL_PIECES];
729 // Add a bonus according if the attacking pieces are minor or major
732 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
734 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
736 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
738 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
742 Tracing::terms[Us][Tracing::THREAT] = score;
748 // evaluate_passed_pawns() evaluates the passed pawns of the given color
750 template<Color Us, bool Trace>
751 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
753 const Color Them = (Us == WHITE ? BLACK : WHITE);
755 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
756 Score score = SCORE_ZERO;
758 b = ei.pi->passed_pawns(Us);
762 Square s = pop_lsb(&b);
764 assert(pos.pawn_passed(Us, s));
766 int r = int(relative_rank(Us, s) - RANK_2);
767 int rr = r * (r - 1);
769 // Base bonus based on rank
770 Value mbonus = Value(17 * rr);
771 Value ebonus = Value(7 * (rr + r + 1));
775 Square blockSq = s + pawn_push(Us);
777 // Adjust bonus based on the king's proximity
778 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
779 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
781 // If blockSq is not the queening square then consider also a second push
782 if (relative_rank(Us, blockSq) != RANK_8)
783 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
785 // If the pawn is free to advance, then increase the bonus
786 if (pos.empty(blockSq))
788 squaresToQueen = forward_bb(Us, s);
790 // If there is an enemy rook or queen attacking the pawn from behind,
791 // add all X-ray attacks by the rook or queen. Otherwise consider only
792 // the squares in the pawn's path attacked or occupied by the enemy.
793 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
794 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
795 unsafeSquares = squaresToQueen;
797 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
799 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
800 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
801 defendedSquares = squaresToQueen;
803 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
805 // If there aren't any enemy attacks, then assign a huge bonus.
806 // The bonus will be a bit smaller if at least the block square
807 // isn't attacked, otherwise assign the smallest possible bonus.
808 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
810 // Assign a big bonus if the path to the queen is fully defended,
811 // otherwise assign a bit less of a bonus if at least the block
812 // square is defended.
813 if (defendedSquares == squaresToQueen)
816 else if (defendedSquares & blockSq)
817 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
819 mbonus += Value(k * rr), ebonus += Value(k * rr);
823 // Increase the bonus if the passed pawn is supported by a friendly pawn
824 // on the same rank and a bit smaller if it's on the previous rank.
825 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
826 if (supportingPawns & rank_bb(s))
827 ebonus += Value(r * 20);
829 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
830 ebonus += Value(r * 12);
832 // Rook pawns are a special case: They are sometimes worse, and
833 // sometimes better than other passed pawns. It is difficult to find
834 // good rules for determining whether they are good or bad. For now,
835 // we try the following: Increase the value for rook pawns if the
836 // other side has no pieces apart from a knight, and decrease the
837 // value if the other side has a rook or queen.
838 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
840 if (pos.non_pawn_material(Them) <= KnightValueMg)
841 ebonus += ebonus / 4;
843 else if (pos.pieces(Them, ROOK, QUEEN))
844 ebonus -= ebonus / 4;
847 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
848 ebonus += ebonus / 4;
850 score += make_score(mbonus, ebonus);
854 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
856 // Add the scores to the middlegame and endgame eval
857 return apply_weight(score, Weights[PassedPawns]);
861 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
862 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
863 // related to the possibility that pawns are unstoppable.
865 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
867 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
869 if (!b || pos.non_pawn_material(~us))
872 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
876 // evaluate_space() computes the space evaluation for a given side. The
877 // space evaluation is a simple bonus based on the number of safe squares
878 // available for minor pieces on the central four files on ranks 2--4. Safe
879 // squares one, two or three squares behind a friendly pawn are counted
880 // twice. Finally, the space bonus is scaled by a weight taken from the
881 // material hash table. The aim is to improve play on game opening.
883 int evaluate_space(const Position& pos, const EvalInfo& ei) {
885 const Color Them = (Us == WHITE ? BLACK : WHITE);
887 // Find the safe squares for our pieces inside the area defined by
888 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
889 // pawn, or if it is undefended and attacked by an enemy piece.
890 Bitboard safe = SpaceMask[Us]
891 & ~pos.pieces(Us, PAWN)
892 & ~ei.attackedBy[Them][PAWN]
893 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
895 // Find all squares which are at most three squares behind some friendly pawn
896 Bitboard behind = pos.pieces(Us, PAWN);
897 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
898 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
900 // Since SpaceMask[Us] is fully on our half of the board
901 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
903 // Count safe + (behind & safe) with a single popcount
904 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
908 // interpolate() interpolates between a middlegame and an endgame score,
909 // based on game phase. It also scales the return value by a ScaleFactor array.
911 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
913 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
914 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
915 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
917 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
918 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
921 // apply_weight() weights score v by score w trying to prevent overflow
922 Score apply_weight(Score v, const Weight& w) {
924 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
927 // weight_option() computes the value of an evaluation weight, by combining
928 // two UCI-configurable weights (midgame and endgame) with an internal weight.
930 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
932 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
933 Options[egOpt] * eg_value(internalWeight) / 100 };
938 // Tracing function definitions
940 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
942 void Tracing::add_term(int idx, Score wScore, Score bScore) {
944 terms[WHITE][idx] = wScore;
945 terms[BLACK][idx] = bScore;
948 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
950 Score wScore = terms[WHITE][idx];
951 Score bScore = terms[BLACK][idx];
954 case PST: case IMBALANCE: case PAWN: case TOTAL:
955 ss << std::setw(20) << name << " | --- --- | --- --- | "
956 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
957 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
960 ss << std::setw(20) << name << " | " << std::noshowpos
961 << std::setw(5) << to_cp(mg_value(wScore)) << " "
962 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
963 << std::setw(5) << to_cp(mg_value(bScore)) << " "
964 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
965 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
966 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
970 std::string Tracing::do_trace(const Position& pos) {
972 std::memset(terms, 0, sizeof(terms));
974 Value v = do_evaluate<true>(pos);
975 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
977 std::stringstream ss;
978 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
979 << " Eval term | White | Black | Total \n"
980 << " | MG EG | MG EG | MG EG \n"
981 << "---------------------+-------------+-------------+-------------\n";
983 format_row(ss, "Material, PST, Tempo", PST);
984 format_row(ss, "Material imbalance", IMBALANCE);
985 format_row(ss, "Pawns", PAWN);
986 format_row(ss, "Knights", KNIGHT);
987 format_row(ss, "Bishops", BISHOP);
988 format_row(ss, "Rooks", ROOK);
989 format_row(ss, "Queens", QUEEN);
990 format_row(ss, "Mobility", MOBILITY);
991 format_row(ss, "King safety", KING);
992 format_row(ss, "Threats", THREAT);
993 format_row(ss, "Passed pawns", PASSED);
994 format_row(ss, "Space", SPACE);
996 ss << "---------------------+-------------+-------------+-------------\n";
997 format_row(ss, "Total", TOTAL);
999 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";