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(-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 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<Color Us, bool Trace>
217 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility);
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 // Evaluate pieces and mobility
320 score += evaluate_pieces<WHITE, Trace>(pos, ei, mobility)
321 - evaluate_pieces<BLACK, Trace>(pos, ei, mobility);
323 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
325 // Evaluate kings after all other pieces because we need complete attack
326 // information when computing the king safety evaluation.
327 score += evaluate_king<WHITE, Trace>(pos, ei)
328 - evaluate_king<BLACK, Trace>(pos, ei);
330 // Evaluate tactical threats, we need full attack information including king
331 score += evaluate_threats<WHITE, Trace>(pos, ei)
332 - evaluate_threats<BLACK, Trace>(pos, ei);
334 // Evaluate passed pawns, we need full attack information including king
335 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
336 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
338 // If one side has only a king, score for potential unstoppable pawns
339 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
340 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
341 - evaluate_unstoppable_pawns(pos, BLACK, ei);
343 // Evaluate space for both sides, only in middlegame
344 if (ei.mi->space_weight())
346 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
347 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
350 // Scale winning side if position is more drawish than it appears
351 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
352 : ei.mi->scale_factor(pos, BLACK);
354 // If we don't already have an unusual scale factor, check for opposite
355 // colored bishop endgames, and use a lower scale for those.
356 if ( ei.mi->game_phase() < PHASE_MIDGAME
357 && pos.opposite_bishops()
358 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
360 // Ignoring any pawns, do both sides only have a single bishop and no
362 if ( pos.non_pawn_material(WHITE) == BishopValueMg
363 && pos.non_pawn_material(BLACK) == BishopValueMg)
365 // Check for KBP vs KB with only a single pawn that is almost
366 // certainly a draw or at least two pawns.
367 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
368 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
371 // Endgame with opposite-colored bishops, but also other pieces. Still
372 // a bit drawish, but not as drawish as with only the two bishops.
373 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
376 Value v = interpolate(score, ei.mi->game_phase(), sf);
378 // In case of tracing add all single evaluation contributions for both white and black
381 Tracing::add_term(Tracing::PST, pos.psq_score());
382 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
383 Tracing::add_term(PAWN, ei.pi->pawns_value());
384 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
385 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
386 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
387 Tracing::add_term(Tracing::TOTAL, score);
392 return pos.side_to_move() == WHITE ? v : -v;
396 // init_eval_info() initializes king bitboards for given color adding
397 // pawn attacks. To be done at the beginning of the evaluation.
400 void init_eval_info(const Position& pos, EvalInfo& ei) {
402 const Color Them = (Us == WHITE ? BLACK : WHITE);
403 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
405 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
407 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
408 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
410 // Init king safety tables only if we are going to use them
411 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
413 ei.kingRing[Them] = b | shift_bb<Down>(b);
414 b &= ei.attackedBy[Us][PAWN];
415 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
416 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
419 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
423 // evaluate_outposts() evaluates bishop and knight outpost squares
425 template<PieceType Pt, Color Us>
426 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
428 const Color Them = (Us == WHITE ? BLACK : WHITE);
430 assert (Pt == BISHOP || Pt == KNIGHT);
432 // Initial bonus based on square
433 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
435 // Increase bonus if supported by pawn, especially if the opponent has
436 // no minor piece which can trade with the outpost piece.
437 if (bonus && (ei.attackedBy[Us][PAWN] & s))
439 if ( !pos.pieces(Them, KNIGHT)
440 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
441 bonus += bonus + bonus / 2;
446 return make_score(bonus, bonus);
450 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
452 template<PieceType Pt, Color Us, bool Trace>
453 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
457 Score score = SCORE_ZERO;
459 const Color Them = (Us == WHITE ? BLACK : WHITE);
460 const Square* pl = pos.list<Pt>(Us);
462 ei.attackedBy[Us][Pt] = 0;
464 while ((s = *pl++) != SQ_NONE)
466 // Find attacked squares, including x-ray attacks for bishops and rooks
467 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
468 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
469 : pos.attacks_from<Pt>(s);
471 if (ei.pinnedPieces[Us] & s)
472 b &= LineBB[pos.king_square(Us)][s];
474 ei.attackedBy[Us][Pt] |= b;
476 if (b & ei.kingRing[Them])
478 ei.kingAttackersCount[Us]++;
479 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
480 Bitboard bb = b & ei.attackedBy[Them][KING];
482 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
485 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea)
486 : popcount<Full >(b & mobilityArea);
488 mobility[Us] += MobilityBonus[Pt][mob];
490 // Decrease score if we are attacked by an enemy pawn. The remaining part
491 // of threat evaluation must be done later when we have full attack info.
492 if (ei.attackedBy[Them][PAWN] & s)
493 score -= ThreatenedByPawn[Pt];
495 if (Pt == BISHOP || Pt == KNIGHT)
497 // Penalty for bishop with same colored pawns
499 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
501 // Penalty for knight when there are few enemy pawns
503 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
505 // Bishop and knight outposts squares
506 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
507 score += evaluate_outposts<Pt, Us>(pos, ei, s);
509 // Bishop or knight behind a pawn
510 if ( relative_rank(Us, s) < RANK_5
511 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
512 score += MinorBehindPawn;
517 // Rook on 7th rank and enemy king trapped on 8th
518 if ( relative_rank(Us, s) == RANK_7
519 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
522 // Rook piece attacking enemy pawns on the same rank/file
523 if (relative_rank(Us, s) >= RANK_5)
525 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
527 score += popcount<Max15>(pawns) * RookOnPawn;
530 // Give a bonus for a rook on a open or semi-open file
531 if (ei.pi->semiopen(Us, file_of(s)))
532 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
534 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
537 Square ksq = pos.king_square(Us);
539 // Penalize rooks which are trapped by a king. Penalize more if the
540 // king has lost its castling capability.
541 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
542 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
543 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
544 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
547 // An important Chess960 pattern: A cornered bishop blocked by a friendly
548 // pawn diagonally in front of it is a very serious problem, especially
549 // when that pawn is also blocked.
552 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
554 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
555 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
556 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
557 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
563 Tracing::terms[Us][Pt] = score;
569 // evaluate_pieces() assigns bonuses and penalties to all the
570 // pieces of a given color.
572 template<Color Us, bool Trace>
573 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
575 const Color Them = (Us == WHITE ? BLACK : WHITE);
577 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
578 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
580 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
581 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
582 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
583 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
585 // Sum up all attacked squares (updated in evaluate_pieces)
586 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
587 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
588 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
590 Tracing::terms[Us][Tracing::MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
596 // evaluate_king() assigns bonuses and penalties to a king of a given color
598 template<Color Us, bool Trace>
599 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
601 const Color Them = (Us == WHITE ? BLACK : WHITE);
603 Bitboard undefended, b, b1, b2, safe;
605 const Square ksq = pos.king_square(Us);
607 // King shelter and enemy pawns storm
608 Score score = ei.pi->king_safety<Us>(pos, ksq);
610 // Main king safety evaluation
611 if (ei.kingAttackersCount[Them])
613 // Find the attacked squares around the king which have no defenders
614 // apart from the king itself
615 undefended = ei.attackedBy[Them][ALL_PIECES]
616 & ei.attackedBy[Us][KING]
617 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
618 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
619 | ei.attackedBy[Us][QUEEN]);
621 // Initialize the 'attackUnits' variable, which is used later on as an
622 // index to the KingDanger[] array. The initial value is based on the
623 // number and types of the enemy's attacking pieces, the number of
624 // attacked and undefended squares around our king and the quality of
625 // the pawn shelter (current 'score' value).
626 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
627 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
628 + 2 * (ei.pinnedPieces[Us] != 0)
629 - mg_value(score) / 32;
631 // Analyse the enemy's safe queen contact checks. Firstly, find the
632 // undefended squares around the king that are attacked by the enemy's
634 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
637 // ...and then remove squares not supported by another enemy piece
638 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
639 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
642 attackUnits += QueenContactCheck
644 * (Them == pos.side_to_move() ? 2 : 1);
647 // Analyse the enemy's safe rook contact checks. Firstly, find the
648 // undefended squares around the king that are attacked by the enemy's
650 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
652 // Consider only squares where the enemy's rook gives check
653 b &= PseudoAttacks[ROOK][ksq];
657 // ...and then remove squares not supported by another enemy piece
658 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
659 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
662 attackUnits += RookContactCheck
664 * (Them == pos.side_to_move() ? 2 : 1);
667 // Analyse the enemy's safe distance checks for sliders and knights
668 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
670 b1 = pos.attacks_from<ROOK>(ksq) & safe;
671 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
673 // Enemy queen safe checks
674 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
676 attackUnits += QueenCheck * popcount<Max15>(b);
678 // Enemy rooks safe checks
679 b = b1 & ei.attackedBy[Them][ROOK];
681 attackUnits += RookCheck * popcount<Max15>(b);
683 // Enemy bishops safe checks
684 b = b2 & ei.attackedBy[Them][BISHOP];
686 attackUnits += BishopCheck * popcount<Max15>(b);
688 // Enemy knights safe checks
689 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
691 attackUnits += KnightCheck * popcount<Max15>(b);
693 // To index KingDanger[] attackUnits must be in [0, 99] range
694 attackUnits = std::min(99, std::max(0, attackUnits));
696 // Finally, extract the king danger score from the KingDanger[]
697 // array and subtract the score from evaluation.
698 score -= KingDanger[Us == Search::RootColor][attackUnits];
702 Tracing::terms[Us][KING] = score;
708 // evaluate_threats() assigns bonuses according to the type of attacking piece
709 // and the type of attacked one.
711 template<Color Us, bool Trace>
712 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
714 const Color Them = (Us == WHITE ? BLACK : WHITE);
716 Bitboard b, undefendedMinors, weakEnemies;
717 Score score = SCORE_ZERO;
719 // Undefended minors get penalized even if they are not under attack
720 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
721 & ~ei.attackedBy[Them][ALL_PIECES];
723 if (undefendedMinors)
724 score += UndefendedMinor;
726 // Enemy pieces not defended by a pawn and under our attack
727 weakEnemies = pos.pieces(Them)
728 & ~ei.attackedBy[Them][PAWN]
729 & ei.attackedBy[Us][ALL_PIECES];
731 // Add a bonus according if the attacking pieces are minor or major
734 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
736 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
738 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
740 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
744 Tracing::terms[Us][Tracing::THREAT] = score;
750 // evaluate_passed_pawns() evaluates the passed pawns of the given color
752 template<Color Us, bool Trace>
753 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
755 const Color Them = (Us == WHITE ? BLACK : WHITE);
757 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
758 Score score = SCORE_ZERO;
760 b = ei.pi->passed_pawns(Us);
764 Square s = pop_lsb(&b);
766 assert(pos.pawn_passed(Us, s));
768 int r = int(relative_rank(Us, s) - RANK_2);
769 int rr = r * (r - 1);
771 // Base bonus based on rank
772 Value mbonus = Value(17 * rr);
773 Value ebonus = Value(7 * (rr + r + 1));
777 Square blockSq = s + pawn_push(Us);
779 // Adjust bonus based on the king's proximity
780 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
781 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
783 // If blockSq is not the queening square then consider also a second push
784 if (relative_rank(Us, blockSq) != RANK_8)
785 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
787 // If the pawn is free to advance, then increase the bonus
788 if (pos.empty(blockSq))
790 squaresToQueen = forward_bb(Us, s);
792 // If there is an enemy rook or queen attacking the pawn from behind,
793 // add all X-ray attacks by the rook or queen. Otherwise consider only
794 // the squares in the pawn's path attacked or occupied by the enemy.
795 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
796 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
797 unsafeSquares = squaresToQueen;
799 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
801 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
802 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
803 defendedSquares = squaresToQueen;
805 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
807 // If there aren't any enemy attacks, then assign a huge bonus.
808 // The bonus will be a bit smaller if at least the block square
809 // isn't attacked, otherwise assign the smallest possible bonus.
810 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
812 // Assign a big bonus if the path to the queen is fully defended,
813 // otherwise assign a bit less of a bonus if at least the block
814 // square is defended.
815 if (defendedSquares == squaresToQueen)
818 else if (defendedSquares & blockSq)
819 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
821 mbonus += Value(k * rr), ebonus += Value(k * rr);
825 // Increase the bonus if the passed pawn is supported by a friendly pawn
826 // on the same rank and a bit smaller if it's on the previous rank.
827 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
828 if (supportingPawns & rank_bb(s))
829 ebonus += Value(r * 20);
831 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
832 ebonus += Value(r * 12);
834 // Rook pawns are a special case: They are sometimes worse, and
835 // sometimes better than other passed pawns. It is difficult to find
836 // good rules for determining whether they are good or bad. For now,
837 // we try the following: Increase the value for rook pawns if the
838 // other side has no pieces apart from a knight, and decrease the
839 // value if the other side has a rook or queen.
840 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
842 if (pos.non_pawn_material(Them) <= KnightValueMg)
843 ebonus += ebonus / 4;
845 else if (pos.pieces(Them, ROOK, QUEEN))
846 ebonus -= ebonus / 4;
849 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
850 ebonus += ebonus / 4;
852 score += make_score(mbonus, ebonus);
856 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
858 // Add the scores to the middlegame and endgame eval
859 return apply_weight(score, Weights[PassedPawns]);
863 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
864 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
865 // related to the possibility that pawns are unstoppable.
867 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
869 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
871 if (!b || pos.non_pawn_material(~us))
874 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
878 // evaluate_space() computes the space evaluation for a given side. The
879 // space evaluation is a simple bonus based on the number of safe squares
880 // available for minor pieces on the central four files on ranks 2--4. Safe
881 // squares one, two or three squares behind a friendly pawn are counted
882 // twice. Finally, the space bonus is scaled by a weight taken from the
883 // material hash table. The aim is to improve play on game opening.
885 int evaluate_space(const Position& pos, const EvalInfo& ei) {
887 const Color Them = (Us == WHITE ? BLACK : WHITE);
889 // Find the safe squares for our pieces inside the area defined by
890 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
891 // pawn, or if it is undefended and attacked by an enemy piece.
892 Bitboard safe = SpaceMask[Us]
893 & ~pos.pieces(Us, PAWN)
894 & ~ei.attackedBy[Them][PAWN]
895 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
897 // Find all squares which are at most three squares behind some friendly pawn
898 Bitboard behind = pos.pieces(Us, PAWN);
899 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
900 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
902 // Since SpaceMask[Us] is fully on our half of the board
903 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
905 // Count safe + (behind & safe) with a single popcount
906 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
910 // interpolate() interpolates between a middlegame and an endgame score,
911 // based on game phase. It also scales the return value by a ScaleFactor array.
913 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
915 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
916 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
917 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
919 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
920 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
923 // apply_weight() weights score v by score w trying to prevent overflow
924 Score apply_weight(Score v, const Weight& w) {
926 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
929 // weight_option() computes the value of an evaluation weight, by combining
930 // two UCI-configurable weights (midgame and endgame) with an internal weight.
932 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
934 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
935 Options[egOpt] * eg_value(internalWeight) / 100 };
940 // Tracing function definitions
942 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
944 void Tracing::add_term(int idx, Score wScore, Score bScore) {
946 terms[WHITE][idx] = wScore;
947 terms[BLACK][idx] = bScore;
950 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
952 Score wScore = terms[WHITE][idx];
953 Score bScore = terms[BLACK][idx];
956 case PST: case IMBALANCE: case PAWN: case TOTAL:
957 ss << std::setw(20) << name << " | --- --- | --- --- | "
958 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
959 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
962 ss << std::setw(20) << name << " | " << std::noshowpos
963 << std::setw(5) << to_cp(mg_value(wScore)) << " "
964 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
965 << std::setw(5) << to_cp(mg_value(bScore)) << " "
966 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
967 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
968 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
972 std::string Tracing::do_trace(const Position& pos) {
974 std::memset(terms, 0, sizeof(terms));
976 Value v = do_evaluate<true>(pos);
977 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
979 std::stringstream ss;
980 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
981 << " Eval term | White | Black | Total \n"
982 << " | MG EG | MG EG | MG EG \n"
983 << "---------------------+-------------+-------------+-------------\n";
985 format_row(ss, "Material, PST, Tempo", PST);
986 format_row(ss, "Material imbalance", IMBALANCE);
987 format_row(ss, "Pawns", PAWN);
988 format_row(ss, "Knights", KNIGHT);
989 format_row(ss, "Bishops", BISHOP);
990 format_row(ss, "Rooks", ROOK);
991 format_row(ss, "Queens", QUEEN);
992 format_row(ss, "Mobility", MOBILITY);
993 format_row(ss, "King safety", KING);
994 format_row(ss, "Threats", THREAT);
995 format_row(ss, "Passed pawns", PASSED);
996 format_row(ss, "Space", SPACE);
998 ss << "---------------------+-------------+-------------+-------------\n";
999 format_row(ss, "Total", TOTAL);
1001 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";