2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 // Struct EvalInfo contains various information computed and collected
35 // by the evaluation functions.
38 // Pointers to material and pawn hash table entries
42 // attackedBy[color][piece type] is a bitboard representing all squares
43 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
44 // contains all squares attacked by the given color.
45 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
47 // kingRing[color] is the zone around the king which is considered
48 // by the king safety evaluation. This consists of the squares directly
49 // adjacent to the king, and the three (or two, for a king on an edge file)
50 // squares two ranks in front of the king. For instance, if black's king
51 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
52 // f7, g7, h7, f6, g6 and h6.
53 Bitboard kingRing[COLOR_NB];
55 // kingAttackersCount[color] is the number of pieces of the given color
56 // which attack a square in the kingRing of the enemy king.
57 int kingAttackersCount[COLOR_NB];
59 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
60 // given color which attack a square in the kingRing of the enemy king. The
61 // weights of the individual piece types are given by the variables
62 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
63 // KnightAttackWeight in evaluate.cpp
64 int kingAttackersWeight[COLOR_NB];
66 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
67 // directly adjacent to the king of the given color. Pieces which attack
68 // more than one square are counted multiple times. For instance, if black's
69 // king is on g8 and there's a white knight on g5, this knight adds
70 // 2 to kingAdjacentZoneAttacksCount[BLACK].
71 int kingAdjacentZoneAttacksCount[COLOR_NB];
73 Bitboard pinnedPieces[COLOR_NB];
78 enum Terms { // First 8 entries are for PieceType
79 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
82 Score terms[COLOR_NB][TERMS_NB];
86 double to_cp(Value v);
87 void add_term(int idx, Score term_w, Score term_b = SCORE_ZERO);
88 void format_row(std::stringstream& ss, const char* name, int idx);
89 std::string do_trace(const Position& pos);
92 // Evaluation weights, initialized from UCI options
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
97 #define S(mg, eg) make_score(mg, eg)
99 // Internal evaluation weights. These are applied on top of the evaluation
100 // weights read from UCI parameters. The purpose is to be able to change
101 // the evaluation weights while keeping the default values of the UCI
102 // parameters at 100, which looks prettier.
104 // Values modified by Joona Kiiski
105 const Score WeightsInternal[] = {
106 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
109 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
110 // game, indexed by piece type and number of attacked squares not occupied by
112 const Score MobilityBonus[][32] = {
114 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
115 S( 37, 28), S( 42, 31), S(44, 33) },
116 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
117 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
118 S( 84, 79), S( 86, 81) },
119 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
120 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
121 S( 35,122), S( 36,123), S(37,124) },
122 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
123 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
124 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
129 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
130 // indexed by piece type and square (from white's point of view).
131 const Value Outpost[][SQUARE_NB] = {
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
134 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
135 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
136 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
137 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
138 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
140 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
141 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
142 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
143 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
144 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
145 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
148 // Threat[attacking][attacked] contains bonuses according to which piece
149 // type attacks which one.
150 const Score Threat[][PIECE_TYPE_NB] = {
151 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
152 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[] = {
158 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
163 const Score Tempo = make_score(24, 11);
164 const Score RookOn7th = make_score(11, 20);
165 const Score QueenOn7th = make_score( 3, 8);
166 const Score RookOnPawn = make_score(10, 28);
167 const Score QueenOnPawn = make_score( 4, 20);
168 const Score RookOpenFile = make_score(43, 21);
169 const Score RookSemiopenFile = make_score(19, 10);
170 const Score BishopPawns = make_score( 8, 12);
171 const Score KnightPawns = make_score( 8, 4);
172 const Score MinorBehindPawn = make_score(16, 0);
173 const Score UndefendedMinor = make_score(25, 10);
174 const Score TrappedRook = make_score(90, 0);
175 const Score Unstoppable = make_score( 0, 20);
177 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
178 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
179 // happen in Chess960 games.
180 const Score TrappedBishopA1H1 = make_score(50, 50);
182 // SpaceMask[Color] contains the area of the board which is considered
183 // by the space evaluation. In the middlegame, each side is given a bonus
184 // based on how many squares inside this area are safe and available for
185 // friendly minor pieces.
186 const Bitboard SpaceMask[] = {
187 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
188 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
191 // King danger constants and variables. The king danger scores are taken
192 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
193 // of the enemy attack are added up into an integer, which is used as an
194 // index to KingDanger[].
196 // KingAttackWeights[PieceType] contains king attack weights by piece type
197 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
199 // Bonuses for enemy's safe checks
200 const int QueenContactCheck = 24;
201 const int RookContactCheck = 16;
202 const int QueenCheck = 12;
203 const int RookCheck = 8;
204 const int BishopCheck = 2;
205 const int KnightCheck = 3;
207 const int UnsupportedPinnedPiece = 2;
209 // KingDanger[Color][attackUnits] contains the actual king danger weighted
210 // scores, indexed by color and by a calculated integer number.
211 Score KingDanger[COLOR_NB][128];
213 // Function prototypes
215 Value do_evaluate(const Position& pos);
218 void init_eval_info(const Position& pos, EvalInfo& ei);
220 template<Color Us, bool Trace>
221 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility);
223 template<Color Us, bool Trace>
224 Score evaluate_king(const Position& pos, const EvalInfo& ei);
226 template<Color Us, bool Trace>
227 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
229 template<Color Us, bool Trace>
230 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
233 int evaluate_space(const Position& pos, const EvalInfo& ei);
235 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
237 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
238 Score apply_weight(Score v, Score w);
239 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
245 /// evaluate() is the main evaluation function. It always computes two
246 /// values, an endgame score and a middlegame score, and interpolates
247 /// between them based on the remaining material.
249 Value evaluate(const Position& pos) {
250 return do_evaluate<false>(pos);
254 /// trace() is like evaluate(), but instead of returning a value, it returns
255 /// a string (suitable for outputting to stdout) that contains the detailed
256 /// descriptions and values of each evaluation term. It's mainly used for
258 std::string trace(const Position& pos) {
259 return Tracing::do_trace(pos);
263 /// init() computes evaluation weights from the corresponding UCI parameters
264 /// and setup king tables.
268 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
269 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
270 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
271 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
272 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
273 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
275 const int MaxSlope = 30;
276 const int Peak = 1280;
278 for (int t = 0, i = 1; i < 100; ++i)
280 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
282 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
283 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
293 Value do_evaluate(const Position& pos) {
295 assert(!pos.checkers());
298 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
299 Thread* thisThread = pos.this_thread();
301 // Initialize score by reading the incrementally updated scores included
302 // in the position object (material + piece square tables) and adding a
303 // Tempo bonus. Score is computed from the point of view of white.
304 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
306 // Probe the material hash table
307 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
308 score += ei.mi->material_value();
310 // If we have a specialized evaluation function for the current material
311 // configuration, call it and return.
312 if (ei.mi->specialized_eval_exists())
313 return ei.mi->evaluate(pos);
315 // Probe the pawn hash table
316 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
317 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
319 // Initialize attack and king safety bitboards
320 init_eval_info<WHITE>(pos, ei);
321 init_eval_info<BLACK>(pos, ei);
323 // Evaluate pieces and mobility
324 score += evaluate_pieces<WHITE, Trace>(pos, ei, mobility)
325 - evaluate_pieces<BLACK, Trace>(pos, ei, mobility);
327 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
329 // Evaluate kings after all other pieces because we need complete attack
330 // information when computing the king safety evaluation.
331 score += evaluate_king<WHITE, Trace>(pos, ei)
332 - evaluate_king<BLACK, Trace>(pos, ei);
334 // Evaluate tactical threats, we need full attack information including king
335 score += evaluate_threats<WHITE, Trace>(pos, ei)
336 - evaluate_threats<BLACK, Trace>(pos, ei);
338 // Evaluate passed pawns, we need full attack information including king
339 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
340 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
342 // If one side has only a king, score for potential unstoppable pawns
343 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
344 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
345 - evaluate_unstoppable_pawns(pos, BLACK, ei);
347 // Evaluate space for both sides, only in middlegame
348 if (ei.mi->space_weight())
350 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
351 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
354 // Scale winning side if position is more drawish than it appears
355 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
356 : ei.mi->scale_factor(pos, BLACK);
358 // If we don't already have an unusual scale factor, check for opposite
359 // colored bishop endgames, and use a lower scale for those.
360 if ( ei.mi->game_phase() < PHASE_MIDGAME
361 && pos.opposite_bishops()
362 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
364 // Ignoring any pawns, do both sides only have a single bishop and no
366 if ( pos.non_pawn_material(WHITE) == BishopValueMg
367 && pos.non_pawn_material(BLACK) == BishopValueMg)
369 // Check for KBP vs KB with only a single pawn that is almost
370 // certainly a draw or at least two pawns.
371 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
372 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
375 // Endgame with opposite-colored bishops, but also other pieces. Still
376 // a bit drawish, but not as drawish as with only the two bishops.
377 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
380 Value v = interpolate(score, ei.mi->game_phase(), sf);
382 // In case of tracing add all single evaluation contributions for both white and black
385 Tracing::add_term(Tracing::PST, pos.psq_score());
386 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
387 Tracing::add_term(PAWN, ei.pi->pawns_value());
388 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
389 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
390 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
391 Tracing::add_term(Tracing::TOTAL, score);
396 return pos.side_to_move() == WHITE ? v : -v;
400 // init_eval_info() initializes king bitboards for given color adding
401 // pawn attacks. To be done at the beginning of the evaluation.
404 void init_eval_info(const Position& pos, EvalInfo& ei) {
406 const Color Them = (Us == WHITE ? BLACK : WHITE);
407 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
409 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
411 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
412 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
414 // Init king safety tables only if we are going to use them
415 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
417 ei.kingRing[Them] = b | shift_bb<Down>(b);
418 b &= ei.attackedBy[Us][PAWN];
419 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
420 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
423 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
427 // evaluate_outposts() evaluates bishop and knight outpost squares
429 template<PieceType Pt, Color Us>
430 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
432 const Color Them = (Us == WHITE ? BLACK : WHITE);
434 assert (Pt == BISHOP || Pt == KNIGHT);
436 // Initial bonus based on square
437 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
439 // Increase bonus if supported by pawn, especially if the opponent has
440 // no minor piece which can trade with the outpost piece.
441 if (bonus && (ei.attackedBy[Us][PAWN] & s))
443 if ( !pos.pieces(Them, KNIGHT)
444 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
445 bonus += bonus + bonus / 2;
450 return make_score(bonus, bonus);
454 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
456 template<PieceType Pt, Color Us, bool Trace>
457 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
461 Score score = SCORE_ZERO;
463 const Color Them = (Us == WHITE ? BLACK : WHITE);
464 const Square* pl = pos.list<Pt>(Us);
466 ei.attackedBy[Us][Pt] = 0;
468 while ((s = *pl++) != SQ_NONE)
470 // Find attacked squares, including x-ray attacks for bishops and rooks
471 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
472 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
473 : pos.attacks_from<Pt>(s);
475 if (ei.pinnedPieces[Us] & s)
476 b &= LineBB[pos.king_square(Us)][s];
478 ei.attackedBy[Us][Pt] |= b;
480 if (b & ei.kingRing[Them])
482 ei.kingAttackersCount[Us]++;
483 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
484 Bitboard bb = b & ei.attackedBy[Them][KING];
486 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
489 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea)
490 : popcount<Full >(b & mobilityArea);
492 mobility[Us] += MobilityBonus[Pt][mob];
494 // Decrease score if we are attacked by an enemy pawn. The remaining part
495 // of threat evaluation must be done later when we have full attack info.
496 if (ei.attackedBy[Them][PAWN] & s)
497 score -= ThreatenedByPawn[Pt];
499 if (Pt == BISHOP || Pt == KNIGHT)
501 // Penalty for bishop with same colored pawns
503 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
505 // Penalty for knight when there are few enemy pawns
507 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
509 // Bishop and knight outposts squares
510 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
511 score += evaluate_outposts<Pt, Us>(pos, ei, s);
513 // Bishop or knight behind a pawn
514 if ( relative_rank(Us, s) < RANK_5
515 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
516 score += MinorBehindPawn;
519 if ( (Pt == ROOK || Pt == QUEEN)
520 && relative_rank(Us, s) >= RANK_5)
522 // Major piece on 7th rank and enemy king trapped on 8th
523 if ( relative_rank(Us, s) == RANK_7
524 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
525 score += Pt == ROOK ? RookOn7th : QueenOn7th;
527 // Major piece attacking enemy pawns on the same rank/file
528 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
530 score += popcount<Max15>(pawns) * (Pt == ROOK ? RookOnPawn : QueenOnPawn);
533 // Special extra evaluation for rooks
536 // Give a bonus for a rook on a open or semi-open file
537 if (ei.pi->semiopen(Us, file_of(s)))
538 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
540 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
543 Square ksq = pos.king_square(Us);
545 // Penalize rooks which are trapped by a king. Penalize more if the
546 // king has lost its castling capability.
547 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
548 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
549 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
550 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
553 // An important Chess960 pattern: A cornered bishop blocked by a friendly
554 // pawn diagonally in front of it is a very serious problem, especially
555 // when that pawn is also blocked.
558 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
560 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
561 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
562 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
563 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
569 Tracing::terms[Us][Pt] = score;
575 // evaluate_pieces() assigns bonuses and penalties to all the
576 // pieces of a given color.
578 template<Color Us, bool Trace>
579 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
581 const Color Them = (Us == WHITE ? BLACK : WHITE);
583 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
584 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
586 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
587 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
588 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
589 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
591 // Sum up all attacked squares (updated in evaluate_pieces)
592 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
593 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
594 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
596 Tracing::terms[Us][Tracing::MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
602 // evaluate_king() assigns bonuses and penalties to a king of a given color
604 template<Color Us, bool Trace>
605 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
607 const Color Them = (Us == WHITE ? BLACK : WHITE);
609 Bitboard undefended, b, b1, b2, safe;
611 const Square ksq = pos.king_square(Us);
613 // King shelter and enemy pawns storm
614 Score score = ei.pi->king_safety<Us>(pos, ksq);
616 // Main king safety evaluation
617 if (ei.kingAttackersCount[Them])
619 // Find the attacked squares around the king which have no defenders
620 // apart from the king itself
621 undefended = ei.attackedBy[Them][ALL_PIECES]
622 & ei.attackedBy[Us][KING]
623 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
624 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
625 | ei.attackedBy[Us][QUEEN]);
627 // Initialize the 'attackUnits' variable, which is used later on as an
628 // index to the KingDanger[] array. The initial value is based on the
629 // number and types of the enemy's attacking pieces, the number of
630 // attacked and undefended squares around our king and the quality of
631 // the pawn shelter (current 'score' value).
632 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
633 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
634 - mg_value(score) / 32;
636 // Analyse the enemy's safe queen contact checks. Firstly, find the
637 // undefended squares around the king that are attacked by the enemy's
639 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
642 // ...and then remove squares not supported by another enemy piece
643 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
644 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
647 attackUnits += QueenContactCheck
649 * (Them == pos.side_to_move() ? 2 : 1);
652 // Analyse the enemy's safe rook contact checks. Firstly, find the
653 // undefended squares around the king that are attacked by the enemy's
655 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
657 // Consider only squares where the enemy's rook gives check
658 b &= PseudoAttacks[ROOK][ksq];
662 // ...and then remove squares not supported by another enemy piece
663 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
664 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
667 attackUnits += RookContactCheck
669 * (Them == pos.side_to_move() ? 2 : 1);
672 // Analyse the enemy's safe distance checks for sliders and knights
673 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
675 b1 = pos.attacks_from<ROOK>(ksq) & safe;
676 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
678 // Enemy queen safe checks
679 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
681 attackUnits += QueenCheck * popcount<Max15>(b);
683 // Enemy rooks safe checks
684 b = b1 & ei.attackedBy[Them][ROOK];
686 attackUnits += RookCheck * popcount<Max15>(b);
688 // Enemy bishops safe checks
689 b = b2 & ei.attackedBy[Them][BISHOP];
691 attackUnits += BishopCheck * popcount<Max15>(b);
693 // Enemy knights safe checks
694 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
696 attackUnits += KnightCheck * popcount<Max15>(b);
698 // Penalty for pinned pieces not defended by a pawn
699 if (ei.pinnedPieces[Us] & ~ei.attackedBy[Us][PAWN])
700 attackUnits += UnsupportedPinnedPiece;
702 // To index KingDanger[] attackUnits must be in [0, 99] range
703 attackUnits = std::min(99, std::max(0, attackUnits));
705 // Finally, extract the king danger score from the KingDanger[]
706 // array and subtract the score from evaluation.
707 score -= KingDanger[Us == Search::RootColor][attackUnits];
711 Tracing::terms[Us][KING] = score;
717 // evaluate_threats() assigns bonuses according to the type of attacking piece
718 // and the type of attacked one.
720 template<Color Us, bool Trace>
721 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
723 const Color Them = (Us == WHITE ? BLACK : WHITE);
725 Bitboard b, undefendedMinors, weakEnemies;
726 Score score = SCORE_ZERO;
728 // Undefended minors get penalized even if they are not under attack
729 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
730 & ~ei.attackedBy[Them][ALL_PIECES];
732 if (undefendedMinors)
733 score += UndefendedMinor;
735 // Enemy pieces not defended by a pawn and under our attack
736 weakEnemies = pos.pieces(Them)
737 & ~ei.attackedBy[Them][PAWN]
738 & ei.attackedBy[Us][ALL_PIECES];
740 // Add a bonus according if the attacking pieces are minor or major
743 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
745 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
747 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
749 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
753 Tracing::terms[Us][Tracing::THREAT] = score;
759 // evaluate_passed_pawns() evaluates the passed pawns of the given color
761 template<Color Us, bool Trace>
762 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
764 const Color Them = (Us == WHITE ? BLACK : WHITE);
766 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
767 Score score = SCORE_ZERO;
769 b = ei.pi->passed_pawns(Us);
773 Square s = pop_lsb(&b);
775 assert(pos.pawn_passed(Us, s));
777 int r = int(relative_rank(Us, s) - RANK_2);
778 int rr = r * (r - 1);
780 // Base bonus based on rank
781 Value mbonus = Value(17 * rr);
782 Value ebonus = Value(7 * (rr + r + 1));
786 Square blockSq = s + pawn_push(Us);
788 // Adjust bonus based on the king's proximity
789 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
790 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
792 // If blockSq is not the queening square then consider also a second push
793 if (relative_rank(Us, blockSq) != RANK_8)
794 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
796 // If the pawn is free to advance, then increase the bonus
797 if (pos.empty(blockSq))
799 squaresToQueen = forward_bb(Us, s);
801 // If there is an enemy rook or queen attacking the pawn from behind,
802 // add all X-ray attacks by the rook or queen. Otherwise consider only
803 // the squares in the pawn's path attacked or occupied by the enemy.
804 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
805 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
806 unsafeSquares = squaresToQueen;
808 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
810 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
811 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
812 defendedSquares = squaresToQueen;
814 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
816 // If there aren't any enemy attacks, then assign a huge bonus.
817 // The bonus will be a bit smaller if at least the block square
818 // isn't attacked, otherwise assign the smallest possible bonus.
819 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
821 // Assign a big bonus if the path to the queen is fully defended,
822 // otherwise assign a bit less of a bonus if at least the block
823 // square is defended.
824 if (defendedSquares == squaresToQueen)
827 else if (defendedSquares & blockSq)
828 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
830 mbonus += Value(k * rr), ebonus += Value(k * rr);
834 // Increase the bonus if the passed pawn is supported by a friendly pawn
835 // on the same rank and a bit smaller if it's on the previous rank.
836 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
837 if (supportingPawns & rank_bb(s))
838 ebonus += Value(r * 20);
840 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
841 ebonus += Value(r * 12);
843 // Rook pawns are a special case: They are sometimes worse, and
844 // sometimes better than other passed pawns. It is difficult to find
845 // good rules for determining whether they are good or bad. For now,
846 // we try the following: Increase the value for rook pawns if the
847 // other side has no pieces apart from a knight, and decrease the
848 // value if the other side has a rook or queen.
849 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
851 if (pos.non_pawn_material(Them) <= KnightValueMg)
852 ebonus += ebonus / 4;
854 else if (pos.pieces(Them, ROOK, QUEEN))
855 ebonus -= ebonus / 4;
858 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
859 ebonus += ebonus / 4;
861 score += make_score(mbonus, ebonus);
865 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
867 // Add the scores to the middlegame and endgame eval
868 return apply_weight(score, Weights[PassedPawns]);
872 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
873 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
874 // related to the possibility that pawns are unstoppable.
876 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
878 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
880 if (!b || pos.non_pawn_material(~us))
883 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
887 // evaluate_space() computes the space evaluation for a given side. The
888 // space evaluation is a simple bonus based on the number of safe squares
889 // available for minor pieces on the central four files on ranks 2--4. Safe
890 // squares one, two or three squares behind a friendly pawn are counted
891 // twice. Finally, the space bonus is scaled by a weight taken from the
892 // material hash table. The aim is to improve play on game opening.
894 int evaluate_space(const Position& pos, const EvalInfo& ei) {
896 const Color Them = (Us == WHITE ? BLACK : WHITE);
898 // Find the safe squares for our pieces inside the area defined by
899 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
900 // pawn, or if it is undefended and attacked by an enemy piece.
901 Bitboard safe = SpaceMask[Us]
902 & ~pos.pieces(Us, PAWN)
903 & ~ei.attackedBy[Them][PAWN]
904 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
906 // Find all squares which are at most three squares behind some friendly pawn
907 Bitboard behind = pos.pieces(Us, PAWN);
908 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
909 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
911 // Since SpaceMask[Us] is fully on our half of the board
912 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
914 // Count safe + (behind & safe) with a single popcount
915 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
919 // interpolate() interpolates between a middlegame and an endgame score,
920 // based on game phase. It also scales the return value by a ScaleFactor array.
922 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
924 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
925 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
926 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
928 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
929 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
932 // apply_weight() weights score v by score w trying to prevent overflow
933 Score apply_weight(Score v, Score w) {
935 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
936 (int(eg_value(v)) * eg_value(w)) / 0x100);
939 // weight_option() computes the value of an evaluation weight, by combining
940 // two UCI-configurable weights (midgame and endgame) with an internal weight.
942 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
944 // Scale option value from 100 to 256
945 int mg = Options[mgOpt] * 256 / 100;
946 int eg = Options[egOpt] * 256 / 100;
948 return apply_weight(make_score(mg, eg), internalWeight);
952 // Tracing function definitions
954 double Tracing::to_cp(Value v) { return double(v) / PawnValueMg; }
956 void Tracing::add_term(int idx, Score wScore, Score bScore) {
958 terms[WHITE][idx] = wScore;
959 terms[BLACK][idx] = bScore;
962 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
964 Score wScore = terms[WHITE][idx];
965 Score bScore = terms[BLACK][idx];
968 case PST: case IMBALANCE: case PAWN: case TOTAL:
969 ss << std::setw(20) << name << " | --- --- | --- --- | "
970 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
971 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
974 ss << std::setw(20) << name << " | " << std::noshowpos
975 << std::setw(5) << to_cp(mg_value(wScore)) << " "
976 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
977 << std::setw(5) << to_cp(mg_value(bScore)) << " "
978 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
979 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
980 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
984 std::string Tracing::do_trace(const Position& pos) {
986 std::memset(terms, 0, sizeof(terms));
988 Value v = do_evaluate<true>(pos);
989 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
991 std::stringstream ss;
992 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
993 << " Eval term | White | Black | Total \n"
994 << " | MG EG | MG EG | MG EG \n"
995 << "---------------------+-------------+-------------+-------------\n";
997 format_row(ss, "Material, PST, Tempo", PST);
998 format_row(ss, "Material imbalance", IMBALANCE);
999 format_row(ss, "Pawns", PAWN);
1000 format_row(ss, "Knights", KNIGHT);
1001 format_row(ss, "Bishops", BISHOP);
1002 format_row(ss, "Rooks", ROOK);
1003 format_row(ss, "Queens", QUEEN);
1004 format_row(ss, "Mobility", MOBILITY);
1005 format_row(ss, "King safety", KING);
1006 format_row(ss, "Threats", THREAT);
1007 format_row(ss, "Passed pawns", PASSED);
1008 format_row(ss, "Space", SPACE);
1010 ss << "---------------------+-------------+-------------+-------------\n";
1011 format_row(ss, "Total", TOTAL);
1013 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";