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);
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);
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<Trace>(pos, ei, mobility);
322 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
324 // Evaluate kings after all other pieces because we need complete attack
325 // information when computing the king safety evaluation.
326 score += evaluate_king<WHITE, Trace>(pos, ei)
327 - evaluate_king<BLACK, Trace>(pos, ei);
329 // Evaluate tactical threats, we need full attack information including king
330 score += evaluate_threats<WHITE, Trace>(pos, ei)
331 - evaluate_threats<BLACK, Trace>(pos, ei);
333 // Evaluate passed pawns, we need full attack information including king
334 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
335 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
337 // If one side has only a king, score for potential unstoppable pawns
338 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
339 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
340 - evaluate_unstoppable_pawns(pos, BLACK, ei);
342 // Evaluate space for both sides, only in middlegame
343 if (ei.mi->space_weight())
345 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
346 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
349 // Scale winning side if position is more drawish than it appears
350 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
351 : ei.mi->scale_factor(pos, BLACK);
353 // If we don't already have an unusual scale factor, check for opposite
354 // colored bishop endgames, and use a lower scale for those.
355 if ( ei.mi->game_phase() < PHASE_MIDGAME
356 && pos.opposite_bishops()
357 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
359 // Ignoring any pawns, do both sides only have a single bishop and no
361 if ( pos.non_pawn_material(WHITE) == BishopValueMg
362 && pos.non_pawn_material(BLACK) == BishopValueMg)
364 // Check for KBP vs KB with only a single pawn that is almost
365 // certainly a draw or at least two pawns.
366 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
367 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
370 // Endgame with opposite-colored bishops, but also other pieces. Still
371 // a bit drawish, but not as drawish as with only the two bishops.
372 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
375 Value v = interpolate(score, ei.mi->game_phase(), sf);
377 // In case of tracing add all single evaluation contributions for both white and black
380 Tracing::add_term(Tracing::PST, pos.psq_score());
381 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
382 Tracing::add_term(PAWN, ei.pi->pawns_value());
383 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
384 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
385 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
386 Tracing::add_term(Tracing::TOTAL, score);
391 return pos.side_to_move() == WHITE ? v : -v;
395 // init_eval_info() initializes king bitboards for given color adding
396 // pawn attacks. To be done at the beginning of the evaluation.
399 void init_eval_info(const Position& pos, EvalInfo& ei) {
401 const Color Them = (Us == WHITE ? BLACK : WHITE);
402 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
404 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
406 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
407 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
409 // Init king safety tables only if we are going to use them
410 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
412 ei.kingRing[Them] = b | shift_bb<Down>(b);
413 b &= ei.attackedBy[Us][PAWN];
414 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
415 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
418 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
422 // evaluate_outposts() evaluates bishop and knight outpost squares
424 template<PieceType Pt, Color Us>
425 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
427 const Color Them = (Us == WHITE ? BLACK : WHITE);
429 assert (Pt == BISHOP || Pt == KNIGHT);
431 // Initial bonus based on square
432 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
434 // Increase bonus if supported by pawn, especially if the opponent has
435 // no minor piece which can trade with the outpost piece.
436 if (bonus && (ei.attackedBy[Us][PAWN] & s))
438 if ( !pos.pieces(Them, KNIGHT)
439 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
440 bonus += bonus + bonus / 2;
445 return make_score(bonus, bonus);
449 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
451 template<PieceType Pt, Color Us, bool Trace>
452 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
456 Score score = SCORE_ZERO;
458 const Color Them = (Us == WHITE ? BLACK : WHITE);
459 const Square* pl = pos.list<Pt>(Us);
461 ei.attackedBy[Us][Pt] = 0;
463 while ((s = *pl++) != SQ_NONE)
465 // Find attacked squares, including x-ray attacks for bishops and rooks
466 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
467 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
468 : pos.attacks_from<Pt>(s);
470 if (ei.pinnedPieces[Us] & s)
471 b &= LineBB[pos.king_square(Us)][s];
473 ei.attackedBy[Us][Pt] |= b;
475 if (b & ei.kingRing[Them])
477 ei.kingAttackersCount[Us]++;
478 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
479 Bitboard bb = b & ei.attackedBy[Them][KING];
481 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
485 b &= ~( ei.attackedBy[Them][KNIGHT]
486 | ei.attackedBy[Them][BISHOP]
487 | ei.attackedBy[Them][ROOK]);
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;
521 // Rook on 7th rank and enemy king trapped on 8th
522 if ( relative_rank(Us, s) == RANK_7
523 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
526 // Rook piece attacking enemy pawns on the same rank/file
527 if (relative_rank(Us, s) >= RANK_5)
529 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
531 score += popcount<Max15>(pawns) * RookOnPawn;
534 // Give a bonus for a rook on a open or semi-open file
535 if (ei.pi->semiopen(Us, file_of(s)))
536 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
538 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
541 Square ksq = pos.king_square(Us);
543 // Penalize rooks which are trapped by a king. Penalize more if the
544 // king has lost its castling capability.
545 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
546 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
547 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
548 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
551 // An important Chess960 pattern: A cornered bishop blocked by a friendly
552 // pawn diagonally in front of it is a very serious problem, especially
553 // when that pawn is also blocked.
556 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
558 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
559 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
560 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
561 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
567 Tracing::terms[Us][Pt] = score;
573 // evaluate_pieces() assigns bonuses and penalties to all the pieces of both colors
576 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility) {
578 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
579 const Bitboard whiteMobilityArea = ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING));
580 const Bitboard blackMobilityArea = ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING));
584 score = evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
585 - evaluate_pieces<KNIGHT, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
586 score += evaluate_pieces<BISHOP, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
587 - evaluate_pieces<BISHOP, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
588 score += evaluate_pieces< ROOK, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
589 - evaluate_pieces< ROOK, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
590 score += evaluate_pieces< QUEEN, WHITE, Trace>(pos, ei, mobility, whiteMobilityArea)
591 - evaluate_pieces< QUEEN, BLACK, Trace>(pos, ei, mobility, blackMobilityArea);
593 // Sum up all attacked squares (updated in evaluate_pieces)
594 ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[WHITE][PAWN] | ei.attackedBy[WHITE][KNIGHT]
595 | ei.attackedBy[WHITE][BISHOP] | ei.attackedBy[WHITE][ROOK]
596 | ei.attackedBy[WHITE][QUEEN] | ei.attackedBy[WHITE][KING];
598 ei.attackedBy[BLACK][ALL_PIECES] = ei.attackedBy[BLACK][PAWN] | ei.attackedBy[BLACK][KNIGHT]
599 | ei.attackedBy[BLACK][BISHOP] | ei.attackedBy[BLACK][ROOK]
600 | ei.attackedBy[BLACK][QUEEN] | ei.attackedBy[BLACK][KING];
603 Tracing::terms[WHITE][Tracing::MOBILITY] = apply_weight(mobility[WHITE], Weights[Mobility]);
604 Tracing::terms[BLACK][Tracing::MOBILITY] = apply_weight(mobility[BLACK], Weights[Mobility]);
611 // evaluate_king() assigns bonuses and penalties to a king of a given color
613 template<Color Us, bool Trace>
614 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
616 const Color Them = (Us == WHITE ? BLACK : WHITE);
618 Bitboard undefended, b, b1, b2, safe;
620 const Square ksq = pos.king_square(Us);
622 // King shelter and enemy pawns storm
623 Score score = ei.pi->king_safety<Us>(pos, ksq);
625 // Main king safety evaluation
626 if (ei.kingAttackersCount[Them])
628 // Find the attacked squares around the king which have no defenders
629 // apart from the king itself
630 undefended = ei.attackedBy[Them][ALL_PIECES]
631 & ei.attackedBy[Us][KING]
632 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
633 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
634 | ei.attackedBy[Us][QUEEN]);
636 // Initialize the 'attackUnits' variable, which is used later on as an
637 // index to the KingDanger[] array. The initial value is based on the
638 // number and types of the enemy's attacking pieces, the number of
639 // attacked and undefended squares around our king and the quality of
640 // the pawn shelter (current 'score' value).
641 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
642 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
643 + 2 * (ei.pinnedPieces[Us] != 0)
644 - mg_value(score) / 32;
646 // Analyse the enemy's safe queen contact checks. Firstly, find the
647 // undefended squares around the king that are attacked by the enemy's
649 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
652 // ...and then remove squares not supported by another enemy piece
653 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
654 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
657 attackUnits += QueenContactCheck
659 * (Them == pos.side_to_move() ? 2 : 1);
662 // Analyse the enemy's safe rook contact checks. Firstly, find the
663 // undefended squares around the king that are attacked by the enemy's
665 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
667 // Consider only squares where the enemy's rook gives check
668 b &= PseudoAttacks[ROOK][ksq];
672 // ...and then remove squares not supported by another enemy piece
673 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
674 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
677 attackUnits += RookContactCheck
679 * (Them == pos.side_to_move() ? 2 : 1);
682 // Analyse the enemy's safe distance checks for sliders and knights
683 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
685 b1 = pos.attacks_from<ROOK>(ksq) & safe;
686 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
688 // Enemy queen safe checks
689 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
691 attackUnits += QueenCheck * popcount<Max15>(b);
693 // Enemy rooks safe checks
694 b = b1 & ei.attackedBy[Them][ROOK];
696 attackUnits += RookCheck * popcount<Max15>(b);
698 // Enemy bishops safe checks
699 b = b2 & ei.attackedBy[Them][BISHOP];
701 attackUnits += BishopCheck * popcount<Max15>(b);
703 // Enemy knights safe checks
704 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
706 attackUnits += KnightCheck * popcount<Max15>(b);
708 // To index KingDanger[] attackUnits must be in [0, 99] range
709 attackUnits = std::min(99, std::max(0, attackUnits));
711 // Finally, extract the king danger score from the KingDanger[]
712 // array and subtract the score from evaluation.
713 score -= KingDanger[Us == Search::RootColor][attackUnits];
717 Tracing::terms[Us][KING] = score;
723 // evaluate_threats() assigns bonuses according to the type of attacking piece
724 // and the type of attacked one.
726 template<Color Us, bool Trace>
727 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
729 const Color Them = (Us == WHITE ? BLACK : WHITE);
731 Bitboard b, undefendedMinors, weakEnemies;
732 Score score = SCORE_ZERO;
734 // Undefended minors get penalized even if they are not under attack
735 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
736 & ~ei.attackedBy[Them][ALL_PIECES];
738 if (undefendedMinors)
739 score += UndefendedMinor;
741 // Enemy pieces not defended by a pawn and under our attack
742 weakEnemies = pos.pieces(Them)
743 & ~ei.attackedBy[Them][PAWN]
744 & ei.attackedBy[Us][ALL_PIECES];
746 // Add a bonus according if the attacking pieces are minor or major
749 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
751 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
753 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
755 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
759 Tracing::terms[Us][Tracing::THREAT] = score;
765 // evaluate_passed_pawns() evaluates the passed pawns of the given color
767 template<Color Us, bool Trace>
768 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
770 const Color Them = (Us == WHITE ? BLACK : WHITE);
772 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
773 Score score = SCORE_ZERO;
775 b = ei.pi->passed_pawns(Us);
779 Square s = pop_lsb(&b);
781 assert(pos.pawn_passed(Us, s));
783 int r = int(relative_rank(Us, s) - RANK_2);
784 int rr = r * (r - 1);
786 // Base bonus based on rank
787 Value mbonus = Value(17 * rr);
788 Value ebonus = Value(7 * (rr + r + 1));
792 Square blockSq = s + pawn_push(Us);
794 // Adjust bonus based on the king's proximity
795 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
796 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
798 // If blockSq is not the queening square then consider also a second push
799 if (relative_rank(Us, blockSq) != RANK_8)
800 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
802 // If the pawn is free to advance, then increase the bonus
803 if (pos.empty(blockSq))
805 squaresToQueen = forward_bb(Us, s);
807 // If there is an enemy rook or queen attacking the pawn from behind,
808 // add all X-ray attacks by the rook or queen. Otherwise consider only
809 // the squares in the pawn's path attacked or occupied by the enemy.
810 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
811 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
812 unsafeSquares = squaresToQueen;
814 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
816 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
817 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
818 defendedSquares = squaresToQueen;
820 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
822 // If there aren't any enemy attacks, then assign a huge bonus.
823 // The bonus will be a bit smaller if at least the block square
824 // isn't attacked, otherwise assign the smallest possible bonus.
825 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
827 // Assign a big bonus if the path to the queen is fully defended,
828 // otherwise assign a bit less of a bonus if at least the block
829 // square is defended.
830 if (defendedSquares == squaresToQueen)
833 else if (defendedSquares & blockSq)
834 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
836 mbonus += Value(k * rr), ebonus += Value(k * rr);
840 // Increase the bonus if the passed pawn is supported by a friendly pawn
841 // on the same rank and a bit smaller if it's on the previous rank.
842 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
843 if (supportingPawns & rank_bb(s))
844 ebonus += Value(r * 20);
846 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
847 ebonus += Value(r * 12);
849 // Rook pawns are a special case: They are sometimes worse, and
850 // sometimes better than other passed pawns. It is difficult to find
851 // good rules for determining whether they are good or bad. For now,
852 // we try the following: Increase the value for rook pawns if the
853 // other side has no pieces apart from a knight, and decrease the
854 // value if the other side has a rook or queen.
855 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
857 if (pos.non_pawn_material(Them) <= KnightValueMg)
858 ebonus += ebonus / 4;
860 else if (pos.pieces(Them, ROOK, QUEEN))
861 ebonus -= ebonus / 4;
864 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
865 ebonus += ebonus / 4;
867 score += make_score(mbonus, ebonus);
871 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
873 // Add the scores to the middlegame and endgame eval
874 return apply_weight(score, Weights[PassedPawns]);
878 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
879 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
880 // related to the possibility that pawns are unstoppable.
882 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
884 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
886 if (!b || pos.non_pawn_material(~us))
889 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
893 // evaluate_space() computes the space evaluation for a given side. The
894 // space evaluation is a simple bonus based on the number of safe squares
895 // available for minor pieces on the central four files on ranks 2--4. Safe
896 // squares one, two or three squares behind a friendly pawn are counted
897 // twice. Finally, the space bonus is scaled by a weight taken from the
898 // material hash table. The aim is to improve play on game opening.
900 int evaluate_space(const Position& pos, const EvalInfo& ei) {
902 const Color Them = (Us == WHITE ? BLACK : WHITE);
904 // Find the safe squares for our pieces inside the area defined by
905 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
906 // pawn, or if it is undefended and attacked by an enemy piece.
907 Bitboard safe = SpaceMask[Us]
908 & ~pos.pieces(Us, PAWN)
909 & ~ei.attackedBy[Them][PAWN]
910 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
912 // Find all squares which are at most three squares behind some friendly pawn
913 Bitboard behind = pos.pieces(Us, PAWN);
914 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
915 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
917 // Since SpaceMask[Us] is fully on our half of the board
918 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
920 // Count safe + (behind & safe) with a single popcount
921 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
925 // interpolate() interpolates between a middlegame and an endgame score,
926 // based on game phase. It also scales the return value by a ScaleFactor array.
928 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
930 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
931 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
932 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
934 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
935 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
938 // apply_weight() weights score v by score w trying to prevent overflow
939 Score apply_weight(Score v, const Weight& w) {
941 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
944 // weight_option() computes the value of an evaluation weight, by combining
945 // two UCI-configurable weights (midgame and endgame) with an internal weight.
947 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
949 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
950 Options[egOpt] * eg_value(internalWeight) / 100 };
955 // Tracing function definitions
957 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
959 void Tracing::add_term(int idx, Score wScore, Score bScore) {
961 terms[WHITE][idx] = wScore;
962 terms[BLACK][idx] = bScore;
965 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
967 Score wScore = terms[WHITE][idx];
968 Score bScore = terms[BLACK][idx];
971 case PST: case IMBALANCE: case PAWN: case TOTAL:
972 ss << std::setw(20) << name << " | --- --- | --- --- | "
973 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
974 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
977 ss << std::setw(20) << name << " | " << std::noshowpos
978 << std::setw(5) << to_cp(mg_value(wScore)) << " "
979 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
980 << std::setw(5) << to_cp(mg_value(bScore)) << " "
981 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
982 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
983 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
987 std::string Tracing::do_trace(const Position& pos) {
989 std::memset(terms, 0, sizeof(terms));
991 Value v = do_evaluate<true>(pos);
992 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
994 std::stringstream ss;
995 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
996 << " Eval term | White | Black | Total \n"
997 << " | MG EG | MG EG | MG EG \n"
998 << "---------------------+-------------+-------------+-------------\n";
1000 format_row(ss, "Material, PST, Tempo", PST);
1001 format_row(ss, "Material imbalance", IMBALANCE);
1002 format_row(ss, "Pawns", PAWN);
1003 format_row(ss, "Knights", KNIGHT);
1004 format_row(ss, "Bishops", BISHOP);
1005 format_row(ss, "Rooks", ROOK);
1006 format_row(ss, "Queens", QUEEN);
1007 format_row(ss, "Mobility", MOBILITY);
1008 format_row(ss, "King safety", KING);
1009 format_row(ss, "Threats", THREAT);
1010 format_row(ss, "Passed pawns", PASSED);
1011 format_row(ss, "Space", SPACE);
1013 ss << "---------------------+-------------+-------------+-------------\n";
1014 format_row(ss, "Total", TOTAL);
1016 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";