2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 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 enum ExtendedPieceType { // Used for tracing
35 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL
40 Score scores[COLOR_NB][TOTAL + 1];
41 std::stringstream stream;
43 void add(int idx, Score term_w, Score term_b = SCORE_ZERO);
44 void row(const char* name, int idx);
45 std::string do_trace(const Position& pos);
48 // Struct EvalInfo contains various information computed and collected
49 // by the evaluation functions.
52 // Pointers to material and pawn hash table entries
56 // attackedBy[color][piece type] is a bitboard representing all squares
57 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
58 // contains all squares attacked by the given color.
59 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
61 // kingRing[color] is the zone around the king which is considered
62 // by the king safety evaluation. This consists of the squares directly
63 // adjacent to the king, and the three (or two, for a king on an edge file)
64 // squares two ranks in front of the king. For instance, if black's king
65 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
66 // f7, g7, h7, f6, g6 and h6.
67 Bitboard kingRing[COLOR_NB];
69 // kingAttackersCount[color] is the number of pieces of the given color
70 // which attack a square in the kingRing of the enemy king.
71 int kingAttackersCount[COLOR_NB];
73 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
74 // given color which attack a square in the kingRing of the enemy king. The
75 // weights of the individual piece types are given by the variables
76 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
77 // KnightAttackWeight in evaluate.cpp
78 int kingAttackersWeight[COLOR_NB];
80 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
81 // directly adjacent to the king of the given color. Pieces which attack
82 // more than one square are counted multiple times. For instance, if black's
83 // king is on g8 and there's a white knight on g5, this knight adds
84 // 2 to kingAdjacentZoneAttacksCount[BLACK].
85 int kingAdjacentZoneAttacksCount[COLOR_NB];
87 Bitboard pinnedPieces[COLOR_NB];
90 // Evaluation grain size, must be a power of 2
91 const int GrainSize = 4;
93 // Evaluation weights, initialized from UCI options
94 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
98 #define S(mg, eg) make_score(mg, eg)
100 // Internal evaluation weights. These are applied on top of the evaluation
101 // weights read from UCI parameters. The purpose is to be able to change
102 // the evaluation weights while keeping the default values of the UCI
103 // parameters at 100, which looks prettier.
105 // Values modified by Joona Kiiski
106 const Score WeightsInternal[] = {
107 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
110 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
111 // game, indexed by piece type and number of attacked squares not occupied by
113 const Score MobilityBonus[][32] = {
115 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
116 S( 37, 28), S( 42, 31), S(44, 33) },
117 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
118 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
119 S( 84, 79), S( 86, 81) },
120 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
121 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
122 S( 35,122), S( 36,123), S(37,124) },
123 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
124 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
125 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
127 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
130 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
131 // indexed by piece type and square (from white's point of view).
132 const Value Outpost[][SQUARE_NB] = {
135 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
136 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
137 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
138 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
139 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
140 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
142 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
143 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
144 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
145 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
146 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
147 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
150 // Threat[attacking][attacked] contains bonuses according to which piece
151 // type attacks which one.
152 const Score Threat[][PIECE_TYPE_NB] = {
154 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
155 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
156 { S(0, 0), S( 0, 22), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
157 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
160 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
161 // type is attacked by an enemy pawn.
162 const Score ThreatenedByPawn[] = {
163 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
168 const Score Tempo = make_score(24, 11);
169 const Score BishopPin = make_score(66, 11);
170 const Score RookOn7th = make_score(11, 20);
171 const Score QueenOn7th = make_score( 3, 8);
172 const Score RookOnPawn = make_score(10, 28);
173 const Score QueenOnPawn = make_score( 4, 20);
174 const Score RookOpenFile = make_score(43, 21);
175 const Score RookSemiopenFile = make_score(19, 10);
176 const Score BishopPawns = make_score( 8, 12);
177 const Score KnightPawns = make_score( 8, 4);
178 const Score MinorBehindPawn = make_score(16, 0);
179 const Score UndefendedMinor = make_score(25, 10);
180 const Score TrappedRook = make_score(90, 0);
181 const Score Unstoppable = make_score( 0, 20);
183 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
184 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
185 // happen in Chess960 games.
186 const Score TrappedBishopA1H1 = make_score(50, 50);
188 // SpaceMask[Color] contains the area of the board which is considered
189 // by the space evaluation. In the middlegame, each side is given a bonus
190 // based on how many squares inside this area are safe and available for
191 // friendly minor pieces.
192 const Bitboard SpaceMask[] = {
193 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
194 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
197 // King danger constants and variables. The king danger scores are taken
198 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
199 // of the enemy attack are added up into an integer, which is used as an
200 // index to KingDanger[].
202 // KingAttackWeights[PieceType] contains king attack weights by piece type
203 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
205 // Bonuses for enemy's safe checks
206 const int QueenContactCheck = 24;
207 const int RookContactCheck = 16;
208 const int QueenCheck = 12;
209 const int RookCheck = 8;
210 const int BishopCheck = 2;
211 const int KnightCheck = 3;
213 // KingExposed[Square] contains penalties based on the position of the
214 // defending king, indexed by king's square (from white's point of view).
215 const int KingExposed[] = {
216 2, 0, 2, 5, 5, 2, 0, 2,
217 2, 2, 4, 8, 8, 4, 2, 2,
218 7, 10, 12, 12, 12, 12, 10, 7,
219 15, 15, 15, 15, 15, 15, 15, 15,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15,
222 15, 15, 15, 15, 15, 15, 15, 15,
223 15, 15, 15, 15, 15, 15, 15, 15
226 // KingDanger[Color][attackUnits] contains the actual king danger weighted
227 // scores, indexed by color and by a calculated integer number.
228 Score KingDanger[COLOR_NB][128];
230 // Function prototypes
232 Value do_evaluate(const Position& pos);
235 void init_eval_info(const Position& pos, EvalInfo& ei);
237 template<Color Us, bool Trace>
238 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
240 template<Color Us, bool Trace>
241 Score evaluate_king(const Position& pos, const EvalInfo& ei);
243 template<Color Us, bool Trace>
244 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
246 template<Color Us, bool Trace>
247 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
250 int evaluate_space(const Position& pos, const EvalInfo& ei);
252 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
254 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
255 Score apply_weight(Score v, Score w);
256 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
257 double to_cp(Value v);
263 /// evaluate() is the main evaluation function. It always computes two
264 /// values, an endgame score and a middlegame score, and interpolates
265 /// between them based on the remaining material.
267 Value evaluate(const Position& pos) {
268 return do_evaluate<false>(pos);
272 /// trace() is like evaluate(), but instead of returning a value, it returns
273 /// a string (suitable for outputting to stdout) that contains the detailed
274 /// descriptions and values of each evaluation term. It's mainly used for
276 std::string trace(const Position& pos) {
277 return Tracing::do_trace(pos);
281 /// init() computes evaluation weights from the corresponding UCI parameters
282 /// and setup king tables.
286 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
287 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
288 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
289 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
290 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
291 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
293 const int MaxSlope = 30;
294 const int Peak = 1280;
296 for (int t = 0, i = 1; i < 100; ++i)
298 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
300 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
301 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
311 Value do_evaluate(const Position& pos) {
313 assert(!pos.checkers());
316 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
317 Thread* th = pos.this_thread();
319 // Initialize score by reading the incrementally updated scores included
320 // in the position object (material + piece square tables) and adding a
321 // Tempo bonus. Score is computed from the point of view of white.
322 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
324 // Probe the material hash table
325 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
326 score += ei.mi->material_value();
328 // If we have a specialized evaluation function for the current material
329 // configuration, call it and return.
330 if (ei.mi->specialized_eval_exists())
331 return ei.mi->evaluate(pos);
333 // Probe the pawn hash table
334 ei.pi = Pawns::probe(pos, th->pawnsTable);
335 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
337 // Initialize attack and king safety bitboards
338 init_eval_info<WHITE>(pos, ei);
339 init_eval_info<BLACK>(pos, ei);
341 // Evaluate pieces and mobility
342 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
343 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
345 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
347 // Evaluate kings after all other pieces because we need complete attack
348 // information when computing the king safety evaluation.
349 score += evaluate_king<WHITE, Trace>(pos, ei)
350 - evaluate_king<BLACK, Trace>(pos, ei);
352 // Evaluate tactical threats, we need full attack information including king
353 score += evaluate_threats<WHITE, Trace>(pos, ei)
354 - evaluate_threats<BLACK, Trace>(pos, ei);
356 // Evaluate passed pawns, we need full attack information including king
357 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
358 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
360 // If one side has only a king, score for potential unstoppable pawns
361 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
362 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
363 - evaluate_unstoppable_pawns(pos, BLACK, ei);
365 // Evaluate space for both sides, only in middlegame
366 if (ei.mi->space_weight())
368 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
369 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
372 // Scale winning side if position is more drawish than it appears
373 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
374 : ei.mi->scale_factor(pos, BLACK);
376 // If we don't already have an unusual scale factor, check for opposite
377 // colored bishop endgames, and use a lower scale for those.
378 if ( ei.mi->game_phase() < PHASE_MIDGAME
379 && pos.opposite_bishops()
380 && sf == SCALE_FACTOR_NORMAL)
382 // Ignoring any pawns, do both sides only have a single bishop and no
384 if ( pos.non_pawn_material(WHITE) == BishopValueMg
385 && pos.non_pawn_material(BLACK) == BishopValueMg)
387 // Check for KBP vs KB with only a single pawn that is almost
388 // certainly a draw or at least two pawns.
389 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
390 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
393 // Endgame with opposite-colored bishops, but also other pieces. Still
394 // a bit drawish, but not as drawish as with only the two bishops.
395 sf = ScaleFactor(50);
398 Value v = interpolate(score, ei.mi->game_phase(), sf);
400 // In case of tracing add all single evaluation contributions for both white and black
403 Tracing::add(PST, pos.psq_score());
404 Tracing::add(IMBALANCE, ei.mi->material_value());
405 Tracing::add(PAWN, ei.pi->pawns_value());
406 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
407 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
408 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
409 Tracing::add(TOTAL, score);
410 Tracing::stream << "\nScaling: " << std::noshowpos
411 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
412 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
413 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
414 << "Total evaluation: " << to_cp(v);
417 return pos.side_to_move() == WHITE ? v : -v;
421 // init_eval_info() initializes king bitboards for given color adding
422 // pawn attacks. To be done at the beginning of the evaluation.
425 void init_eval_info(const Position& pos, EvalInfo& ei) {
427 const Color Them = (Us == WHITE ? BLACK : WHITE);
428 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
430 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
432 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
433 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
435 // Init king safety tables only if we are going to use them
436 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
438 ei.kingRing[Them] = b | shift_bb<Down>(b);
439 b &= ei.attackedBy[Us][PAWN];
440 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
441 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
444 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
448 // evaluate_outposts() evaluates bishop and knight outpost squares
450 template<PieceType Piece, Color Us>
451 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
453 const Color Them = (Us == WHITE ? BLACK : WHITE);
455 assert (Piece == BISHOP || Piece == KNIGHT);
457 // Initial bonus based on square
458 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
460 // Increase bonus if supported by pawn, especially if the opponent has
461 // no minor piece which can trade with the outpost piece.
462 if (bonus && (ei.attackedBy[Us][PAWN] & s))
464 if ( !pos.pieces(Them, KNIGHT)
465 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
466 bonus += bonus + bonus / 2;
471 return make_score(bonus, bonus);
475 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
477 template<PieceType Piece, Color Us, bool Trace>
478 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
482 Score score = SCORE_ZERO;
484 const Color Them = (Us == WHITE ? BLACK : WHITE);
485 const Square* pl = pos.list<Piece>(Us);
487 ei.attackedBy[Us][Piece] = 0;
489 while ((s = *pl++) != SQ_NONE)
491 // Find attacked squares, including x-ray attacks for bishops and rooks
492 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
493 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
494 : pos.attacks_from<Piece>(s);
496 if (ei.pinnedPieces[Us] & s)
497 b &= LineBB[pos.king_square(Us)][s];
499 ei.attackedBy[Us][Piece] |= b;
501 if (b & ei.kingRing[Them])
503 ei.kingAttackersCount[Us]++;
504 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
505 Bitboard bb = b & ei.attackedBy[Them][KING];
507 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
510 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
511 : popcount<Full >(b & mobilityArea);
513 mobility[Us] += MobilityBonus[Piece][mob];
515 // Decrease score if we are attacked by an enemy pawn. The remaining part
516 // of threat evaluation must be done later when we have full attack info.
517 if (ei.attackedBy[Them][PAWN] & s)
518 score -= ThreatenedByPawn[Piece];
520 // Otherwise give a bonus if we are a bishop and can pin a piece or can
521 // give a discovered check through an x-ray attack.
522 else if ( Piece == BISHOP
523 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
524 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
527 // Penalty for bishop with same coloured pawns
529 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
531 // Penalty for knight when there are few enemy pawns
533 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
535 if (Piece == BISHOP || Piece == KNIGHT)
537 // Bishop and knight outposts squares
538 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
539 score += evaluate_outposts<Piece, Us>(pos, ei, s);
541 // Bishop or knight behind a pawn
542 if ( relative_rank(Us, s) < RANK_5
543 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
544 score += MinorBehindPawn;
547 if ( (Piece == ROOK || Piece == QUEEN)
548 && relative_rank(Us, s) >= RANK_5)
550 // Major piece on 7th rank and enemy king trapped on 8th
551 if ( relative_rank(Us, s) == RANK_7
552 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
553 score += Piece == ROOK ? RookOn7th : QueenOn7th;
555 // Major piece attacking enemy pawns on the same rank/file
556 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
558 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
561 // Special extra evaluation for rooks
564 // Give a bonus for a rook on a open or semi-open file
565 if (ei.pi->semiopen(Us, file_of(s)))
566 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
568 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
571 Square ksq = pos.king_square(Us);
573 // Penalize rooks which are trapped by a king. Penalize more if the
574 // king has lost its castling capability.
575 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
576 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
577 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
578 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
581 // An important Chess960 pattern: A cornered bishop blocked by a friendly
582 // pawn diagonally in front of it is a very serious problem, especially
583 // when that pawn is also blocked.
586 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
588 const enum Piece P = make_piece(Us, PAWN);
589 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
590 if (pos.piece_on(s + d) == P)
591 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
592 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
598 Tracing::scores[Us][Piece] = score;
604 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
605 // pieces of a given color.
607 template<Color Us, bool Trace>
608 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
610 const Color Them = (Us == WHITE ? BLACK : WHITE);
612 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
613 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
615 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
616 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
617 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
618 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
620 // Sum up all attacked squares (updated in evaluate_pieces)
621 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
622 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
623 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
625 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
631 // evaluate_king() assigns bonuses and penalties to a king of a given color
633 template<Color Us, bool Trace>
634 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
636 const Color Them = (Us == WHITE ? BLACK : WHITE);
638 Bitboard undefended, b, b1, b2, safe;
640 const Square ksq = pos.king_square(Us);
642 // King shelter and enemy pawns storm
643 Score score = ei.pi->king_safety<Us>(pos, ksq);
645 // Main king safety evaluation
646 if ( ei.kingAttackersCount[Them] >= 2
647 && ei.kingAdjacentZoneAttacksCount[Them])
649 // Find the attacked squares around the king which have no defenders
650 // apart from the king itself
651 undefended = ei.attackedBy[Them][ALL_PIECES]
652 & ei.attackedBy[Us][KING]
653 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
654 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
655 | ei.attackedBy[Us][QUEEN]);
657 // Initialize the 'attackUnits' variable, which is used later on as an
658 // index to the KingDanger[] array. The initial value is based on the
659 // number and types of the enemy's attacking pieces, the number of
660 // attacked and undefended squares around our king, the square of the
661 // king, and the quality of the pawn shelter.
662 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
663 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
664 + KingExposed[relative_square(Us, ksq)]
665 - mg_value(score) / 32;
667 // Analyse the enemy's safe queen contact checks. Firstly, find the
668 // undefended squares around the king that are attacked by the enemy's
670 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
673 // ...and then remove squares not supported by another enemy piece
674 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
675 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
677 attackUnits += QueenContactCheck
679 * (Them == pos.side_to_move() ? 2 : 1);
682 // Analyse the enemy's safe rook contact checks. Firstly, find the
683 // undefended squares around the king that are attacked by the enemy's
685 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
687 // Consider only squares where the enemy's rook gives check
688 b &= PseudoAttacks[ROOK][ksq];
692 // ...and then remove squares not supported by another enemy piece
693 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
694 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
696 attackUnits += RookContactCheck
698 * (Them == pos.side_to_move() ? 2 : 1);
701 // Analyse the enemy's safe distance checks for sliders and knights
702 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
704 b1 = pos.attacks_from<ROOK>(ksq) & safe;
705 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
707 // Enemy queen safe checks
708 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
710 attackUnits += QueenCheck * popcount<Max15>(b);
712 // Enemy rooks safe checks
713 b = b1 & ei.attackedBy[Them][ROOK];
715 attackUnits += RookCheck * popcount<Max15>(b);
717 // Enemy bishops safe checks
718 b = b2 & ei.attackedBy[Them][BISHOP];
720 attackUnits += BishopCheck * popcount<Max15>(b);
722 // Enemy knights safe checks
723 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
725 attackUnits += KnightCheck * popcount<Max15>(b);
727 // To index KingDanger[] attackUnits must be in [0, 99] range
728 attackUnits = std::min(99, std::max(0, attackUnits));
730 // Finally, extract the king danger score from the KingDanger[]
731 // array and subtract the score from evaluation.
732 score -= KingDanger[Us == Search::RootColor][attackUnits];
736 Tracing::scores[Us][KING] = score;
742 // evaluate_threats() assigns bonuses according to the type of attacking piece
743 // and the type of attacked one.
745 template<Color Us, bool Trace>
746 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
748 const Color Them = (Us == WHITE ? BLACK : WHITE);
750 Bitboard b, undefendedMinors, weakEnemies;
751 Score score = SCORE_ZERO;
753 // Undefended minors get penalized even if they are not under attack
754 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
755 & ~ei.attackedBy[Them][ALL_PIECES];
757 if (undefendedMinors)
758 score += UndefendedMinor;
760 // Enemy pieces not defended by a pawn and under our attack
761 weakEnemies = pos.pieces(Them)
762 & ~ei.attackedBy[Them][PAWN]
763 & ei.attackedBy[Us][ALL_PIECES];
765 // Add bonus according to type of attacked enemy piece and to the
766 // type of attacking piece, from knights to queens. Kings are not
767 // considered because they are already handled in king evaluation.
769 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
771 b = ei.attackedBy[Us][pt1] & weakEnemies;
773 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
774 if (b & pos.pieces(pt2))
775 score += Threat[pt1][pt2];
779 Tracing::scores[Us][THREAT] = score;
785 // evaluate_passed_pawns() evaluates the passed pawns of the given color
787 template<Color Us, bool Trace>
788 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
790 const Color Them = (Us == WHITE ? BLACK : WHITE);
792 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
793 Score score = SCORE_ZERO;
795 b = ei.pi->passed_pawns(Us);
799 Square s = pop_lsb(&b);
801 assert(pos.pawn_passed(Us, s));
803 int r = int(relative_rank(Us, s) - RANK_2);
804 int rr = r * (r - 1);
806 // Base bonus based on rank
807 Value mbonus = Value(17 * rr);
808 Value ebonus = Value(7 * (rr + r + 1));
812 Square blockSq = s + pawn_push(Us);
814 // Adjust bonus based on the king's proximity
815 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
816 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
818 // If blockSq is not the queening square then consider also a second push
819 if (relative_rank(Us, blockSq) != RANK_8)
820 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
822 // If the pawn is free to advance, then increase the bonus
823 if (pos.empty(blockSq))
825 squaresToQueen = forward_bb(Us, s);
827 // If there is an enemy rook or queen attacking the pawn from behind,
828 // add all X-ray attacks by the rook or queen. Otherwise consider only
829 // the squares in the pawn's path attacked or occupied by the enemy.
830 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
831 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
832 unsafeSquares = squaresToQueen;
834 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
836 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
837 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
838 defendedSquares = squaresToQueen;
840 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
842 // If there aren't any enemy attacks, then assign a huge bonus.
843 // The bonus will be a bit smaller if at least the block square
844 // isn't attacked, otherwise assign the smallest possible bonus.
845 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
847 // Assign a big bonus if the path to the queen is fully defended,
848 // otherwise assign a bit less of a bonus if at least the block
849 // square is defended.
850 if (defendedSquares == squaresToQueen)
853 else if (defendedSquares & blockSq)
854 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
856 mbonus += Value(k * rr), ebonus += Value(k * rr);
860 // Increase the bonus if the passed pawn is supported by a friendly pawn
861 // on the same rank and a bit smaller if it's on the previous rank.
862 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
863 if (supportingPawns & rank_bb(s))
864 ebonus += Value(r * 20);
866 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
867 ebonus += Value(r * 12);
869 // Rook pawns are a special case: They are sometimes worse, and
870 // sometimes better than other passed pawns. It is difficult to find
871 // good rules for determining whether they are good or bad. For now,
872 // we try the following: Increase the value for rook pawns if the
873 // other side has no pieces apart from a knight, and decrease the
874 // value if the other side has a rook or queen.
875 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
877 if (pos.non_pawn_material(Them) <= KnightValueMg)
878 ebonus += ebonus / 4;
880 else if (pos.pieces(Them, ROOK, QUEEN))
881 ebonus -= ebonus / 4;
884 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
885 ebonus += ebonus / 4;
887 score += make_score(mbonus, ebonus);
892 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
894 // Add the scores to the middlegame and endgame eval
895 return apply_weight(score, Weights[PassedPawns]);
899 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
900 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
901 // related to the possibility that pawns are unstoppable.
903 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
905 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
907 if (!b || pos.non_pawn_material(~us))
910 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
914 // evaluate_space() computes the space evaluation for a given side. The
915 // space evaluation is a simple bonus based on the number of safe squares
916 // available for minor pieces on the central four files on ranks 2--4. Safe
917 // squares one, two or three squares behind a friendly pawn are counted
918 // twice. Finally, the space bonus is scaled by a weight taken from the
919 // material hash table. The aim is to improve play on game opening.
921 int evaluate_space(const Position& pos, const EvalInfo& ei) {
923 const Color Them = (Us == WHITE ? BLACK : WHITE);
925 // Find the safe squares for our pieces inside the area defined by
926 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
927 // pawn, or if it is undefended and attacked by an enemy piece.
928 Bitboard safe = SpaceMask[Us]
929 & ~pos.pieces(Us, PAWN)
930 & ~ei.attackedBy[Them][PAWN]
931 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
933 // Find all squares which are at most three squares behind some friendly pawn
934 Bitboard behind = pos.pieces(Us, PAWN);
935 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
936 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
938 // Since SpaceMask[Us] is fully on our half of the board
939 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
941 // Count safe + (behind & safe) with a single popcount
942 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
946 // interpolate() interpolates between a middlegame and an endgame score,
947 // based on game phase. It also scales the return value by a ScaleFactor array.
949 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
951 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
952 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
953 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
955 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
956 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
957 return Value((r / GrainSize) * GrainSize); // Sign independent
960 // apply_weight() weights score v by score w trying to prevent overflow
961 Score apply_weight(Score v, Score w) {
962 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
963 (int(eg_value(v)) * eg_value(w)) / 0x100);
966 // weight_option() computes the value of an evaluation weight, by combining
967 // two UCI-configurable weights (midgame and endgame) with an internal weight.
969 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
971 // Scale option value from 100 to 256
972 int mg = Options[mgOpt] * 256 / 100;
973 int eg = Options[egOpt] * 256 / 100;
975 return apply_weight(make_score(mg, eg), internalWeight);
979 // Tracing functions definitions
981 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
983 void Tracing::add(int idx, Score wScore, Score bScore) {
985 scores[WHITE][idx] = wScore;
986 scores[BLACK][idx] = bScore;
989 void Tracing::row(const char* name, int idx) {
991 Score wScore = scores[WHITE][idx];
992 Score bScore = scores[BLACK][idx];
995 case PST: case IMBALANCE: case PAWN: case TOTAL:
996 stream << std::setw(20) << name << " | --- --- | --- --- | "
997 << std::setw(6) << to_cp(mg_value(wScore)) << " "
998 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
1001 stream << std::setw(20) << name << " | " << std::noshowpos
1002 << std::setw(5) << to_cp(mg_value(wScore)) << " "
1003 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1004 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1005 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1007 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1008 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1012 std::string Tracing::do_trace(const Position& pos) {
1015 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1016 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1018 do_evaluate<true>(pos);
1020 std::string totals = stream.str();
1023 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1024 << " | MG EG | MG EG | MG EG \n"
1025 << "---------------------+-------------+-------------+---------------\n";
1027 row("Material, PST, Tempo", PST);
1028 row("Material imbalance", IMBALANCE);
1030 row("Knights", KNIGHT);
1031 row("Bishops", BISHOP);
1033 row("Queens", QUEEN);
1034 row("Mobility", MOBILITY);
1035 row("King safety", KING);
1036 row("Threats", THREAT);
1037 row("Passed pawns", PASSED);
1038 row("Space", SPACE);
1040 stream << "---------------------+-------------+-------------+---------------\n";
1041 row("Total", TOTAL);
1044 return stream.str();