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 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 weights, initialized from UCI options
91 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
95 #define S(mg, eg) make_score(mg, eg)
97 // Internal evaluation weights. These are applied on top of the evaluation
98 // weights read from UCI parameters. The purpose is to be able to change
99 // the evaluation weights while keeping the default values of the UCI
100 // parameters at 100, which looks prettier.
102 // Values modified by Joona Kiiski
103 const Score WeightsInternal[] = {
104 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
107 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
108 // game, indexed by piece type and number of attacked squares not occupied by
110 const Score MobilityBonus[][32] = {
112 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
113 S( 37, 28), S( 42, 31), S(44, 33) },
114 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
115 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
116 S( 84, 79), S( 86, 81) },
117 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
118 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
119 S( 35,122), S( 36,123), S(37,124) },
120 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
121 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
122 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
123 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
124 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
127 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
128 // indexed by piece type and square (from white's point of view).
129 const Value Outpost[][SQUARE_NB] = {
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
134 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
135 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
136 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
137 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
139 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
140 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
141 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
142 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
143 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
144 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
147 // Threat[attacking][attacked] contains bonuses according to which piece
148 // type attacks which one.
149 const Score Threat[][PIECE_TYPE_NB] = {
150 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
151 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) }, // Major
154 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
155 // type is attacked by an enemy pawn.
156 const Score ThreatenedByPawn[] = {
157 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
162 const Score Tempo = make_score(24, 11);
163 const Score RookOn7th = make_score(11, 20);
164 const Score QueenOn7th = make_score( 3, 8);
165 const Score RookOnPawn = make_score(10, 28);
166 const Score QueenOnPawn = make_score( 4, 20);
167 const Score RookOpenFile = make_score(43, 21);
168 const Score RookSemiopenFile = make_score(19, 10);
169 const Score BishopPawns = make_score( 8, 12);
170 const Score KnightPawns = make_score( 8, 4);
171 const Score MinorBehindPawn = make_score(16, 0);
172 const Score UndefendedMinor = make_score(25, 10);
173 const Score TrappedRook = make_score(90, 0);
174 const Score Unstoppable = make_score( 0, 20);
176 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
177 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
178 // happen in Chess960 games.
179 const Score TrappedBishopA1H1 = make_score(50, 50);
181 // SpaceMask[Color] contains the area of the board which is considered
182 // by the space evaluation. In the middlegame, each side is given a bonus
183 // based on how many squares inside this area are safe and available for
184 // friendly minor pieces.
185 const Bitboard SpaceMask[] = {
186 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
187 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
190 // King danger constants and variables. The king danger scores are taken
191 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
192 // of the enemy attack are added up into an integer, which is used as an
193 // index to KingDanger[].
195 // KingAttackWeights[PieceType] contains king attack weights by piece type
196 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
198 // Bonuses for enemy's safe checks
199 const int QueenContactCheck = 24;
200 const int RookContactCheck = 16;
201 const int QueenCheck = 12;
202 const int RookCheck = 8;
203 const int BishopCheck = 2;
204 const int KnightCheck = 3;
206 // KingDanger[Color][attackUnits] contains the actual king danger weighted
207 // scores, indexed by color and by a calculated integer number.
208 Score KingDanger[COLOR_NB][128];
210 // Function prototypes
212 Value do_evaluate(const Position& pos);
215 void init_eval_info(const Position& pos, EvalInfo& ei);
217 template<Color Us, bool Trace>
218 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
220 template<Color Us, bool Trace>
221 Score evaluate_king(const Position& pos, const EvalInfo& ei);
223 template<Color Us, bool Trace>
224 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
226 template<Color Us, bool Trace>
227 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
230 int evaluate_space(const Position& pos, const EvalInfo& ei);
232 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
234 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
235 Score apply_weight(Score v, Score w);
236 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
237 double to_cp(Value v);
243 /// evaluate() is the main evaluation function. It always computes two
244 /// values, an endgame score and a middlegame score, and interpolates
245 /// between them based on the remaining material.
247 Value evaluate(const Position& pos) {
248 return do_evaluate<false>(pos);
252 /// trace() is like evaluate(), but instead of returning a value, it returns
253 /// a string (suitable for outputting to stdout) that contains the detailed
254 /// descriptions and values of each evaluation term. It's mainly used for
256 std::string trace(const Position& pos) {
257 return Tracing::do_trace(pos);
261 /// init() computes evaluation weights from the corresponding UCI parameters
262 /// and setup king tables.
266 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
267 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
268 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
269 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
270 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
271 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
273 const int MaxSlope = 30;
274 const int Peak = 1280;
276 for (int t = 0, i = 1; i < 100; ++i)
278 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
280 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
281 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
291 Value do_evaluate(const Position& pos) {
293 assert(!pos.checkers());
296 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
297 Thread* th = pos.this_thread();
299 // Initialize score by reading the incrementally updated scores included
300 // in the position object (material + piece square tables) and adding a
301 // Tempo bonus. Score is computed from the point of view of white.
302 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
304 // Probe the material hash table
305 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
306 score += ei.mi->material_value();
308 // If we have a specialized evaluation function for the current material
309 // configuration, call it and return.
310 if (ei.mi->specialized_eval_exists())
311 return ei.mi->evaluate(pos);
313 // Probe the pawn hash table
314 ei.pi = Pawns::probe(pos, th->pawnsTable);
315 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
317 // Initialize attack and king safety bitboards
318 init_eval_info<WHITE>(pos, ei);
319 init_eval_info<BLACK>(pos, ei);
321 // Evaluate pieces and mobility
322 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
323 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
325 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
327 // Evaluate kings after all other pieces because we need complete attack
328 // information when computing the king safety evaluation.
329 score += evaluate_king<WHITE, Trace>(pos, ei)
330 - evaluate_king<BLACK, Trace>(pos, ei);
332 // Evaluate tactical threats, we need full attack information including king
333 score += evaluate_threats<WHITE, Trace>(pos, ei)
334 - evaluate_threats<BLACK, Trace>(pos, ei);
336 // Evaluate passed pawns, we need full attack information including king
337 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
338 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
340 // If one side has only a king, score for potential unstoppable pawns
341 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
342 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
343 - evaluate_unstoppable_pawns(pos, BLACK, ei);
345 // Evaluate space for both sides, only in middlegame
346 if (ei.mi->space_weight())
348 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
349 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
352 // Scale winning side if position is more drawish than it appears
353 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
354 : ei.mi->scale_factor(pos, BLACK);
356 // If we don't already have an unusual scale factor, check for opposite
357 // colored bishop endgames, and use a lower scale for those.
358 if ( ei.mi->game_phase() < PHASE_MIDGAME
359 && pos.opposite_bishops()
360 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
362 // Ignoring any pawns, do both sides only have a single bishop and no
364 if ( pos.non_pawn_material(WHITE) == BishopValueMg
365 && pos.non_pawn_material(BLACK) == BishopValueMg)
367 // Check for KBP vs KB with only a single pawn that is almost
368 // certainly a draw or at least two pawns.
369 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
370 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
373 // Endgame with opposite-colored bishops, but also other pieces. Still
374 // a bit drawish, but not as drawish as with only the two bishops.
375 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
378 Value v = interpolate(score, ei.mi->game_phase(), sf);
380 // In case of tracing add all single evaluation contributions for both white and black
383 Tracing::add(PST, pos.psq_score());
384 Tracing::add(IMBALANCE, ei.mi->material_value());
385 Tracing::add(PAWN, ei.pi->pawns_value());
386 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
387 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
388 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
389 Tracing::add(TOTAL, score);
390 Tracing::stream << "\nScaling: " << std::noshowpos
391 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
392 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
393 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
394 << "Total evaluation: " << to_cp(v);
397 return pos.side_to_move() == WHITE ? v : -v;
401 // init_eval_info() initializes king bitboards for given color adding
402 // pawn attacks. To be done at the beginning of the evaluation.
405 void init_eval_info(const Position& pos, EvalInfo& ei) {
407 const Color Them = (Us == WHITE ? BLACK : WHITE);
408 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
410 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
412 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
413 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
415 // Init king safety tables only if we are going to use them
416 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
418 ei.kingRing[Them] = b | shift_bb<Down>(b);
419 b &= ei.attackedBy[Us][PAWN];
420 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
421 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
424 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
428 // evaluate_outposts() evaluates bishop and knight outpost squares
430 template<PieceType Piece, Color Us>
431 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
433 const Color Them = (Us == WHITE ? BLACK : WHITE);
435 assert (Piece == BISHOP || Piece == KNIGHT);
437 // Initial bonus based on square
438 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
440 // Increase bonus if supported by pawn, especially if the opponent has
441 // no minor piece which can trade with the outpost piece.
442 if (bonus && (ei.attackedBy[Us][PAWN] & s))
444 if ( !pos.pieces(Them, KNIGHT)
445 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
446 bonus += bonus + bonus / 2;
451 return make_score(bonus, bonus);
455 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
457 template<PieceType Piece, Color Us, bool Trace>
458 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
462 Score score = SCORE_ZERO;
464 const Color Them = (Us == WHITE ? BLACK : WHITE);
465 const Square* pl = pos.list<Piece>(Us);
467 ei.attackedBy[Us][Piece] = 0;
469 while ((s = *pl++) != SQ_NONE)
471 // Find attacked squares, including x-ray attacks for bishops and rooks
472 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
473 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
474 : pos.attacks_from<Piece>(s);
476 if (ei.pinnedPieces[Us] & s)
477 b &= LineBB[pos.king_square(Us)][s];
479 ei.attackedBy[Us][Piece] |= b;
481 if (b & ei.kingRing[Them])
483 ei.kingAttackersCount[Us]++;
484 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
485 Bitboard bb = b & ei.attackedBy[Them][KING];
487 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
490 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
491 : popcount<Full >(b & mobilityArea);
493 mobility[Us] += MobilityBonus[Piece][mob];
495 // Decrease score if we are attacked by an enemy pawn. The remaining part
496 // of threat evaluation must be done later when we have full attack info.
497 if (ei.attackedBy[Them][PAWN] & s)
498 score -= ThreatenedByPawn[Piece];
500 // Penalty for bishop with same coloured pawns
502 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
504 // Penalty for knight when there are few enemy pawns
506 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
508 if (Piece == BISHOP || Piece == KNIGHT)
510 // Bishop and knight outposts squares
511 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
512 score += evaluate_outposts<Piece, Us>(pos, ei, s);
514 // Bishop or knight behind a pawn
515 if ( relative_rank(Us, s) < RANK_5
516 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
517 score += MinorBehindPawn;
520 if ( (Piece == ROOK || Piece == QUEEN)
521 && relative_rank(Us, s) >= RANK_5)
523 // Major piece on 7th rank and enemy king trapped on 8th
524 if ( relative_rank(Us, s) == RANK_7
525 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
526 score += Piece == ROOK ? RookOn7th : QueenOn7th;
528 // Major piece attacking enemy pawns on the same rank/file
529 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
531 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
534 // Special extra evaluation for rooks
537 // Give a bonus for a rook on a open or semi-open file
538 if (ei.pi->semiopen(Us, file_of(s)))
539 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
541 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
544 Square ksq = pos.king_square(Us);
546 // Penalize rooks which are trapped by a king. Penalize more if the
547 // king has lost its castling capability.
548 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
549 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
550 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
551 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
554 // An important Chess960 pattern: A cornered bishop blocked by a friendly
555 // pawn diagonally in front of it is a very serious problem, especially
556 // when that pawn is also blocked.
559 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
561 const enum Piece P = make_piece(Us, PAWN);
562 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
563 if (pos.piece_on(s + d) == P)
564 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
565 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
571 Tracing::scores[Us][Piece] = score;
577 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
578 // pieces of a given color.
580 template<Color Us, bool Trace>
581 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
583 const Color Them = (Us == WHITE ? BLACK : WHITE);
585 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
586 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
588 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
589 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
590 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
591 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
593 // Sum up all attacked squares (updated in evaluate_pieces)
594 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
595 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
596 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
598 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
604 // evaluate_king() assigns bonuses and penalties to a king of a given color
606 template<Color Us, bool Trace>
607 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
609 const Color Them = (Us == WHITE ? BLACK : WHITE);
611 Bitboard undefended, b, b1, b2, safe;
613 const Square ksq = pos.king_square(Us);
615 // King shelter and enemy pawns storm
616 Score score = ei.pi->king_safety<Us>(pos, ksq);
618 // Main king safety evaluation
619 if (ei.kingAttackersCount[Them])
621 // Find the attacked squares around the king which have no defenders
622 // apart from the king itself
623 undefended = ei.attackedBy[Them][ALL_PIECES]
624 & ei.attackedBy[Us][KING]
625 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
626 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
627 | ei.attackedBy[Us][QUEEN]);
629 // Initialize the 'attackUnits' variable, which is used later on as an
630 // index to the KingDanger[] array. The initial value is based on the
631 // number and types of the enemy's attacking pieces, the number of
632 // attacked and undefended squares around our king and the quality of
633 // the pawn shelter (current 'score' value).
634 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
635 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
636 - mg_value(score) / 32;
638 // Analyse the enemy's safe queen contact checks. Firstly, find the
639 // undefended squares around the king that are attacked by the enemy's
641 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
644 // ...and then remove squares not supported by another enemy piece
645 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
646 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
648 attackUnits += QueenContactCheck
650 * (Them == pos.side_to_move() ? 2 : 1);
653 // Analyse the enemy's safe rook contact checks. Firstly, find the
654 // undefended squares around the king that are attacked by the enemy's
656 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
658 // Consider only squares where the enemy's rook gives check
659 b &= PseudoAttacks[ROOK][ksq];
663 // ...and then remove squares not supported by another enemy piece
664 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
665 | 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 // To index KingDanger[] attackUnits must be in [0, 99] range
699 attackUnits = std::min(99, std::max(0, attackUnits));
701 // Finally, extract the king danger score from the KingDanger[]
702 // array and subtract the score from evaluation.
703 score -= KingDanger[Us == Search::RootColor][attackUnits];
707 Tracing::scores[Us][KING] = score;
713 // evaluate_threats() assigns bonuses according to the type of attacking piece
714 // and the type of attacked one.
716 template<Color Us, bool Trace>
717 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
719 const Color Them = (Us == WHITE ? BLACK : WHITE);
721 Bitboard b, undefendedMinors, weakEnemies;
722 Score score = SCORE_ZERO;
724 // Undefended minors get penalized even if they are not under attack
725 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
726 & ~ei.attackedBy[Them][ALL_PIECES];
728 if (undefendedMinors)
729 score += UndefendedMinor;
731 // Enemy pieces not defended by a pawn and under our attack
732 weakEnemies = pos.pieces(Them)
733 & ~ei.attackedBy[Them][PAWN]
734 & ei.attackedBy[Us][ALL_PIECES];
736 // Add a bonus according if the attacking pieces are minor or major
739 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
741 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
743 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
745 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
749 Tracing::scores[Us][THREAT] = score;
755 // evaluate_passed_pawns() evaluates the passed pawns of the given color
757 template<Color Us, bool Trace>
758 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
760 const Color Them = (Us == WHITE ? BLACK : WHITE);
762 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
763 Score score = SCORE_ZERO;
765 b = ei.pi->passed_pawns(Us);
769 Square s = pop_lsb(&b);
771 assert(pos.pawn_passed(Us, s));
773 int r = int(relative_rank(Us, s) - RANK_2);
774 int rr = r * (r - 1);
776 // Base bonus based on rank
777 Value mbonus = Value(17 * rr);
778 Value ebonus = Value(7 * (rr + r + 1));
782 Square blockSq = s + pawn_push(Us);
784 // Adjust bonus based on the king's proximity
785 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
786 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
788 // If blockSq is not the queening square then consider also a second push
789 if (relative_rank(Us, blockSq) != RANK_8)
790 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
792 // If the pawn is free to advance, then increase the bonus
793 if (pos.empty(blockSq))
795 squaresToQueen = forward_bb(Us, s);
797 // If there is an enemy rook or queen attacking the pawn from behind,
798 // add all X-ray attacks by the rook or queen. Otherwise consider only
799 // the squares in the pawn's path attacked or occupied by the enemy.
800 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
801 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
802 unsafeSquares = squaresToQueen;
804 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
806 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
807 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
808 defendedSquares = squaresToQueen;
810 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
812 // If there aren't any enemy attacks, then assign a huge bonus.
813 // The bonus will be a bit smaller if at least the block square
814 // isn't attacked, otherwise assign the smallest possible bonus.
815 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
817 // Assign a big bonus if the path to the queen is fully defended,
818 // otherwise assign a bit less of a bonus if at least the block
819 // square is defended.
820 if (defendedSquares == squaresToQueen)
823 else if (defendedSquares & blockSq)
824 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
826 mbonus += Value(k * rr), ebonus += Value(k * rr);
830 // Increase the bonus if the passed pawn is supported by a friendly pawn
831 // on the same rank and a bit smaller if it's on the previous rank.
832 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
833 if (supportingPawns & rank_bb(s))
834 ebonus += Value(r * 20);
836 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
837 ebonus += Value(r * 12);
839 // Rook pawns are a special case: They are sometimes worse, and
840 // sometimes better than other passed pawns. It is difficult to find
841 // good rules for determining whether they are good or bad. For now,
842 // we try the following: Increase the value for rook pawns if the
843 // other side has no pieces apart from a knight, and decrease the
844 // value if the other side has a rook or queen.
845 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
847 if (pos.non_pawn_material(Them) <= KnightValueMg)
848 ebonus += ebonus / 4;
850 else if (pos.pieces(Them, ROOK, QUEEN))
851 ebonus -= ebonus / 4;
854 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
855 ebonus += ebonus / 4;
857 score += make_score(mbonus, ebonus);
862 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
864 // Add the scores to the middlegame and endgame eval
865 return apply_weight(score, Weights[PassedPawns]);
869 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
870 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
871 // related to the possibility that pawns are unstoppable.
873 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
875 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
877 if (!b || pos.non_pawn_material(~us))
880 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
884 // evaluate_space() computes the space evaluation for a given side. The
885 // space evaluation is a simple bonus based on the number of safe squares
886 // available for minor pieces on the central four files on ranks 2--4. Safe
887 // squares one, two or three squares behind a friendly pawn are counted
888 // twice. Finally, the space bonus is scaled by a weight taken from the
889 // material hash table. The aim is to improve play on game opening.
891 int evaluate_space(const Position& pos, const EvalInfo& ei) {
893 const Color Them = (Us == WHITE ? BLACK : WHITE);
895 // Find the safe squares for our pieces inside the area defined by
896 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
897 // pawn, or if it is undefended and attacked by an enemy piece.
898 Bitboard safe = SpaceMask[Us]
899 & ~pos.pieces(Us, PAWN)
900 & ~ei.attackedBy[Them][PAWN]
901 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
903 // Find all squares which are at most three squares behind some friendly pawn
904 Bitboard behind = pos.pieces(Us, PAWN);
905 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
906 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
908 // Since SpaceMask[Us] is fully on our half of the board
909 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
911 // Count safe + (behind & safe) with a single popcount
912 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
916 // interpolate() interpolates between a middlegame and an endgame score,
917 // based on game phase. It also scales the return value by a ScaleFactor array.
919 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
921 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
922 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
923 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
925 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
926 return Value((mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
929 // apply_weight() weights score v by score w trying to prevent overflow
930 Score apply_weight(Score v, Score w) {
931 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
932 (int(eg_value(v)) * eg_value(w)) / 0x100);
935 // weight_option() computes the value of an evaluation weight, by combining
936 // two UCI-configurable weights (midgame and endgame) with an internal weight.
938 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
940 // Scale option value from 100 to 256
941 int mg = Options[mgOpt] * 256 / 100;
942 int eg = Options[egOpt] * 256 / 100;
944 return apply_weight(make_score(mg, eg), internalWeight);
948 // Tracing functions definitions
950 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
952 void Tracing::add(int idx, Score wScore, Score bScore) {
954 scores[WHITE][idx] = wScore;
955 scores[BLACK][idx] = bScore;
958 void Tracing::row(const char* name, int idx) {
960 Score wScore = scores[WHITE][idx];
961 Score bScore = scores[BLACK][idx];
964 case PST: case IMBALANCE: case PAWN: case TOTAL:
965 stream << std::setw(20) << name << " | --- --- | --- --- | "
966 << std::setw(6) << to_cp(mg_value(wScore)) << " "
967 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
970 stream << std::setw(20) << name << " | " << std::noshowpos
971 << std::setw(5) << to_cp(mg_value(wScore)) << " "
972 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
973 << std::setw(5) << to_cp(mg_value(bScore)) << " "
974 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
976 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
977 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
981 std::string Tracing::do_trace(const Position& pos) {
984 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
985 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
987 do_evaluate<true>(pos);
989 std::string totals = stream.str();
992 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
993 << " | MG EG | MG EG | MG EG \n"
994 << "---------------------+-------------+-------------+---------------\n";
996 row("Material, PST, Tempo", PST);
997 row("Material imbalance", IMBALANCE);
999 row("Knights", KNIGHT);
1000 row("Bishops", BISHOP);
1002 row("Queens", QUEEN);
1003 row("Mobility", MOBILITY);
1004 row("King safety", KING);
1005 row("Threats", THREAT);
1006 row("Passed pawns", PASSED);
1007 row("Space", SPACE);
1009 stream << "---------------------+-------------+-------------+---------------\n";
1010 row("Total", TOTAL);
1013 return stream.str();