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, UNSTOPPABLE, 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];
88 // Evaluation grain size, must be a power of 2
89 const int GrainSize = 4;
91 // Evaluation weights, initialized from UCI options
92 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
96 #define S(mg, eg) make_score(mg, eg)
98 // Internal evaluation weights. These are applied on top of the evaluation
99 // weights read from UCI parameters. The purpose is to be able to change
100 // the evaluation weights while keeping the default values of the UCI
101 // parameters at 100, which looks prettier.
103 // Values modified by Joona Kiiski
104 const Score WeightsInternal[] = {
105 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
108 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
109 // game, indexed by piece type and number of attacked squares not occupied by
111 const Score MobilityBonus[][32] = {
113 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
114 S( 37, 28), S( 42, 31), S(44, 33) },
115 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
116 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
117 S( 84, 79), S( 86, 81) },
118 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
119 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
120 S( 35,122), S( 36,123), S(37,124) },
121 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
122 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
123 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
124 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
128 // Outpost[PieceType][Square] contains bonuses of knights and bishops, indexed
129 // by piece type and square (from white's point of view).
130 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] = {
152 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
153 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
154 { S(0, 0), S( 0, 22), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
155 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
158 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
159 // type is attacked by an enemy pawn.
160 const Score ThreatenedByPawn[] = {
161 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
166 const Score Tempo = make_score(24, 11);
167 const Score BishopPin = make_score(66, 11);
168 const Score RookOn7th = make_score(11, 20);
169 const Score QueenOn7th = make_score( 3, 8);
170 const Score RookOnPawn = make_score(10, 28);
171 const Score QueenOnPawn = make_score( 4, 20);
172 const Score RookOpenFile = make_score(43, 21);
173 const Score RookSemiopenFile = make_score(19, 10);
174 const Score BishopPawns = make_score( 8, 12);
175 const Score MinorBehindPawn = make_score(16, 0);
176 const Score UndefendedMinor = make_score(25, 10);
177 const Score TrappedRook = make_score(90, 0);
179 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
180 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
181 // happen in Chess960 games.
182 const Score TrappedBishopA1H1 = make_score(50, 50);
184 // The SpaceMask[Color] contains the area of the board which is considered
185 // by the space evaluation. In the middle game, each side is given a bonus
186 // based on how many squares inside this area are safe and available for
187 // friendly minor pieces.
188 const Bitboard SpaceMask[] = {
189 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
193 // King danger constants and variables. The king danger scores are taken
194 // from the KingDanger[]. Various little "meta-bonuses" measuring
195 // the strength of the enemy attack are added up into an integer, which
196 // is used as an index to KingDanger[].
198 // KingAttackWeights[PieceType] contains king attack weights by piece type
199 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
201 // Bonuses for enemy's safe checks
202 const int QueenContactCheck = 6;
203 const int RookContactCheck = 4;
204 const int QueenCheck = 3;
205 const int RookCheck = 2;
206 const int BishopCheck = 1;
207 const int KnightCheck = 1;
209 // KingExposed[Square] contains penalties based on the position of the
210 // defending king, indexed by king's square (from white's point of view).
211 const int KingExposed[] = {
212 2, 0, 2, 5, 5, 2, 0, 2,
213 2, 2, 4, 8, 8, 4, 2, 2,
214 7, 10, 12, 12, 12, 12, 10, 7,
215 15, 15, 15, 15, 15, 15, 15, 15,
216 15, 15, 15, 15, 15, 15, 15, 15,
217 15, 15, 15, 15, 15, 15, 15, 15,
218 15, 15, 15, 15, 15, 15, 15, 15,
219 15, 15, 15, 15, 15, 15, 15, 15
222 // KingDanger[Color][attackUnits] contains the actual king danger weighted
223 // scores, indexed by color and by a calculated integer number.
224 Score KingDanger[COLOR_NB][128];
226 // Function prototypes
228 Value do_evaluate(const Position& pos, Value& margin);
231 void init_eval_info(const Position& pos, EvalInfo& ei);
233 template<Color Us, bool Trace>
234 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
236 template<Color Us, bool Trace>
237 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]);
239 template<Color Us, bool Trace>
240 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
242 template<Color Us, bool Trace>
243 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
246 int evaluate_space(const Position& pos, const EvalInfo& ei);
248 Score evaluate_unstoppable_pawns(const Position& pos, const EvalInfo& ei);
250 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
251 Score apply_weight(Score v, Score w);
252 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
253 double to_cp(Value v);
259 /// evaluate() is the main evaluation function. It always computes two
260 /// values, an endgame score and a middle game score, and interpolates
261 /// between them based on the remaining material.
263 Value evaluate(const Position& pos, Value& margin) {
264 return do_evaluate<false>(pos, margin);
268 /// trace() is like evaluate() but instead of a value returns a string suitable
269 /// to be print on stdout with the detailed descriptions and values of each
270 /// evaluation term. Used mainly for debugging.
271 std::string trace(const Position& pos) {
272 return Tracing::do_trace(pos);
276 /// init() computes evaluation weights from the corresponding UCI parameters
277 /// and setup king tables.
281 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
282 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
283 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
284 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
285 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
286 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
288 const int MaxSlope = 30;
289 const int Peak = 1280;
291 for (int t = 0, i = 1; i < 100; ++i)
293 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
295 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
296 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
306 Value do_evaluate(const Position& pos, Value& margin) {
308 assert(!pos.checkers());
311 Value margins[COLOR_NB];
312 Score score, mobilityWhite, mobilityBlack;
313 Thread* th = pos.this_thread();
315 // margins[] store the uncertainty estimation of position's evaluation
316 // that typically is used by the search for pruning decisions.
317 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
319 // Initialize score by reading the incrementally updated scores included
320 // in the position object (material + piece square tables) and adding
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())
333 return ei.mi->evaluate(pos);
336 // Probe the pawn hash table
337 ei.pi = Pawns::probe(pos, th->pawnsTable);
338 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
340 // Initialize attack and king safety bitboards
341 init_eval_info<WHITE>(pos, ei);
342 init_eval_info<BLACK>(pos, ei);
344 // Evaluate pieces and mobility
345 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobilityWhite)
346 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobilityBlack);
348 score += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
350 // Evaluate kings after all other pieces because we need complete attack
351 // information when computing the king safety evaluation.
352 score += evaluate_king<WHITE, Trace>(pos, ei, margins)
353 - evaluate_king<BLACK, Trace>(pos, ei, margins);
355 // Evaluate tactical threats, we need full attack information including king
356 score += evaluate_threats<WHITE, Trace>(pos, ei)
357 - evaluate_threats<BLACK, Trace>(pos, ei);
359 // Evaluate passed pawns, we need full attack information including king
360 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
361 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
363 // If one side has only a king, check whether exists any unstoppable passed pawn
364 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
365 score += evaluate_unstoppable_pawns(pos, ei);
367 // Evaluate space for both sides, only in middle-game.
368 if (ei.mi->space_weight())
370 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
371 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
374 // Scale winning side if position is more drawish that what it appears
375 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
376 : ei.mi->scale_factor(pos, BLACK);
378 // If we don't already have an unusual scale factor, check for opposite
379 // colored bishop endgames, and use a lower scale for those.
380 if ( ei.mi->game_phase() < PHASE_MIDGAME
381 && pos.opposite_bishops()
382 && sf == SCALE_FACTOR_NORMAL)
384 // Only the two bishops ?
385 if ( pos.non_pawn_material(WHITE) == BishopValueMg
386 && pos.non_pawn_material(BLACK) == BishopValueMg)
388 // Check for KBP vs KB with only a single pawn that is almost
389 // certainly a draw or at least two pawns.
390 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
391 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
394 // Endgame with opposite-colored bishops, but also other pieces. Still
395 // a bit drawish, but not as drawish as with only the two bishops.
396 sf = ScaleFactor(50);
399 margin = margins[pos.side_to_move()];
400 Value v = interpolate(score, ei.mi->game_phase(), sf);
402 // In case of tracing add all single evaluation contributions for both white and black
405 Tracing::add(PST, pos.psq_score());
406 Tracing::add(IMBALANCE, ei.mi->material_value());
407 Tracing::add(PAWN, ei.pi->pawns_value());
408 Tracing::add(UNSTOPPABLE, evaluate_unstoppable_pawns(pos, ei));
409 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
410 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
411 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
412 Tracing::add(TOTAL, score);
413 Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
414 << ", Black: " << to_cp(margins[BLACK])
415 << "\nScaling: " << std::noshowpos
416 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
417 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
418 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
419 << "Total evaluation: " << to_cp(v);
422 return pos.side_to_move() == WHITE ? v : -v;
426 // init_eval_info() initializes king bitboards for given color adding
427 // pawn attacks. To be done at the beginning of the evaluation.
430 void init_eval_info(const Position& pos, EvalInfo& ei) {
432 const Color Them = (Us == WHITE ? BLACK : WHITE);
433 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
435 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
436 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
438 // Init king safety tables only if we are going to use them
439 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
441 ei.kingRing[Them] = b | shift_bb<Down>(b);
442 b &= ei.attackedBy[Us][PAWN];
443 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
444 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
446 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
450 // evaluate_outposts() evaluates bishop and knight outposts squares
452 template<PieceType Piece, Color Us>
453 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
455 const Color Them = (Us == WHITE ? BLACK : WHITE);
457 assert (Piece == BISHOP || Piece == KNIGHT);
459 // Initial bonus based on square
460 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
462 // Increase bonus if supported by pawn, especially if the opponent has
463 // no minor piece which can exchange the outpost piece.
464 if (bonus && (ei.attackedBy[Us][PAWN] & s))
466 if ( !pos.pieces(Them, KNIGHT)
467 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
468 bonus += bonus + bonus / 2;
472 return make_score(bonus, bonus);
476 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
478 template<PieceType Piece, Color Us, bool Trace>
479 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
483 Score score = SCORE_ZERO;
485 const Color Them = (Us == WHITE ? BLACK : WHITE);
486 const Square* pl = pos.list<Piece>(Us);
488 ei.attackedBy[Us][Piece] = 0;
490 while ((s = *pl++) != SQ_NONE)
492 // Find attacked squares, including x-ray attacks for bishops and rooks
493 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
494 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
495 : pos.attacks_from<Piece>(s);
497 ei.attackedBy[Us][Piece] |= b;
499 if (b & ei.kingRing[Them])
501 ei.kingAttackersCount[Us]++;
502 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
503 Bitboard bb = (b & ei.attackedBy[Them][KING]);
505 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
508 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
509 : popcount<Full >(b & mobilityArea);
511 mobility += MobilityBonus[Piece][mob];
513 // Decrease score if we are attacked by an enemy pawn. Remaining part
514 // of threat evaluation must be done later when we have full attack info.
515 if (ei.attackedBy[Them][PAWN] & s)
516 score -= ThreatenedByPawn[Piece];
518 // Otherwise give a bonus if we are a bishop and can pin a piece or can
519 // give a discovered check through an x-ray attack.
520 else if ( Piece == BISHOP
521 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
522 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
525 // Penalty for bishop with same coloured pawns
527 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
529 if (Piece == BISHOP || Piece == KNIGHT)
531 // Bishop and knight outposts squares
532 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
533 score += evaluate_outposts<Piece, Us>(pos, ei, s);
535 // Bishop or knight behind a pawn
536 if ( relative_rank(Us, s) < RANK_5
537 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
538 score += MinorBehindPawn;
541 if ( (Piece == ROOK || Piece == QUEEN)
542 && relative_rank(Us, s) >= RANK_5)
544 // Major piece on 7th rank and enemy king trapped on 8th
545 if ( relative_rank(Us, s) == RANK_7
546 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
547 score += Piece == ROOK ? RookOn7th : QueenOn7th;
549 // Major piece attacking enemy pawns on the same rank/file
550 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
552 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
555 // Special extra evaluation for rooks
558 // Give a bonus for a rook on a open or semi-open file
559 if (ei.pi->semiopen(Us, file_of(s)))
560 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
562 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
565 Square ksq = pos.king_square(Us);
567 // Penalize rooks which are trapped inside a king. Penalize more if
568 // king has lost right to castle.
569 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
570 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
571 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
572 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
575 // An important Chess960 pattern: A cornered bishop blocked by a friendly
576 // pawn diagonally in front of it is a very serious problem, especially
577 // when that pawn is also blocked.
580 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
582 const enum Piece P = make_piece(Us, PAWN);
583 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
584 if (pos.piece_on(s + d) == P)
585 score -= !pos.is_empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
586 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
592 Tracing::scores[Us][Piece] = score;
598 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
599 // and the type of attacked one.
601 template<Color Us, bool Trace>
602 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
604 const Color Them = (Us == WHITE ? BLACK : WHITE);
606 Bitboard b, undefendedMinors, weakEnemies;
607 Score score = SCORE_ZERO;
609 // Undefended minors get penalized even if not under attack
610 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
611 & ~ei.attackedBy[Them][ALL_PIECES];
613 if (undefendedMinors)
614 score += UndefendedMinor;
616 // Enemy pieces not defended by a pawn and under our attack
617 weakEnemies = pos.pieces(Them)
618 & ~ei.attackedBy[Them][PAWN]
619 & ei.attackedBy[Us][ALL_PIECES];
621 // Add bonus according to type of attacked enemy piece and to the
622 // type of attacking piece, from knights to queens. Kings are not
623 // considered because are already handled in king evaluation.
625 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
627 b = ei.attackedBy[Us][pt1] & weakEnemies;
629 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
630 if (b & pos.pieces(pt2))
631 score += Threat[pt1][pt2];
635 Tracing::scores[Us][THREAT] = score;
641 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
642 // pieces of a given color.
644 template<Color Us, bool Trace>
645 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
647 const Color Them = (Us == WHITE ? BLACK : WHITE);
649 Score score = mobility = SCORE_ZERO;
651 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
652 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
654 score += evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea);
655 score += evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea);
656 score += evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea);
657 score += evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
659 // Sum up all attacked squares
660 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
661 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
662 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
664 Tracing::scores[Us][MOBILITY] = apply_weight(mobility, Weights[Mobility]);
670 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
672 template<Color Us, bool Trace>
673 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
675 const Color Them = (Us == WHITE ? BLACK : WHITE);
677 Bitboard undefended, b, b1, b2, safe;
679 const Square ksq = pos.king_square(Us);
681 // King shelter and enemy pawns storm
682 Score score = ei.pi->king_safety<Us>(pos, ksq);
684 // King safety. This is quite complicated, and is almost certainly far
685 // from optimally tuned.
686 if ( ei.kingAttackersCount[Them] >= 2
687 && ei.kingAdjacentZoneAttacksCount[Them])
689 // Find the attacked squares around the king which has no defenders
690 // apart from the king itself
691 undefended = ei.attackedBy[Them][ALL_PIECES] & ei.attackedBy[Us][KING];
692 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
693 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
694 | ei.attackedBy[Us][QUEEN]);
696 // Initialize the 'attackUnits' variable, which is used later on as an
697 // index to the KingDanger[] array. The initial value is based on the
698 // number and types of the enemy's attacking pieces, the number of
699 // attacked and undefended squares around our king, the square of the
700 // king, and the quality of the pawn shelter.
701 attackUnits = std::min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
702 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
703 + KingExposed[relative_square(Us, ksq)]
704 - mg_value(score) / 32;
706 // Analyse enemy's safe queen contact checks. First find undefended
707 // squares around the king attacked by enemy queen...
708 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
711 // ...then remove squares not supported by another enemy piece
712 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
713 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
715 attackUnits += QueenContactCheck
717 * (Them == pos.side_to_move() ? 2 : 1);
720 // Analyse enemy's safe rook contact checks. First find undefended
721 // squares around the king attacked by enemy rooks...
722 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
724 // Consider only squares where the enemy rook gives check
725 b &= PseudoAttacks[ROOK][ksq];
729 // ...then remove squares not supported by another enemy piece
730 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
731 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
733 attackUnits += RookContactCheck
735 * (Them == pos.side_to_move() ? 2 : 1);
738 // Analyse enemy's safe distance checks for sliders and knights
739 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
741 b1 = pos.attacks_from<ROOK>(ksq) & safe;
742 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
744 // Enemy queen safe checks
745 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
747 attackUnits += QueenCheck * popcount<Max15>(b);
749 // Enemy rooks safe checks
750 b = b1 & ei.attackedBy[Them][ROOK];
752 attackUnits += RookCheck * popcount<Max15>(b);
754 // Enemy bishops safe checks
755 b = b2 & ei.attackedBy[Them][BISHOP];
757 attackUnits += BishopCheck * popcount<Max15>(b);
759 // Enemy knights safe checks
760 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
762 attackUnits += KnightCheck * popcount<Max15>(b);
764 // To index KingDanger[] attackUnits must be in [0, 99] range
765 attackUnits = std::min(99, std::max(0, attackUnits));
767 // Finally, extract the king danger score from the KingDanger[]
768 // array and subtract the score from evaluation. Set also margins[]
769 // value that will be used for pruning because this value can sometimes
770 // be very big, and so capturing a single attacking piece can therefore
771 // result in a score change far bigger than the value of the captured piece.
772 score -= KingDanger[Us == Search::RootColor][attackUnits];
773 margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
777 Tracing::scores[Us][KING] = score;
783 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
785 template<Color Us, bool Trace>
786 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
788 const Color Them = (Us == WHITE ? BLACK : WHITE);
790 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
791 Score score = SCORE_ZERO;
793 b = ei.pi->passed_pawns(Us);
797 Square s = pop_lsb(&b);
799 assert(pos.pawn_is_passed(Us, s));
801 int r = int(relative_rank(Us, s) - RANK_2);
802 int rr = r * (r - 1);
804 // Base bonus based on rank
805 Value mbonus = Value(17 * rr);
806 Value ebonus = Value(7 * (rr + r + 1));
810 Square blockSq = s + pawn_push(Us);
812 // Adjust bonus based on kings proximity
813 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr);
814 ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 2 * rr);
816 // If blockSq is not the queening square then consider also a second push
817 if (relative_rank(Us, blockSq) != RANK_8)
818 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
820 // If the pawn is free to advance, increase bonus
821 if (pos.is_empty(blockSq))
823 squaresToQueen = forward_bb(Us, s);
825 // If there is an enemy rook or queen attacking the pawn from behind,
826 // add all X-ray attacks by the rook or queen. Otherwise consider only
827 // the squares in the pawn's path attacked or occupied by the enemy.
828 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
829 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
830 unsafeSquares = squaresToQueen;
832 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
834 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
835 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
836 defendedSquares = squaresToQueen;
838 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
840 // If there aren't enemy attacks huge bonus, a bit smaller if at
841 // least block square is not attacked, otherwise smallest bonus.
842 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
844 // Big bonus if the path to queen is fully defended, a bit less
845 // if at least block square is defended.
846 if (defendedSquares == squaresToQueen)
849 else if (defendedSquares & blockSq)
850 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
852 mbonus += Value(k * rr), ebonus += Value(k * rr);
856 // Increase the bonus if the passed pawn is supported by a friendly pawn
857 // on the same rank and a bit smaller if it's on the previous rank.
858 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
859 if (supportingPawns & rank_bb(s))
860 ebonus += Value(r * 20);
862 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
863 ebonus += Value(r * 12);
865 // Rook pawns are a special case: They are sometimes worse, and
866 // sometimes better than other passed pawns. It is difficult to find
867 // good rules for determining whether they are good or bad. For now,
868 // we try the following: Increase the value for rook pawns if the
869 // other side has no pieces apart from a knight, and decrease the
870 // value if the other side has a rook or queen.
871 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
873 if (pos.non_pawn_material(Them) <= KnightValueMg)
874 ebonus += ebonus / 4;
876 else if (pos.pieces(Them, ROOK, QUEEN))
877 ebonus -= ebonus / 4;
880 // Increase the bonus if we have more non-pawn pieces
881 if (pos.count<ALL_PIECES>( Us) - pos.count<PAWN>( Us) >
882 pos.count<ALL_PIECES>(Them) - pos.count<PAWN>(Them))
883 ebonus += ebonus / 4;
885 score += make_score(mbonus, ebonus);
890 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
892 // Add the scores to the middle game and endgame eval
893 return apply_weight(score, Weights[PassedPawns]);
897 // evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides, this is quite
898 // conservative and returns a winning score only when we are very sure that the pawn is winning.
900 Score evaluate_unstoppable_pawns(const Position& pos, const EvalInfo& ei) {
902 Bitboard b, b2, blockers, supporters, queeningPath, candidates;
903 Square s, blockSq, queeningSquare;
904 Color c, winnerSide, loserSide;
905 bool pathDefended, opposed;
906 int pliesToGo, movesToGo, oppMovesToGo, sacptg, blockersCount, minKingDist, kingptg, d;
907 int pliesToQueen[] = { 256, 256 };
909 // Step 1. Hunt for unstoppable passed pawns. If we find at least one,
910 // record how many plies are required for promotion.
911 for (c = WHITE; c <= BLACK; ++c)
913 // Skip if other side has non-pawn pieces
914 if (pos.non_pawn_material(~c))
917 b = ei.pi->passed_pawns(c);
922 queeningSquare = relative_square(c, file_of(s) | RANK_8);
923 queeningPath = forward_bb(c, s);
925 // Compute plies to queening and check direct advancement
926 movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(c, s) == RANK_2);
927 oppMovesToGo = square_distance(pos.king_square(~c), queeningSquare) - int(c != pos.side_to_move());
928 pathDefended = ((ei.attackedBy[c][ALL_PIECES] & queeningPath) == queeningPath);
930 if (movesToGo >= oppMovesToGo && !pathDefended)
933 // Opponent king cannot block because path is defended and position
934 // is not in check. So only friendly pieces can be blockers.
935 assert(!pos.checkers());
936 assert((queeningPath & pos.pieces()) == (queeningPath & pos.pieces(c)));
938 // Add moves needed to free the path from friendly pieces and retest condition
939 movesToGo += popcount<Max15>(queeningPath & pos.pieces(c));
941 if (movesToGo >= oppMovesToGo && !pathDefended)
944 pliesToGo = 2 * movesToGo - int(c == pos.side_to_move());
945 pliesToQueen[c] = std::min(pliesToQueen[c], pliesToGo);
949 // Step 2. If either side cannot promote at least three plies before the other side then situation
950 // becomes too complex and we give up. Otherwise we determine the possibly "winning side"
951 if (abs(pliesToQueen[WHITE] - pliesToQueen[BLACK]) < 3)
954 winnerSide = (pliesToQueen[WHITE] < pliesToQueen[BLACK] ? WHITE : BLACK);
955 loserSide = ~winnerSide;
957 // Step 3. Can the losing side possibly create a new passed pawn and thus prevent the loss?
958 b = candidates = pos.pieces(loserSide, PAWN);
964 // Compute plies from queening
965 queeningSquare = relative_square(loserSide, file_of(s) | RANK_8);
966 movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(loserSide, s) == RANK_2);
967 pliesToGo = 2 * movesToGo - int(loserSide == pos.side_to_move());
969 // Check if (without even considering any obstacles) we're too far away or doubled
970 if ( pliesToQueen[winnerSide] + 3 <= pliesToGo
971 || (forward_bb(loserSide, s) & pos.pieces(loserSide, PAWN)))
975 // If any candidate is already a passed pawn it _may_ promote in time. We give up.
976 if (candidates & ei.pi->passed_pawns(loserSide))
979 // Step 4. Check new passed pawn creation through king capturing and pawn sacrifices
985 sacptg = blockersCount = 0;
986 minKingDist = kingptg = 256;
988 // Compute plies from queening
989 queeningSquare = relative_square(loserSide, file_of(s) | RANK_8);
990 movesToGo = rank_distance(s, queeningSquare) - int(relative_rank(loserSide, s) == RANK_2);
991 pliesToGo = 2 * movesToGo - int(loserSide == pos.side_to_move());
993 // Generate list of blocking pawns and supporters
994 supporters = adjacent_files_bb(file_of(s)) & candidates;
995 opposed = forward_bb(loserSide, s) & pos.pieces(winnerSide, PAWN);
996 blockers = passed_pawn_mask(loserSide, s) & pos.pieces(winnerSide, PAWN);
1000 // How many plies does it take to remove all the blocking pawns?
1003 blockSq = pop_lsb(&blockers);
1006 // Check pawns that can give support to overcome obstacle, for instance
1007 // black pawns: a4, b4 white: b2 then pawn in b4 is giving support.
1010 b2 = supporters & in_front_bb(winnerSide, rank_of(blockSq + pawn_push(winnerSide)));
1014 d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;
1015 movesToGo = std::min(movesToGo, d);
1019 // Check pawns that can be sacrificed against the blocking pawn
1020 b2 = pawn_attack_span(winnerSide, blockSq) & candidates & ~SquareBB[s];
1024 d = square_distance(blockSq, backmost_sq(winnerSide, b2)) - 2;
1025 movesToGo = std::min(movesToGo, d);
1028 // If obstacle can be destroyed with an immediate pawn exchange / sacrifice,
1029 // it's not a real obstacle and we have nothing to add to pliesToGo.
1033 // Plies needed to sacrifice against all the blocking pawns
1034 sacptg += movesToGo * 2;
1037 // Plies needed for the king to capture all the blocking pawns
1038 d = square_distance(pos.king_square(loserSide), blockSq);
1039 minKingDist = std::min(minKingDist, d);
1040 kingptg = (minKingDist + blockersCount) * 2;
1043 // Check if pawn sacrifice or king capture plan _may_ save the day
1044 if (pliesToQueen[winnerSide] + 3 > pliesToGo + std::min(kingptg, sacptg))
1048 // Winning pawn is unstoppable and will promote as first, return big score
1049 Score score = make_score(0, (Value) 1280 - 32 * pliesToQueen[winnerSide]);
1050 return winnerSide == WHITE ? score : -score;
1054 // evaluate_space() computes the space evaluation for a given side. The
1055 // space evaluation is a simple bonus based on the number of safe squares
1056 // available for minor pieces on the central four files on ranks 2--4. Safe
1057 // squares one, two or three squares behind a friendly pawn are counted
1058 // twice. Finally, the space bonus is scaled by a weight taken from the
1059 // material hash table. The aim is to improve play on game opening.
1061 int evaluate_space(const Position& pos, const EvalInfo& ei) {
1063 const Color Them = (Us == WHITE ? BLACK : WHITE);
1065 // Find the safe squares for our pieces inside the area defined by
1066 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
1067 // pawn, or if it is undefended and attacked by an enemy piece.
1068 Bitboard safe = SpaceMask[Us]
1069 & ~pos.pieces(Us, PAWN)
1070 & ~ei.attackedBy[Them][PAWN]
1071 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
1073 // Find all squares which are at most three squares behind some friendly pawn
1074 Bitboard behind = pos.pieces(Us, PAWN);
1075 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
1076 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
1078 // Since SpaceMask[Us] is fully on our half of the board
1079 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
1081 // Count safe + (behind & safe) with a single popcount
1082 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
1086 // interpolate() interpolates between a middle game and an endgame score,
1087 // based on game phase. It also scales the return value by a ScaleFactor array.
1089 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
1091 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
1092 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
1093 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1095 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
1096 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
1097 return Value((r / GrainSize) * GrainSize); // Sign independent
1100 // apply_weight() weights score v by score w trying to prevent overflow
1101 Score apply_weight(Score v, Score w) {
1102 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
1103 (int(eg_value(v)) * eg_value(w)) / 0x100);
1106 // weight_option() computes the value of an evaluation weight, by combining
1107 // two UCI-configurable weights (midgame and endgame) with an internal weight.
1109 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
1111 // Scale option value from 100 to 256
1112 int mg = Options[mgOpt] * 256 / 100;
1113 int eg = Options[egOpt] * 256 / 100;
1115 return apply_weight(make_score(mg, eg), internalWeight);
1119 // Tracing functions definitions
1121 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
1123 void Tracing::add(int idx, Score wScore, Score bScore) {
1125 scores[WHITE][idx] = wScore;
1126 scores[BLACK][idx] = bScore;
1129 void Tracing::row(const char* name, int idx) {
1131 Score wScore = scores[WHITE][idx];
1132 Score bScore = scores[BLACK][idx];
1135 case PST: case IMBALANCE: case PAWN: case UNSTOPPABLE: case TOTAL:
1136 stream << std::setw(20) << name << " | --- --- | --- --- | "
1137 << std::setw(6) << to_cp(mg_value(wScore)) << " "
1138 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
1141 stream << std::setw(20) << name << " | " << std::noshowpos
1142 << std::setw(5) << to_cp(mg_value(wScore)) << " "
1143 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1144 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1145 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1147 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1148 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1152 std::string Tracing::do_trace(const Position& pos) {
1155 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1156 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1159 do_evaluate<true>(pos, margin);
1161 std::string totals = stream.str();
1164 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1165 << " | MG EG | MG EG | MG EG \n"
1166 << "---------------------+-------------+-------------+---------------\n";
1168 row("Material, PST, Tempo", PST);
1169 row("Material imbalance", IMBALANCE);
1171 row("Knights", KNIGHT);
1172 row("Bishops", BISHOP);
1174 row("Queens", QUEEN);
1175 row("Mobility", MOBILITY);
1176 row("King safety", KING);
1177 row("Threats", THREAT);
1178 row("Passed pawns", PASSED);
1179 row("Unstoppable pawns", UNSTOPPABLE);
1180 row("Space", SPACE);
1182 stream << "---------------------+-------------+-------------+---------------\n";
1183 row("Total", TOTAL);
1186 return stream.str();