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 of knights and bishops, indexed
131 // 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 // The SpaceMask[Color] contains the area of the board which is considered
189 // by the space evaluation. In the middle game, 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 the KingDanger[]. Various little "meta-bonuses" measuring
199 // the strength of the enemy attack are added up into an integer, which
200 // is used as an 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, Value& margin);
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, Value margins[]);
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 middle game score, and interpolates
265 /// between them based on the remaining material.
267 Value evaluate(const Position& pos, Value& margin) {
268 return do_evaluate<false>(pos, margin);
272 /// trace() is like evaluate() but instead of a value returns a string suitable
273 /// to be print on stdout with the detailed descriptions and values of each
274 /// evaluation term. Used mainly for debugging.
275 std::string trace(const Position& pos) {
276 return Tracing::do_trace(pos);
280 /// init() computes evaluation weights from the corresponding UCI parameters
281 /// and setup king tables.
285 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
286 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
287 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
288 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
289 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
290 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
292 const int MaxSlope = 30;
293 const int Peak = 1280;
295 for (int t = 0, i = 1; i < 100; ++i)
297 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
299 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
300 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
310 Value do_evaluate(const Position& pos, Value& margin) {
312 assert(!pos.checkers());
315 Value margins[COLOR_NB];
316 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
317 Thread* th = pos.this_thread();
319 // margins[] store the uncertainty estimation of position's evaluation
320 // that typically is used by the search for pruning decisions.
321 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
323 // Initialize score by reading the incrementally updated scores included
324 // in the position object (material + piece square tables) and adding
325 // Tempo bonus. Score is computed from the point of view of white.
326 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
328 // Probe the material hash table
329 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
330 score += ei.mi->material_value();
332 // If we have a specialized evaluation function for the current material
333 // configuration, call it and return.
334 if (ei.mi->specialized_eval_exists())
337 return ei.mi->evaluate(pos);
340 // Probe the pawn hash table
341 ei.pi = Pawns::probe(pos, th->pawnsTable);
342 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
344 // Initialize attack and king safety bitboards
345 init_eval_info<WHITE>(pos, ei);
346 init_eval_info<BLACK>(pos, ei);
348 // Evaluate pieces and mobility
349 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
350 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
352 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
354 // Evaluate kings after all other pieces because we need complete attack
355 // information when computing the king safety evaluation.
356 score += evaluate_king<WHITE, Trace>(pos, ei, margins)
357 - evaluate_king<BLACK, Trace>(pos, ei, margins);
359 // Evaluate tactical threats, we need full attack information including king
360 score += evaluate_threats<WHITE, Trace>(pos, ei)
361 - evaluate_threats<BLACK, Trace>(pos, ei);
363 // Evaluate passed pawns, we need full attack information including king
364 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
365 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
367 // If one side has only a king, score for potential unstoppable pawns
368 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
369 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
370 - evaluate_unstoppable_pawns(pos, BLACK, ei);
372 // Evaluate space for both sides, only in middle-game.
373 if (ei.mi->space_weight())
375 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
376 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
379 // Scale winning side if position is more drawish that what it appears
380 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
381 : ei.mi->scale_factor(pos, BLACK);
383 // If we don't already have an unusual scale factor, check for opposite
384 // colored bishop endgames, and use a lower scale for those.
385 if ( ei.mi->game_phase() < PHASE_MIDGAME
386 && pos.opposite_bishops()
387 && sf == SCALE_FACTOR_NORMAL)
389 // Only the two bishops ?
390 if ( pos.non_pawn_material(WHITE) == BishopValueMg
391 && pos.non_pawn_material(BLACK) == BishopValueMg)
393 // Check for KBP vs KB with only a single pawn that is almost
394 // certainly a draw or at least two pawns.
395 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
396 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
399 // Endgame with opposite-colored bishops, but also other pieces. Still
400 // a bit drawish, but not as drawish as with only the two bishops.
401 sf = ScaleFactor(50);
404 margin = margins[pos.side_to_move()];
405 Value v = interpolate(score, ei.mi->game_phase(), sf);
407 // In case of tracing add all single evaluation contributions for both white and black
410 Tracing::add(PST, pos.psq_score());
411 Tracing::add(IMBALANCE, ei.mi->material_value());
412 Tracing::add(PAWN, ei.pi->pawns_value());
413 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
414 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
415 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
416 Tracing::add(TOTAL, score);
417 Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
418 << ", Black: " << to_cp(margins[BLACK])
419 << "\nScaling: " << std::noshowpos
420 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
421 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
422 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
423 << "Total evaluation: " << to_cp(v);
426 return pos.side_to_move() == WHITE ? v : -v;
430 // init_eval_info() initializes king bitboards for given color adding
431 // pawn attacks. To be done at the beginning of the evaluation.
434 void init_eval_info(const Position& pos, EvalInfo& ei) {
436 const Color Them = (Us == WHITE ? BLACK : WHITE);
437 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
439 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
441 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
442 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
444 // Init king safety tables only if we are going to use them
445 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
447 ei.kingRing[Them] = b | shift_bb<Down>(b);
448 b &= ei.attackedBy[Us][PAWN];
449 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
450 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
453 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
457 // evaluate_outposts() evaluates bishop and knight outposts squares
459 template<PieceType Piece, Color Us>
460 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
462 const Color Them = (Us == WHITE ? BLACK : WHITE);
464 assert (Piece == BISHOP || Piece == KNIGHT);
466 // Initial bonus based on square
467 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
469 // Increase bonus if supported by pawn, especially if the opponent has
470 // no minor piece which can exchange the outpost piece.
471 if (bonus && (ei.attackedBy[Us][PAWN] & s))
473 if ( !pos.pieces(Them, KNIGHT)
474 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
475 bonus += bonus + bonus / 2;
480 return make_score(bonus, bonus);
484 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
486 template<PieceType Piece, Color Us, bool Trace>
487 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
491 Score score = SCORE_ZERO;
493 const Color Them = (Us == WHITE ? BLACK : WHITE);
494 const Square* pl = pos.list<Piece>(Us);
496 ei.attackedBy[Us][Piece] = 0;
498 while ((s = *pl++) != SQ_NONE)
500 // Find attacked squares, including x-ray attacks for bishops and rooks
501 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
502 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
503 : pos.attacks_from<Piece>(s);
505 if (ei.pinnedPieces[Us] & s)
506 b &= PseudoAttacks[QUEEN][pos.king_square(Us)];
508 ei.attackedBy[Us][Piece] |= b;
510 if (b & ei.kingRing[Them])
512 ei.kingAttackersCount[Us]++;
513 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
514 Bitboard bb = b & ei.attackedBy[Them][KING];
516 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
519 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
520 : popcount<Full >(b & mobilityArea);
522 mobility[Us] += MobilityBonus[Piece][mob];
524 // Decrease score if we are attacked by an enemy pawn. Remaining part
525 // of threat evaluation must be done later when we have full attack info.
526 if (ei.attackedBy[Them][PAWN] & s)
527 score -= ThreatenedByPawn[Piece];
529 // Otherwise give a bonus if we are a bishop and can pin a piece or can
530 // give a discovered check through an x-ray attack.
531 else if ( Piece == BISHOP
532 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
533 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
536 // Penalty for bishop with same coloured pawns
538 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
540 // Penalty for knight when there are few enemy pawns
542 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
544 if (Piece == BISHOP || Piece == KNIGHT)
546 // Bishop and knight outposts squares
547 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
548 score += evaluate_outposts<Piece, Us>(pos, ei, s);
550 // Bishop or knight behind a pawn
551 if ( relative_rank(Us, s) < RANK_5
552 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
553 score += MinorBehindPawn;
556 if ( (Piece == ROOK || Piece == QUEEN)
557 && relative_rank(Us, s) >= RANK_5)
559 // Major piece on 7th rank and enemy king trapped on 8th
560 if ( relative_rank(Us, s) == RANK_7
561 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
562 score += Piece == ROOK ? RookOn7th : QueenOn7th;
564 // Major piece attacking enemy pawns on the same rank/file
565 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
567 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
570 // Special extra evaluation for rooks
573 // Give a bonus for a rook on a open or semi-open file
574 if (ei.pi->semiopen(Us, file_of(s)))
575 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
577 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
580 Square ksq = pos.king_square(Us);
582 // Penalize rooks which are trapped inside a king. Penalize more if
583 // king has lost right to castle.
584 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
585 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
586 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
587 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
590 // An important Chess960 pattern: A cornered bishop blocked by a friendly
591 // pawn diagonally in front of it is a very serious problem, especially
592 // when that pawn is also blocked.
595 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
597 const enum Piece P = make_piece(Us, PAWN);
598 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
599 if (pos.piece_on(s + d) == P)
600 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
601 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
607 Tracing::scores[Us][Piece] = score;
613 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
614 // pieces of a given color.
616 template<Color Us, bool Trace>
617 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
619 const Color Them = (Us == WHITE ? BLACK : WHITE);
621 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
622 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
624 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
625 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
626 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
627 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
629 // Sum up all attacked squares (updated in evaluate_pieces)
630 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
631 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
632 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
634 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
640 // evaluate_king() assigns bonuses and penalties to a king of a given color
642 template<Color Us, bool Trace>
643 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
645 const Color Them = (Us == WHITE ? BLACK : WHITE);
647 Bitboard undefended, b, b1, b2, safe;
649 const Square ksq = pos.king_square(Us);
651 // King shelter and enemy pawns storm
652 Score score = ei.pi->king_safety<Us>(pos, ksq);
654 // Main king safety evaluation
655 if ( ei.kingAttackersCount[Them] >= 2
656 && ei.kingAdjacentZoneAttacksCount[Them])
658 // Find the attacked squares around the king which has no defenders
659 // apart from the king itself
660 undefended = ei.attackedBy[Them][ALL_PIECES]
661 & ei.attackedBy[Us][KING]
662 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
663 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
664 | ei.attackedBy[Us][QUEEN]);
666 // Initialize the 'attackUnits' variable, which is used later on as an
667 // index to the KingDanger[] array. The initial value is based on the
668 // number and types of the enemy's attacking pieces, the number of
669 // attacked and undefended squares around our king, the square of the
670 // king, and the quality of the pawn shelter.
671 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
672 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
673 + KingExposed[relative_square(Us, ksq)]
674 - mg_value(score) / 32;
676 // Analyse enemy's safe queen contact checks. First find undefended
677 // squares around the king attacked by enemy queen...
678 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
681 // ...then remove squares not supported by another enemy piece
682 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
683 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
685 attackUnits += QueenContactCheck
687 * (Them == pos.side_to_move() ? 2 : 1);
690 // Analyse enemy's safe rook contact checks. First find undefended
691 // squares around the king attacked by enemy rooks...
692 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
694 // Consider only squares where the enemy rook gives check
695 b &= PseudoAttacks[ROOK][ksq];
699 // ...then remove squares not supported by another enemy piece
700 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
701 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
703 attackUnits += RookContactCheck
705 * (Them == pos.side_to_move() ? 2 : 1);
708 // Analyse enemy's safe distance checks for sliders and knights
709 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
711 b1 = pos.attacks_from<ROOK>(ksq) & safe;
712 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
714 // Enemy queen safe checks
715 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
717 attackUnits += QueenCheck * popcount<Max15>(b);
719 // Enemy rooks safe checks
720 b = b1 & ei.attackedBy[Them][ROOK];
722 attackUnits += RookCheck * popcount<Max15>(b);
724 // Enemy bishops safe checks
725 b = b2 & ei.attackedBy[Them][BISHOP];
727 attackUnits += BishopCheck * popcount<Max15>(b);
729 // Enemy knights safe checks
730 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
732 attackUnits += KnightCheck * popcount<Max15>(b);
734 // To index KingDanger[] attackUnits must be in [0, 99] range
735 attackUnits = std::min(99, std::max(0, attackUnits));
737 // Finally, extract the king danger score from the KingDanger[]
738 // array and subtract the score from evaluation. Set also margins[]
739 // value that will be used for pruning because this value can sometimes
740 // be very big, and so capturing a single attacking piece can therefore
741 // result in a score change far bigger than the value of the captured piece.
742 score -= KingDanger[Us == Search::RootColor][attackUnits];
743 margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
747 Tracing::scores[Us][KING] = score;
753 // evaluate_threats() assigns bonuses according to the type of attacking piece
754 // and the type of attacked one.
756 template<Color Us, bool Trace>
757 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
759 const Color Them = (Us == WHITE ? BLACK : WHITE);
761 Bitboard b, undefendedMinors, weakEnemies;
762 Score score = SCORE_ZERO;
764 // Undefended minors get penalized even if not under attack
765 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
766 & ~ei.attackedBy[Them][ALL_PIECES];
768 if (undefendedMinors)
769 score += UndefendedMinor;
771 // Enemy pieces not defended by a pawn and under our attack
772 weakEnemies = pos.pieces(Them)
773 & ~ei.attackedBy[Them][PAWN]
774 & ei.attackedBy[Us][ALL_PIECES];
776 // Add bonus according to type of attacked enemy piece and to the
777 // type of attacking piece, from knights to queens. Kings are not
778 // considered because are already handled in king evaluation.
780 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
782 b = ei.attackedBy[Us][pt1] & weakEnemies;
784 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
785 if (b & pos.pieces(pt2))
786 score += Threat[pt1][pt2];
790 Tracing::scores[Us][THREAT] = score;
796 // evaluate_passed_pawns() evaluates the passed pawns of the given color
798 template<Color Us, bool Trace>
799 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
801 const Color Them = (Us == WHITE ? BLACK : WHITE);
803 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
804 Score score = SCORE_ZERO;
806 b = ei.pi->passed_pawns(Us);
810 Square s = pop_lsb(&b);
812 assert(pos.pawn_passed(Us, s));
814 int r = int(relative_rank(Us, s) - RANK_2);
815 int rr = r * (r - 1);
817 // Base bonus based on rank
818 Value mbonus = Value(17 * rr);
819 Value ebonus = Value(7 * (rr + r + 1));
823 Square blockSq = s + pawn_push(Us);
825 // Adjust bonus based on kings proximity
826 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
827 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
829 // If blockSq is not the queening square then consider also a second push
830 if (relative_rank(Us, blockSq) != RANK_8)
831 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
833 // If the pawn is free to advance, increase bonus
834 if (pos.empty(blockSq))
836 squaresToQueen = forward_bb(Us, s);
838 // If there is an enemy rook or queen attacking the pawn from behind,
839 // add all X-ray attacks by the rook or queen. Otherwise consider only
840 // the squares in the pawn's path attacked or occupied by the enemy.
841 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
842 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
843 unsafeSquares = squaresToQueen;
845 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
847 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
848 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
849 defendedSquares = squaresToQueen;
851 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
853 // If there aren't enemy attacks huge bonus, a bit smaller if at
854 // least block square is not attacked, otherwise smallest bonus.
855 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
857 // Big bonus if the path to queen is fully defended, a bit less
858 // if at least block square is defended.
859 if (defendedSquares == squaresToQueen)
862 else if (defendedSquares & blockSq)
863 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
865 mbonus += Value(k * rr), ebonus += Value(k * rr);
869 // Increase the bonus if the passed pawn is supported by a friendly pawn
870 // on the same rank and a bit smaller if it's on the previous rank.
871 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
872 if (supportingPawns & rank_bb(s))
873 ebonus += Value(r * 20);
875 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
876 ebonus += Value(r * 12);
878 // Rook pawns are a special case: They are sometimes worse, and
879 // sometimes better than other passed pawns. It is difficult to find
880 // good rules for determining whether they are good or bad. For now,
881 // we try the following: Increase the value for rook pawns if the
882 // other side has no pieces apart from a knight, and decrease the
883 // value if the other side has a rook or queen.
884 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
886 if (pos.non_pawn_material(Them) <= KnightValueMg)
887 ebonus += ebonus / 4;
889 else if (pos.pieces(Them, ROOK, QUEEN))
890 ebonus -= ebonus / 4;
893 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
894 ebonus += ebonus / 4;
896 score += make_score(mbonus, ebonus);
901 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
903 // Add the scores to the middle game and endgame eval
904 return apply_weight(score, Weights[PassedPawns]);
908 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
909 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
910 // related to the possibility pawns are unstoppable.
912 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
914 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
916 if (!b || pos.non_pawn_material(~us))
919 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
923 // evaluate_space() computes the space evaluation for a given side. The
924 // space evaluation is a simple bonus based on the number of safe squares
925 // available for minor pieces on the central four files on ranks 2--4. Safe
926 // squares one, two or three squares behind a friendly pawn are counted
927 // twice. Finally, the space bonus is scaled by a weight taken from the
928 // material hash table. The aim is to improve play on game opening.
930 int evaluate_space(const Position& pos, const EvalInfo& ei) {
932 const Color Them = (Us == WHITE ? BLACK : WHITE);
934 // Find the safe squares for our pieces inside the area defined by
935 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
936 // pawn, or if it is undefended and attacked by an enemy piece.
937 Bitboard safe = SpaceMask[Us]
938 & ~pos.pieces(Us, PAWN)
939 & ~ei.attackedBy[Them][PAWN]
940 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
942 // Find all squares which are at most three squares behind some friendly pawn
943 Bitboard behind = pos.pieces(Us, PAWN);
944 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
945 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
947 // Since SpaceMask[Us] is fully on our half of the board
948 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
950 // Count safe + (behind & safe) with a single popcount
951 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
955 // interpolate() interpolates between a middle game and an endgame score,
956 // based on game phase. It also scales the return value by a ScaleFactor array.
958 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
960 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
961 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
962 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
964 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
965 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
966 return Value((r / GrainSize) * GrainSize); // Sign independent
969 // apply_weight() weights score v by score w trying to prevent overflow
970 Score apply_weight(Score v, Score w) {
971 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
972 (int(eg_value(v)) * eg_value(w)) / 0x100);
975 // weight_option() computes the value of an evaluation weight, by combining
976 // two UCI-configurable weights (midgame and endgame) with an internal weight.
978 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
980 // Scale option value from 100 to 256
981 int mg = Options[mgOpt] * 256 / 100;
982 int eg = Options[egOpt] * 256 / 100;
984 return apply_weight(make_score(mg, eg), internalWeight);
988 // Tracing functions definitions
990 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
992 void Tracing::add(int idx, Score wScore, Score bScore) {
994 scores[WHITE][idx] = wScore;
995 scores[BLACK][idx] = bScore;
998 void Tracing::row(const char* name, int idx) {
1000 Score wScore = scores[WHITE][idx];
1001 Score bScore = scores[BLACK][idx];
1004 case PST: case IMBALANCE: case PAWN: case TOTAL:
1005 stream << std::setw(20) << name << " | --- --- | --- --- | "
1006 << std::setw(6) << to_cp(mg_value(wScore)) << " "
1007 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
1010 stream << std::setw(20) << name << " | " << std::noshowpos
1011 << std::setw(5) << to_cp(mg_value(wScore)) << " "
1012 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1013 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1014 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1016 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1017 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1021 std::string Tracing::do_trace(const Position& pos) {
1024 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1025 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1028 do_evaluate<true>(pos, margin);
1030 std::string totals = stream.str();
1033 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1034 << " | MG EG | MG EG | MG EG \n"
1035 << "---------------------+-------------+-------------+---------------\n";
1037 row("Material, PST, Tempo", PST);
1038 row("Material imbalance", IMBALANCE);
1040 row("Knights", KNIGHT);
1041 row("Bishops", BISHOP);
1043 row("Queens", QUEEN);
1044 row("Mobility", MOBILITY);
1045 row("King safety", KING);
1046 row("Threats", THREAT);
1047 row("Passed pawns", PASSED);
1048 row("Space", SPACE);
1050 stream << "---------------------+-------------+-------------+---------------\n";
1051 row("Total", TOTAL);
1054 return stream.str();