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];
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 KnightPawns = make_score( 8, 4);
176 const Score MinorBehindPawn = make_score(16, 0);
177 const Score UndefendedMinor = make_score(25, 10);
178 const Score TrappedRook = make_score(90, 0);
179 const Score Unstoppable = make_score( 0, 20);
181 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
182 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
183 // happen in Chess960 games.
184 const Score TrappedBishopA1H1 = make_score(50, 50);
186 // The SpaceMask[Color] contains the area of the board which is considered
187 // by the space evaluation. In the middle game, each side is given a bonus
188 // based on how many squares inside this area are safe and available for
189 // friendly minor pieces.
190 const Bitboard SpaceMask[] = {
191 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
192 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
195 // King danger constants and variables. The king danger scores are taken
196 // from the KingDanger[]. Various little "meta-bonuses" measuring
197 // the strength of the enemy attack are added up into an integer, which
198 // is used as an index to KingDanger[].
200 // KingAttackWeights[PieceType] contains king attack weights by piece type
201 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
203 // Bonuses for enemy's safe checks
204 const int QueenContactCheck = 24;
205 const int RookContactCheck = 16;
206 const int QueenCheck = 12;
207 const int RookCheck = 8;
208 const int BishopCheck = 2;
209 const int KnightCheck = 3;
211 // KingExposed[Square] contains penalties based on the position of the
212 // defending king, indexed by king's square (from white's point of view).
213 const int KingExposed[] = {
214 2, 0, 2, 5, 5, 2, 0, 2,
215 2, 2, 4, 8, 8, 4, 2, 2,
216 7, 10, 12, 12, 12, 12, 10, 7,
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,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15
224 // KingDanger[Color][attackUnits] contains the actual king danger weighted
225 // scores, indexed by color and by a calculated integer number.
226 Score KingDanger[COLOR_NB][128];
228 // Function prototypes
230 Value do_evaluate(const Position& pos, Value& margin);
233 void init_eval_info(const Position& pos, EvalInfo& ei);
235 template<Color Us, bool Trace>
236 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
238 template<Color Us, bool Trace>
239 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]);
241 template<Color Us, bool Trace>
242 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
244 template<Color Us, bool Trace>
245 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
248 int evaluate_space(const Position& pos, const EvalInfo& ei);
250 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
252 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
253 Score apply_weight(Score v, Score w);
254 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
255 double to_cp(Value v);
261 /// evaluate() is the main evaluation function. It always computes two
262 /// values, an endgame score and a middle game score, and interpolates
263 /// between them based on the remaining material.
265 Value evaluate(const Position& pos, Value& margin) {
266 return do_evaluate<false>(pos, margin);
270 /// trace() is like evaluate() but instead of a value returns a string suitable
271 /// to be print on stdout with the detailed descriptions and values of each
272 /// evaluation term. Used mainly for debugging.
273 std::string trace(const Position& pos) {
274 return Tracing::do_trace(pos);
278 /// init() computes evaluation weights from the corresponding UCI parameters
279 /// and setup king tables.
283 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
284 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
285 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
286 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
287 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
288 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
290 const int MaxSlope = 30;
291 const int Peak = 1280;
293 for (int t = 0, i = 1; i < 100; ++i)
295 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
297 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
298 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
308 Value do_evaluate(const Position& pos, Value& margin) {
310 assert(!pos.checkers());
313 Value margins[COLOR_NB];
314 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
315 Thread* th = pos.this_thread();
317 // margins[] store the uncertainty estimation of position's evaluation
318 // that typically is used by the search for pruning decisions.
319 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
321 // Initialize score by reading the incrementally updated scores included
322 // in the position object (material + piece square tables) and adding
323 // Tempo bonus. Score is computed from the point of view of white.
324 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
326 // Probe the material hash table
327 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
328 score += ei.mi->material_value();
330 // If we have a specialized evaluation function for the current material
331 // configuration, call it and return.
332 if (ei.mi->specialized_eval_exists())
335 return ei.mi->evaluate(pos);
338 // Probe the pawn hash table
339 ei.pi = Pawns::probe(pos, th->pawnsTable);
340 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
342 // Initialize attack and king safety bitboards
343 init_eval_info<WHITE>(pos, ei);
344 init_eval_info<BLACK>(pos, ei);
346 // Evaluate pieces and mobility
347 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
348 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
350 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
352 // Evaluate kings after all other pieces because we need complete attack
353 // information when computing the king safety evaluation.
354 score += evaluate_king<WHITE, Trace>(pos, ei, margins)
355 - evaluate_king<BLACK, Trace>(pos, ei, margins);
357 // Evaluate tactical threats, we need full attack information including king
358 score += evaluate_threats<WHITE, Trace>(pos, ei)
359 - evaluate_threats<BLACK, Trace>(pos, ei);
361 // Evaluate passed pawns, we need full attack information including king
362 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
363 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
365 // If one side has only a king, score for potential unstoppable pawns
366 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
367 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
368 - evaluate_unstoppable_pawns(pos, BLACK, ei);
370 // Evaluate space for both sides, only in middle-game.
371 if (ei.mi->space_weight())
373 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
374 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
377 // Scale winning side if position is more drawish that what it appears
378 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
379 : ei.mi->scale_factor(pos, BLACK);
381 // If we don't already have an unusual scale factor, check for opposite
382 // colored bishop endgames, and use a lower scale for those.
383 if ( ei.mi->game_phase() < PHASE_MIDGAME
384 && pos.opposite_bishops()
385 && sf == SCALE_FACTOR_NORMAL)
387 // Only the two bishops ?
388 if ( pos.non_pawn_material(WHITE) == BishopValueMg
389 && pos.non_pawn_material(BLACK) == BishopValueMg)
391 // Check for KBP vs KB with only a single pawn that is almost
392 // certainly a draw or at least two pawns.
393 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
394 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
397 // Endgame with opposite-colored bishops, but also other pieces. Still
398 // a bit drawish, but not as drawish as with only the two bishops.
399 sf = ScaleFactor(50);
402 margin = margins[pos.side_to_move()];
403 Value v = interpolate(score, ei.mi->game_phase(), sf);
405 // In case of tracing add all single evaluation contributions for both white and black
408 Tracing::add(PST, pos.psq_score());
409 Tracing::add(IMBALANCE, ei.mi->material_value());
410 Tracing::add(PAWN, ei.pi->pawns_value());
411 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
412 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
413 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
414 Tracing::add(TOTAL, score);
415 Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
416 << ", Black: " << to_cp(margins[BLACK])
417 << "\nScaling: " << std::noshowpos
418 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
419 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
420 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
421 << "Total evaluation: " << to_cp(v);
424 return pos.side_to_move() == WHITE ? v : -v;
428 // init_eval_info() initializes king bitboards for given color adding
429 // pawn attacks. To be done at the beginning of the evaluation.
432 void init_eval_info(const Position& pos, EvalInfo& ei) {
434 const Color Them = (Us == WHITE ? BLACK : WHITE);
435 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
437 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
438 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
440 // Init king safety tables only if we are going to use them
441 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
443 ei.kingRing[Them] = b | shift_bb<Down>(b);
444 b &= ei.attackedBy[Us][PAWN];
445 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
446 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
449 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
453 // evaluate_outposts() evaluates bishop and knight outposts squares
455 template<PieceType Piece, Color Us>
456 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
458 const Color Them = (Us == WHITE ? BLACK : WHITE);
460 assert (Piece == BISHOP || Piece == KNIGHT);
462 // Initial bonus based on square
463 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
465 // Increase bonus if supported by pawn, especially if the opponent has
466 // no minor piece which can exchange the outpost piece.
467 if (bonus && (ei.attackedBy[Us][PAWN] & s))
469 if ( !pos.pieces(Them, KNIGHT)
470 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
471 bonus += bonus + bonus / 2;
476 return make_score(bonus, bonus);
480 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
482 template<PieceType Piece, Color Us, bool Trace>
483 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
487 Score score = SCORE_ZERO;
489 const Color Them = (Us == WHITE ? BLACK : WHITE);
490 const Square* pl = pos.list<Piece>(Us);
492 ei.attackedBy[Us][Piece] = 0;
494 while ((s = *pl++) != SQ_NONE)
496 // Find attacked squares, including x-ray attacks for bishops and rooks
497 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
498 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
499 : pos.attacks_from<Piece>(s);
501 ei.attackedBy[Us][Piece] |= b;
503 if (b & ei.kingRing[Them])
505 ei.kingAttackersCount[Us]++;
506 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
507 Bitboard bb = b & ei.attackedBy[Them][KING];
509 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
512 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
513 : popcount<Full >(b & mobilityArea);
515 mobility[Us] += MobilityBonus[Piece][mob];
517 // Decrease score if we are attacked by an enemy pawn. Remaining part
518 // of threat evaluation must be done later when we have full attack info.
519 if (ei.attackedBy[Them][PAWN] & s)
520 score -= ThreatenedByPawn[Piece];
522 // Otherwise give a bonus if we are a bishop and can pin a piece or can
523 // give a discovered check through an x-ray attack.
524 else if ( Piece == BISHOP
525 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
526 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
529 // Penalty for bishop with same coloured pawns
531 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
533 // Penalty for knight when there are few enemy pawns
535 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
537 if (Piece == BISHOP || Piece == KNIGHT)
539 // Bishop and knight outposts squares
540 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
541 score += evaluate_outposts<Piece, Us>(pos, ei, s);
543 // Bishop or knight behind a pawn
544 if ( relative_rank(Us, s) < RANK_5
545 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
546 score += MinorBehindPawn;
549 if ( (Piece == ROOK || Piece == QUEEN)
550 && relative_rank(Us, s) >= RANK_5)
552 // Major piece on 7th rank and enemy king trapped on 8th
553 if ( relative_rank(Us, s) == RANK_7
554 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
555 score += Piece == ROOK ? RookOn7th : QueenOn7th;
557 // Major piece attacking enemy pawns on the same rank/file
558 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
560 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
563 // Special extra evaluation for rooks
566 // Give a bonus for a rook on a open or semi-open file
567 if (ei.pi->semiopen(Us, file_of(s)))
568 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
570 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
573 Square ksq = pos.king_square(Us);
575 // Penalize rooks which are trapped inside a king. Penalize more if
576 // king has lost right to castle.
577 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
578 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
579 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
580 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
583 // An important Chess960 pattern: A cornered bishop blocked by a friendly
584 // pawn diagonally in front of it is a very serious problem, especially
585 // when that pawn is also blocked.
588 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
590 const enum Piece P = make_piece(Us, PAWN);
591 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
592 if (pos.piece_on(s + d) == P)
593 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
594 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
600 Tracing::scores[Us][Piece] = score;
606 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
607 // pieces of a given color.
609 template<Color Us, bool Trace>
610 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
612 const Color Them = (Us == WHITE ? BLACK : WHITE);
614 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
615 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
617 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
618 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
619 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
620 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
622 // Sum up all attacked squares (updated in evaluate_pieces)
623 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
624 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
625 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
627 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
633 // evaluate_king() assigns bonuses and penalties to a king of a given color
635 template<Color Us, bool Trace>
636 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
638 const Color Them = (Us == WHITE ? BLACK : WHITE);
640 Bitboard undefended, b, b1, b2, safe;
642 const Square ksq = pos.king_square(Us);
644 // King shelter and enemy pawns storm
645 Score score = ei.pi->king_safety<Us>(pos, ksq);
647 // Main king safety evaluation
648 if ( ei.kingAttackersCount[Them] >= 2
649 && ei.kingAdjacentZoneAttacksCount[Them])
651 // Find the attacked squares around the king which has no defenders
652 // apart from the king itself
653 undefended = ei.attackedBy[Them][ALL_PIECES]
654 & ei.attackedBy[Us][KING]
655 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
656 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
657 | ei.attackedBy[Us][QUEEN]);
659 // Initialize the 'attackUnits' variable, which is used later on as an
660 // index to the KingDanger[] array. The initial value is based on the
661 // number and types of the enemy's attacking pieces, the number of
662 // attacked and undefended squares around our king, the square of the
663 // king, and the quality of the pawn shelter.
664 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
665 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
666 + KingExposed[relative_square(Us, ksq)]
667 - mg_value(score) / 32;
669 // Analyse enemy's safe queen contact checks. First find undefended
670 // squares around the king attacked by enemy queen...
671 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
674 // ...then remove squares not supported by another enemy piece
675 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
676 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
678 attackUnits += QueenContactCheck
680 * (Them == pos.side_to_move() ? 2 : 1);
683 // Analyse enemy's safe rook contact checks. First find undefended
684 // squares around the king attacked by enemy rooks...
685 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
687 // Consider only squares where the enemy rook gives check
688 b &= PseudoAttacks[ROOK][ksq];
692 // ...then remove squares not supported by another enemy piece
693 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
694 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
696 attackUnits += RookContactCheck
698 * (Them == pos.side_to_move() ? 2 : 1);
701 // Analyse enemy's safe distance checks for sliders and knights
702 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
704 b1 = pos.attacks_from<ROOK>(ksq) & safe;
705 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
707 // Enemy queen safe checks
708 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
710 attackUnits += QueenCheck * popcount<Max15>(b);
712 // Enemy rooks safe checks
713 b = b1 & ei.attackedBy[Them][ROOK];
715 attackUnits += RookCheck * popcount<Max15>(b);
717 // Enemy bishops safe checks
718 b = b2 & ei.attackedBy[Them][BISHOP];
720 attackUnits += BishopCheck * popcount<Max15>(b);
722 // Enemy knights safe checks
723 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
725 attackUnits += KnightCheck * popcount<Max15>(b);
727 // To index KingDanger[] attackUnits must be in [0, 99] range
728 attackUnits = std::min(99, std::max(0, attackUnits));
730 // Finally, extract the king danger score from the KingDanger[]
731 // array and subtract the score from evaluation. Set also margins[]
732 // value that will be used for pruning because this value can sometimes
733 // be very big, and so capturing a single attacking piece can therefore
734 // result in a score change far bigger than the value of the captured piece.
735 score -= KingDanger[Us == Search::RootColor][attackUnits];
736 margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
740 Tracing::scores[Us][KING] = score;
746 // evaluate_threats() assigns bonuses according to the type of attacking piece
747 // and the type of attacked one.
749 template<Color Us, bool Trace>
750 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
752 const Color Them = (Us == WHITE ? BLACK : WHITE);
754 Bitboard b, undefendedMinors, weakEnemies;
755 Score score = SCORE_ZERO;
757 // Undefended minors get penalized even if not under attack
758 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
759 & ~ei.attackedBy[Them][ALL_PIECES];
761 if (undefendedMinors)
762 score += UndefendedMinor;
764 // Enemy pieces not defended by a pawn and under our attack
765 weakEnemies = pos.pieces(Them)
766 & ~ei.attackedBy[Them][PAWN]
767 & ei.attackedBy[Us][ALL_PIECES];
769 // Add bonus according to type of attacked enemy piece and to the
770 // type of attacking piece, from knights to queens. Kings are not
771 // considered because are already handled in king evaluation.
773 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
775 b = ei.attackedBy[Us][pt1] & weakEnemies;
777 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
778 if (b & pos.pieces(pt2))
779 score += Threat[pt1][pt2];
783 Tracing::scores[Us][THREAT] = score;
789 // evaluate_passed_pawns() evaluates the passed pawns of the given color
791 template<Color Us, bool Trace>
792 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
794 const Color Them = (Us == WHITE ? BLACK : WHITE);
796 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
797 Score score = SCORE_ZERO;
799 b = ei.pi->passed_pawns(Us);
803 Square s = pop_lsb(&b);
805 assert(pos.pawn_passed(Us, s));
807 int r = int(relative_rank(Us, s) - RANK_2);
808 int rr = r * (r - 1);
810 // Base bonus based on rank
811 Value mbonus = Value(17 * rr);
812 Value ebonus = Value(7 * (rr + r + 1));
816 Square blockSq = s + pawn_push(Us);
818 // Adjust bonus based on kings proximity
819 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
820 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
822 // If blockSq is not the queening square then consider also a second push
823 if (relative_rank(Us, blockSq) != RANK_8)
824 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
826 // If the pawn is free to advance, increase bonus
827 if (pos.empty(blockSq))
829 squaresToQueen = forward_bb(Us, s);
831 // If there is an enemy rook or queen attacking the pawn from behind,
832 // add all X-ray attacks by the rook or queen. Otherwise consider only
833 // the squares in the pawn's path attacked or occupied by the enemy.
834 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
835 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
836 unsafeSquares = squaresToQueen;
838 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
840 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
841 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
842 defendedSquares = squaresToQueen;
844 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
846 // If there aren't enemy attacks huge bonus, a bit smaller if at
847 // least block square is not attacked, otherwise smallest bonus.
848 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
850 // Big bonus if the path to queen is fully defended, a bit less
851 // if at least block square is defended.
852 if (defendedSquares == squaresToQueen)
855 else if (defendedSquares & blockSq)
856 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
858 mbonus += Value(k * rr), ebonus += Value(k * rr);
862 // Increase the bonus if the passed pawn is supported by a friendly pawn
863 // on the same rank and a bit smaller if it's on the previous rank.
864 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
865 if (supportingPawns & rank_bb(s))
866 ebonus += Value(r * 20);
868 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
869 ebonus += Value(r * 12);
871 // Rook pawns are a special case: They are sometimes worse, and
872 // sometimes better than other passed pawns. It is difficult to find
873 // good rules for determining whether they are good or bad. For now,
874 // we try the following: Increase the value for rook pawns if the
875 // other side has no pieces apart from a knight, and decrease the
876 // value if the other side has a rook or queen.
877 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
879 if (pos.non_pawn_material(Them) <= KnightValueMg)
880 ebonus += ebonus / 4;
882 else if (pos.pieces(Them, ROOK, QUEEN))
883 ebonus -= ebonus / 4;
886 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
887 ebonus += ebonus / 4;
889 score += make_score(mbonus, ebonus);
894 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
896 // Add the scores to the middle game and endgame eval
897 return apply_weight(score, Weights[PassedPawns]);
901 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
902 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
903 // related to the possibility pawns are unstoppable.
905 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
907 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
909 if (!b || pos.non_pawn_material(~us))
912 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
916 // evaluate_space() computes the space evaluation for a given side. The
917 // space evaluation is a simple bonus based on the number of safe squares
918 // available for minor pieces on the central four files on ranks 2--4. Safe
919 // squares one, two or three squares behind a friendly pawn are counted
920 // twice. Finally, the space bonus is scaled by a weight taken from the
921 // material hash table. The aim is to improve play on game opening.
923 int evaluate_space(const Position& pos, const EvalInfo& ei) {
925 const Color Them = (Us == WHITE ? BLACK : WHITE);
927 // Find the safe squares for our pieces inside the area defined by
928 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
929 // pawn, or if it is undefended and attacked by an enemy piece.
930 Bitboard safe = SpaceMask[Us]
931 & ~pos.pieces(Us, PAWN)
932 & ~ei.attackedBy[Them][PAWN]
933 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
935 // Find all squares which are at most three squares behind some friendly pawn
936 Bitboard behind = pos.pieces(Us, PAWN);
937 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
938 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
940 // Since SpaceMask[Us] is fully on our half of the board
941 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
943 // Count safe + (behind & safe) with a single popcount
944 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
948 // interpolate() interpolates between a middle game and an endgame score,
949 // based on game phase. It also scales the return value by a ScaleFactor array.
951 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
953 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
954 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
955 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
957 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
958 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
959 return Value((r / GrainSize) * GrainSize); // Sign independent
962 // apply_weight() weights score v by score w trying to prevent overflow
963 Score apply_weight(Score v, Score w) {
964 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
965 (int(eg_value(v)) * eg_value(w)) / 0x100);
968 // weight_option() computes the value of an evaluation weight, by combining
969 // two UCI-configurable weights (midgame and endgame) with an internal weight.
971 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
973 // Scale option value from 100 to 256
974 int mg = Options[mgOpt] * 256 / 100;
975 int eg = Options[egOpt] * 256 / 100;
977 return apply_weight(make_score(mg, eg), internalWeight);
981 // Tracing functions definitions
983 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
985 void Tracing::add(int idx, Score wScore, Score bScore) {
987 scores[WHITE][idx] = wScore;
988 scores[BLACK][idx] = bScore;
991 void Tracing::row(const char* name, int idx) {
993 Score wScore = scores[WHITE][idx];
994 Score bScore = scores[BLACK][idx];
997 case PST: case IMBALANCE: case PAWN: case TOTAL:
998 stream << std::setw(20) << name << " | --- --- | --- --- | "
999 << std::setw(6) << to_cp(mg_value(wScore)) << " "
1000 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
1003 stream << std::setw(20) << name << " | " << std::noshowpos
1004 << std::setw(5) << to_cp(mg_value(wScore)) << " "
1005 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1006 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1007 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1009 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1010 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1014 std::string Tracing::do_trace(const Position& pos) {
1017 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1018 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1021 do_evaluate<true>(pos, margin);
1023 std::string totals = stream.str();
1026 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1027 << " | MG EG | MG EG | MG EG \n"
1028 << "---------------------+-------------+-------------+---------------\n";
1030 row("Material, PST, Tempo", PST);
1031 row("Material imbalance", IMBALANCE);
1033 row("Knights", KNIGHT);
1034 row("Bishops", BISHOP);
1036 row("Queens", QUEEN);
1037 row("Mobility", MOBILITY);
1038 row("King safety", KING);
1039 row("Threats", THREAT);
1040 row("Passed pawns", PASSED);
1041 row("Space", SPACE);
1043 stream << "---------------------+-------------+-------------+---------------\n";
1044 row("Total", TOTAL);
1047 return stream.str();