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 MinorBehindPawn = make_score(16, 0);
176 const Score UndefendedMinor = make_score(25, 10);
177 const Score TrappedRook = make_score(90, 0);
178 const Score Unstoppable = make_score( 0, 20);
180 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
181 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
182 // happen in Chess960 games.
183 const Score TrappedBishopA1H1 = make_score(50, 50);
185 // The SpaceMask[Color] contains the area of the board which is considered
186 // by the space evaluation. In the middle game, each side is given a bonus
187 // based on how many squares inside this area are safe and available for
188 // friendly minor pieces.
189 const Bitboard SpaceMask[] = {
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
191 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
194 // King danger constants and variables. The king danger scores are taken
195 // from the KingDanger[]. Various little "meta-bonuses" measuring
196 // the strength of the enemy attack are added up into an integer, which
197 // is used as an index to KingDanger[].
199 // KingAttackWeights[PieceType] contains king attack weights by piece type
200 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
202 // Bonuses for enemy's safe checks
203 const int QueenContactCheck = 6;
204 const int RookContactCheck = 4;
205 const int QueenCheck = 3;
206 const int RookCheck = 2;
207 const int BishopCheck = 1;
208 const int KnightCheck = 1;
210 // KingExposed[Square] contains penalties based on the position of the
211 // defending king, indexed by king's square (from white's point of view).
212 const int KingExposed[] = {
213 2, 0, 2, 5, 5, 2, 0, 2,
214 2, 2, 4, 8, 8, 4, 2, 2,
215 7, 10, 12, 12, 12, 12, 10, 7,
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,
220 15, 15, 15, 15, 15, 15, 15, 15
223 // KingDanger[Color][attackUnits] contains the actual king danger weighted
224 // scores, indexed by color and by a calculated integer number.
225 Score KingDanger[COLOR_NB][128];
227 // Function prototypes
229 Value do_evaluate(const Position& pos, Value& margin);
232 void init_eval_info(const Position& pos, EvalInfo& ei);
234 template<Color Us, bool Trace>
235 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility);
237 template<Color Us, bool Trace>
238 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]);
240 template<Color Us, bool Trace>
241 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
243 template<Color Us, bool Trace>
244 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
247 int evaluate_space(const Position& pos, const EvalInfo& ei);
249 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
251 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
252 Score apply_weight(Score v, Score w);
253 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
254 double to_cp(Value v);
260 /// evaluate() is the main evaluation function. It always computes two
261 /// values, an endgame score and a middle game score, and interpolates
262 /// between them based on the remaining material.
264 Value evaluate(const Position& pos, Value& margin) {
265 return do_evaluate<false>(pos, margin);
269 /// trace() is like evaluate() but instead of a value returns a string suitable
270 /// to be print on stdout with the detailed descriptions and values of each
271 /// evaluation term. Used mainly for debugging.
272 std::string trace(const Position& pos) {
273 return Tracing::do_trace(pos);
277 /// init() computes evaluation weights from the corresponding UCI parameters
278 /// and setup king tables.
282 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
283 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
284 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
285 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
286 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
287 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
289 const int MaxSlope = 30;
290 const int Peak = 1280;
292 for (int t = 0, i = 1; i < 100; ++i)
294 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
296 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
297 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
307 Value do_evaluate(const Position& pos, Value& margin) {
309 assert(!pos.checkers());
312 Value margins[COLOR_NB];
313 Score score, mobilityWhite, mobilityBlack;
314 Thread* th = pos.this_thread();
316 // margins[] store the uncertainty estimation of position's evaluation
317 // that typically is used by the search for pruning decisions.
318 margins[WHITE] = margins[BLACK] = VALUE_ZERO;
320 // Initialize score by reading the incrementally updated scores included
321 // in the position object (material + piece square tables) and adding
322 // Tempo bonus. Score is computed from the point of view of white.
323 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
325 // Probe the material hash table
326 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
327 score += ei.mi->material_value();
329 // If we have a specialized evaluation function for the current material
330 // configuration, call it and return.
331 if (ei.mi->specialized_eval_exists())
334 return ei.mi->evaluate(pos);
337 // Probe the pawn hash table
338 ei.pi = Pawns::probe(pos, th->pawnsTable);
339 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
341 // Initialize attack and king safety bitboards
342 init_eval_info<WHITE>(pos, ei);
343 init_eval_info<BLACK>(pos, ei);
345 // Evaluate pieces and mobility
346 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobilityWhite)
347 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobilityBlack);
349 score += apply_weight(mobilityWhite - mobilityBlack, Weights[Mobility]);
351 // Evaluate kings after all other pieces because we need complete attack
352 // information when computing the king safety evaluation.
353 score += evaluate_king<WHITE, Trace>(pos, ei, margins)
354 - evaluate_king<BLACK, Trace>(pos, ei, margins);
356 // Evaluate tactical threats, we need full attack information including king
357 score += evaluate_threats<WHITE, Trace>(pos, ei)
358 - evaluate_threats<BLACK, Trace>(pos, ei);
360 // Evaluate passed pawns, we need full attack information including king
361 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
362 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
364 // If one side has only a king, score for potential unstoppable pawns
365 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
366 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
367 - evaluate_unstoppable_pawns(pos, BLACK, ei);
369 // Evaluate space for both sides, only in middle-game.
370 if (ei.mi->space_weight())
372 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
373 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
376 // Scale winning side if position is more drawish that what it appears
377 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
378 : ei.mi->scale_factor(pos, BLACK);
380 // If we don't already have an unusual scale factor, check for opposite
381 // colored bishop endgames, and use a lower scale for those.
382 if ( ei.mi->game_phase() < PHASE_MIDGAME
383 && pos.opposite_bishops()
384 && sf == SCALE_FACTOR_NORMAL)
386 // Only the two bishops ?
387 if ( pos.non_pawn_material(WHITE) == BishopValueMg
388 && pos.non_pawn_material(BLACK) == BishopValueMg)
390 // Check for KBP vs KB with only a single pawn that is almost
391 // certainly a draw or at least two pawns.
392 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
393 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
396 // Endgame with opposite-colored bishops, but also other pieces. Still
397 // a bit drawish, but not as drawish as with only the two bishops.
398 sf = ScaleFactor(50);
401 margin = margins[pos.side_to_move()];
402 Value v = interpolate(score, ei.mi->game_phase(), sf);
404 // In case of tracing add all single evaluation contributions for both white and black
407 Tracing::add(PST, pos.psq_score());
408 Tracing::add(IMBALANCE, ei.mi->material_value());
409 Tracing::add(PAWN, ei.pi->pawns_value());
410 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
411 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
412 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
413 Tracing::add(TOTAL, score);
414 Tracing::stream << "\nUncertainty margin: White: " << to_cp(margins[WHITE])
415 << ", Black: " << to_cp(margins[BLACK])
416 << "\nScaling: " << std::noshowpos
417 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
418 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
419 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
420 << "Total evaluation: " << to_cp(v);
423 return pos.side_to_move() == WHITE ? v : -v;
427 // init_eval_info() initializes king bitboards for given color adding
428 // pawn attacks. To be done at the beginning of the evaluation.
431 void init_eval_info(const Position& pos, EvalInfo& ei) {
433 const Color Them = (Us == WHITE ? BLACK : WHITE);
434 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
436 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
437 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
439 // Init king safety tables only if we are going to use them
440 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
442 ei.kingRing[Them] = b | shift_bb<Down>(b);
443 b &= ei.attackedBy[Us][PAWN];
444 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
445 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
447 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
451 // evaluate_outposts() evaluates bishop and knight outposts squares
453 template<PieceType Piece, Color Us>
454 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
456 const Color Them = (Us == WHITE ? BLACK : WHITE);
458 assert (Piece == BISHOP || Piece == KNIGHT);
460 // Initial bonus based on square
461 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
463 // Increase bonus if supported by pawn, especially if the opponent has
464 // no minor piece which can exchange the outpost piece.
465 if (bonus && (ei.attackedBy[Us][PAWN] & s))
467 if ( !pos.pieces(Them, KNIGHT)
468 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
469 bonus += bonus + bonus / 2;
473 return make_score(bonus, bonus);
477 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
479 template<PieceType Piece, Color Us, bool Trace>
480 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score& mobility, Bitboard mobilityArea) {
484 Score score = SCORE_ZERO;
486 const Color Them = (Us == WHITE ? BLACK : WHITE);
487 const Square* pl = pos.list<Piece>(Us);
489 ei.attackedBy[Us][Piece] = 0;
491 while ((s = *pl++) != SQ_NONE)
493 // Find attacked squares, including x-ray attacks for bishops and rooks
494 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
495 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
496 : pos.attacks_from<Piece>(s);
498 ei.attackedBy[Us][Piece] |= b;
500 if (b & ei.kingRing[Them])
502 ei.kingAttackersCount[Us]++;
503 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
504 Bitboard bb = (b & ei.attackedBy[Them][KING]);
506 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
509 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
510 : popcount<Full >(b & mobilityArea);
512 mobility += MobilityBonus[Piece][mob];
514 // Decrease score if we are attacked by an enemy pawn. Remaining part
515 // of threat evaluation must be done later when we have full attack info.
516 if (ei.attackedBy[Them][PAWN] & s)
517 score -= ThreatenedByPawn[Piece];
519 // Otherwise give a bonus if we are a bishop and can pin a piece or can
520 // give a discovered check through an x-ray attack.
521 else if ( Piece == BISHOP
522 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
523 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
526 // Penalty for bishop with same coloured pawns
528 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
530 if (Piece == BISHOP || Piece == KNIGHT)
532 // Bishop and knight outposts squares
533 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
534 score += evaluate_outposts<Piece, Us>(pos, ei, s);
536 // Bishop or knight behind a pawn
537 if ( relative_rank(Us, s) < RANK_5
538 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
539 score += MinorBehindPawn;
542 if ( (Piece == ROOK || Piece == QUEEN)
543 && relative_rank(Us, s) >= RANK_5)
545 // Major piece on 7th rank and enemy king trapped on 8th
546 if ( relative_rank(Us, s) == RANK_7
547 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
548 score += Piece == ROOK ? RookOn7th : QueenOn7th;
550 // Major piece attacking enemy pawns on the same rank/file
551 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
553 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
556 // Special extra evaluation for rooks
559 // Give a bonus for a rook on a open or semi-open file
560 if (ei.pi->semiopen(Us, file_of(s)))
561 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
563 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
566 Square ksq = pos.king_square(Us);
568 // Penalize rooks which are trapped inside a king. Penalize more if
569 // king has lost right to castle.
570 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
571 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
572 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
573 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
576 // An important Chess960 pattern: A cornered bishop blocked by a friendly
577 // pawn diagonally in front of it is a very serious problem, especially
578 // when that pawn is also blocked.
581 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
583 const enum Piece P = make_piece(Us, PAWN);
584 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
585 if (pos.piece_on(s + d) == P)
586 score -= !pos.is_empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
587 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
593 Tracing::scores[Us][Piece] = score;
599 // evaluate_threats<>() assigns bonuses according to the type of attacking piece
600 // and the type of attacked one.
602 template<Color Us, bool Trace>
603 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
605 const Color Them = (Us == WHITE ? BLACK : WHITE);
607 Bitboard b, undefendedMinors, weakEnemies;
608 Score score = SCORE_ZERO;
610 // Undefended minors get penalized even if not under attack
611 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
612 & ~ei.attackedBy[Them][ALL_PIECES];
614 if (undefendedMinors)
615 score += UndefendedMinor;
617 // Enemy pieces not defended by a pawn and under our attack
618 weakEnemies = pos.pieces(Them)
619 & ~ei.attackedBy[Them][PAWN]
620 & ei.attackedBy[Us][ALL_PIECES];
622 // Add bonus according to type of attacked enemy piece and to the
623 // type of attacking piece, from knights to queens. Kings are not
624 // considered because are already handled in king evaluation.
626 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
628 b = ei.attackedBy[Us][pt1] & weakEnemies;
630 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
631 if (b & pos.pieces(pt2))
632 score += Threat[pt1][pt2];
636 Tracing::scores[Us][THREAT] = score;
642 // evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
643 // pieces of a given color.
645 template<Color Us, bool Trace>
646 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score& mobility) {
648 const Color Them = (Us == WHITE ? BLACK : WHITE);
650 Score score = mobility = SCORE_ZERO;
652 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
653 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
655 score += evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea);
656 score += evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea);
657 score += evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea);
658 score += evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
660 // Sum up all attacked squares
661 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
662 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
663 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
665 Tracing::scores[Us][MOBILITY] = apply_weight(mobility, Weights[Mobility]);
671 // evaluate_king<>() assigns bonuses and penalties to a king of a given color
673 template<Color Us, bool Trace>
674 Score evaluate_king(const Position& pos, const EvalInfo& ei, Value margins[]) {
676 const Color Them = (Us == WHITE ? BLACK : WHITE);
678 Bitboard undefended, b, b1, b2, safe;
680 const Square ksq = pos.king_square(Us);
682 // King shelter and enemy pawns storm
683 Score score = ei.pi->king_safety<Us>(pos, ksq);
685 // King safety. This is quite complicated, and is almost certainly far
686 // from optimally tuned.
687 if ( ei.kingAttackersCount[Them] >= 2
688 && ei.kingAdjacentZoneAttacksCount[Them])
690 // Find the attacked squares around the king which has no defenders
691 // apart from the king itself
692 undefended = ei.attackedBy[Them][ALL_PIECES] & ei.attackedBy[Us][KING];
693 undefended &= ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
694 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
695 | ei.attackedBy[Us][QUEEN]);
697 // Initialize the 'attackUnits' variable, which is used later on as an
698 // index to the KingDanger[] array. The initial value is based on the
699 // number and types of the enemy's attacking pieces, the number of
700 // attacked and undefended squares around our king, the square of the
701 // king, and the quality of the pawn shelter.
702 attackUnits = std::min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
703 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
704 + KingExposed[relative_square(Us, ksq)]
705 - mg_value(score) / 32;
707 // Analyse enemy's safe queen contact checks. First find undefended
708 // squares around the king attacked by enemy queen...
709 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
712 // ...then remove squares not supported by another enemy piece
713 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
714 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
716 attackUnits += QueenContactCheck
718 * (Them == pos.side_to_move() ? 2 : 1);
721 // Analyse enemy's safe rook contact checks. First find undefended
722 // squares around the king attacked by enemy rooks...
723 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
725 // Consider only squares where the enemy rook gives check
726 b &= PseudoAttacks[ROOK][ksq];
730 // ...then remove squares not supported by another enemy piece
731 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
732 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
734 attackUnits += RookContactCheck
736 * (Them == pos.side_to_move() ? 2 : 1);
739 // Analyse enemy's safe distance checks for sliders and knights
740 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
742 b1 = pos.attacks_from<ROOK>(ksq) & safe;
743 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
745 // Enemy queen safe checks
746 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
748 attackUnits += QueenCheck * popcount<Max15>(b);
750 // Enemy rooks safe checks
751 b = b1 & ei.attackedBy[Them][ROOK];
753 attackUnits += RookCheck * popcount<Max15>(b);
755 // Enemy bishops safe checks
756 b = b2 & ei.attackedBy[Them][BISHOP];
758 attackUnits += BishopCheck * popcount<Max15>(b);
760 // Enemy knights safe checks
761 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
763 attackUnits += KnightCheck * popcount<Max15>(b);
765 // To index KingDanger[] attackUnits must be in [0, 99] range
766 attackUnits = std::min(99, std::max(0, attackUnits));
768 // Finally, extract the king danger score from the KingDanger[]
769 // array and subtract the score from evaluation. Set also margins[]
770 // value that will be used for pruning because this value can sometimes
771 // be very big, and so capturing a single attacking piece can therefore
772 // result in a score change far bigger than the value of the captured piece.
773 score -= KingDanger[Us == Search::RootColor][attackUnits];
774 margins[Us] += mg_value(KingDanger[Us == Search::RootColor][attackUnits]);
778 Tracing::scores[Us][KING] = score;
784 // evaluate_passed_pawns<>() evaluates the passed pawns of the given color
786 template<Color Us, bool Trace>
787 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
789 const Color Them = (Us == WHITE ? BLACK : WHITE);
791 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
792 Score score = SCORE_ZERO;
794 b = ei.pi->passed_pawns(Us);
798 Square s = pop_lsb(&b);
800 assert(pos.pawn_is_passed(Us, s));
802 int r = int(relative_rank(Us, s) - RANK_2);
803 int rr = r * (r - 1);
805 // Base bonus based on rank
806 Value mbonus = Value(17 * rr);
807 Value ebonus = Value(7 * (rr + r + 1));
811 Square blockSq = s + pawn_push(Us);
813 // Adjust bonus based on kings proximity
814 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
815 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
817 // If blockSq is not the queening square then consider also a second push
818 if (relative_rank(Us, blockSq) != RANK_8)
819 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
821 // If the pawn is free to advance, increase bonus
822 if (pos.is_empty(blockSq))
824 squaresToQueen = forward_bb(Us, s);
826 // If there is an enemy rook or queen attacking the pawn from behind,
827 // add all X-ray attacks by the rook or queen. Otherwise consider only
828 // the squares in the pawn's path attacked or occupied by the enemy.
829 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
830 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
831 unsafeSquares = squaresToQueen;
833 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
835 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
836 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
837 defendedSquares = squaresToQueen;
839 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
841 // If there aren't enemy attacks huge bonus, a bit smaller if at
842 // least block square is not attacked, otherwise smallest bonus.
843 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
845 // Big bonus if the path to queen is fully defended, a bit less
846 // if at least block square is defended.
847 if (defendedSquares == squaresToQueen)
850 else if (defendedSquares & blockSq)
851 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
853 mbonus += Value(k * rr), ebonus += Value(k * rr);
857 // Increase the bonus if the passed pawn is supported by a friendly pawn
858 // on the same rank and a bit smaller if it's on the previous rank.
859 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
860 if (supportingPawns & rank_bb(s))
861 ebonus += Value(r * 20);
863 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
864 ebonus += Value(r * 12);
866 // Rook pawns are a special case: They are sometimes worse, and
867 // sometimes better than other passed pawns. It is difficult to find
868 // good rules for determining whether they are good or bad. For now,
869 // we try the following: Increase the value for rook pawns if the
870 // other side has no pieces apart from a knight, and decrease the
871 // value if the other side has a rook or queen.
872 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
874 if (pos.non_pawn_material(Them) <= KnightValueMg)
875 ebonus += ebonus / 4;
877 else if (pos.pieces(Them, ROOK, QUEEN))
878 ebonus -= ebonus / 4;
881 // Increase the bonus if we have more non-pawn pieces
882 if (pos.count<ALL_PIECES>( Us) - pos.count<PAWN>( Us) >
883 pos.count<ALL_PIECES>(Them) - pos.count<PAWN>(Them))
884 ebonus += ebonus / 4;
886 score += make_score(mbonus, ebonus);
891 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
893 // Add the scores to the middle game and endgame eval
894 return apply_weight(score, Weights[PassedPawns]);
898 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
899 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
900 // related to the possibility pawns are unstoppable.
902 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
904 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
906 if (!b || pos.non_pawn_material(~us))
909 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
913 // evaluate_space() computes the space evaluation for a given side. The
914 // space evaluation is a simple bonus based on the number of safe squares
915 // available for minor pieces on the central four files on ranks 2--4. Safe
916 // squares one, two or three squares behind a friendly pawn are counted
917 // twice. Finally, the space bonus is scaled by a weight taken from the
918 // material hash table. The aim is to improve play on game opening.
920 int evaluate_space(const Position& pos, const EvalInfo& ei) {
922 const Color Them = (Us == WHITE ? BLACK : WHITE);
924 // Find the safe squares for our pieces inside the area defined by
925 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
926 // pawn, or if it is undefended and attacked by an enemy piece.
927 Bitboard safe = SpaceMask[Us]
928 & ~pos.pieces(Us, PAWN)
929 & ~ei.attackedBy[Them][PAWN]
930 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
932 // Find all squares which are at most three squares behind some friendly pawn
933 Bitboard behind = pos.pieces(Us, PAWN);
934 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
935 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
937 // Since SpaceMask[Us] is fully on our half of the board
938 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
940 // Count safe + (behind & safe) with a single popcount
941 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
945 // interpolate() interpolates between a middle game and an endgame score,
946 // based on game phase. It also scales the return value by a ScaleFactor array.
948 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
950 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
951 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
952 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
954 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
955 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
956 return Value((r / GrainSize) * GrainSize); // Sign independent
959 // apply_weight() weights score v by score w trying to prevent overflow
960 Score apply_weight(Score v, Score w) {
961 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
962 (int(eg_value(v)) * eg_value(w)) / 0x100);
965 // weight_option() computes the value of an evaluation weight, by combining
966 // two UCI-configurable weights (midgame and endgame) with an internal weight.
968 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
970 // Scale option value from 100 to 256
971 int mg = Options[mgOpt] * 256 / 100;
972 int eg = Options[egOpt] * 256 / 100;
974 return apply_weight(make_score(mg, eg), internalWeight);
978 // Tracing functions definitions
980 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
982 void Tracing::add(int idx, Score wScore, Score bScore) {
984 scores[WHITE][idx] = wScore;
985 scores[BLACK][idx] = bScore;
988 void Tracing::row(const char* name, int idx) {
990 Score wScore = scores[WHITE][idx];
991 Score bScore = scores[BLACK][idx];
994 case PST: case IMBALANCE: case PAWN: case TOTAL:
995 stream << std::setw(20) << name << " | --- --- | --- --- | "
996 << std::setw(6) << to_cp(mg_value(wScore)) << " "
997 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
1000 stream << std::setw(20) << name << " | " << std::noshowpos
1001 << std::setw(5) << to_cp(mg_value(wScore)) << " "
1002 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1003 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1004 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1006 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1007 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1011 std::string Tracing::do_trace(const Position& pos) {
1014 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1015 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1018 do_evaluate<true>(pos, margin);
1020 std::string totals = stream.str();
1023 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1024 << " | MG EG | MG EG | MG EG \n"
1025 << "---------------------+-------------+-------------+---------------\n";
1027 row("Material, PST, Tempo", PST);
1028 row("Material imbalance", IMBALANCE);
1030 row("Knights", KNIGHT);
1031 row("Bishops", BISHOP);
1033 row("Queens", QUEEN);
1034 row("Mobility", MOBILITY);
1035 row("King safety", KING);
1036 row("Threats", THREAT);
1037 row("Passed pawns", PASSED);
1038 row("Space", SPACE);
1040 stream << "---------------------+-------------+-------------+---------------\n";
1041 row("Total", TOTAL);
1044 return stream.str();