2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 // Struct EvalInfo contains various information computed and collected
35 // by the evaluation functions.
38 // Pointers to material and pawn hash table entries
42 // attackedBy[color][piece type] is a bitboard representing all squares
43 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
44 // contains all squares attacked by the given color.
45 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
47 // kingRing[color] is the zone around the king which is considered
48 // by the king safety evaluation. This consists of the squares directly
49 // adjacent to the king, and the three (or two, for a king on an edge file)
50 // squares two ranks in front of the king. For instance, if black's king
51 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
52 // f7, g7, h7, f6, g6 and h6.
53 Bitboard kingRing[COLOR_NB];
55 // kingAttackersCount[color] is the number of pieces of the given color
56 // which attack a square in the kingRing of the enemy king.
57 int kingAttackersCount[COLOR_NB];
59 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
60 // given color which attack a square in the kingRing of the enemy king. The
61 // weights of the individual piece types are given by the variables
62 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
63 // KnightAttackWeight in evaluate.cpp
64 int kingAttackersWeight[COLOR_NB];
66 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
67 // directly adjacent to the king of the given color. Pieces which attack
68 // more than one square are counted multiple times. For instance, if black's
69 // king is on g8 and there's a white knight on g5, this knight adds
70 // 2 to kingAdjacentZoneAttacksCount[BLACK].
71 int kingAdjacentZoneAttacksCount[COLOR_NB];
73 Bitboard pinnedPieces[COLOR_NB];
78 enum Terms { // First 8 entries are for PieceType
79 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
82 Score terms[COLOR_NB][TERMS_NB];
86 double to_cp(Value v);
87 void add_term(int idx, Score term_w, Score term_b = SCORE_ZERO);
88 void format_row(std::stringstream& ss, const char* name, int idx);
89 std::string do_trace(const Position& pos);
92 // Evaluation weights, initialized from UCI options
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
94 struct Weight { int mg, eg; } Weights[6];
97 #define S(mg, eg) make_score(mg, eg)
99 // Internal evaluation weights. These are applied on top of the evaluation
100 // weights read from UCI parameters. The purpose is to be able to change
101 // the evaluation weights while keeping the default values of the UCI
102 // parameters at 100, which looks prettier.
104 // Values modified by Joona Kiiski
105 const Score WeightsInternal[] = {
106 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
109 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
110 // game, indexed by piece type and number of attacked squares not occupied by
112 const Score MobilityBonus[][32] = {
114 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
115 S( 37, 28), S( 42, 31), S(44, 33) },
116 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
117 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
118 S( 84, 79), S( 86, 81) },
119 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
120 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
121 S( 35,122), S( 36,123), S(37,124) },
122 { S(-12,-20), S( -8,-13), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
123 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
124 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
129 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
130 // indexed by piece type and square (from white's point of view).
131 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] = {
151 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
152 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[] = {
158 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
163 const Score Tempo = make_score(24, 11);
164 const Score RookOn7th = make_score(11, 20);
165 const Score RookOnPawn = make_score(10, 28);
166 const Score RookOpenFile = make_score(43, 21);
167 const Score RookSemiopenFile = make_score(19, 10);
168 const Score BishopPawns = make_score( 8, 12);
169 const Score KnightPawns = make_score( 8, 4);
170 const Score MinorBehindPawn = make_score(16, 0);
171 const Score UndefendedMinor = make_score(25, 10);
172 const Score TrappedRook = make_score(90, 0);
173 const Score Unstoppable = make_score( 0, 20);
174 const Score LowMobPenalty = make_score(40, 20);
176 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
177 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
178 // happen in Chess960 games.
179 const Score TrappedBishopA1H1 = make_score(50, 50);
181 // SpaceMask[Color] contains the area of the board which is considered
182 // by the space evaluation. In the middlegame, each side is given a bonus
183 // based on how many squares inside this area are safe and available for
184 // friendly minor pieces.
185 const Bitboard SpaceMask[] = {
186 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
187 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
190 const Bitboard EdgeBB = Rank1BB | Rank8BB | FileABB | FileHBB;
192 // King danger constants and variables. The king danger scores are taken
193 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
194 // of the enemy attack are added up into an integer, which is used as an
195 // index to KingDanger[].
197 // KingAttackWeights[PieceType] contains king attack weights by piece type
198 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
200 // Bonuses for enemy's safe checks
201 const int QueenContactCheck = 24;
202 const int RookContactCheck = 16;
203 const int QueenCheck = 12;
204 const int RookCheck = 8;
205 const int BishopCheck = 2;
206 const int KnightCheck = 3;
208 // KingDanger[Color][attackUnits] contains the actual king danger weighted
209 // scores, indexed by color and by a calculated integer number.
210 Score KingDanger[COLOR_NB][128];
212 // Function prototypes
214 Value do_evaluate(const Position& pos);
217 void init_eval_info(const Position& pos, EvalInfo& ei);
219 template<PieceType Pt, Color Us, bool Trace>
220 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea);
222 template<Color Us, bool Trace>
223 Score evaluate_king(const Position& pos, const EvalInfo& ei);
225 template<Color Us, bool Trace>
226 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
228 template<Color Us, bool Trace>
229 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
232 int evaluate_space(const Position& pos, const EvalInfo& ei);
234 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
236 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
237 Score apply_weight(Score v, const Weight& w);
238 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
244 /// evaluate() is the main evaluation function. It always computes two
245 /// values, an endgame score and a middlegame score, and interpolates
246 /// between them based on the remaining material.
248 Value evaluate(const Position& pos) {
249 return do_evaluate<false>(pos);
253 /// trace() is like evaluate(), but instead of returning a value, it returns
254 /// a string (suitable for outputting to stdout) that contains the detailed
255 /// descriptions and values of each evaluation term. It's mainly used for
257 std::string trace(const Position& pos) {
258 return Tracing::do_trace(pos);
262 /// init() computes evaluation weights from the corresponding UCI parameters
263 /// and setup king tables.
267 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
268 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
269 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
270 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
271 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
272 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
274 const int MaxSlope = 30;
275 const int Peak = 1280;
277 for (int t = 0, i = 1; i < 100; ++i)
279 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
281 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
282 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
292 Value do_evaluate(const Position& pos) {
294 assert(!pos.checkers());
297 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
298 Thread* thisThread = pos.this_thread();
300 // Initialize score by reading the incrementally updated scores included
301 // in the position object (material + piece square tables) and adding a
302 // Tempo bonus. Score is computed from the point of view of white.
303 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
305 // Probe the material hash table
306 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
307 score += ei.mi->material_value();
309 // If we have a specialized evaluation function for the current material
310 // configuration, call it and return.
311 if (ei.mi->specialized_eval_exists())
312 return ei.mi->evaluate(pos);
314 // Probe the pawn hash table
315 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
316 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
318 // Initialize attack and king safety bitboards
319 init_eval_info<WHITE>(pos, ei);
320 init_eval_info<BLACK>(pos, ei);
322 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
323 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
324 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
326 // Evaluate pieces and mobility
327 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
329 // Sum up all attacked squares (updated in evaluate_pieces)
330 ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[WHITE][PAWN] | ei.attackedBy[WHITE][KNIGHT]
331 | ei.attackedBy[WHITE][BISHOP] | ei.attackedBy[WHITE][ROOK]
332 | ei.attackedBy[WHITE][QUEEN] | ei.attackedBy[WHITE][KING];
334 ei.attackedBy[BLACK][ALL_PIECES] = ei.attackedBy[BLACK][PAWN] | ei.attackedBy[BLACK][KNIGHT]
335 | ei.attackedBy[BLACK][BISHOP] | ei.attackedBy[BLACK][ROOK]
336 | ei.attackedBy[BLACK][QUEEN] | ei.attackedBy[BLACK][KING];
338 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
340 // Evaluate kings after all other pieces because we need complete attack
341 // information when computing the king safety evaluation.
342 score += evaluate_king<WHITE, Trace>(pos, ei)
343 - evaluate_king<BLACK, Trace>(pos, ei);
345 // Evaluate tactical threats, we need full attack information including king
346 score += evaluate_threats<WHITE, Trace>(pos, ei)
347 - evaluate_threats<BLACK, Trace>(pos, ei);
349 // Evaluate passed pawns, we need full attack information including king
350 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
351 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
353 // If one side has only a king, score for potential unstoppable pawns
354 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
355 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
356 - evaluate_unstoppable_pawns(pos, BLACK, ei);
358 // Evaluate space for both sides, only in middlegame
359 if (ei.mi->space_weight())
361 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
362 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
365 // Scale winning side if position is more drawish than it appears
366 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
367 : ei.mi->scale_factor(pos, BLACK);
369 // If we don't already have an unusual scale factor, check for opposite
370 // colored bishop endgames, and use a lower scale for those.
371 if ( ei.mi->game_phase() < PHASE_MIDGAME
372 && pos.opposite_bishops()
373 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
375 // Ignoring any pawns, do both sides only have a single bishop and no
377 if ( pos.non_pawn_material(WHITE) == BishopValueMg
378 && pos.non_pawn_material(BLACK) == BishopValueMg)
380 // Check for KBP vs KB with only a single pawn that is almost
381 // certainly a draw or at least two pawns.
382 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
383 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
386 // Endgame with opposite-colored bishops, but also other pieces. Still
387 // a bit drawish, but not as drawish as with only the two bishops.
388 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
391 Value v = interpolate(score, ei.mi->game_phase(), sf);
393 // In case of tracing add all single evaluation contributions for both white and black
396 Tracing::add_term(Tracing::PST, pos.psq_score());
397 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
398 Tracing::add_term(PAWN, ei.pi->pawns_value());
399 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
400 , apply_weight(mobility[BLACK], Weights[Mobility]));
401 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
402 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
403 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
404 Tracing::add_term(Tracing::TOTAL, score);
409 return pos.side_to_move() == WHITE ? v : -v;
413 // init_eval_info() initializes king bitboards for given color adding
414 // pawn attacks. To be done at the beginning of the evaluation.
417 void init_eval_info(const Position& pos, EvalInfo& ei) {
419 const Color Them = (Us == WHITE ? BLACK : WHITE);
420 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
422 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
424 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
425 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
427 // Init king safety tables only if we are going to use them
428 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
430 ei.kingRing[Them] = b | shift_bb<Down>(b);
431 b &= ei.attackedBy[Us][PAWN];
432 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
433 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
436 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
440 // evaluate_outposts() evaluates bishop and knight outpost squares
442 template<PieceType Pt, Color Us>
443 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
445 const Color Them = (Us == WHITE ? BLACK : WHITE);
447 assert (Pt == BISHOP || Pt == KNIGHT);
449 // Initial bonus based on square
450 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
452 // Increase bonus if supported by pawn, especially if the opponent has
453 // no minor piece which can trade with the outpost piece.
454 if (bonus && (ei.attackedBy[Us][PAWN] & s))
456 if ( !pos.pieces(Them, KNIGHT)
457 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
458 bonus += bonus + bonus / 2;
463 return make_score(bonus, bonus);
467 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
469 template<PieceType Pt, Color Us, bool Trace>
470 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
474 Score score = SCORE_ZERO;
476 const Color Them = (Us == WHITE ? BLACK : WHITE);
477 const Square* pl = pos.list<Pt>(Us);
479 ei.attackedBy[Us][Pt] = 0;
481 while ((s = *pl++) != SQ_NONE)
483 // Find attacked squares, including x-ray attacks for bishops and rooks
484 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
485 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
486 : pos.attacks_from<Pt>(s);
488 if (ei.pinnedPieces[Us] & s)
489 b &= LineBB[pos.king_square(Us)][s];
491 ei.attackedBy[Us][Pt] |= b;
493 if (b & ei.kingRing[Them])
495 ei.kingAttackersCount[Us]++;
496 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
497 Bitboard bb = b & ei.attackedBy[Them][KING];
499 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
503 b &= ~( ei.attackedBy[Them][KNIGHT]
504 | ei.attackedBy[Them][BISHOP]
505 | ei.attackedBy[Them][ROOK]);
507 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
508 : popcount<Full >(b & mobilityArea[Us]);
510 mobility[Us] += MobilityBonus[Pt][mob];
512 if (mob <= 1 && (EdgeBB & s))
513 score -= LowMobPenalty;
515 // Decrease score if we are attacked by an enemy pawn. The remaining part
516 // of threat evaluation must be done later when we have full attack info.
517 if (ei.attackedBy[Them][PAWN] & s)
518 score -= ThreatenedByPawn[Pt];
520 if (Pt == BISHOP || Pt == KNIGHT)
522 // Penalty for bishop with same colored pawns
524 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
526 // Penalty for knight when there are few enemy pawns
528 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
530 // Bishop and knight outposts squares
531 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
532 score += evaluate_outposts<Pt, Us>(pos, ei, s);
534 // Bishop or knight behind a pawn
535 if ( relative_rank(Us, s) < RANK_5
536 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
537 score += MinorBehindPawn;
542 // Rook on 7th rank and enemy king trapped on 8th
543 if ( relative_rank(Us, s) == RANK_7
544 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
547 // Rook piece attacking enemy pawns on the same rank/file
548 if (relative_rank(Us, s) >= RANK_5)
550 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
552 score += popcount<Max15>(pawns) * RookOnPawn;
555 // Give a bonus for a rook on a open or semi-open file
556 if (ei.pi->semiopen(Us, file_of(s)))
557 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
559 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
562 Square ksq = pos.king_square(Us);
564 // Penalize rooks which are trapped by a king. Penalize more if the
565 // king has lost its castling capability.
566 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
567 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
568 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
569 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
572 // An important Chess960 pattern: A cornered bishop blocked by a friendly
573 // pawn diagonally in front of it is a very serious problem, especially
574 // when that pawn is also blocked.
577 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
579 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
580 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
581 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
582 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
588 Tracing::terms[Us][Pt] = score;
590 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
592 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
596 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
598 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
601 // evaluate_king() assigns bonuses and penalties to a king of a given color
603 template<Color Us, bool Trace>
604 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
606 const Color Them = (Us == WHITE ? BLACK : WHITE);
608 Bitboard undefended, b, b1, b2, safe;
610 const Square ksq = pos.king_square(Us);
612 // King shelter and enemy pawns storm
613 Score score = ei.pi->king_safety<Us>(pos, ksq);
615 // Main king safety evaluation
616 if (ei.kingAttackersCount[Them])
618 // Find the attacked squares around the king which have no defenders
619 // apart from the king itself
620 undefended = ei.attackedBy[Them][ALL_PIECES]
621 & ei.attackedBy[Us][KING]
622 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
623 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
624 | ei.attackedBy[Us][QUEEN]);
626 // Initialize the 'attackUnits' variable, which is used later on as an
627 // index to the KingDanger[] array. The initial value is based on the
628 // number and types of the enemy's attacking pieces, the number of
629 // attacked and undefended squares around our king and the quality of
630 // the pawn shelter (current 'score' value).
631 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
632 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
633 + 2 * (ei.pinnedPieces[Us] != 0)
634 - mg_value(score) / 32;
636 // Analyse the enemy's safe queen contact checks. Firstly, find the
637 // undefended squares around the king that are attacked by the enemy's
639 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
642 // ...and then remove squares not supported by another enemy piece
643 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
644 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
647 attackUnits += QueenContactCheck
649 * (Them == pos.side_to_move() ? 2 : 1);
652 // Analyse the enemy's safe rook contact checks. Firstly, find the
653 // undefended squares around the king that are attacked by the enemy's
655 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
657 // Consider only squares where the enemy's rook gives check
658 b &= PseudoAttacks[ROOK][ksq];
662 // ...and then remove squares not supported by another enemy piece
663 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
664 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
667 attackUnits += RookContactCheck
669 * (Them == pos.side_to_move() ? 2 : 1);
672 // Analyse the enemy's safe distance checks for sliders and knights
673 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
675 b1 = pos.attacks_from<ROOK>(ksq) & safe;
676 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
678 // Enemy queen safe checks
679 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
681 attackUnits += QueenCheck * popcount<Max15>(b);
683 // Enemy rooks safe checks
684 b = b1 & ei.attackedBy[Them][ROOK];
686 attackUnits += RookCheck * popcount<Max15>(b);
688 // Enemy bishops safe checks
689 b = b2 & ei.attackedBy[Them][BISHOP];
691 attackUnits += BishopCheck * popcount<Max15>(b);
693 // Enemy knights safe checks
694 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
696 attackUnits += KnightCheck * popcount<Max15>(b);
698 // To index KingDanger[] attackUnits must be in [0, 99] range
699 attackUnits = std::min(99, std::max(0, attackUnits));
701 // Finally, extract the king danger score from the KingDanger[]
702 // array and subtract the score from evaluation.
703 score -= KingDanger[Us == Search::RootColor][attackUnits];
707 Tracing::terms[Us][KING] = score;
713 // evaluate_threats() assigns bonuses according to the type of attacking piece
714 // and the type of attacked one.
716 template<Color Us, bool Trace>
717 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
719 const Color Them = (Us == WHITE ? BLACK : WHITE);
721 Bitboard b, undefendedMinors, weakEnemies;
722 Score score = SCORE_ZERO;
724 // Undefended minors get penalized even if they are not under attack
725 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
726 & ~ei.attackedBy[Them][ALL_PIECES];
728 if (undefendedMinors)
729 score += UndefendedMinor;
731 // Enemy pieces not defended by a pawn and under our attack
732 weakEnemies = pos.pieces(Them)
733 & ~ei.attackedBy[Them][PAWN]
734 & ei.attackedBy[Us][ALL_PIECES];
736 // Add a bonus according if the attacking pieces are minor or major
739 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
741 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
743 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
745 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
749 Tracing::terms[Us][Tracing::THREAT] = score;
755 // evaluate_passed_pawns() evaluates the passed pawns of the given color
757 template<Color Us, bool Trace>
758 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
760 const Color Them = (Us == WHITE ? BLACK : WHITE);
762 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
763 Score score = SCORE_ZERO;
765 b = ei.pi->passed_pawns(Us);
769 Square s = pop_lsb(&b);
771 assert(pos.pawn_passed(Us, s));
773 int r = int(relative_rank(Us, s) - RANK_2);
774 int rr = r * (r - 1);
776 // Base bonus based on rank
777 Value mbonus = Value(17 * rr);
778 Value ebonus = Value(7 * (rr + r + 1));
782 Square blockSq = s + pawn_push(Us);
784 // Adjust bonus based on the king's proximity
785 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
786 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
788 // If blockSq is not the queening square then consider also a second push
789 if (relative_rank(Us, blockSq) != RANK_8)
790 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
792 // If the pawn is free to advance, then increase the bonus
793 if (pos.empty(blockSq))
795 squaresToQueen = forward_bb(Us, s);
797 // If there is an enemy rook or queen attacking the pawn from behind,
798 // add all X-ray attacks by the rook or queen. Otherwise consider only
799 // the squares in the pawn's path attacked or occupied by the enemy.
800 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
801 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
802 unsafeSquares = squaresToQueen;
804 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
806 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
807 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
808 defendedSquares = squaresToQueen;
810 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
812 // If there aren't any enemy attacks, then assign a huge bonus.
813 // The bonus will be a bit smaller if at least the block square
814 // isn't attacked, otherwise assign the smallest possible bonus.
815 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
817 // Assign a big bonus if the path to the queen is fully defended,
818 // otherwise assign a bit less of a bonus if at least the block
819 // square is defended.
820 if (defendedSquares == squaresToQueen)
823 else if (defendedSquares & blockSq)
824 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
826 mbonus += Value(k * rr), ebonus += Value(k * rr);
830 // Increase the bonus if the passed pawn is supported by a friendly pawn
831 // on the same rank and a bit smaller if it's on the previous rank.
832 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
833 if (supportingPawns & rank_bb(s))
834 ebonus += Value(r * 20);
836 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
837 ebonus += Value(r * 12);
839 // Rook pawns are a special case: They are sometimes worse, and
840 // sometimes better than other passed pawns. It is difficult to find
841 // good rules for determining whether they are good or bad. For now,
842 // we try the following: Increase the value for rook pawns if the
843 // other side has no pieces apart from a knight, and decrease the
844 // value if the other side has a rook or queen.
845 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
847 if (pos.non_pawn_material(Them) <= KnightValueMg)
848 ebonus += ebonus / 4;
850 else if (pos.pieces(Them, ROOK, QUEEN))
851 ebonus -= ebonus / 4;
854 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
855 ebonus += ebonus / 4;
857 score += make_score(mbonus, ebonus);
861 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
863 // Add the scores to the middlegame and endgame eval
864 return apply_weight(score, Weights[PassedPawns]);
868 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
869 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
870 // related to the possibility that pawns are unstoppable.
872 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
874 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
876 if (!b || pos.non_pawn_material(~us))
879 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
883 // evaluate_space() computes the space evaluation for a given side. The
884 // space evaluation is a simple bonus based on the number of safe squares
885 // available for minor pieces on the central four files on ranks 2--4. Safe
886 // squares one, two or three squares behind a friendly pawn are counted
887 // twice. Finally, the space bonus is scaled by a weight taken from the
888 // material hash table. The aim is to improve play on game opening.
890 int evaluate_space(const Position& pos, const EvalInfo& ei) {
892 const Color Them = (Us == WHITE ? BLACK : WHITE);
894 // Find the safe squares for our pieces inside the area defined by
895 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
896 // pawn, or if it is undefended and attacked by an enemy piece.
897 Bitboard safe = SpaceMask[Us]
898 & ~pos.pieces(Us, PAWN)
899 & ~ei.attackedBy[Them][PAWN]
900 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
902 // Find all squares which are at most three squares behind some friendly pawn
903 Bitboard behind = pos.pieces(Us, PAWN);
904 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
905 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
907 // Since SpaceMask[Us] is fully on our half of the board
908 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
910 // Count safe + (behind & safe) with a single popcount
911 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
915 // interpolate() interpolates between a middlegame and an endgame score,
916 // based on game phase. It also scales the return value by a ScaleFactor array.
918 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
920 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
921 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
922 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
924 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
925 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
928 // apply_weight() weights score v by score w trying to prevent overflow
929 Score apply_weight(Score v, const Weight& w) {
931 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
934 // weight_option() computes the value of an evaluation weight, by combining
935 // two UCI-configurable weights (midgame and endgame) with an internal weight.
937 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
939 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
940 Options[egOpt] * eg_value(internalWeight) / 100 };
945 // Tracing function definitions
947 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
949 void Tracing::add_term(int idx, Score wScore, Score bScore) {
951 terms[WHITE][idx] = wScore;
952 terms[BLACK][idx] = bScore;
955 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
957 Score wScore = terms[WHITE][idx];
958 Score bScore = terms[BLACK][idx];
961 case PST: case IMBALANCE: case PAWN: case TOTAL:
962 ss << std::setw(20) << name << " | --- --- | --- --- | "
963 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
964 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
967 ss << std::setw(20) << name << " | " << std::noshowpos
968 << std::setw(5) << to_cp(mg_value(wScore)) << " "
969 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
970 << std::setw(5) << to_cp(mg_value(bScore)) << " "
971 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
972 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
973 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
977 std::string Tracing::do_trace(const Position& pos) {
979 std::memset(terms, 0, sizeof(terms));
981 Value v = do_evaluate<true>(pos);
982 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
984 std::stringstream ss;
985 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
986 << " Eval term | White | Black | Total \n"
987 << " | MG EG | MG EG | MG EG \n"
988 << "---------------------+-------------+-------------+-------------\n";
990 format_row(ss, "Material, PST, Tempo", PST);
991 format_row(ss, "Material imbalance", IMBALANCE);
992 format_row(ss, "Pawns", PAWN);
993 format_row(ss, "Knights", KNIGHT);
994 format_row(ss, "Bishops", BISHOP);
995 format_row(ss, "Rooks", ROOK);
996 format_row(ss, "Queens", QUEEN);
997 format_row(ss, "Mobility", MOBILITY);
998 format_row(ss, "King safety", KING);
999 format_row(ss, "Threats", THREAT);
1000 format_row(ss, "Passed pawns", PASSED);
1001 format_row(ss, "Space", SPACE);
1003 ss << "---------------------+-------------+-------------+-------------\n";
1004 format_row(ss, "Total", TOTAL);
1006 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";