2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 enum ExtendedPieceType { // Used for tracing
35 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL
40 Score scores[COLOR_NB][TOTAL + 1];
41 std::stringstream stream;
43 void add(int idx, Score term_w, Score term_b = SCORE_ZERO);
44 void row(const char* name, int idx);
45 std::string do_trace(const Position& pos);
48 // Struct EvalInfo contains various information computed and collected
49 // by the evaluation functions.
52 // Pointers to material and pawn hash table entries
56 // attackedBy[color][piece type] is a bitboard representing all squares
57 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
58 // contains all squares attacked by the given color.
59 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
61 // kingRing[color] is the zone around the king which is considered
62 // by the king safety evaluation. This consists of the squares directly
63 // adjacent to the king, and the three (or two, for a king on an edge file)
64 // squares two ranks in front of the king. For instance, if black's king
65 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
66 // f7, g7, h7, f6, g6 and h6.
67 Bitboard kingRing[COLOR_NB];
69 // kingAttackersCount[color] is the number of pieces of the given color
70 // which attack a square in the kingRing of the enemy king.
71 int kingAttackersCount[COLOR_NB];
73 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
74 // given color which attack a square in the kingRing of the enemy king. The
75 // weights of the individual piece types are given by the variables
76 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
77 // KnightAttackWeight in evaluate.cpp
78 int kingAttackersWeight[COLOR_NB];
80 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
81 // directly adjacent to the king of the given color. Pieces which attack
82 // more than one square are counted multiple times. For instance, if black's
83 // king is on g8 and there's a white knight on g5, this knight adds
84 // 2 to kingAdjacentZoneAttacksCount[BLACK].
85 int kingAdjacentZoneAttacksCount[COLOR_NB];
87 Bitboard pinnedPieces[COLOR_NB];
90 // Evaluation grain size, must be a power of 2
91 const int GrainSize = 4;
93 // Evaluation weights, initialized from UCI options
94 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
98 #define S(mg, eg) make_score(mg, eg)
100 // Internal evaluation weights. These are applied on top of the evaluation
101 // weights read from UCI parameters. The purpose is to be able to change
102 // the evaluation weights while keeping the default values of the UCI
103 // parameters at 100, which looks prettier.
105 // Values modified by Joona Kiiski
106 const Score WeightsInternal[] = {
107 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
110 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
111 // game, indexed by piece type and number of attacked squares not occupied by
113 const Score MobilityBonus[][32] = {
115 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
116 S( 37, 28), S( 42, 31), S(44, 33) },
117 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
118 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
119 S( 84, 79), S( 86, 81) },
120 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
121 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
122 S( 35,122), S( 36,123), S(37,124) },
123 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
124 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
125 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
127 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
130 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
131 // indexed by piece type and square (from white's point of view).
132 const Value Outpost[][SQUARE_NB] = {
135 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
136 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
137 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
138 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
139 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
140 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
142 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
143 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
144 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
145 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
146 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
147 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
150 // Threat[attacking][attacked] contains bonuses according to which piece
151 // type attacks which one.
152 const Score Threat[][PIECE_TYPE_NB] = {
153 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
154 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) }, // Major
157 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
158 // type is attacked by an enemy pawn.
159 const Score ThreatenedByPawn[] = {
160 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
165 const Score Tempo = make_score(24, 11);
166 const Score RookOn7th = make_score(11, 20);
167 const Score QueenOn7th = make_score( 3, 8);
168 const Score RookOnPawn = make_score(10, 28);
169 const Score QueenOnPawn = make_score( 4, 20);
170 const Score RookOpenFile = make_score(43, 21);
171 const Score RookSemiopenFile = make_score(19, 10);
172 const Score BishopPawns = make_score( 8, 12);
173 const Score KnightPawns = make_score( 8, 4);
174 const Score MinorBehindPawn = make_score(16, 0);
175 const Score UndefendedMinor = make_score(25, 10);
176 const Score TrappedRook = make_score(90, 0);
177 const Score Unstoppable = make_score( 0, 20);
179 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
180 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
181 // happen in Chess960 games.
182 const Score TrappedBishopA1H1 = make_score(50, 50);
184 // SpaceMask[Color] contains the area of the board which is considered
185 // by the space evaluation. In the middlegame, each side is given a bonus
186 // based on how many squares inside this area are safe and available for
187 // friendly minor pieces.
188 const Bitboard SpaceMask[] = {
189 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
193 // King danger constants and variables. The king danger scores are taken
194 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
195 // of the enemy attack are added up into an integer, which is used as an
196 // index to KingDanger[].
198 // KingAttackWeights[PieceType] contains king attack weights by piece type
199 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
201 // Bonuses for enemy's safe checks
202 const int QueenContactCheck = 24;
203 const int RookContactCheck = 16;
204 const int QueenCheck = 12;
205 const int RookCheck = 8;
206 const int BishopCheck = 2;
207 const int KnightCheck = 3;
209 // KingDanger[Color][attackUnits] contains the actual king danger weighted
210 // scores, indexed by color and by a calculated integer number.
211 Score KingDanger[COLOR_NB][128];
213 // Function prototypes
215 Value do_evaluate(const Position& pos);
218 void init_eval_info(const Position& pos, EvalInfo& ei);
220 template<Color Us, bool Trace>
221 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
223 template<Color Us, bool Trace>
224 Score evaluate_king(const Position& pos, const EvalInfo& ei);
226 template<Color Us, bool Trace>
227 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
229 template<Color Us, bool Trace>
230 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
233 int evaluate_space(const Position& pos, const EvalInfo& ei);
235 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
237 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
238 Score apply_weight(Score v, Score w);
239 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
240 double to_cp(Value v);
246 /// evaluate() is the main evaluation function. It always computes two
247 /// values, an endgame score and a middlegame score, and interpolates
248 /// between them based on the remaining material.
250 Value evaluate(const Position& pos) {
251 return do_evaluate<false>(pos);
255 /// trace() is like evaluate(), but instead of returning a value, it returns
256 /// a string (suitable for outputting to stdout) that contains the detailed
257 /// descriptions and values of each evaluation term. It's mainly used for
259 std::string trace(const Position& pos) {
260 return Tracing::do_trace(pos);
264 /// init() computes evaluation weights from the corresponding UCI parameters
265 /// and setup king tables.
269 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
270 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
271 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
272 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
273 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
274 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
276 const int MaxSlope = 30;
277 const int Peak = 1280;
279 for (int t = 0, i = 1; i < 100; ++i)
281 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
283 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
284 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
294 Value do_evaluate(const Position& pos) {
296 assert(!pos.checkers());
299 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
300 Thread* th = pos.this_thread();
302 // Initialize score by reading the incrementally updated scores included
303 // in the position object (material + piece square tables) and adding a
304 // Tempo bonus. Score is computed from the point of view of white.
305 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
307 // Probe the material hash table
308 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
309 score += ei.mi->material_value();
311 // If we have a specialized evaluation function for the current material
312 // configuration, call it and return.
313 if (ei.mi->specialized_eval_exists())
314 return ei.mi->evaluate(pos);
316 // Probe the pawn hash table
317 ei.pi = Pawns::probe(pos, th->pawnsTable);
318 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
320 // Initialize attack and king safety bitboards
321 init_eval_info<WHITE>(pos, ei);
322 init_eval_info<BLACK>(pos, ei);
324 // Evaluate pieces and mobility
325 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
326 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
328 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
330 // Evaluate kings after all other pieces because we need complete attack
331 // information when computing the king safety evaluation.
332 score += evaluate_king<WHITE, Trace>(pos, ei)
333 - evaluate_king<BLACK, Trace>(pos, ei);
335 // Evaluate tactical threats, we need full attack information including king
336 score += evaluate_threats<WHITE, Trace>(pos, ei)
337 - evaluate_threats<BLACK, Trace>(pos, ei);
339 // Evaluate passed pawns, we need full attack information including king
340 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
341 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
343 // If one side has only a king, score for potential unstoppable pawns
344 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
345 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
346 - evaluate_unstoppable_pawns(pos, BLACK, ei);
348 // Evaluate space for both sides, only in middlegame
349 if (ei.mi->space_weight())
351 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
352 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
355 // Scale winning side if position is more drawish than it appears
356 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
357 : ei.mi->scale_factor(pos, BLACK);
359 // If we don't already have an unusual scale factor, check for opposite
360 // colored bishop endgames, and use a lower scale for those.
361 if ( ei.mi->game_phase() < PHASE_MIDGAME
362 && pos.opposite_bishops()
363 && sf == SCALE_FACTOR_NORMAL)
365 // Ignoring any pawns, do both sides only have a single bishop and no
367 if ( pos.non_pawn_material(WHITE) == BishopValueMg
368 && pos.non_pawn_material(BLACK) == BishopValueMg)
370 // Check for KBP vs KB with only a single pawn that is almost
371 // certainly a draw or at least two pawns.
372 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
373 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
376 // Endgame with opposite-colored bishops, but also other pieces. Still
377 // a bit drawish, but not as drawish as with only the two bishops.
378 sf = ScaleFactor(50);
381 Value v = interpolate(score, ei.mi->game_phase(), sf);
383 // In case of tracing add all single evaluation contributions for both white and black
386 Tracing::add(PST, pos.psq_score());
387 Tracing::add(IMBALANCE, ei.mi->material_value());
388 Tracing::add(PAWN, ei.pi->pawns_value());
389 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
390 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
391 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
392 Tracing::add(TOTAL, score);
393 Tracing::stream << "\nScaling: " << std::noshowpos
394 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
395 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
396 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
397 << "Total evaluation: " << to_cp(v);
400 return pos.side_to_move() == WHITE ? v : -v;
404 // init_eval_info() initializes king bitboards for given color adding
405 // pawn attacks. To be done at the beginning of the evaluation.
408 void init_eval_info(const Position& pos, EvalInfo& ei) {
410 const Color Them = (Us == WHITE ? BLACK : WHITE);
411 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
413 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
415 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
416 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
418 // Init king safety tables only if we are going to use them
419 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
421 ei.kingRing[Them] = b | shift_bb<Down>(b);
422 b &= ei.attackedBy[Us][PAWN];
423 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
424 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
427 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
431 // evaluate_outposts() evaluates bishop and knight outpost squares
433 template<PieceType Piece, Color Us>
434 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
436 const Color Them = (Us == WHITE ? BLACK : WHITE);
438 assert (Piece == BISHOP || Piece == KNIGHT);
440 // Initial bonus based on square
441 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
443 // Increase bonus if supported by pawn, especially if the opponent has
444 // no minor piece which can trade with the outpost piece.
445 if (bonus && (ei.attackedBy[Us][PAWN] & s))
447 if ( !pos.pieces(Them, KNIGHT)
448 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
449 bonus += bonus + bonus / 2;
454 return make_score(bonus, bonus);
458 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
460 template<PieceType Piece, Color Us, bool Trace>
461 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
465 Score score = SCORE_ZERO;
467 const Color Them = (Us == WHITE ? BLACK : WHITE);
468 const Square* pl = pos.list<Piece>(Us);
470 ei.attackedBy[Us][Piece] = 0;
472 while ((s = *pl++) != SQ_NONE)
474 // Find attacked squares, including x-ray attacks for bishops and rooks
475 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
476 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
477 : pos.attacks_from<Piece>(s);
479 if (ei.pinnedPieces[Us] & s)
480 b &= LineBB[pos.king_square(Us)][s];
482 ei.attackedBy[Us][Piece] |= b;
484 if (b & ei.kingRing[Them])
486 ei.kingAttackersCount[Us]++;
487 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
488 Bitboard bb = b & ei.attackedBy[Them][KING];
490 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
493 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
494 : popcount<Full >(b & mobilityArea);
496 mobility[Us] += MobilityBonus[Piece][mob];
498 // Decrease score if we are attacked by an enemy pawn. The remaining part
499 // of threat evaluation must be done later when we have full attack info.
500 if (ei.attackedBy[Them][PAWN] & s)
501 score -= ThreatenedByPawn[Piece];
503 // Penalty for bishop with same coloured pawns
505 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
507 // Penalty for knight when there are few enemy pawns
509 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
511 if (Piece == BISHOP || Piece == KNIGHT)
513 // Bishop and knight outposts squares
514 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
515 score += evaluate_outposts<Piece, Us>(pos, ei, s);
517 // Bishop or knight behind a pawn
518 if ( relative_rank(Us, s) < RANK_5
519 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
520 score += MinorBehindPawn;
523 if ( (Piece == ROOK || Piece == QUEEN)
524 && relative_rank(Us, s) >= RANK_5)
526 // Major piece on 7th rank and enemy king trapped on 8th
527 if ( relative_rank(Us, s) == RANK_7
528 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
529 score += Piece == ROOK ? RookOn7th : QueenOn7th;
531 // Major piece attacking enemy pawns on the same rank/file
532 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
534 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
537 // Special extra evaluation for rooks
540 // Give a bonus for a rook on a open or semi-open file
541 if (ei.pi->semiopen(Us, file_of(s)))
542 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
544 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
547 Square ksq = pos.king_square(Us);
549 // Penalize rooks which are trapped by a king. Penalize more if the
550 // king has lost its castling capability.
551 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
552 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
553 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
554 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
557 // An important Chess960 pattern: A cornered bishop blocked by a friendly
558 // pawn diagonally in front of it is a very serious problem, especially
559 // when that pawn is also blocked.
562 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
564 const enum Piece P = make_piece(Us, PAWN);
565 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
566 if (pos.piece_on(s + d) == P)
567 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
568 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
574 Tracing::scores[Us][Piece] = score;
580 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
581 // pieces of a given color.
583 template<Color Us, bool Trace>
584 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
586 const Color Them = (Us == WHITE ? BLACK : WHITE);
588 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
589 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
591 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
592 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
593 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
594 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
596 // Sum up all attacked squares (updated in evaluate_pieces)
597 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
598 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
599 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
601 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
607 // evaluate_king() assigns bonuses and penalties to a king of a given color
609 template<Color Us, bool Trace>
610 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
612 const Color Them = (Us == WHITE ? BLACK : WHITE);
614 Bitboard undefended, b, b1, b2, safe;
616 const Square ksq = pos.king_square(Us);
618 // King shelter and enemy pawns storm
619 Score score = ei.pi->king_safety<Us>(pos, ksq);
621 // Main king safety evaluation
622 if (ei.kingAttackersCount[Them])
624 // Find the attacked squares around the king which have no defenders
625 // apart from the king itself
626 undefended = ei.attackedBy[Them][ALL_PIECES]
627 & ei.attackedBy[Us][KING]
628 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
629 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
630 | ei.attackedBy[Us][QUEEN]);
632 // Initialize the 'attackUnits' variable, which is used later on as an
633 // index to the KingDanger[] array. The initial value is based on the
634 // number and types of the enemy's attacking pieces, the number of
635 // attacked and undefended squares around our king and the quality of
636 // the pawn shelter (current 'score' value).
637 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
638 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
639 - mg_value(score) / 32;
641 // Analyse the enemy's safe queen contact checks. Firstly, find the
642 // undefended squares around the king that are attacked by the enemy's
644 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
647 // ...and then remove squares not supported by another enemy piece
648 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
649 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
651 attackUnits += QueenContactCheck
653 * (Them == pos.side_to_move() ? 2 : 1);
656 // Analyse the enemy's safe rook contact checks. Firstly, find the
657 // undefended squares around the king that are attacked by the enemy's
659 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
661 // Consider only squares where the enemy's rook gives check
662 b &= PseudoAttacks[ROOK][ksq];
666 // ...and then remove squares not supported by another enemy piece
667 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
668 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
670 attackUnits += RookContactCheck
672 * (Them == pos.side_to_move() ? 2 : 1);
675 // Analyse the enemy's safe distance checks for sliders and knights
676 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
678 b1 = pos.attacks_from<ROOK>(ksq) & safe;
679 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
681 // Enemy queen safe checks
682 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
684 attackUnits += QueenCheck * popcount<Max15>(b);
686 // Enemy rooks safe checks
687 b = b1 & ei.attackedBy[Them][ROOK];
689 attackUnits += RookCheck * popcount<Max15>(b);
691 // Enemy bishops safe checks
692 b = b2 & ei.attackedBy[Them][BISHOP];
694 attackUnits += BishopCheck * popcount<Max15>(b);
696 // Enemy knights safe checks
697 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
699 attackUnits += KnightCheck * popcount<Max15>(b);
701 // To index KingDanger[] attackUnits must be in [0, 99] range
702 attackUnits = std::min(99, std::max(0, attackUnits));
704 // Finally, extract the king danger score from the KingDanger[]
705 // array and subtract the score from evaluation.
706 score -= KingDanger[Us == Search::RootColor][attackUnits];
710 Tracing::scores[Us][KING] = score;
716 // evaluate_threats() assigns bonuses according to the type of attacking piece
717 // and the type of attacked one.
719 template<Color Us, bool Trace>
720 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
722 const Color Them = (Us == WHITE ? BLACK : WHITE);
724 Bitboard b, undefendedMinors, weakEnemies;
725 Score score = SCORE_ZERO;
727 // Undefended minors get penalized even if they are not under attack
728 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
729 & ~ei.attackedBy[Them][ALL_PIECES];
731 if (undefendedMinors)
732 score += UndefendedMinor;
734 // Enemy pieces not defended by a pawn and under our attack
735 weakEnemies = pos.pieces(Them)
736 & ~ei.attackedBy[Them][PAWN]
737 & ei.attackedBy[Us][ALL_PIECES];
739 // Add a bonus according if the attacking pieces are minor or major
742 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
744 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
746 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
748 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
752 Tracing::scores[Us][THREAT] = score;
758 // evaluate_passed_pawns() evaluates the passed pawns of the given color
760 template<Color Us, bool Trace>
761 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
763 const Color Them = (Us == WHITE ? BLACK : WHITE);
765 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
766 Score score = SCORE_ZERO;
768 b = ei.pi->passed_pawns(Us);
772 Square s = pop_lsb(&b);
774 assert(pos.pawn_passed(Us, s));
776 int r = int(relative_rank(Us, s) - RANK_2);
777 int rr = r * (r - 1);
779 // Base bonus based on rank
780 Value mbonus = Value(17 * rr);
781 Value ebonus = Value(7 * (rr + r + 1));
785 Square blockSq = s + pawn_push(Us);
787 // Adjust bonus based on the king's proximity
788 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
789 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
791 // If blockSq is not the queening square then consider also a second push
792 if (relative_rank(Us, blockSq) != RANK_8)
793 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
795 // If the pawn is free to advance, then increase the bonus
796 if (pos.empty(blockSq))
798 squaresToQueen = forward_bb(Us, s);
800 // If there is an enemy rook or queen attacking the pawn from behind,
801 // add all X-ray attacks by the rook or queen. Otherwise consider only
802 // the squares in the pawn's path attacked or occupied by the enemy.
803 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
804 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
805 unsafeSquares = squaresToQueen;
807 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
809 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
810 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
811 defendedSquares = squaresToQueen;
813 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
815 // If there aren't any enemy attacks, then assign a huge bonus.
816 // The bonus will be a bit smaller if at least the block square
817 // isn't attacked, otherwise assign the smallest possible bonus.
818 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
820 // Assign a big bonus if the path to the queen is fully defended,
821 // otherwise assign a bit less of a bonus if at least the block
822 // square is defended.
823 if (defendedSquares == squaresToQueen)
826 else if (defendedSquares & blockSq)
827 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
829 mbonus += Value(k * rr), ebonus += Value(k * rr);
833 // Increase the bonus if the passed pawn is supported by a friendly pawn
834 // on the same rank and a bit smaller if it's on the previous rank.
835 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
836 if (supportingPawns & rank_bb(s))
837 ebonus += Value(r * 20);
839 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
840 ebonus += Value(r * 12);
842 // Rook pawns are a special case: They are sometimes worse, and
843 // sometimes better than other passed pawns. It is difficult to find
844 // good rules for determining whether they are good or bad. For now,
845 // we try the following: Increase the value for rook pawns if the
846 // other side has no pieces apart from a knight, and decrease the
847 // value if the other side has a rook or queen.
848 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
850 if (pos.non_pawn_material(Them) <= KnightValueMg)
851 ebonus += ebonus / 4;
853 else if (pos.pieces(Them, ROOK, QUEEN))
854 ebonus -= ebonus / 4;
857 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
858 ebonus += ebonus / 4;
860 score += make_score(mbonus, ebonus);
865 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
867 // Add the scores to the middlegame and endgame eval
868 return apply_weight(score, Weights[PassedPawns]);
872 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
873 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
874 // related to the possibility that pawns are unstoppable.
876 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
878 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
880 if (!b || pos.non_pawn_material(~us))
883 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
887 // evaluate_space() computes the space evaluation for a given side. The
888 // space evaluation is a simple bonus based on the number of safe squares
889 // available for minor pieces on the central four files on ranks 2--4. Safe
890 // squares one, two or three squares behind a friendly pawn are counted
891 // twice. Finally, the space bonus is scaled by a weight taken from the
892 // material hash table. The aim is to improve play on game opening.
894 int evaluate_space(const Position& pos, const EvalInfo& ei) {
896 const Color Them = (Us == WHITE ? BLACK : WHITE);
898 // Find the safe squares for our pieces inside the area defined by
899 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
900 // pawn, or if it is undefended and attacked by an enemy piece.
901 Bitboard safe = SpaceMask[Us]
902 & ~pos.pieces(Us, PAWN)
903 & ~ei.attackedBy[Them][PAWN]
904 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
906 // Find all squares which are at most three squares behind some friendly pawn
907 Bitboard behind = pos.pieces(Us, PAWN);
908 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
909 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
911 // Since SpaceMask[Us] is fully on our half of the board
912 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
914 // Count safe + (behind & safe) with a single popcount
915 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
919 // interpolate() interpolates between a middlegame and an endgame score,
920 // based on game phase. It also scales the return value by a ScaleFactor array.
922 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
924 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
925 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
926 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
928 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
929 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
930 return Value((r / GrainSize) * GrainSize); // Sign independent
933 // apply_weight() weights score v by score w trying to prevent overflow
934 Score apply_weight(Score v, Score w) {
935 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
936 (int(eg_value(v)) * eg_value(w)) / 0x100);
939 // weight_option() computes the value of an evaluation weight, by combining
940 // two UCI-configurable weights (midgame and endgame) with an internal weight.
942 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
944 // Scale option value from 100 to 256
945 int mg = Options[mgOpt] * 256 / 100;
946 int eg = Options[egOpt] * 256 / 100;
948 return apply_weight(make_score(mg, eg), internalWeight);
952 // Tracing functions definitions
954 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
956 void Tracing::add(int idx, Score wScore, Score bScore) {
958 scores[WHITE][idx] = wScore;
959 scores[BLACK][idx] = bScore;
962 void Tracing::row(const char* name, int idx) {
964 Score wScore = scores[WHITE][idx];
965 Score bScore = scores[BLACK][idx];
968 case PST: case IMBALANCE: case PAWN: case TOTAL:
969 stream << std::setw(20) << name << " | --- --- | --- --- | "
970 << std::setw(6) << to_cp(mg_value(wScore)) << " "
971 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
974 stream << std::setw(20) << name << " | " << std::noshowpos
975 << std::setw(5) << to_cp(mg_value(wScore)) << " "
976 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
977 << std::setw(5) << to_cp(mg_value(bScore)) << " "
978 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
980 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
981 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
985 std::string Tracing::do_trace(const Position& pos) {
988 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
989 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
991 do_evaluate<true>(pos);
993 std::string totals = stream.str();
996 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
997 << " | MG EG | MG EG | MG EG \n"
998 << "---------------------+-------------+-------------+---------------\n";
1000 row("Material, PST, Tempo", PST);
1001 row("Material imbalance", IMBALANCE);
1003 row("Knights", KNIGHT);
1004 row("Bishops", BISHOP);
1006 row("Queens", QUEEN);
1007 row("Mobility", MOBILITY);
1008 row("King safety", KING);
1009 row("Threats", THREAT);
1010 row("Passed pawns", PASSED);
1011 row("Space", SPACE);
1013 stream << "---------------------+-------------+-------------+---------------\n";
1014 row("Total", TOTAL);
1017 return stream.str();