2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 enum ExtendedPieceType { // Used for tracing
35 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL
40 Score scores[COLOR_NB][TOTAL + 1];
41 std::stringstream stream;
43 void add(int idx, Score term_w, Score term_b = SCORE_ZERO);
44 void row(const char* name, int idx);
45 std::string do_trace(const Position& pos);
48 // Struct EvalInfo contains various information computed and collected
49 // by the evaluation functions.
52 // Pointers to material and pawn hash table entries
56 // attackedBy[color][piece type] is a bitboard representing all squares
57 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
58 // contains all squares attacked by the given color.
59 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
61 // kingRing[color] is the zone around the king which is considered
62 // by the king safety evaluation. This consists of the squares directly
63 // adjacent to the king, and the three (or two, for a king on an edge file)
64 // squares two ranks in front of the king. For instance, if black's king
65 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
66 // f7, g7, h7, f6, g6 and h6.
67 Bitboard kingRing[COLOR_NB];
69 // kingAttackersCount[color] is the number of pieces of the given color
70 // which attack a square in the kingRing of the enemy king.
71 int kingAttackersCount[COLOR_NB];
73 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
74 // given color which attack a square in the kingRing of the enemy king. The
75 // weights of the individual piece types are given by the variables
76 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
77 // KnightAttackWeight in evaluate.cpp
78 int kingAttackersWeight[COLOR_NB];
80 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
81 // directly adjacent to the king of the given color. Pieces which attack
82 // more than one square are counted multiple times. For instance, if black's
83 // king is on g8 and there's a white knight on g5, this knight adds
84 // 2 to kingAdjacentZoneAttacksCount[BLACK].
85 int kingAdjacentZoneAttacksCount[COLOR_NB];
87 Bitboard pinnedPieces[COLOR_NB];
90 // Evaluation grain size, must be a power of 2
91 const int GrainSize = 4;
93 // Evaluation weights, initialized from UCI options
94 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
98 #define S(mg, eg) make_score(mg, eg)
100 // Internal evaluation weights. These are applied on top of the evaluation
101 // weights read from UCI parameters. The purpose is to be able to change
102 // the evaluation weights while keeping the default values of the UCI
103 // parameters at 100, which looks prettier.
105 // Values modified by Joona Kiiski
106 const Score WeightsInternal[] = {
107 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
110 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
111 // game, indexed by piece type and number of attacked squares not occupied by
113 const Score MobilityBonus[][32] = {
115 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
116 S( 37, 28), S( 42, 31), S(44, 33) },
117 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
118 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
119 S( 84, 79), S( 86, 81) },
120 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
121 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
122 S( 35,122), S( 36,123), S(37,124) },
123 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
124 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
125 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
127 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
130 // Outpost[PieceType][Square] contains bonuses of knights and bishops, indexed
131 // by piece type and square (from white's point of view).
132 const Value Outpost[][SQUARE_NB] = {
135 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
136 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
137 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
138 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
139 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
140 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
142 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
143 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
144 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
145 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
146 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
147 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
150 // Threat[attacking][attacked] contains bonuses according to which piece
151 // type attacks which one.
152 const Score Threat[][PIECE_TYPE_NB] = {
154 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
155 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
156 { S(0, 0), S( 0, 22), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
157 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
160 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
161 // type is attacked by an enemy pawn.
162 const Score ThreatenedByPawn[] = {
163 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
168 const Score Tempo = make_score(24, 11);
169 const Score BishopPin = make_score(66, 11);
170 const Score RookOn7th = make_score(11, 20);
171 const Score QueenOn7th = make_score( 3, 8);
172 const Score RookOnPawn = make_score(10, 28);
173 const Score QueenOnPawn = make_score( 4, 20);
174 const Score RookOpenFile = make_score(43, 21);
175 const Score RookSemiopenFile = make_score(19, 10);
176 const Score BishopPawns = make_score( 8, 12);
177 const Score KnightPawns = make_score( 8, 4);
178 const Score MinorBehindPawn = make_score(16, 0);
179 const Score UndefendedMinor = make_score(25, 10);
180 const Score TrappedRook = make_score(90, 0);
181 const Score Unstoppable = make_score( 0, 20);
183 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
184 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
185 // happen in Chess960 games.
186 const Score TrappedBishopA1H1 = make_score(50, 50);
188 // The SpaceMask[Color] contains the area of the board which is considered
189 // by the space evaluation. In the middle game, each side is given a bonus
190 // based on how many squares inside this area are safe and available for
191 // friendly minor pieces.
192 const Bitboard SpaceMask[] = {
193 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
194 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
197 // King danger constants and variables. The king danger scores are taken
198 // from the KingDanger[]. Various little "meta-bonuses" measuring
199 // the strength of the enemy attack are added up into an integer, which
200 // is used as an index to KingDanger[].
202 // KingAttackWeights[PieceType] contains king attack weights by piece type
203 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
205 // Bonuses for enemy's safe checks
206 const int QueenContactCheck = 24;
207 const int RookContactCheck = 16;
208 const int QueenCheck = 12;
209 const int RookCheck = 8;
210 const int BishopCheck = 2;
211 const int KnightCheck = 3;
213 // KingExposed[Square] contains penalties based on the position of the
214 // defending king, indexed by king's square (from white's point of view).
215 const int KingExposed[] = {
216 2, 0, 2, 5, 5, 2, 0, 2,
217 2, 2, 4, 8, 8, 4, 2, 2,
218 7, 10, 12, 12, 12, 12, 10, 7,
219 15, 15, 15, 15, 15, 15, 15, 15,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15,
222 15, 15, 15, 15, 15, 15, 15, 15,
223 15, 15, 15, 15, 15, 15, 15, 15
226 // KingDanger[Color][attackUnits] contains the actual king danger weighted
227 // scores, indexed by color and by a calculated integer number.
228 Score KingDanger[COLOR_NB][128];
230 // Function prototypes
232 Value do_evaluate(const Position& pos);
235 void init_eval_info(const Position& pos, EvalInfo& ei);
237 template<Color Us, bool Trace>
238 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
240 template<Color Us, bool Trace>
241 Score evaluate_king(const Position& pos, const EvalInfo& ei);
243 template<Color Us, bool Trace>
244 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
246 template<Color Us, bool Trace>
247 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
250 int evaluate_space(const Position& pos, const EvalInfo& ei);
252 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
254 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
255 Score apply_weight(Score v, Score w);
256 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
257 double to_cp(Value v);
263 /// evaluate() is the main evaluation function. It always computes two
264 /// values, an endgame score and a middle game score, and interpolates
265 /// between them based on the remaining material.
267 Value evaluate(const Position& pos) {
268 return do_evaluate<false>(pos);
272 /// trace() is like evaluate() but instead of a value returns a string suitable
273 /// to be print on stdout with the detailed descriptions and values of each
274 /// evaluation term. Used mainly for debugging.
275 std::string trace(const Position& pos) {
276 return Tracing::do_trace(pos);
280 /// init() computes evaluation weights from the corresponding UCI parameters
281 /// and setup king tables.
285 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
286 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
287 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
288 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
289 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
290 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
292 const int MaxSlope = 30;
293 const int Peak = 1280;
295 for (int t = 0, i = 1; i < 100; ++i)
297 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
299 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
300 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
310 Value do_evaluate(const Position& pos) {
312 assert(!pos.checkers());
315 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
316 Thread* th = pos.this_thread();
318 // Initialize score by reading the incrementally updated scores included
319 // in the position object (material + piece square tables) and adding
320 // Tempo bonus. Score is computed from the point of view of white.
321 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
323 // Probe the material hash table
324 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
325 score += ei.mi->material_value();
327 // If we have a specialized evaluation function for the current material
328 // configuration, call it and return.
329 if (ei.mi->specialized_eval_exists())
330 return ei.mi->evaluate(pos);
332 // Probe the pawn hash table
333 ei.pi = Pawns::probe(pos, th->pawnsTable);
334 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
336 // Initialize attack and king safety bitboards
337 init_eval_info<WHITE>(pos, ei);
338 init_eval_info<BLACK>(pos, ei);
340 // Evaluate pieces and mobility
341 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
342 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
344 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
346 // Evaluate kings after all other pieces because we need complete attack
347 // information when computing the king safety evaluation.
348 score += evaluate_king<WHITE, Trace>(pos, ei)
349 - evaluate_king<BLACK, Trace>(pos, ei);
351 // Evaluate tactical threats, we need full attack information including king
352 score += evaluate_threats<WHITE, Trace>(pos, ei)
353 - evaluate_threats<BLACK, Trace>(pos, ei);
355 // Evaluate passed pawns, we need full attack information including king
356 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
357 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
359 // If one side has only a king, score for potential unstoppable pawns
360 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
361 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
362 - evaluate_unstoppable_pawns(pos, BLACK, ei);
364 // Evaluate space for both sides, only in middle-game.
365 if (ei.mi->space_weight())
367 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
368 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
371 // Scale winning side if position is more drawish that what it appears
372 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
373 : ei.mi->scale_factor(pos, BLACK);
375 // If we don't already have an unusual scale factor, check for opposite
376 // colored bishop endgames, and use a lower scale for those.
377 if ( ei.mi->game_phase() < PHASE_MIDGAME
378 && pos.opposite_bishops()
379 && sf == SCALE_FACTOR_NORMAL)
381 // Only the two bishops ?
382 if ( pos.non_pawn_material(WHITE) == BishopValueMg
383 && pos.non_pawn_material(BLACK) == BishopValueMg)
385 // Check for KBP vs KB with only a single pawn that is almost
386 // certainly a draw or at least two pawns.
387 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
388 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
391 // Endgame with opposite-colored bishops, but also other pieces. Still
392 // a bit drawish, but not as drawish as with only the two bishops.
393 sf = ScaleFactor(50);
396 Value v = interpolate(score, ei.mi->game_phase(), sf);
398 // In case of tracing add all single evaluation contributions for both white and black
401 Tracing::add(PST, pos.psq_score());
402 Tracing::add(IMBALANCE, ei.mi->material_value());
403 Tracing::add(PAWN, ei.pi->pawns_value());
404 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
405 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
406 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
407 Tracing::add(TOTAL, score);
408 Tracing::stream << "\nScaling: " << std::noshowpos
409 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
410 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
411 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
412 << "Total evaluation: " << to_cp(v);
415 return pos.side_to_move() == WHITE ? v : -v;
419 // init_eval_info() initializes king bitboards for given color adding
420 // pawn attacks. To be done at the beginning of the evaluation.
423 void init_eval_info(const Position& pos, EvalInfo& ei) {
425 const Color Them = (Us == WHITE ? BLACK : WHITE);
426 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
428 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
430 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
431 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
433 // Init king safety tables only if we are going to use them
434 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
436 ei.kingRing[Them] = b | shift_bb<Down>(b);
437 b &= ei.attackedBy[Us][PAWN];
438 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
439 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
442 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
446 // evaluate_outposts() evaluates bishop and knight outposts squares
448 template<PieceType Piece, Color Us>
449 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
451 const Color Them = (Us == WHITE ? BLACK : WHITE);
453 assert (Piece == BISHOP || Piece == KNIGHT);
455 // Initial bonus based on square
456 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
458 // Increase bonus if supported by pawn, especially if the opponent has
459 // no minor piece which can exchange the outpost piece.
460 if (bonus && (ei.attackedBy[Us][PAWN] & s))
462 if ( !pos.pieces(Them, KNIGHT)
463 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
464 bonus += bonus + bonus / 2;
469 return make_score(bonus, bonus);
473 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
475 template<PieceType Piece, Color Us, bool Trace>
476 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
480 Score score = SCORE_ZERO;
482 const Color Them = (Us == WHITE ? BLACK : WHITE);
483 const Square* pl = pos.list<Piece>(Us);
485 ei.attackedBy[Us][Piece] = 0;
487 while ((s = *pl++) != SQ_NONE)
489 // Find attacked squares, including x-ray attacks for bishops and rooks
490 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
491 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
492 : pos.attacks_from<Piece>(s);
494 if (ei.pinnedPieces[Us] & s)
495 b &= LineBB[pos.king_square(Us)][s];
497 ei.attackedBy[Us][Piece] |= b;
499 if (b & ei.kingRing[Them])
501 ei.kingAttackersCount[Us]++;
502 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
503 Bitboard bb = b & ei.attackedBy[Them][KING];
505 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
508 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
509 : popcount<Full >(b & mobilityArea);
511 mobility[Us] += MobilityBonus[Piece][mob];
513 // Decrease score if we are attacked by an enemy pawn. Remaining part
514 // of threat evaluation must be done later when we have full attack info.
515 if (ei.attackedBy[Them][PAWN] & s)
516 score -= ThreatenedByPawn[Piece];
518 // Otherwise give a bonus if we are a bishop and can pin a piece or can
519 // give a discovered check through an x-ray attack.
520 else if ( Piece == BISHOP
521 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
522 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
525 // Penalty for bishop with same coloured pawns
527 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
529 // Penalty for knight when there are few enemy pawns
531 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
533 if (Piece == BISHOP || Piece == KNIGHT)
535 // Bishop and knight outposts squares
536 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
537 score += evaluate_outposts<Piece, Us>(pos, ei, s);
539 // Bishop or knight behind a pawn
540 if ( relative_rank(Us, s) < RANK_5
541 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
542 score += MinorBehindPawn;
545 if ( (Piece == ROOK || Piece == QUEEN)
546 && relative_rank(Us, s) >= RANK_5)
548 // Major piece on 7th rank and enemy king trapped on 8th
549 if ( relative_rank(Us, s) == RANK_7
550 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
551 score += Piece == ROOK ? RookOn7th : QueenOn7th;
553 // Major piece attacking enemy pawns on the same rank/file
554 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
556 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
559 // Special extra evaluation for rooks
562 // Give a bonus for a rook on a open or semi-open file
563 if (ei.pi->semiopen(Us, file_of(s)))
564 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
566 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
569 Square ksq = pos.king_square(Us);
571 // Penalize rooks which are trapped inside a king. Penalize more if
572 // king has lost right to castle.
573 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
574 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
575 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
576 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
579 // An important Chess960 pattern: A cornered bishop blocked by a friendly
580 // pawn diagonally in front of it is a very serious problem, especially
581 // when that pawn is also blocked.
584 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
586 const enum Piece P = make_piece(Us, PAWN);
587 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
588 if (pos.piece_on(s + d) == P)
589 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
590 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
596 Tracing::scores[Us][Piece] = score;
602 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
603 // pieces of a given color.
605 template<Color Us, bool Trace>
606 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
608 const Color Them = (Us == WHITE ? BLACK : WHITE);
610 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
611 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
613 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
614 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
615 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
616 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
618 // Sum up all attacked squares (updated in evaluate_pieces)
619 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
620 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
621 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
623 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
629 // evaluate_king() assigns bonuses and penalties to a king of a given color
631 template<Color Us, bool Trace>
632 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
634 const Color Them = (Us == WHITE ? BLACK : WHITE);
636 Bitboard undefended, b, b1, b2, safe;
638 const Square ksq = pos.king_square(Us);
640 // King shelter and enemy pawns storm
641 Score score = ei.pi->king_safety<Us>(pos, ksq);
643 // Main king safety evaluation
644 if ( ei.kingAttackersCount[Them] >= 2
645 && ei.kingAdjacentZoneAttacksCount[Them])
647 // Find the attacked squares around the king which has no defenders
648 // apart from the king itself
649 undefended = ei.attackedBy[Them][ALL_PIECES]
650 & ei.attackedBy[Us][KING]
651 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
652 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
653 | ei.attackedBy[Us][QUEEN]);
655 // Initialize the 'attackUnits' variable, which is used later on as an
656 // index to the KingDanger[] array. The initial value is based on the
657 // number and types of the enemy's attacking pieces, the number of
658 // attacked and undefended squares around our king, the square of the
659 // king, and the quality of the pawn shelter.
660 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
661 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
662 + KingExposed[relative_square(Us, ksq)]
663 - mg_value(score) / 32;
665 // Analyse enemy's safe queen contact checks. First find undefended
666 // squares around the king attacked by enemy queen...
667 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
670 // ...then remove squares not supported by another enemy piece
671 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
672 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
674 attackUnits += QueenContactCheck
676 * (Them == pos.side_to_move() ? 2 : 1);
679 // Analyse enemy's safe rook contact checks. First find undefended
680 // squares around the king attacked by enemy rooks...
681 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
683 // Consider only squares where the enemy rook gives check
684 b &= PseudoAttacks[ROOK][ksq];
688 // ...then remove squares not supported by another enemy piece
689 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
690 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
692 attackUnits += RookContactCheck
694 * (Them == pos.side_to_move() ? 2 : 1);
697 // Analyse enemy's safe distance checks for sliders and knights
698 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
700 b1 = pos.attacks_from<ROOK>(ksq) & safe;
701 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
703 // Enemy queen safe checks
704 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
706 attackUnits += QueenCheck * popcount<Max15>(b);
708 // Enemy rooks safe checks
709 b = b1 & ei.attackedBy[Them][ROOK];
711 attackUnits += RookCheck * popcount<Max15>(b);
713 // Enemy bishops safe checks
714 b = b2 & ei.attackedBy[Them][BISHOP];
716 attackUnits += BishopCheck * popcount<Max15>(b);
718 // Enemy knights safe checks
719 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
721 attackUnits += KnightCheck * popcount<Max15>(b);
723 // To index KingDanger[] attackUnits must be in [0, 99] range
724 attackUnits = std::min(99, std::max(0, attackUnits));
726 // Finally, extract the king danger score from the KingDanger[]
727 // array and subtract the score from evaluation.
728 score -= KingDanger[Us == Search::RootColor][attackUnits];
732 Tracing::scores[Us][KING] = score;
738 // evaluate_threats() assigns bonuses according to the type of attacking piece
739 // and the type of attacked one.
741 template<Color Us, bool Trace>
742 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
744 const Color Them = (Us == WHITE ? BLACK : WHITE);
746 Bitboard b, undefendedMinors, weakEnemies;
747 Score score = SCORE_ZERO;
749 // Undefended minors get penalized even if not under attack
750 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
751 & ~ei.attackedBy[Them][ALL_PIECES];
753 if (undefendedMinors)
754 score += UndefendedMinor;
756 // Enemy pieces not defended by a pawn and under our attack
757 weakEnemies = pos.pieces(Them)
758 & ~ei.attackedBy[Them][PAWN]
759 & ei.attackedBy[Us][ALL_PIECES];
761 // Add bonus according to type of attacked enemy piece and to the
762 // type of attacking piece, from knights to queens. Kings are not
763 // considered because are already handled in king evaluation.
765 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
767 b = ei.attackedBy[Us][pt1] & weakEnemies;
769 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
770 if (b & pos.pieces(pt2))
771 score += Threat[pt1][pt2];
775 Tracing::scores[Us][THREAT] = score;
781 // evaluate_passed_pawns() evaluates the passed pawns of the given color
783 template<Color Us, bool Trace>
784 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
786 const Color Them = (Us == WHITE ? BLACK : WHITE);
788 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
789 Score score = SCORE_ZERO;
791 b = ei.pi->passed_pawns(Us);
795 Square s = pop_lsb(&b);
797 assert(pos.pawn_passed(Us, s));
799 int r = int(relative_rank(Us, s) - RANK_2);
800 int rr = r * (r - 1);
802 // Base bonus based on rank
803 Value mbonus = Value(17 * rr);
804 Value ebonus = Value(7 * (rr + r + 1));
808 Square blockSq = s + pawn_push(Us);
810 // Adjust bonus based on kings proximity
811 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
812 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
814 // If blockSq is not the queening square then consider also a second push
815 if (relative_rank(Us, blockSq) != RANK_8)
816 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
818 // If the pawn is free to advance, increase bonus
819 if (pos.empty(blockSq))
821 squaresToQueen = forward_bb(Us, s);
823 // If there is an enemy rook or queen attacking the pawn from behind,
824 // add all X-ray attacks by the rook or queen. Otherwise consider only
825 // the squares in the pawn's path attacked or occupied by the enemy.
826 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
827 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
828 unsafeSquares = squaresToQueen;
830 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
832 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
833 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
834 defendedSquares = squaresToQueen;
836 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
838 // If there aren't enemy attacks huge bonus, a bit smaller if at
839 // least block square is not attacked, otherwise smallest bonus.
840 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
842 // Big bonus if the path to queen is fully defended, a bit less
843 // if at least block square is defended.
844 if (defendedSquares == squaresToQueen)
847 else if (defendedSquares & blockSq)
848 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
850 mbonus += Value(k * rr), ebonus += Value(k * rr);
854 // Increase the bonus if the passed pawn is supported by a friendly pawn
855 // on the same rank and a bit smaller if it's on the previous rank.
856 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
857 if (supportingPawns & rank_bb(s))
858 ebonus += Value(r * 20);
860 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
861 ebonus += Value(r * 12);
863 // Rook pawns are a special case: They are sometimes worse, and
864 // sometimes better than other passed pawns. It is difficult to find
865 // good rules for determining whether they are good or bad. For now,
866 // we try the following: Increase the value for rook pawns if the
867 // other side has no pieces apart from a knight, and decrease the
868 // value if the other side has a rook or queen.
869 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
871 if (pos.non_pawn_material(Them) <= KnightValueMg)
872 ebonus += ebonus / 4;
874 else if (pos.pieces(Them, ROOK, QUEEN))
875 ebonus -= ebonus / 4;
878 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
879 ebonus += ebonus / 4;
881 score += make_score(mbonus, ebonus);
886 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
888 // Add the scores to the middle game and endgame eval
889 return apply_weight(score, Weights[PassedPawns]);
893 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
894 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
895 // related to the possibility pawns are unstoppable.
897 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
899 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
901 if (!b || pos.non_pawn_material(~us))
904 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
908 // evaluate_space() computes the space evaluation for a given side. The
909 // space evaluation is a simple bonus based on the number of safe squares
910 // available for minor pieces on the central four files on ranks 2--4. Safe
911 // squares one, two or three squares behind a friendly pawn are counted
912 // twice. Finally, the space bonus is scaled by a weight taken from the
913 // material hash table. The aim is to improve play on game opening.
915 int evaluate_space(const Position& pos, const EvalInfo& ei) {
917 const Color Them = (Us == WHITE ? BLACK : WHITE);
919 // Find the safe squares for our pieces inside the area defined by
920 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
921 // pawn, or if it is undefended and attacked by an enemy piece.
922 Bitboard safe = SpaceMask[Us]
923 & ~pos.pieces(Us, PAWN)
924 & ~ei.attackedBy[Them][PAWN]
925 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
927 // Find all squares which are at most three squares behind some friendly pawn
928 Bitboard behind = pos.pieces(Us, PAWN);
929 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
930 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
932 // Since SpaceMask[Us] is fully on our half of the board
933 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
935 // Count safe + (behind & safe) with a single popcount
936 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
940 // interpolate() interpolates between a middle game and an endgame score,
941 // based on game phase. It also scales the return value by a ScaleFactor array.
943 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
945 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
946 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
947 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
949 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
950 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
951 return Value((r / GrainSize) * GrainSize); // Sign independent
954 // apply_weight() weights score v by score w trying to prevent overflow
955 Score apply_weight(Score v, Score w) {
956 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
957 (int(eg_value(v)) * eg_value(w)) / 0x100);
960 // weight_option() computes the value of an evaluation weight, by combining
961 // two UCI-configurable weights (midgame and endgame) with an internal weight.
963 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
965 // Scale option value from 100 to 256
966 int mg = Options[mgOpt] * 256 / 100;
967 int eg = Options[egOpt] * 256 / 100;
969 return apply_weight(make_score(mg, eg), internalWeight);
973 // Tracing functions definitions
975 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
977 void Tracing::add(int idx, Score wScore, Score bScore) {
979 scores[WHITE][idx] = wScore;
980 scores[BLACK][idx] = bScore;
983 void Tracing::row(const char* name, int idx) {
985 Score wScore = scores[WHITE][idx];
986 Score bScore = scores[BLACK][idx];
989 case PST: case IMBALANCE: case PAWN: case TOTAL:
990 stream << std::setw(20) << name << " | --- --- | --- --- | "
991 << std::setw(6) << to_cp(mg_value(wScore)) << " "
992 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
995 stream << std::setw(20) << name << " | " << std::noshowpos
996 << std::setw(5) << to_cp(mg_value(wScore)) << " "
997 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
998 << std::setw(5) << to_cp(mg_value(bScore)) << " "
999 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1001 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1002 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1006 std::string Tracing::do_trace(const Position& pos) {
1009 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1010 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1012 do_evaluate<true>(pos);
1014 std::string totals = stream.str();
1017 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1018 << " | MG EG | MG EG | MG EG \n"
1019 << "---------------------+-------------+-------------+---------------\n";
1021 row("Material, PST, Tempo", PST);
1022 row("Material imbalance", IMBALANCE);
1024 row("Knights", KNIGHT);
1025 row("Bishops", BISHOP);
1027 row("Queens", QUEEN);
1028 row("Mobility", MOBILITY);
1029 row("King safety", KING);
1030 row("Threats", THREAT);
1031 row("Passed pawns", PASSED);
1032 row("Space", SPACE);
1034 stream << "---------------------+-------------+-------------+---------------\n";
1035 row("Total", TOTAL);
1038 return stream.str();