2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
30 #include "ucioption.h"
34 enum ExtendedPieceType { // Used for tracing
35 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL
40 Score scores[COLOR_NB][TOTAL + 1];
41 std::stringstream stream;
43 void add(int idx, Score term_w, Score term_b = SCORE_ZERO);
44 void row(const char* name, int idx);
45 std::string do_trace(const Position& pos);
48 // Struct EvalInfo contains various information computed and collected
49 // by the evaluation functions.
52 // Pointers to material and pawn hash table entries
56 // attackedBy[color][piece type] is a bitboard representing all squares
57 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
58 // contains all squares attacked by the given color.
59 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
61 // kingRing[color] is the zone around the king which is considered
62 // by the king safety evaluation. This consists of the squares directly
63 // adjacent to the king, and the three (or two, for a king on an edge file)
64 // squares two ranks in front of the king. For instance, if black's king
65 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
66 // f7, g7, h7, f6, g6 and h6.
67 Bitboard kingRing[COLOR_NB];
69 // kingAttackersCount[color] is the number of pieces of the given color
70 // which attack a square in the kingRing of the enemy king.
71 int kingAttackersCount[COLOR_NB];
73 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
74 // given color which attack a square in the kingRing of the enemy king. The
75 // weights of the individual piece types are given by the variables
76 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
77 // KnightAttackWeight in evaluate.cpp
78 int kingAttackersWeight[COLOR_NB];
80 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
81 // directly adjacent to the king of the given color. Pieces which attack
82 // more than one square are counted multiple times. For instance, if black's
83 // king is on g8 and there's a white knight on g5, this knight adds
84 // 2 to kingAdjacentZoneAttacksCount[BLACK].
85 int kingAdjacentZoneAttacksCount[COLOR_NB];
88 // Evaluation grain size, must be a power of 2
89 const int GrainSize = 4;
91 // Evaluation weights, initialized from UCI options
92 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
96 #define S(mg, eg) make_score(mg, eg)
98 // Internal evaluation weights. These are applied on top of the evaluation
99 // weights read from UCI parameters. The purpose is to be able to change
100 // the evaluation weights while keeping the default values of the UCI
101 // parameters at 100, which looks prettier.
103 // Values modified by Joona Kiiski
104 const Score WeightsInternal[] = {
105 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
108 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
109 // game, indexed by piece type and number of attacked squares not occupied by
111 const Score MobilityBonus[][32] = {
113 { S(-35,-30), S(-22,-20), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
114 S( 37, 28), S( 42, 31), S(44, 33) },
115 { S(-22,-27), S( -8,-13), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
116 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
117 S( 84, 79), S( 86, 81) },
118 { S(-17,-33), S(-11,-16), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
119 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
120 S( 35,122), S( 36,123), S(37,124) },
121 { S(-12,-20), S( -8,-13), S(-5, -7), S(-2, -1), S( 1, 5), S( 4, 11), // Queens
122 S( 7, 17), S( 10, 23), S(13, 29), S(16, 34), S(18, 38), S(20, 40),
123 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
124 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
128 // Outpost[PieceType][Square] contains bonuses of knights and bishops, indexed
129 // by piece type and square (from white's point of view).
130 const Value Outpost[][SQUARE_NB] = {
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
134 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
135 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
136 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
137 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
138 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
140 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
141 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
142 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
143 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
144 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
145 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
148 // Threat[attacking][attacked] contains bonuses according to which piece
149 // type attacks which one.
150 const Score Threat[][PIECE_TYPE_NB] = {
152 { S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
153 { S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
154 { S(0, 0), S( 0, 22), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
155 { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
158 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
159 // type is attacked by an enemy pawn.
160 const Score ThreatenedByPawn[] = {
161 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
166 const Score Tempo = make_score(24, 11);
167 const Score BishopPin = make_score(66, 11);
168 const Score RookOn7th = make_score(11, 20);
169 const Score QueenOn7th = make_score( 3, 8);
170 const Score RookOnPawn = make_score(10, 28);
171 const Score QueenOnPawn = make_score( 4, 20);
172 const Score RookOpenFile = make_score(43, 21);
173 const Score RookSemiopenFile = make_score(19, 10);
174 const Score BishopPawns = make_score( 8, 12);
175 const Score KnightPawns = make_score( 8, 4);
176 const Score MinorBehindPawn = make_score(16, 0);
177 const Score UndefendedMinor = make_score(25, 10);
178 const Score TrappedRook = make_score(90, 0);
179 const Score Unstoppable = make_score( 0, 20);
181 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
182 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
183 // happen in Chess960 games.
184 const Score TrappedBishopA1H1 = make_score(50, 50);
186 // The SpaceMask[Color] contains the area of the board which is considered
187 // by the space evaluation. In the middle game, each side is given a bonus
188 // based on how many squares inside this area are safe and available for
189 // friendly minor pieces.
190 const Bitboard SpaceMask[] = {
191 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
192 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
195 // King danger constants and variables. The king danger scores are taken
196 // from the KingDanger[]. Various little "meta-bonuses" measuring
197 // the strength of the enemy attack are added up into an integer, which
198 // is used as an index to KingDanger[].
200 // KingAttackWeights[PieceType] contains king attack weights by piece type
201 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
203 // Bonuses for enemy's safe checks
204 const int QueenContactCheck = 24;
205 const int RookContactCheck = 16;
206 const int QueenCheck = 12;
207 const int RookCheck = 8;
208 const int BishopCheck = 2;
209 const int KnightCheck = 3;
211 // KingExposed[Square] contains penalties based on the position of the
212 // defending king, indexed by king's square (from white's point of view).
213 const int KingExposed[] = {
214 2, 0, 2, 5, 5, 2, 0, 2,
215 2, 2, 4, 8, 8, 4, 2, 2,
216 7, 10, 12, 12, 12, 12, 10, 7,
217 15, 15, 15, 15, 15, 15, 15, 15,
218 15, 15, 15, 15, 15, 15, 15, 15,
219 15, 15, 15, 15, 15, 15, 15, 15,
220 15, 15, 15, 15, 15, 15, 15, 15,
221 15, 15, 15, 15, 15, 15, 15, 15
224 // KingDanger[Color][attackUnits] contains the actual king danger weighted
225 // scores, indexed by color and by a calculated integer number.
226 Score KingDanger[COLOR_NB][128];
228 // Function prototypes
230 Value do_evaluate(const Position& pos);
233 void init_eval_info(const Position& pos, EvalInfo& ei);
235 template<Color Us, bool Trace>
236 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
238 template<Color Us, bool Trace>
239 Score evaluate_king(const Position& pos, const EvalInfo& ei);
241 template<Color Us, bool Trace>
242 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
244 template<Color Us, bool Trace>
245 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
248 int evaluate_space(const Position& pos, const EvalInfo& ei);
250 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
252 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
253 Score apply_weight(Score v, Score w);
254 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
255 double to_cp(Value v);
261 /// evaluate() is the main evaluation function. It always computes two
262 /// values, an endgame score and a middle game score, and interpolates
263 /// between them based on the remaining material.
265 Value evaluate(const Position& pos) {
266 return do_evaluate<false>(pos);
270 /// trace() is like evaluate() but instead of a value returns a string suitable
271 /// to be print on stdout with the detailed descriptions and values of each
272 /// evaluation term. Used mainly for debugging.
273 std::string trace(const Position& pos) {
274 return Tracing::do_trace(pos);
278 /// init() computes evaluation weights from the corresponding UCI parameters
279 /// and setup king tables.
283 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
284 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
285 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
286 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
287 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
288 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
290 const int MaxSlope = 30;
291 const int Peak = 1280;
293 for (int t = 0, i = 1; i < 100; ++i)
295 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
297 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
298 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
308 Value do_evaluate(const Position& pos) {
310 assert(!pos.checkers());
313 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
314 Thread* th = pos.this_thread();
316 // Initialize score by reading the incrementally updated scores included
317 // in the position object (material + piece square tables) and adding
318 // Tempo bonus. Score is computed from the point of view of white.
319 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
321 // Probe the material hash table
322 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
323 score += ei.mi->material_value();
325 // If we have a specialized evaluation function for the current material
326 // configuration, call it and return.
327 if (ei.mi->specialized_eval_exists())
328 return ei.mi->evaluate(pos);
330 // Probe the pawn hash table
331 ei.pi = Pawns::probe(pos, th->pawnsTable);
332 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
334 // Initialize attack and king safety bitboards
335 init_eval_info<WHITE>(pos, ei);
336 init_eval_info<BLACK>(pos, ei);
338 // Evaluate pieces and mobility
339 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
340 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
342 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
344 // Evaluate kings after all other pieces because we need complete attack
345 // information when computing the king safety evaluation.
346 score += evaluate_king<WHITE, Trace>(pos, ei)
347 - evaluate_king<BLACK, Trace>(pos, ei);
349 // Evaluate tactical threats, we need full attack information including king
350 score += evaluate_threats<WHITE, Trace>(pos, ei)
351 - evaluate_threats<BLACK, Trace>(pos, ei);
353 // Evaluate passed pawns, we need full attack information including king
354 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
355 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
357 // If one side has only a king, score for potential unstoppable pawns
358 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
359 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
360 - evaluate_unstoppable_pawns(pos, BLACK, ei);
362 // Evaluate space for both sides, only in middle-game.
363 if (ei.mi->space_weight())
365 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
366 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
369 // Scale winning side if position is more drawish that what it appears
370 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
371 : ei.mi->scale_factor(pos, BLACK);
373 // If we don't already have an unusual scale factor, check for opposite
374 // colored bishop endgames, and use a lower scale for those.
375 if ( ei.mi->game_phase() < PHASE_MIDGAME
376 && pos.opposite_bishops()
377 && sf == SCALE_FACTOR_NORMAL)
379 // Only the two bishops ?
380 if ( pos.non_pawn_material(WHITE) == BishopValueMg
381 && pos.non_pawn_material(BLACK) == BishopValueMg)
383 // Check for KBP vs KB with only a single pawn that is almost
384 // certainly a draw or at least two pawns.
385 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
386 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
389 // Endgame with opposite-colored bishops, but also other pieces. Still
390 // a bit drawish, but not as drawish as with only the two bishops.
391 sf = ScaleFactor(50);
394 Value v = interpolate(score, ei.mi->game_phase(), sf);
396 // In case of tracing add all single evaluation contributions for both white and black
399 Tracing::add(PST, pos.psq_score());
400 Tracing::add(IMBALANCE, ei.mi->material_value());
401 Tracing::add(PAWN, ei.pi->pawns_value());
402 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
403 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
404 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
405 Tracing::add(TOTAL, score);
406 Tracing::stream << "\nScaling: " << std::noshowpos
407 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
408 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
409 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
410 << "Total evaluation: " << to_cp(v);
413 return pos.side_to_move() == WHITE ? v : -v;
417 // init_eval_info() initializes king bitboards for given color adding
418 // pawn attacks. To be done at the beginning of the evaluation.
421 void init_eval_info(const Position& pos, EvalInfo& ei) {
423 const Color Them = (Us == WHITE ? BLACK : WHITE);
424 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
426 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
427 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
429 // Init king safety tables only if we are going to use them
430 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
432 ei.kingRing[Them] = b | shift_bb<Down>(b);
433 b &= ei.attackedBy[Us][PAWN];
434 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
435 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
438 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
442 // evaluate_outposts() evaluates bishop and knight outposts squares
444 template<PieceType Piece, Color Us>
445 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
447 const Color Them = (Us == WHITE ? BLACK : WHITE);
449 assert (Piece == BISHOP || Piece == KNIGHT);
451 // Initial bonus based on square
452 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
454 // Increase bonus if supported by pawn, especially if the opponent has
455 // no minor piece which can exchange the outpost piece.
456 if (bonus && (ei.attackedBy[Us][PAWN] & s))
458 if ( !pos.pieces(Them, KNIGHT)
459 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
460 bonus += bonus + bonus / 2;
465 return make_score(bonus, bonus);
469 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
471 template<PieceType Piece, Color Us, bool Trace>
472 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
476 Score score = SCORE_ZERO;
478 const Color Them = (Us == WHITE ? BLACK : WHITE);
479 const Square* pl = pos.list<Piece>(Us);
481 ei.attackedBy[Us][Piece] = 0;
483 while ((s = *pl++) != SQ_NONE)
485 // Find attacked squares, including x-ray attacks for bishops and rooks
486 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
487 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
488 : pos.attacks_from<Piece>(s);
490 ei.attackedBy[Us][Piece] |= b;
492 if (b & ei.kingRing[Them])
494 ei.kingAttackersCount[Us]++;
495 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
496 Bitboard bb = b & ei.attackedBy[Them][KING];
498 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
501 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
502 : popcount<Full >(b & mobilityArea);
504 mobility[Us] += MobilityBonus[Piece][mob];
506 // Decrease score if we are attacked by an enemy pawn. Remaining part
507 // of threat evaluation must be done later when we have full attack info.
508 if (ei.attackedBy[Them][PAWN] & s)
509 score -= ThreatenedByPawn[Piece];
511 // Otherwise give a bonus if we are a bishop and can pin a piece or can
512 // give a discovered check through an x-ray attack.
513 else if ( Piece == BISHOP
514 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
515 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
518 // Penalty for bishop with same coloured pawns
520 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
522 // Penalty for knight when there are few enemy pawns
524 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
526 if (Piece == BISHOP || Piece == KNIGHT)
528 // Bishop and knight outposts squares
529 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
530 score += evaluate_outposts<Piece, Us>(pos, ei, s);
532 // Bishop or knight behind a pawn
533 if ( relative_rank(Us, s) < RANK_5
534 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
535 score += MinorBehindPawn;
538 if ( (Piece == ROOK || Piece == QUEEN)
539 && relative_rank(Us, s) >= RANK_5)
541 // Major piece on 7th rank and enemy king trapped on 8th
542 if ( relative_rank(Us, s) == RANK_7
543 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
544 score += Piece == ROOK ? RookOn7th : QueenOn7th;
546 // Major piece attacking enemy pawns on the same rank/file
547 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
549 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
552 // Special extra evaluation for rooks
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 inside a king. Penalize more if
565 // king has lost right to castle.
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 const enum Piece P = make_piece(Us, PAWN);
580 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
581 if (pos.piece_on(s + d) == P)
582 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
583 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
589 Tracing::scores[Us][Piece] = score;
595 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
596 // pieces of a given color.
598 template<Color Us, bool Trace>
599 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
601 const Color Them = (Us == WHITE ? BLACK : WHITE);
603 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
604 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
606 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
607 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
608 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
609 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
611 // Sum up all attacked squares (updated in evaluate_pieces)
612 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
613 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
614 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
616 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
622 // evaluate_king() assigns bonuses and penalties to a king of a given color
624 template<Color Us, bool Trace>
625 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
627 const Color Them = (Us == WHITE ? BLACK : WHITE);
629 Bitboard undefended, b, b1, b2, safe;
631 const Square ksq = pos.king_square(Us);
633 // King shelter and enemy pawns storm
634 Score score = ei.pi->king_safety<Us>(pos, ksq);
636 // Main king safety evaluation
637 if ( ei.kingAttackersCount[Them] >= 2
638 && ei.kingAdjacentZoneAttacksCount[Them])
640 // Find the attacked squares around the king which has no defenders
641 // apart from the king itself
642 undefended = ei.attackedBy[Them][ALL_PIECES]
643 & ei.attackedBy[Us][KING]
644 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
645 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
646 | ei.attackedBy[Us][QUEEN]);
648 // Initialize the 'attackUnits' variable, which is used later on as an
649 // index to the KingDanger[] array. The initial value is based on the
650 // number and types of the enemy's attacking pieces, the number of
651 // attacked and undefended squares around our king, the square of the
652 // king, and the quality of the pawn shelter.
653 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
654 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
655 + KingExposed[relative_square(Us, ksq)]
656 - mg_value(score) / 32;
658 // Analyse enemy's safe queen contact checks. First find undefended
659 // squares around the king attacked by enemy queen...
660 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
663 // ...then remove squares not supported by another enemy piece
664 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
665 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
667 attackUnits += QueenContactCheck
669 * (Them == pos.side_to_move() ? 2 : 1);
672 // Analyse enemy's safe rook contact checks. First find undefended
673 // squares around the king attacked by enemy rooks...
674 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
676 // Consider only squares where the enemy rook gives check
677 b &= PseudoAttacks[ROOK][ksq];
681 // ...then remove squares not supported by another enemy piece
682 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
683 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
685 attackUnits += RookContactCheck
687 * (Them == pos.side_to_move() ? 2 : 1);
690 // Analyse enemy's safe distance checks for sliders and knights
691 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
693 b1 = pos.attacks_from<ROOK>(ksq) & safe;
694 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
696 // Enemy queen safe checks
697 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
699 attackUnits += QueenCheck * popcount<Max15>(b);
701 // Enemy rooks safe checks
702 b = b1 & ei.attackedBy[Them][ROOK];
704 attackUnits += RookCheck * popcount<Max15>(b);
706 // Enemy bishops safe checks
707 b = b2 & ei.attackedBy[Them][BISHOP];
709 attackUnits += BishopCheck * popcount<Max15>(b);
711 // Enemy knights safe checks
712 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
714 attackUnits += KnightCheck * popcount<Max15>(b);
716 // To index KingDanger[] attackUnits must be in [0, 99] range
717 attackUnits = std::min(99, std::max(0, attackUnits));
719 // Finally, extract the king danger score from the KingDanger[]
720 // array and subtract the score from evaluation.
721 score -= KingDanger[Us == Search::RootColor][attackUnits];
725 Tracing::scores[Us][KING] = score;
731 // evaluate_threats() assigns bonuses according to the type of attacking piece
732 // and the type of attacked one.
734 template<Color Us, bool Trace>
735 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
737 const Color Them = (Us == WHITE ? BLACK : WHITE);
739 Bitboard b, undefendedMinors, weakEnemies;
740 Score score = SCORE_ZERO;
742 // Undefended minors get penalized even if not under attack
743 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
744 & ~ei.attackedBy[Them][ALL_PIECES];
746 if (undefendedMinors)
747 score += UndefendedMinor;
749 // Enemy pieces not defended by a pawn and under our attack
750 weakEnemies = pos.pieces(Them)
751 & ~ei.attackedBy[Them][PAWN]
752 & ei.attackedBy[Us][ALL_PIECES];
754 // Add bonus according to type of attacked enemy piece and to the
755 // type of attacking piece, from knights to queens. Kings are not
756 // considered because are already handled in king evaluation.
758 for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
760 b = ei.attackedBy[Us][pt1] & weakEnemies;
762 for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
763 if (b & pos.pieces(pt2))
764 score += Threat[pt1][pt2];
768 Tracing::scores[Us][THREAT] = score;
774 // evaluate_passed_pawns() evaluates the passed pawns of the given color
776 template<Color Us, bool Trace>
777 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
779 const Color Them = (Us == WHITE ? BLACK : WHITE);
781 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
782 Score score = SCORE_ZERO;
784 b = ei.pi->passed_pawns(Us);
788 Square s = pop_lsb(&b);
790 assert(pos.pawn_passed(Us, s));
792 int r = int(relative_rank(Us, s) - RANK_2);
793 int rr = r * (r - 1);
795 // Base bonus based on rank
796 Value mbonus = Value(17 * rr);
797 Value ebonus = Value(7 * (rr + r + 1));
801 Square blockSq = s + pawn_push(Us);
803 // Adjust bonus based on kings proximity
804 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
805 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
807 // If blockSq is not the queening square then consider also a second push
808 if (relative_rank(Us, blockSq) != RANK_8)
809 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
811 // If the pawn is free to advance, increase bonus
812 if (pos.empty(blockSq))
814 squaresToQueen = forward_bb(Us, s);
816 // If there is an enemy rook or queen attacking the pawn from behind,
817 // add all X-ray attacks by the rook or queen. Otherwise consider only
818 // the squares in the pawn's path attacked or occupied by the enemy.
819 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
820 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
821 unsafeSquares = squaresToQueen;
823 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
825 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
826 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
827 defendedSquares = squaresToQueen;
829 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
831 // If there aren't enemy attacks huge bonus, a bit smaller if at
832 // least block square is not attacked, otherwise smallest bonus.
833 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
835 // Big bonus if the path to queen is fully defended, a bit less
836 // if at least block square is defended.
837 if (defendedSquares == squaresToQueen)
840 else if (defendedSquares & blockSq)
841 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
843 mbonus += Value(k * rr), ebonus += Value(k * rr);
847 // Increase the bonus if the passed pawn is supported by a friendly pawn
848 // on the same rank and a bit smaller if it's on the previous rank.
849 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
850 if (supportingPawns & rank_bb(s))
851 ebonus += Value(r * 20);
853 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
854 ebonus += Value(r * 12);
856 // Rook pawns are a special case: They are sometimes worse, and
857 // sometimes better than other passed pawns. It is difficult to find
858 // good rules for determining whether they are good or bad. For now,
859 // we try the following: Increase the value for rook pawns if the
860 // other side has no pieces apart from a knight, and decrease the
861 // value if the other side has a rook or queen.
862 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
864 if (pos.non_pawn_material(Them) <= KnightValueMg)
865 ebonus += ebonus / 4;
867 else if (pos.pieces(Them, ROOK, QUEEN))
868 ebonus -= ebonus / 4;
871 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
872 ebonus += ebonus / 4;
874 score += make_score(mbonus, ebonus);
879 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
881 // Add the scores to the middle game and endgame eval
882 return apply_weight(score, Weights[PassedPawns]);
886 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
887 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
888 // related to the possibility pawns are unstoppable.
890 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
892 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
894 if (!b || pos.non_pawn_material(~us))
897 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
901 // evaluate_space() computes the space evaluation for a given side. The
902 // space evaluation is a simple bonus based on the number of safe squares
903 // available for minor pieces on the central four files on ranks 2--4. Safe
904 // squares one, two or three squares behind a friendly pawn are counted
905 // twice. Finally, the space bonus is scaled by a weight taken from the
906 // material hash table. The aim is to improve play on game opening.
908 int evaluate_space(const Position& pos, const EvalInfo& ei) {
910 const Color Them = (Us == WHITE ? BLACK : WHITE);
912 // Find the safe squares for our pieces inside the area defined by
913 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
914 // pawn, or if it is undefended and attacked by an enemy piece.
915 Bitboard safe = SpaceMask[Us]
916 & ~pos.pieces(Us, PAWN)
917 & ~ei.attackedBy[Them][PAWN]
918 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
920 // Find all squares which are at most three squares behind some friendly pawn
921 Bitboard behind = pos.pieces(Us, PAWN);
922 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
923 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
925 // Since SpaceMask[Us] is fully on our half of the board
926 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
928 // Count safe + (behind & safe) with a single popcount
929 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
933 // interpolate() interpolates between a middle game and an endgame score,
934 // based on game phase. It also scales the return value by a ScaleFactor array.
936 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
938 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
939 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
940 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
942 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
943 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
944 return Value((r / GrainSize) * GrainSize); // Sign independent
947 // apply_weight() weights score v by score w trying to prevent overflow
948 Score apply_weight(Score v, Score w) {
949 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
950 (int(eg_value(v)) * eg_value(w)) / 0x100);
953 // weight_option() computes the value of an evaluation weight, by combining
954 // two UCI-configurable weights (midgame and endgame) with an internal weight.
956 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
958 // Scale option value from 100 to 256
959 int mg = Options[mgOpt] * 256 / 100;
960 int eg = Options[egOpt] * 256 / 100;
962 return apply_weight(make_score(mg, eg), internalWeight);
966 // Tracing functions definitions
968 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
970 void Tracing::add(int idx, Score wScore, Score bScore) {
972 scores[WHITE][idx] = wScore;
973 scores[BLACK][idx] = bScore;
976 void Tracing::row(const char* name, int idx) {
978 Score wScore = scores[WHITE][idx];
979 Score bScore = scores[BLACK][idx];
982 case PST: case IMBALANCE: case PAWN: case TOTAL:
983 stream << std::setw(20) << name << " | --- --- | --- --- | "
984 << std::setw(6) << to_cp(mg_value(wScore)) << " "
985 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
988 stream << std::setw(20) << name << " | " << std::noshowpos
989 << std::setw(5) << to_cp(mg_value(wScore)) << " "
990 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
991 << std::setw(5) << to_cp(mg_value(bScore)) << " "
992 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
994 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
995 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
999 std::string Tracing::do_trace(const Position& pos) {
1002 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1003 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1005 do_evaluate<true>(pos);
1007 std::string totals = stream.str();
1010 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1011 << " | MG EG | MG EG | MG EG \n"
1012 << "---------------------+-------------+-------------+---------------\n";
1014 row("Material, PST, Tempo", PST);
1015 row("Material imbalance", IMBALANCE);
1017 row("Knights", KNIGHT);
1018 row("Bishops", BISHOP);
1020 row("Queens", QUEEN);
1021 row("Mobility", MOBILITY);
1022 row("King safety", KING);
1023 row("Threats", THREAT);
1024 row("Passed pawns", PASSED);
1025 row("Space", SPACE);
1027 stream << "---------------------+-------------+-------------+---------------\n";
1028 row("Total", TOTAL);
1031 return stream.str();