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 BishopPin = make_score(66, 11);
167 const Score RookOn7th = make_score(11, 20);
168 const Score QueenOn7th = make_score( 3, 8);
169 const Score RookOnPawn = make_score(10, 28);
170 const Score QueenOnPawn = make_score( 4, 20);
171 const Score RookOpenFile = make_score(43, 21);
172 const Score RookSemiopenFile = make_score(19, 10);
173 const Score BishopPawns = make_score( 8, 12);
174 const Score KnightPawns = make_score( 8, 4);
175 const Score MinorBehindPawn = make_score(16, 0);
176 const Score UndefendedMinor = make_score(25, 10);
177 const Score TrappedRook = make_score(90, 0);
178 const Score Unstoppable = make_score( 0, 20);
180 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
181 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
182 // happen in Chess960 games.
183 const Score TrappedBishopA1H1 = make_score(50, 50);
185 // SpaceMask[Color] contains the area of the board which is considered
186 // by the space evaluation. In the middlegame, each side is given a bonus
187 // based on how many squares inside this area are safe and available for
188 // friendly minor pieces.
189 const Bitboard SpaceMask[] = {
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
191 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
194 // King danger constants and variables. The king danger scores are taken
195 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
196 // of the enemy attack are added up into an integer, which is used as an
197 // index to KingDanger[].
199 // KingAttackWeights[PieceType] contains king attack weights by piece type
200 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
202 // Bonuses for enemy's safe checks
203 const int QueenContactCheck = 24;
204 const int RookContactCheck = 16;
205 const int QueenCheck = 12;
206 const int RookCheck = 8;
207 const int BishopCheck = 2;
208 const int KnightCheck = 3;
210 // KingDanger[Color][attackUnits] contains the actual king danger weighted
211 // scores, indexed by color and by a calculated integer number.
212 Score KingDanger[COLOR_NB][128];
214 // Function prototypes
216 Value do_evaluate(const Position& pos);
219 void init_eval_info(const Position& pos, EvalInfo& ei);
221 template<Color Us, bool Trace>
222 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
224 template<Color Us, bool Trace>
225 Score evaluate_king(const Position& pos, const EvalInfo& ei);
227 template<Color Us, bool Trace>
228 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
230 template<Color Us, bool Trace>
231 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
234 int evaluate_space(const Position& pos, const EvalInfo& ei);
236 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
238 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
239 Score apply_weight(Score v, Score w);
240 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
241 double to_cp(Value v);
247 /// evaluate() is the main evaluation function. It always computes two
248 /// values, an endgame score and a middlegame score, and interpolates
249 /// between them based on the remaining material.
251 Value evaluate(const Position& pos) {
252 return do_evaluate<false>(pos);
256 /// trace() is like evaluate(), but instead of returning a value, it returns
257 /// a string (suitable for outputting to stdout) that contains the detailed
258 /// descriptions and values of each evaluation term. It's mainly used for
260 std::string trace(const Position& pos) {
261 return Tracing::do_trace(pos);
265 /// init() computes evaluation weights from the corresponding UCI parameters
266 /// and setup king tables.
270 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
271 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
272 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
273 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
274 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
275 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
277 const int MaxSlope = 30;
278 const int Peak = 1280;
280 for (int t = 0, i = 1; i < 100; ++i)
282 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
284 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
285 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);
295 Value do_evaluate(const Position& pos) {
297 assert(!pos.checkers());
300 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
301 Thread* th = pos.this_thread();
303 // Initialize score by reading the incrementally updated scores included
304 // in the position object (material + piece square tables) and adding a
305 // Tempo bonus. Score is computed from the point of view of white.
306 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
308 // Probe the material hash table
309 ei.mi = Material::probe(pos, th->materialTable, th->endgames);
310 score += ei.mi->material_value();
312 // If we have a specialized evaluation function for the current material
313 // configuration, call it and return.
314 if (ei.mi->specialized_eval_exists())
315 return ei.mi->evaluate(pos);
317 // Probe the pawn hash table
318 ei.pi = Pawns::probe(pos, th->pawnsTable);
319 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
321 // Initialize attack and king safety bitboards
322 init_eval_info<WHITE>(pos, ei);
323 init_eval_info<BLACK>(pos, ei);
325 // Evaluate pieces and mobility
326 score += evaluate_pieces_of_color<WHITE, Trace>(pos, ei, mobility)
327 - evaluate_pieces_of_color<BLACK, Trace>(pos, ei, mobility);
329 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
331 // Evaluate kings after all other pieces because we need complete attack
332 // information when computing the king safety evaluation.
333 score += evaluate_king<WHITE, Trace>(pos, ei)
334 - evaluate_king<BLACK, Trace>(pos, ei);
336 // Evaluate tactical threats, we need full attack information including king
337 score += evaluate_threats<WHITE, Trace>(pos, ei)
338 - evaluate_threats<BLACK, Trace>(pos, ei);
340 // Evaluate passed pawns, we need full attack information including king
341 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
342 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
344 // If one side has only a king, score for potential unstoppable pawns
345 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
346 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
347 - evaluate_unstoppable_pawns(pos, BLACK, ei);
349 // Evaluate space for both sides, only in middlegame
350 if (ei.mi->space_weight())
352 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
353 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
356 // Scale winning side if position is more drawish than it appears
357 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
358 : ei.mi->scale_factor(pos, BLACK);
360 // If we don't already have an unusual scale factor, check for opposite
361 // colored bishop endgames, and use a lower scale for those.
362 if ( ei.mi->game_phase() < PHASE_MIDGAME
363 && pos.opposite_bishops()
364 && sf == SCALE_FACTOR_NORMAL)
366 // Ignoring any pawns, do both sides only have a single bishop and no
368 if ( pos.non_pawn_material(WHITE) == BishopValueMg
369 && pos.non_pawn_material(BLACK) == BishopValueMg)
371 // Check for KBP vs KB with only a single pawn that is almost
372 // certainly a draw or at least two pawns.
373 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
374 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
377 // Endgame with opposite-colored bishops, but also other pieces. Still
378 // a bit drawish, but not as drawish as with only the two bishops.
379 sf = ScaleFactor(50);
382 Value v = interpolate(score, ei.mi->game_phase(), sf);
384 // In case of tracing add all single evaluation contributions for both white and black
387 Tracing::add(PST, pos.psq_score());
388 Tracing::add(IMBALANCE, ei.mi->material_value());
389 Tracing::add(PAWN, ei.pi->pawns_value());
390 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
391 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
392 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
393 Tracing::add(TOTAL, score);
394 Tracing::stream << "\nScaling: " << std::noshowpos
395 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
396 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
397 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
398 << "Total evaluation: " << to_cp(v);
401 return pos.side_to_move() == WHITE ? v : -v;
405 // init_eval_info() initializes king bitboards for given color adding
406 // pawn attacks. To be done at the beginning of the evaluation.
409 void init_eval_info(const Position& pos, EvalInfo& ei) {
411 const Color Them = (Us == WHITE ? BLACK : WHITE);
412 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
414 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
416 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
417 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
419 // Init king safety tables only if we are going to use them
420 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
422 ei.kingRing[Them] = b | shift_bb<Down>(b);
423 b &= ei.attackedBy[Us][PAWN];
424 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
425 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
428 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
432 // evaluate_outposts() evaluates bishop and knight outpost squares
434 template<PieceType Piece, Color Us>
435 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
437 const Color Them = (Us == WHITE ? BLACK : WHITE);
439 assert (Piece == BISHOP || Piece == KNIGHT);
441 // Initial bonus based on square
442 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
444 // Increase bonus if supported by pawn, especially if the opponent has
445 // no minor piece which can trade with the outpost piece.
446 if (bonus && (ei.attackedBy[Us][PAWN] & s))
448 if ( !pos.pieces(Them, KNIGHT)
449 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
450 bonus += bonus + bonus / 2;
455 return make_score(bonus, bonus);
459 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
461 template<PieceType Piece, Color Us, bool Trace>
462 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
466 Score score = SCORE_ZERO;
468 const Color Them = (Us == WHITE ? BLACK : WHITE);
469 const Square* pl = pos.list<Piece>(Us);
471 ei.attackedBy[Us][Piece] = 0;
473 while ((s = *pl++) != SQ_NONE)
475 // Find attacked squares, including x-ray attacks for bishops and rooks
476 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
477 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
478 : pos.attacks_from<Piece>(s);
480 if (ei.pinnedPieces[Us] & s)
481 b &= LineBB[pos.king_square(Us)][s];
483 ei.attackedBy[Us][Piece] |= b;
485 if (b & ei.kingRing[Them])
487 ei.kingAttackersCount[Us]++;
488 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
489 Bitboard bb = b & ei.attackedBy[Them][KING];
491 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
494 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
495 : popcount<Full >(b & mobilityArea);
497 mobility[Us] += MobilityBonus[Piece][mob];
499 // Decrease score if we are attacked by an enemy pawn. The remaining part
500 // of threat evaluation must be done later when we have full attack info.
501 if (ei.attackedBy[Them][PAWN] & s)
502 score -= ThreatenedByPawn[Piece];
504 // Otherwise give a bonus if we are a bishop and can pin a piece or can
505 // give a discovered check through an x-ray attack.
506 else if ( Piece == BISHOP
507 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
508 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
511 // Penalty for bishop with same coloured pawns
513 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
515 // Penalty for knight when there are few enemy pawns
517 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
519 if (Piece == BISHOP || Piece == KNIGHT)
521 // Bishop and knight outposts squares
522 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
523 score += evaluate_outposts<Piece, Us>(pos, ei, s);
525 // Bishop or knight behind a pawn
526 if ( relative_rank(Us, s) < RANK_5
527 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
528 score += MinorBehindPawn;
531 if ( (Piece == ROOK || Piece == QUEEN)
532 && relative_rank(Us, s) >= RANK_5)
534 // Major piece on 7th rank and enemy king trapped on 8th
535 if ( relative_rank(Us, s) == RANK_7
536 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
537 score += Piece == ROOK ? RookOn7th : QueenOn7th;
539 // Major piece attacking enemy pawns on the same rank/file
540 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
542 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
545 // Special extra evaluation for rooks
548 // Give a bonus for a rook on a open or semi-open file
549 if (ei.pi->semiopen(Us, file_of(s)))
550 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
552 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
555 Square ksq = pos.king_square(Us);
557 // Penalize rooks which are trapped by a king. Penalize more if the
558 // king has lost its castling capability.
559 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
560 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
561 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
562 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
565 // An important Chess960 pattern: A cornered bishop blocked by a friendly
566 // pawn diagonally in front of it is a very serious problem, especially
567 // when that pawn is also blocked.
570 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
572 const enum Piece P = make_piece(Us, PAWN);
573 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
574 if (pos.piece_on(s + d) == P)
575 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
576 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
582 Tracing::scores[Us][Piece] = score;
588 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
589 // pieces of a given color.
591 template<Color Us, bool Trace>
592 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
594 const Color Them = (Us == WHITE ? BLACK : WHITE);
596 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
597 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
599 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
600 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
601 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
602 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
604 // Sum up all attacked squares (updated in evaluate_pieces)
605 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
606 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
607 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
609 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
615 // evaluate_king() assigns bonuses and penalties to a king of a given color
617 template<Color Us, bool Trace>
618 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
620 const Color Them = (Us == WHITE ? BLACK : WHITE);
622 Bitboard undefended, b, b1, b2, safe;
624 const Square ksq = pos.king_square(Us);
626 // King shelter and enemy pawns storm
627 Score score = ei.pi->king_safety<Us>(pos, ksq);
629 // Main king safety evaluation
630 if (ei.kingAttackersCount[Them])
632 // Find the attacked squares around the king which have no defenders
633 // apart from the king itself
634 undefended = ei.attackedBy[Them][ALL_PIECES]
635 & ei.attackedBy[Us][KING]
636 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
637 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
638 | ei.attackedBy[Us][QUEEN]);
640 // Initialize the 'attackUnits' variable, which is used later on as an
641 // index to the KingDanger[] array. The initial value is based on the
642 // number and types of the enemy's attacking pieces, the number of
643 // attacked and undefended squares around our king and the quality of
644 // the pawn shelter (current 'score' value).
645 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
646 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
647 - mg_value(score) / 32;
649 // Analyse the enemy's safe queen contact checks. Firstly, find the
650 // undefended squares around the king that are attacked by the enemy's
652 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
655 // ...and then remove squares not supported by another enemy piece
656 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
657 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
659 attackUnits += QueenContactCheck
661 * (Them == pos.side_to_move() ? 2 : 1);
664 // Analyse the enemy's safe rook contact checks. Firstly, find the
665 // undefended squares around the king that are attacked by the enemy's
667 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
669 // Consider only squares where the enemy's rook gives check
670 b &= PseudoAttacks[ROOK][ksq];
674 // ...and then remove squares not supported by another enemy piece
675 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
676 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
678 attackUnits += RookContactCheck
680 * (Them == pos.side_to_move() ? 2 : 1);
683 // Analyse the enemy's safe distance checks for sliders and knights
684 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
686 b1 = pos.attacks_from<ROOK>(ksq) & safe;
687 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
689 // Enemy queen safe checks
690 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
692 attackUnits += QueenCheck * popcount<Max15>(b);
694 // Enemy rooks safe checks
695 b = b1 & ei.attackedBy[Them][ROOK];
697 attackUnits += RookCheck * popcount<Max15>(b);
699 // Enemy bishops safe checks
700 b = b2 & ei.attackedBy[Them][BISHOP];
702 attackUnits += BishopCheck * popcount<Max15>(b);
704 // Enemy knights safe checks
705 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
707 attackUnits += KnightCheck * popcount<Max15>(b);
709 // To index KingDanger[] attackUnits must be in [0, 99] range
710 attackUnits = std::min(99, std::max(0, attackUnits));
712 // Finally, extract the king danger score from the KingDanger[]
713 // array and subtract the score from evaluation.
714 score -= KingDanger[Us == Search::RootColor][attackUnits];
718 Tracing::scores[Us][KING] = score;
724 // evaluate_threats() assigns bonuses according to the type of attacking piece
725 // and the type of attacked one.
727 template<Color Us, bool Trace>
728 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
730 const Color Them = (Us == WHITE ? BLACK : WHITE);
732 Bitboard b, undefendedMinors, weakEnemies;
733 Score score = SCORE_ZERO;
735 // Undefended minors get penalized even if they are not under attack
736 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
737 & ~ei.attackedBy[Them][ALL_PIECES];
739 if (undefendedMinors)
740 score += UndefendedMinor;
742 // Enemy pieces not defended by a pawn and under our attack
743 weakEnemies = pos.pieces(Them)
744 & ~ei.attackedBy[Them][PAWN]
745 & ei.attackedBy[Us][ALL_PIECES];
747 // Add a bonus according if the attacking pieces are minor or major
750 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
752 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
754 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
756 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
760 Tracing::scores[Us][THREAT] = score;
766 // evaluate_passed_pawns() evaluates the passed pawns of the given color
768 template<Color Us, bool Trace>
769 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
771 const Color Them = (Us == WHITE ? BLACK : WHITE);
773 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
774 Score score = SCORE_ZERO;
776 b = ei.pi->passed_pawns(Us);
780 Square s = pop_lsb(&b);
782 assert(pos.pawn_passed(Us, s));
784 int r = int(relative_rank(Us, s) - RANK_2);
785 int rr = r * (r - 1);
787 // Base bonus based on rank
788 Value mbonus = Value(17 * rr);
789 Value ebonus = Value(7 * (rr + r + 1));
793 Square blockSq = s + pawn_push(Us);
795 // Adjust bonus based on the king's proximity
796 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
797 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
799 // If blockSq is not the queening square then consider also a second push
800 if (relative_rank(Us, blockSq) != RANK_8)
801 ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr);
803 // If the pawn is free to advance, then increase the bonus
804 if (pos.empty(blockSq))
806 squaresToQueen = forward_bb(Us, s);
808 // If there is an enemy rook or queen attacking the pawn from behind,
809 // add all X-ray attacks by the rook or queen. Otherwise consider only
810 // the squares in the pawn's path attacked or occupied by the enemy.
811 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
812 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
813 unsafeSquares = squaresToQueen;
815 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
817 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
818 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
819 defendedSquares = squaresToQueen;
821 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
823 // If there aren't any enemy attacks, then assign a huge bonus.
824 // The bonus will be a bit smaller if at least the block square
825 // isn't attacked, otherwise assign the smallest possible bonus.
826 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
828 // Assign a big bonus if the path to the queen is fully defended,
829 // otherwise assign a bit less of a bonus if at least the block
830 // square is defended.
831 if (defendedSquares == squaresToQueen)
834 else if (defendedSquares & blockSq)
835 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
837 mbonus += Value(k * rr), ebonus += Value(k * rr);
841 // Increase the bonus if the passed pawn is supported by a friendly pawn
842 // on the same rank and a bit smaller if it's on the previous rank.
843 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
844 if (supportingPawns & rank_bb(s))
845 ebonus += Value(r * 20);
847 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
848 ebonus += Value(r * 12);
850 // Rook pawns are a special case: They are sometimes worse, and
851 // sometimes better than other passed pawns. It is difficult to find
852 // good rules for determining whether they are good or bad. For now,
853 // we try the following: Increase the value for rook pawns if the
854 // other side has no pieces apart from a knight, and decrease the
855 // value if the other side has a rook or queen.
856 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
858 if (pos.non_pawn_material(Them) <= KnightValueMg)
859 ebonus += ebonus / 4;
861 else if (pos.pieces(Them, ROOK, QUEEN))
862 ebonus -= ebonus / 4;
865 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
866 ebonus += ebonus / 4;
868 score += make_score(mbonus, ebonus);
873 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
875 // Add the scores to the middlegame and endgame eval
876 return apply_weight(score, Weights[PassedPawns]);
880 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
881 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
882 // related to the possibility that pawns are unstoppable.
884 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
886 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
888 if (!b || pos.non_pawn_material(~us))
891 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
895 // evaluate_space() computes the space evaluation for a given side. The
896 // space evaluation is a simple bonus based on the number of safe squares
897 // available for minor pieces on the central four files on ranks 2--4. Safe
898 // squares one, two or three squares behind a friendly pawn are counted
899 // twice. Finally, the space bonus is scaled by a weight taken from the
900 // material hash table. The aim is to improve play on game opening.
902 int evaluate_space(const Position& pos, const EvalInfo& ei) {
904 const Color Them = (Us == WHITE ? BLACK : WHITE);
906 // Find the safe squares for our pieces inside the area defined by
907 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
908 // pawn, or if it is undefended and attacked by an enemy piece.
909 Bitboard safe = SpaceMask[Us]
910 & ~pos.pieces(Us, PAWN)
911 & ~ei.attackedBy[Them][PAWN]
912 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
914 // Find all squares which are at most three squares behind some friendly pawn
915 Bitboard behind = pos.pieces(Us, PAWN);
916 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
917 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
919 // Since SpaceMask[Us] is fully on our half of the board
920 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
922 // Count safe + (behind & safe) with a single popcount
923 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
927 // interpolate() interpolates between a middlegame and an endgame score,
928 // based on game phase. It also scales the return value by a ScaleFactor array.
930 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
932 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
933 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
934 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
936 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
937 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
938 return Value((r / GrainSize) * GrainSize); // Sign independent
941 // apply_weight() weights score v by score w trying to prevent overflow
942 Score apply_weight(Score v, Score w) {
943 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
944 (int(eg_value(v)) * eg_value(w)) / 0x100);
947 // weight_option() computes the value of an evaluation weight, by combining
948 // two UCI-configurable weights (midgame and endgame) with an internal weight.
950 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
952 // Scale option value from 100 to 256
953 int mg = Options[mgOpt] * 256 / 100;
954 int eg = Options[egOpt] * 256 / 100;
956 return apply_weight(make_score(mg, eg), internalWeight);
960 // Tracing functions definitions
962 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
964 void Tracing::add(int idx, Score wScore, Score bScore) {
966 scores[WHITE][idx] = wScore;
967 scores[BLACK][idx] = bScore;
970 void Tracing::row(const char* name, int idx) {
972 Score wScore = scores[WHITE][idx];
973 Score bScore = scores[BLACK][idx];
976 case PST: case IMBALANCE: case PAWN: case TOTAL:
977 stream << std::setw(20) << name << " | --- --- | --- --- | "
978 << std::setw(6) << to_cp(mg_value(wScore)) << " "
979 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
982 stream << std::setw(20) << name << " | " << std::noshowpos
983 << std::setw(5) << to_cp(mg_value(wScore)) << " "
984 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
985 << std::setw(5) << to_cp(mg_value(bScore)) << " "
986 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
988 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
989 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
993 std::string Tracing::do_trace(const Position& pos) {
996 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
997 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
999 do_evaluate<true>(pos);
1001 std::string totals = stream.str();
1004 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1005 << " | MG EG | MG EG | MG EG \n"
1006 << "---------------------+-------------+-------------+---------------\n";
1008 row("Material, PST, Tempo", PST);
1009 row("Material imbalance", IMBALANCE);
1011 row("Knights", KNIGHT);
1012 row("Bishops", BISHOP);
1014 row("Queens", QUEEN);
1015 row("Mobility", MOBILITY);
1016 row("King safety", KING);
1017 row("Threats", THREAT);
1018 row("Passed pawns", PASSED);
1019 row("Space", SPACE);
1021 stream << "---------------------+-------------+-------------+---------------\n";
1022 row("Total", TOTAL);
1025 return stream.str();