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 // KingExposed[Square] contains penalties based on the position of the
211 // defending king, indexed by king's square (from white's point of view).
212 const int KingExposed[] = {
213 2, 0, 2, 5, 5, 2, 0, 2,
214 2, 2, 4, 8, 8, 4, 2, 2,
215 7, 10, 12, 12, 12, 12, 10, 7,
216 15, 15, 15, 15, 15, 15, 15, 15,
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
223 // KingDanger[Color][attackUnits] contains the actual king danger weighted
224 // scores, indexed by color and by a calculated integer number.
225 Score KingDanger[COLOR_NB][128];
227 // Function prototypes
229 Value do_evaluate(const Position& pos);
232 void init_eval_info(const Position& pos, EvalInfo& ei);
234 template<Color Us, bool Trace>
235 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility);
237 template<Color Us, bool Trace>
238 Score evaluate_king(const Position& pos, const EvalInfo& ei);
240 template<Color Us, bool Trace>
241 Score evaluate_threats(const Position& pos, const EvalInfo& ei);
243 template<Color Us, bool Trace>
244 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei);
247 int evaluate_space(const Position& pos, const EvalInfo& ei);
249 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei);
251 Value interpolate(const Score& v, Phase ph, ScaleFactor sf);
252 Score apply_weight(Score v, Score w);
253 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
254 double to_cp(Value v);
260 /// evaluate() is the main evaluation function. It always computes two
261 /// values, an endgame score and a middlegame score, and interpolates
262 /// between them based on the remaining material.
264 Value evaluate(const Position& pos) {
265 return do_evaluate<false>(pos);
269 /// trace() is like evaluate(), but instead of returning a value, it returns
270 /// a string (suitable for outputting to stdout) that contains the detailed
271 /// descriptions and values of each evaluation term. It's mainly used for
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 a
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 middlegame
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 than 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 // Ignoring any pawns, do both sides only have a single bishop and no
381 if ( pos.non_pawn_material(WHITE) == BishopValueMg
382 && pos.non_pawn_material(BLACK) == BishopValueMg)
384 // Check for KBP vs KB with only a single pawn that is almost
385 // certainly a draw or at least two pawns.
386 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
387 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
390 // Endgame with opposite-colored bishops, but also other pieces. Still
391 // a bit drawish, but not as drawish as with only the two bishops.
392 sf = ScaleFactor(50);
395 Value v = interpolate(score, ei.mi->game_phase(), sf);
397 // In case of tracing add all single evaluation contributions for both white and black
400 Tracing::add(PST, pos.psq_score());
401 Tracing::add(IMBALANCE, ei.mi->material_value());
402 Tracing::add(PAWN, ei.pi->pawns_value());
403 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
404 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
405 Tracing::add(SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
406 Tracing::add(TOTAL, score);
407 Tracing::stream << "\nScaling: " << std::noshowpos
408 << std::setw(6) << 100.0 * ei.mi->game_phase() / 128.0 << "% MG, "
409 << std::setw(6) << 100.0 * (1.0 - ei.mi->game_phase() / 128.0) << "% * "
410 << std::setw(6) << (100.0 * sf) / SCALE_FACTOR_NORMAL << "% EG.\n"
411 << "Total evaluation: " << to_cp(v);
414 return pos.side_to_move() == WHITE ? v : -v;
418 // init_eval_info() initializes king bitboards for given color adding
419 // pawn attacks. To be done at the beginning of the evaluation.
422 void init_eval_info(const Position& pos, EvalInfo& ei) {
424 const Color Them = (Us == WHITE ? BLACK : WHITE);
425 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
427 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
429 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
430 ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
432 // Init king safety tables only if we are going to use them
433 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
435 ei.kingRing[Them] = b | shift_bb<Down>(b);
436 b &= ei.attackedBy[Us][PAWN];
437 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
438 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
441 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
445 // evaluate_outposts() evaluates bishop and knight outpost squares
447 template<PieceType Piece, Color Us>
448 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
450 const Color Them = (Us == WHITE ? BLACK : WHITE);
452 assert (Piece == BISHOP || Piece == KNIGHT);
454 // Initial bonus based on square
455 Value bonus = Outpost[Piece == BISHOP][relative_square(Us, s)];
457 // Increase bonus if supported by pawn, especially if the opponent has
458 // no minor piece which can trade with the outpost piece.
459 if (bonus && (ei.attackedBy[Us][PAWN] & s))
461 if ( !pos.pieces(Them, KNIGHT)
462 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
463 bonus += bonus + bonus / 2;
468 return make_score(bonus, bonus);
472 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
474 template<PieceType Piece, Color Us, bool Trace>
475 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard mobilityArea) {
479 Score score = SCORE_ZERO;
481 const Color Them = (Us == WHITE ? BLACK : WHITE);
482 const Square* pl = pos.list<Piece>(Us);
484 ei.attackedBy[Us][Piece] = 0;
486 while ((s = *pl++) != SQ_NONE)
488 // Find attacked squares, including x-ray attacks for bishops and rooks
489 b = Piece == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
490 : Piece == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
491 : pos.attacks_from<Piece>(s);
493 if (ei.pinnedPieces[Us] & s)
494 b &= LineBB[pos.king_square(Us)][s];
496 ei.attackedBy[Us][Piece] |= b;
498 if (b & ei.kingRing[Them])
500 ei.kingAttackersCount[Us]++;
501 ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
502 Bitboard bb = b & ei.attackedBy[Them][KING];
504 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
507 int mob = Piece != QUEEN ? popcount<Max15>(b & mobilityArea)
508 : popcount<Full >(b & mobilityArea);
510 mobility[Us] += MobilityBonus[Piece][mob];
512 // Decrease score if we are attacked by an enemy pawn. The remaining part
513 // of threat evaluation must be done later when we have full attack info.
514 if (ei.attackedBy[Them][PAWN] & s)
515 score -= ThreatenedByPawn[Piece];
517 // Otherwise give a bonus if we are a bishop and can pin a piece or can
518 // give a discovered check through an x-ray attack.
519 else if ( Piece == BISHOP
520 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
521 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
524 // Penalty for bishop with same coloured pawns
526 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
528 // Penalty for knight when there are few enemy pawns
530 score -= KnightPawns * std::max(5 - pos.count<PAWN>(Them), 0);
532 if (Piece == BISHOP || Piece == KNIGHT)
534 // Bishop and knight outposts squares
535 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
536 score += evaluate_outposts<Piece, Us>(pos, ei, s);
538 // Bishop or knight behind a pawn
539 if ( relative_rank(Us, s) < RANK_5
540 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
541 score += MinorBehindPawn;
544 if ( (Piece == ROOK || Piece == QUEEN)
545 && relative_rank(Us, s) >= RANK_5)
547 // Major piece on 7th rank and enemy king trapped on 8th
548 if ( relative_rank(Us, s) == RANK_7
549 && relative_rank(Us, pos.king_square(Them)) == RANK_8)
550 score += Piece == ROOK ? RookOn7th : QueenOn7th;
552 // Major piece attacking enemy pawns on the same rank/file
553 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
555 score += popcount<Max15>(pawns) * (Piece == ROOK ? RookOnPawn : QueenOnPawn);
558 // Special extra evaluation for rooks
561 // Give a bonus for a rook on a open or semi-open file
562 if (ei.pi->semiopen(Us, file_of(s)))
563 score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
565 if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
568 Square ksq = pos.king_square(Us);
570 // Penalize rooks which are trapped by a king. Penalize more if the
571 // king has lost its castling capability.
572 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
573 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
574 && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
575 score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
578 // An important Chess960 pattern: A cornered bishop blocked by a friendly
579 // pawn diagonally in front of it is a very serious problem, especially
580 // when that pawn is also blocked.
583 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
585 const enum Piece P = make_piece(Us, PAWN);
586 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
587 if (pos.piece_on(s + d) == P)
588 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
589 : pos.piece_on(s + d + d) == P ? TrappedBishopA1H1 * 2
595 Tracing::scores[Us][Piece] = score;
601 // evaluate_pieces_of_color() assigns bonuses and penalties to all the
602 // pieces of a given color.
604 template<Color Us, bool Trace>
605 Score evaluate_pieces_of_color(const Position& pos, EvalInfo& ei, Score* mobility) {
607 const Color Them = (Us == WHITE ? BLACK : WHITE);
609 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
610 const Bitboard mobilityArea = ~(ei.attackedBy[Them][PAWN] | pos.pieces(Us, PAWN, KING));
612 Score score = evaluate_pieces<KNIGHT, Us, Trace>(pos, ei, mobility, mobilityArea)
613 + evaluate_pieces<BISHOP, Us, Trace>(pos, ei, mobility, mobilityArea)
614 + evaluate_pieces<ROOK, Us, Trace>(pos, ei, mobility, mobilityArea)
615 + evaluate_pieces<QUEEN, Us, Trace>(pos, ei, mobility, mobilityArea);
617 // Sum up all attacked squares (updated in evaluate_pieces)
618 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
619 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
620 | ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
622 Tracing::scores[Us][MOBILITY] = apply_weight(mobility[Us], Weights[Mobility]);
628 // evaluate_king() assigns bonuses and penalties to a king of a given color
630 template<Color Us, bool Trace>
631 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
633 const Color Them = (Us == WHITE ? BLACK : WHITE);
635 Bitboard undefended, b, b1, b2, safe;
637 const Square ksq = pos.king_square(Us);
639 // King shelter and enemy pawns storm
640 Score score = ei.pi->king_safety<Us>(pos, ksq);
642 // Main king safety evaluation
643 if ( ei.kingAttackersCount[Them] >= 2
644 && ei.kingAdjacentZoneAttacksCount[Them])
646 // Find the attacked squares around the king which have no defenders
647 // apart from the king itself
648 undefended = ei.attackedBy[Them][ALL_PIECES]
649 & ei.attackedBy[Us][KING]
650 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
651 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
652 | ei.attackedBy[Us][QUEEN]);
654 // Initialize the 'attackUnits' variable, which is used later on as an
655 // index to the KingDanger[] array. The initial value is based on the
656 // number and types of the enemy's attacking pieces, the number of
657 // attacked and undefended squares around our king, the square of the
658 // king, and the quality of the pawn shelter.
659 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
660 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
661 + KingExposed[relative_square(Us, ksq)]
662 - mg_value(score) / 32;
664 // Analyse the enemy's safe queen contact checks. Firstly, find the
665 // undefended squares around the king that are attacked by the enemy's
667 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
670 // ...and 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 the enemy's safe rook contact checks. Firstly, find the
680 // undefended squares around the king that are attacked by the enemy's
682 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
684 // Consider only squares where the enemy's rook gives check
685 b &= PseudoAttacks[ROOK][ksq];
689 // ...and then remove squares not supported by another enemy piece
690 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
691 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
693 attackUnits += RookContactCheck
695 * (Them == pos.side_to_move() ? 2 : 1);
698 // Analyse the enemy's safe distance checks for sliders and knights
699 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
701 b1 = pos.attacks_from<ROOK>(ksq) & safe;
702 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
704 // Enemy queen safe checks
705 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
707 attackUnits += QueenCheck * popcount<Max15>(b);
709 // Enemy rooks safe checks
710 b = b1 & ei.attackedBy[Them][ROOK];
712 attackUnits += RookCheck * popcount<Max15>(b);
714 // Enemy bishops safe checks
715 b = b2 & ei.attackedBy[Them][BISHOP];
717 attackUnits += BishopCheck * popcount<Max15>(b);
719 // Enemy knights safe checks
720 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
722 attackUnits += KnightCheck * popcount<Max15>(b);
724 // To index KingDanger[] attackUnits must be in [0, 99] range
725 attackUnits = std::min(99, std::max(0, attackUnits));
727 // Finally, extract the king danger score from the KingDanger[]
728 // array and subtract the score from evaluation.
729 score -= KingDanger[Us == Search::RootColor][attackUnits];
733 Tracing::scores[Us][KING] = score;
739 // evaluate_threats() assigns bonuses according to the type of attacking piece
740 // and the type of attacked one.
742 template<Color Us, bool Trace>
743 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
745 const Color Them = (Us == WHITE ? BLACK : WHITE);
747 Bitboard b, undefendedMinors, weakEnemies;
748 Score score = SCORE_ZERO;
750 // Undefended minors get penalized even if they are not under attack
751 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
752 & ~ei.attackedBy[Them][ALL_PIECES];
754 if (undefendedMinors)
755 score += UndefendedMinor;
757 // Enemy pieces not defended by a pawn and under our attack
758 weakEnemies = pos.pieces(Them)
759 & ~ei.attackedBy[Them][PAWN]
760 & ei.attackedBy[Us][ALL_PIECES];
762 // Add a bonus according if the attacking pieces are minor or major
765 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
767 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
769 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
771 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
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 the king's 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, then increase the 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 any enemy attacks, then assign a huge bonus.
839 // The bonus will be a bit smaller if at least the block square
840 // isn't attacked, otherwise assign the smallest possible bonus.
841 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 3;
843 // Assign a big bonus if the path to the queen is fully defended,
844 // otherwise assign a bit less of a bonus if at least the block
845 // square is defended.
846 if (defendedSquares == squaresToQueen)
849 else if (defendedSquares & blockSq)
850 k += (unsafeSquares & defendedSquares) == unsafeSquares ? 4 : 2;
852 mbonus += Value(k * rr), ebonus += Value(k * rr);
856 // Increase the bonus if the passed pawn is supported by a friendly pawn
857 // on the same rank and a bit smaller if it's on the previous rank.
858 supportingPawns = pos.pieces(Us, PAWN) & adjacent_files_bb(file_of(s));
859 if (supportingPawns & rank_bb(s))
860 ebonus += Value(r * 20);
862 else if (supportingPawns & rank_bb(s - pawn_push(Us)))
863 ebonus += Value(r * 12);
865 // Rook pawns are a special case: They are sometimes worse, and
866 // sometimes better than other passed pawns. It is difficult to find
867 // good rules for determining whether they are good or bad. For now,
868 // we try the following: Increase the value for rook pawns if the
869 // other side has no pieces apart from a knight, and decrease the
870 // value if the other side has a rook or queen.
871 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
873 if (pos.non_pawn_material(Them) <= KnightValueMg)
874 ebonus += ebonus / 4;
876 else if (pos.pieces(Them, ROOK, QUEEN))
877 ebonus -= ebonus / 4;
880 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
881 ebonus += ebonus / 4;
883 score += make_score(mbonus, ebonus);
888 Tracing::scores[Us][PASSED] = apply_weight(score, Weights[PassedPawns]);
890 // Add the scores to the middlegame and endgame eval
891 return apply_weight(score, Weights[PassedPawns]);
895 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
896 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
897 // related to the possibility that pawns are unstoppable.
899 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
901 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
903 if (!b || pos.non_pawn_material(~us))
906 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
910 // evaluate_space() computes the space evaluation for a given side. The
911 // space evaluation is a simple bonus based on the number of safe squares
912 // available for minor pieces on the central four files on ranks 2--4. Safe
913 // squares one, two or three squares behind a friendly pawn are counted
914 // twice. Finally, the space bonus is scaled by a weight taken from the
915 // material hash table. The aim is to improve play on game opening.
917 int evaluate_space(const Position& pos, const EvalInfo& ei) {
919 const Color Them = (Us == WHITE ? BLACK : WHITE);
921 // Find the safe squares for our pieces inside the area defined by
922 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
923 // pawn, or if it is undefended and attacked by an enemy piece.
924 Bitboard safe = SpaceMask[Us]
925 & ~pos.pieces(Us, PAWN)
926 & ~ei.attackedBy[Them][PAWN]
927 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
929 // Find all squares which are at most three squares behind some friendly pawn
930 Bitboard behind = pos.pieces(Us, PAWN);
931 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
932 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
934 // Since SpaceMask[Us] is fully on our half of the board
935 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
937 // Count safe + (behind & safe) with a single popcount
938 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
942 // interpolate() interpolates between a middlegame and an endgame score,
943 // based on game phase. It also scales the return value by a ScaleFactor array.
945 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
947 assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
948 assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
949 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
951 int e = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
952 int r = (mg_value(v) * int(ph) + e * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME;
953 return Value((r / GrainSize) * GrainSize); // Sign independent
956 // apply_weight() weights score v by score w trying to prevent overflow
957 Score apply_weight(Score v, Score w) {
958 return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
959 (int(eg_value(v)) * eg_value(w)) / 0x100);
962 // weight_option() computes the value of an evaluation weight, by combining
963 // two UCI-configurable weights (midgame and endgame) with an internal weight.
965 Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
967 // Scale option value from 100 to 256
968 int mg = Options[mgOpt] * 256 / 100;
969 int eg = Options[egOpt] * 256 / 100;
971 return apply_weight(make_score(mg, eg), internalWeight);
975 // Tracing functions definitions
977 double to_cp(Value v) { return double(v) / double(PawnValueMg); }
979 void Tracing::add(int idx, Score wScore, Score bScore) {
981 scores[WHITE][idx] = wScore;
982 scores[BLACK][idx] = bScore;
985 void Tracing::row(const char* name, int idx) {
987 Score wScore = scores[WHITE][idx];
988 Score bScore = scores[BLACK][idx];
991 case PST: case IMBALANCE: case PAWN: case TOTAL:
992 stream << std::setw(20) << name << " | --- --- | --- --- | "
993 << std::setw(6) << to_cp(mg_value(wScore)) << " "
994 << std::setw(6) << to_cp(eg_value(wScore)) << " \n";
997 stream << std::setw(20) << name << " | " << std::noshowpos
998 << std::setw(5) << to_cp(mg_value(wScore)) << " "
999 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
1000 << std::setw(5) << to_cp(mg_value(bScore)) << " "
1001 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
1003 << std::setw(6) << to_cp(mg_value(wScore - bScore)) << " "
1004 << std::setw(6) << to_cp(eg_value(wScore - bScore)) << " \n";
1008 std::string Tracing::do_trace(const Position& pos) {
1011 stream << std::showpoint << std::showpos << std::fixed << std::setprecision(2);
1012 std::memset(scores, 0, 2 * (TOTAL + 1) * sizeof(Score));
1014 do_evaluate<true>(pos);
1016 std::string totals = stream.str();
1019 stream << std::setw(21) << "Eval term " << "| White | Black | Total \n"
1020 << " | MG EG | MG EG | MG EG \n"
1021 << "---------------------+-------------+-------------+---------------\n";
1023 row("Material, PST, Tempo", PST);
1024 row("Material imbalance", IMBALANCE);
1026 row("Knights", KNIGHT);
1027 row("Bishops", BISHOP);
1029 row("Queens", QUEEN);
1030 row("Mobility", MOBILITY);
1031 row("King safety", KING);
1032 row("Threats", THREAT);
1033 row("Passed pawns", PASSED);
1034 row("Space", SPACE);
1036 stream << "---------------------+-------------+-------------+---------------\n";
1037 row("Total", TOTAL);
1040 return stream.str();