2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2014 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 // Struct EvalInfo contains various information computed and collected
35 // by the evaluation functions.
38 // Pointers to material and pawn hash table entries
42 // attackedBy[color][piece type] is a bitboard representing all squares
43 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
44 // contains all squares attacked by the given color.
45 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
47 // kingRing[color] is the zone around the king which is considered
48 // by the king safety evaluation. This consists of the squares directly
49 // adjacent to the king, and the three (or two, for a king on an edge file)
50 // squares two ranks in front of the king. For instance, if black's king
51 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
52 // f7, g7, h7, f6, g6 and h6.
53 Bitboard kingRing[COLOR_NB];
55 // kingAttackersCount[color] is the number of pieces of the given color
56 // which attack a square in the kingRing of the enemy king.
57 int kingAttackersCount[COLOR_NB];
59 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
60 // given color which attack a square in the kingRing of the enemy king. The
61 // weights of the individual piece types are given by the variables
62 // QueenAttackWeight, RookAttackWeight, BishopAttackWeight and
63 // KnightAttackWeight in evaluate.cpp
64 int kingAttackersWeight[COLOR_NB];
66 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
67 // directly adjacent to the king of the given color. Pieces which attack
68 // more than one square are counted multiple times. For instance, if black's
69 // king is on g8 and there's a white knight on g5, this knight adds
70 // 2 to kingAdjacentZoneAttacksCount[BLACK].
71 int kingAdjacentZoneAttacksCount[COLOR_NB];
73 Bitboard pinnedPieces[COLOR_NB];
78 enum Terms { // First 8 entries are for PieceType
79 PST = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
82 Score terms[COLOR_NB][TERMS_NB];
86 double to_cp(Value v);
87 void add_term(int idx, Score term_w, Score term_b = SCORE_ZERO);
88 void format_row(std::stringstream& ss, const char* name, int idx);
89 std::string do_trace(const Position& pos);
92 // Evaluation weights, initialized from UCI options
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
94 struct Weight { int mg, eg; } Weights[6];
97 #define S(mg, eg) make_score(mg, eg)
99 // Internal evaluation weights. These are applied on top of the evaluation
100 // weights read from UCI parameters. The purpose is to be able to change
101 // the evaluation weights while keeping the default values of the UCI
102 // parameters at 100, which looks prettier.
104 // Values modified by Joona Kiiski
105 const Score WeightsInternal[] = {
106 S(289, 344), S(233, 201), S(221, 273), S(46, 0), S(271, 0), S(307, 0)
109 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
110 // game, indexed by piece type and number of attacked squares not occupied by
112 const Score MobilityBonus[][32] = {
114 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
115 S( 37, 28), S( 42, 31), S(44, 33) },
116 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
117 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
118 S( 84, 79), S( 86, 81) },
119 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
120 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
121 S( 35,122), S( 36,123), S(37,124) },
122 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
123 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
124 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
125 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
126 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
129 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
130 // indexed by piece type and square (from white's point of view).
131 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] = {
151 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
152 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[] = {
158 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
163 const Score Tempo = make_score(24, 11);
164 const Score RookOnPawn = make_score(10, 28);
165 const Score RookOpenFile = make_score(43, 21);
166 const Score RookSemiopenFile = make_score(19, 10);
167 const Score BishopPawns = make_score( 8, 12);
168 const Score MinorBehindPawn = make_score(16, 0);
169 const Score UndefendedMinor = make_score(25, 10);
170 const Score TrappedRook = make_score(90, 0);
171 const Score Unstoppable = make_score( 0, 20);
173 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
174 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
175 // happen in Chess960 games.
176 const Score TrappedBishopA1H1 = make_score(50, 50);
178 // SpaceMask[Color] contains the area of the board which is considered
179 // by the space evaluation. In the middlegame, each side is given a bonus
180 // based on how many squares inside this area are safe and available for
181 // friendly minor pieces.
182 const Bitboard SpaceMask[] = {
183 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
184 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
187 // King danger constants and variables. The king danger scores are taken
188 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
189 // of the enemy attack are added up into an integer, which is used as an
190 // index to KingDanger[].
192 // KingAttackWeights[PieceType] contains king attack weights by piece type
193 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
195 // Bonuses for enemy's safe checks
196 const int QueenContactCheck = 24;
197 const int RookContactCheck = 16;
198 const int QueenCheck = 12;
199 const int RookCheck = 8;
200 const int BishopCheck = 2;
201 const int KnightCheck = 3;
203 // KingDanger[Color][attackUnits] contains the actual king danger weighted
204 // scores, indexed by color and by a calculated integer number.
205 Score KingDanger[COLOR_NB][128];
208 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
209 Score apply_weight(Score v, const Weight& w) {
210 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
214 // weight_option() computes the value of an evaluation weight, by combining
215 // two UCI-configurable weights (midgame and endgame) with an internal weight.
217 Weight weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
219 Weight w = { Options[mgOpt] * mg_value(internalWeight) / 100,
220 Options[egOpt] * eg_value(internalWeight) / 100 };
225 // interpolate() interpolates between a middlegame and an endgame score,
226 // based on game phase. It also scales the return value by a ScaleFactor array.
228 Value interpolate(const Score& v, Phase ph, ScaleFactor sf) {
230 assert(-VALUE_INFINITE < mg_value(v) && mg_value(v) < VALUE_INFINITE);
231 assert(-VALUE_INFINITE < eg_value(v) && eg_value(v) < VALUE_INFINITE);
232 assert(PHASE_ENDGAME <= ph && ph <= PHASE_MIDGAME);
234 int eg = (eg_value(v) * int(sf)) / SCALE_FACTOR_NORMAL;
235 return Value((mg_value(v) * int(ph) + eg * int(PHASE_MIDGAME - ph)) / PHASE_MIDGAME);
239 // init_eval_info() initializes king bitboards for given color adding
240 // pawn attacks. To be done at the beginning of the evaluation.
243 void init_eval_info(const Position& pos, EvalInfo& ei) {
245 const Color Them = (Us == WHITE ? BLACK : WHITE);
246 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
248 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
250 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
251 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
253 // Init king safety tables only if we are going to use them
254 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
256 ei.kingRing[Them] = b | shift_bb<Down>(b);
257 b &= ei.attackedBy[Us][PAWN];
258 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
259 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
262 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
266 // evaluate_outposts() evaluates bishop and knight outpost squares
268 template<PieceType Pt, Color Us>
269 Score evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
271 const Color Them = (Us == WHITE ? BLACK : WHITE);
273 assert (Pt == BISHOP || Pt == KNIGHT);
275 // Initial bonus based on square
276 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
278 // Increase bonus if supported by pawn, especially if the opponent has
279 // no minor piece which can trade with the outpost piece.
280 if (bonus && (ei.attackedBy[Us][PAWN] & s))
282 if ( !pos.pieces(Them, KNIGHT)
283 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
284 bonus += bonus + bonus / 2;
289 return make_score(bonus, bonus);
293 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
295 template<PieceType Pt, Color Us, bool Trace>
296 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
300 Score score = SCORE_ZERO;
302 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
303 const Color Them = (Us == WHITE ? BLACK : WHITE);
304 const Square* pl = pos.list<Pt>(Us);
306 ei.attackedBy[Us][Pt] = 0;
308 while ((s = *pl++) != SQ_NONE)
310 // Find attacked squares, including x-ray attacks for bishops and rooks
311 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
312 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
313 : pos.attacks_from<Pt>(s);
315 if (ei.pinnedPieces[Us] & s)
316 b &= LineBB[pos.king_square(Us)][s];
318 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
320 if (b & ei.kingRing[Them])
322 ei.kingAttackersCount[Us]++;
323 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
324 Bitboard bb = b & ei.attackedBy[Them][KING];
326 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
330 b &= ~( ei.attackedBy[Them][KNIGHT]
331 | ei.attackedBy[Them][BISHOP]
332 | ei.attackedBy[Them][ROOK]);
334 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
335 : popcount<Full >(b & mobilityArea[Us]);
337 mobility[Us] += MobilityBonus[Pt][mob];
339 // Decrease score if we are attacked by an enemy pawn. The remaining part
340 // of threat evaluation must be done later when we have full attack info.
341 if (ei.attackedBy[Them][PAWN] & s)
342 score -= ThreatenedByPawn[Pt];
344 if (Pt == BISHOP || Pt == KNIGHT)
346 // Penalty for bishop with same colored pawns
348 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
350 // Bishop and knight outposts squares
351 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
352 score += evaluate_outposts<Pt, Us>(pos, ei, s);
354 // Bishop or knight behind a pawn
355 if ( relative_rank(Us, s) < RANK_5
356 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
357 score += MinorBehindPawn;
362 // Rook piece attacking enemy pawns on the same rank/file
363 if (relative_rank(Us, s) >= RANK_5)
365 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
367 score += popcount<Max15>(pawns) * RookOnPawn;
370 // Give a bonus for a rook on a open or semi-open file
371 if (ei.pi->semiopen_file(Us, file_of(s)))
372 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
374 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
377 Square ksq = pos.king_square(Us);
379 // Penalize rooks which are trapped by a king. Penalize more if the
380 // king has lost its castling capability.
381 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
382 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
383 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
384 score -= (TrappedRook - make_score(mob * 8, 0)) * (1 + !pos.can_castle(Us));
387 // An important Chess960 pattern: A cornered bishop blocked by a friendly
388 // pawn diagonally in front of it is a very serious problem, especially
389 // when that pawn is also blocked.
392 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
394 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
395 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
396 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
397 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
403 Tracing::terms[Us][Pt] = score;
405 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
409 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
411 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
414 // evaluate_king() assigns bonuses and penalties to a king of a given color
416 template<Color Us, bool Trace>
417 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
419 const Color Them = (Us == WHITE ? BLACK : WHITE);
421 Bitboard undefended, b, b1, b2, safe;
423 const Square ksq = pos.king_square(Us);
425 // King shelter and enemy pawns storm
426 Score score = ei.pi->king_safety<Us>(pos, ksq);
428 // Main king safety evaluation
429 if (ei.kingAttackersCount[Them])
431 // Find the attacked squares around the king which have no defenders
432 // apart from the king itself
433 undefended = ei.attackedBy[Them][ALL_PIECES]
434 & ei.attackedBy[Us][KING]
435 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
436 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
437 | ei.attackedBy[Us][QUEEN]);
439 // Initialize the 'attackUnits' variable, which is used later on as an
440 // index to the KingDanger[] array. The initial value is based on the
441 // number and types of the enemy's attacking pieces, the number of
442 // attacked and undefended squares around our king and the quality of
443 // the pawn shelter (current 'score' value).
444 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
445 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
446 + 2 * (ei.pinnedPieces[Us] != 0)
447 - mg_value(score) / 32;
449 // Analyse the enemy's safe queen contact checks. Firstly, find the
450 // undefended squares around the king that are attacked by the enemy's
452 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
455 // ...and then remove squares not supported by another enemy piece
456 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
457 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
460 attackUnits += QueenContactCheck
462 * (Them == pos.side_to_move() ? 2 : 1);
465 // Analyse the enemy's safe rook contact checks. Firstly, find the
466 // undefended squares around the king that are attacked by the enemy's
468 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
470 // Consider only squares where the enemy's rook gives check
471 b &= PseudoAttacks[ROOK][ksq];
475 // ...and then remove squares not supported by another enemy piece
476 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
477 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
480 attackUnits += RookContactCheck
482 * (Them == pos.side_to_move() ? 2 : 1);
485 // Analyse the enemy's safe distance checks for sliders and knights
486 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
488 b1 = pos.attacks_from<ROOK>(ksq) & safe;
489 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
491 // Enemy queen safe checks
492 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
494 attackUnits += QueenCheck * popcount<Max15>(b);
496 // Enemy rooks safe checks
497 b = b1 & ei.attackedBy[Them][ROOK];
499 attackUnits += RookCheck * popcount<Max15>(b);
501 // Enemy bishops safe checks
502 b = b2 & ei.attackedBy[Them][BISHOP];
504 attackUnits += BishopCheck * popcount<Max15>(b);
506 // Enemy knights safe checks
507 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
509 attackUnits += KnightCheck * popcount<Max15>(b);
511 // To index KingDanger[] attackUnits must be in [0, 99] range
512 attackUnits = std::min(99, std::max(0, attackUnits));
514 // Finally, extract the king danger score from the KingDanger[]
515 // array and subtract the score from evaluation.
516 score -= KingDanger[Us == Search::RootColor][attackUnits];
520 Tracing::terms[Us][KING] = score;
526 // evaluate_threats() assigns bonuses according to the type of attacking piece
527 // and the type of attacked one.
529 template<Color Us, bool Trace>
530 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
532 const Color Them = (Us == WHITE ? BLACK : WHITE);
534 Bitboard b, undefendedMinors, weakEnemies;
535 Score score = SCORE_ZERO;
537 // Undefended minors get penalized even if they are not under attack
538 undefendedMinors = pos.pieces(Them, BISHOP, KNIGHT)
539 & ~ei.attackedBy[Them][ALL_PIECES];
541 if (undefendedMinors)
542 score += UndefendedMinor;
544 // Enemy pieces not defended by a pawn and under our attack
545 weakEnemies = pos.pieces(Them)
546 & ~ei.attackedBy[Them][PAWN]
547 & ei.attackedBy[Us][ALL_PIECES];
549 // Add a bonus according if the attacking pieces are minor or major
552 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
554 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
556 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
558 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
562 Tracing::terms[Us][Tracing::THREAT] = score;
568 // evaluate_passed_pawns() evaluates the passed pawns of the given color
570 template<Color Us, bool Trace>
571 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
573 const Color Them = (Us == WHITE ? BLACK : WHITE);
575 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
576 Score score = SCORE_ZERO;
578 b = ei.pi->passed_pawns(Us);
582 Square s = pop_lsb(&b);
584 assert(pos.pawn_passed(Us, s));
586 int r = int(relative_rank(Us, s) - RANK_2);
587 int rr = r * (r - 1);
589 // Base bonus based on rank
590 Value mbonus = Value(17 * rr);
591 Value ebonus = Value(7 * (rr + r + 1));
595 Square blockSq = s + pawn_push(Us);
597 // Adjust bonus based on the king's proximity
598 ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 5 * rr)
599 - Value(square_distance(pos.king_square(Us ), blockSq) * 2 * rr);
601 // If blockSq is not the queening square then consider also a second push
602 if (relative_rank(Us, blockSq) != RANK_8)
603 ebonus -= Value(rr * square_distance(pos.king_square(Us), blockSq + pawn_push(Us)));
605 // If the pawn is free to advance, then increase the bonus
606 if (pos.empty(blockSq))
608 squaresToQueen = forward_bb(Us, s);
610 // If there is an enemy rook or queen attacking the pawn from behind,
611 // add all X-ray attacks by the rook or queen. Otherwise consider only
612 // the squares in the pawn's path attacked or occupied by the enemy.
613 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
614 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
615 unsafeSquares = squaresToQueen;
617 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
619 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
620 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
621 defendedSquares = squaresToQueen;
623 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
625 // If there aren't any enemy attacks, assign a big bonus. Otherwise
626 // assign a smaller bonus if the block square isn't attacked.
627 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
629 // If the path to queen is fully defended, assign a big bonus.
630 // Otherwise assign a smaller bonus if the block square is defended.
631 if (defendedSquares == squaresToQueen)
634 else if (defendedSquares & blockSq)
637 mbonus += Value(k * rr), ebonus += Value(k * rr);
641 // Rook pawns are a special case: They are sometimes worse, and
642 // sometimes better than other passed pawns. It is difficult to find
643 // good rules for determining whether they are good or bad. For now,
644 // we try the following: Increase the value for rook pawns if the
645 // other side has no pieces apart from a knight, and decrease the
646 // value if the other side has a rook or queen.
647 if (file_of(s) == FILE_A || file_of(s) == FILE_H)
649 if (pos.non_pawn_material(Them) <= KnightValueMg)
650 ebonus += ebonus / 4;
652 else if (pos.pieces(Them, ROOK, QUEEN))
653 ebonus -= ebonus / 4;
656 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
657 ebonus += ebonus / 4;
659 score += make_score(mbonus, ebonus);
663 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
665 // Add the scores to the middlegame and endgame eval
666 return apply_weight(score, Weights[PassedPawns]);
670 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
671 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
672 // related to the possibility that pawns are unstoppable.
674 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
676 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
678 if (!b || pos.non_pawn_material(~us))
681 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
685 // evaluate_space() computes the space evaluation for a given side. The
686 // space evaluation is a simple bonus based on the number of safe squares
687 // available for minor pieces on the central four files on ranks 2--4. Safe
688 // squares one, two or three squares behind a friendly pawn are counted
689 // twice. Finally, the space bonus is scaled by a weight taken from the
690 // material hash table. The aim is to improve play on game opening.
692 int evaluate_space(const Position& pos, const EvalInfo& ei) {
694 const Color Them = (Us == WHITE ? BLACK : WHITE);
696 // Find the safe squares for our pieces inside the area defined by
697 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
698 // pawn, or if it is undefended and attacked by an enemy piece.
699 Bitboard safe = SpaceMask[Us]
700 & ~pos.pieces(Us, PAWN)
701 & ~ei.attackedBy[Them][PAWN]
702 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
704 // Find all squares which are at most three squares behind some friendly pawn
705 Bitboard behind = pos.pieces(Us, PAWN);
706 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
707 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
709 // Since SpaceMask[Us] is fully on our half of the board
710 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
712 // Count safe + (behind & safe) with a single popcount
713 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
717 // do_evaluate() is the evaluation entry point, called directly from evaluate()
720 Value do_evaluate(const Position& pos) {
722 assert(!pos.checkers());
725 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
726 Thread* thisThread = pos.this_thread();
728 // Initialize score by reading the incrementally updated scores included
729 // in the position object (material + piece square tables) and adding a
730 // Tempo bonus. Score is computed from the point of view of white.
731 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
733 // Probe the material hash table
734 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
735 score += ei.mi->material_value();
737 // If we have a specialized evaluation function for the current material
738 // configuration, call it and return.
739 if (ei.mi->specialized_eval_exists())
740 return ei.mi->evaluate(pos);
742 // Probe the pawn hash table
743 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
744 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
746 // Initialize attack and king safety bitboards
747 init_eval_info<WHITE>(pos, ei);
748 init_eval_info<BLACK>(pos, ei);
750 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
751 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
753 // Do not include in mobility squares protected by enemy pawns or occupied by our pieces
754 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
755 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
757 // Evaluate pieces and mobility
758 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
759 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
761 // Evaluate kings after all other pieces because we need complete attack
762 // information when computing the king safety evaluation.
763 score += evaluate_king<WHITE, Trace>(pos, ei)
764 - evaluate_king<BLACK, Trace>(pos, ei);
766 // Evaluate tactical threats, we need full attack information including king
767 score += evaluate_threats<WHITE, Trace>(pos, ei)
768 - evaluate_threats<BLACK, Trace>(pos, ei);
770 // Evaluate passed pawns, we need full attack information including king
771 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
772 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
774 // If one side has only a king, score for potential unstoppable pawns
775 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
776 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
777 - evaluate_unstoppable_pawns(pos, BLACK, ei);
779 // Evaluate space for both sides, only in middlegame
780 if (ei.mi->space_weight())
782 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
783 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
786 // Scale winning side if position is more drawish than it appears
787 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
788 : ei.mi->scale_factor(pos, BLACK);
790 // If we don't already have an unusual scale factor, check for opposite
791 // colored bishop endgames, and use a lower scale for those.
792 if ( ei.mi->game_phase() < PHASE_MIDGAME
793 && pos.opposite_bishops()
794 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
796 // Ignoring any pawns, do both sides only have a single bishop and no
798 if ( pos.non_pawn_material(WHITE) == BishopValueMg
799 && pos.non_pawn_material(BLACK) == BishopValueMg)
801 // Check for KBP vs KB with only a single pawn that is almost
802 // certainly a draw or at least two pawns.
803 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
804 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
807 // Endgame with opposite-colored bishops, but also other pieces. Still
808 // a bit drawish, but not as drawish as with only the two bishops.
809 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
812 Value v = interpolate(score, ei.mi->game_phase(), sf);
814 // In case of tracing add all single evaluation contributions for both white and black
817 Tracing::add_term(Tracing::PST, pos.psq_score());
818 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
819 Tracing::add_term(PAWN, ei.pi->pawns_value());
820 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
821 , apply_weight(mobility[BLACK], Weights[Mobility]));
822 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
823 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
824 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
825 Tracing::add_term(Tracing::TOTAL, score);
830 return pos.side_to_move() == WHITE ? v : -v;
834 // Tracing function definitions
836 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
838 void Tracing::add_term(int idx, Score wScore, Score bScore) {
840 terms[WHITE][idx] = wScore;
841 terms[BLACK][idx] = bScore;
844 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
846 Score wScore = terms[WHITE][idx];
847 Score bScore = terms[BLACK][idx];
850 case PST: case IMBALANCE: case PAWN: case TOTAL:
851 ss << std::setw(20) << name << " | --- --- | --- --- | "
852 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
853 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
856 ss << std::setw(20) << name << " | " << std::noshowpos
857 << std::setw(5) << to_cp(mg_value(wScore)) << " "
858 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
859 << std::setw(5) << to_cp(mg_value(bScore)) << " "
860 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
861 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
862 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
866 std::string Tracing::do_trace(const Position& pos) {
868 std::memset(terms, 0, sizeof(terms));
870 Value v = do_evaluate<true>(pos);
871 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
873 std::stringstream ss;
874 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
875 << " Eval term | White | Black | Total \n"
876 << " | MG EG | MG EG | MG EG \n"
877 << "---------------------+-------------+-------------+-------------\n";
879 format_row(ss, "Material, PST, Tempo", PST);
880 format_row(ss, "Material imbalance", IMBALANCE);
881 format_row(ss, "Pawns", PAWN);
882 format_row(ss, "Knights", KNIGHT);
883 format_row(ss, "Bishops", BISHOP);
884 format_row(ss, "Rooks", ROOK);
885 format_row(ss, "Queens", QUEEN);
886 format_row(ss, "Mobility", MOBILITY);
887 format_row(ss, "King safety", KING);
888 format_row(ss, "Threats", THREAT);
889 format_row(ss, "Passed pawns", PASSED);
890 format_row(ss, "Space", SPACE);
892 ss << "---------------------+-------------+-------------+-------------\n";
893 format_row(ss, "Total", TOTAL);
895 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
905 /// evaluate() is the main evaluation function. It returns a static evaluation
906 /// of the position always from the point of view of the side to move.
908 Value evaluate(const Position& pos) {
909 return do_evaluate<false>(pos);
913 /// trace() is like evaluate(), but instead of returning a value, it returns
914 /// a string (suitable for outputting to stdout) that contains the detailed
915 /// descriptions and values of each evaluation term. It's mainly used for
917 std::string trace(const Position& pos) {
918 return Tracing::do_trace(pos);
922 /// init() computes evaluation weights from the corresponding UCI parameters
923 /// and setup king tables.
927 Weights[Mobility] = weight_option("Mobility (Midgame)", "Mobility (Endgame)", WeightsInternal[Mobility]);
928 Weights[PawnStructure] = weight_option("Pawn Structure (Midgame)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
929 Weights[PassedPawns] = weight_option("Passed Pawns (Midgame)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
930 Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
931 Weights[KingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
932 Weights[KingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
934 const int MaxSlope = 30;
935 const int Peak = 1280;
937 for (int t = 0, i = 1; i < 100; ++i)
939 t = std::min(Peak, std::min(int(0.4 * i * i), t + MaxSlope));
941 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
942 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);