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/>.
33 // Struct EvalInfo contains various information computed and collected
34 // by the evaluation functions.
37 // Pointers to material and pawn hash table entries
41 // attackedBy[color][piece type] is a bitboard representing all squares
42 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
43 // contains all squares attacked by the given color.
44 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
46 // kingRing[color] is the zone around the king which is considered
47 // by the king safety evaluation. This consists of the squares directly
48 // adjacent to the king, and the three (or two, for a king on an edge file)
49 // squares two ranks in front of the king. For instance, if black's king
50 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
51 // f7, g7, h7, f6, g6 and h6.
52 Bitboard kingRing[COLOR_NB];
54 // kingAttackersCount[color] is the number of pieces of the given color
55 // which attack a square in the kingRing of the enemy king.
56 int kingAttackersCount[COLOR_NB];
58 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
59 // given color which attack a square in the kingRing of the enemy king. The
60 // weights of the individual piece types are given by the elements in the
61 // KingAttackWeights array.
62 int kingAttackersWeight[COLOR_NB];
64 // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
65 // directly adjacent to the king of the given color. Pieces which attack
66 // more than one square are counted multiple times. For instance, if black's
67 // king is on g8 and there's a white knight on g5, this knight adds
68 // 2 to kingAdjacentZoneAttacksCount[BLACK].
69 int kingAdjacentZoneAttacksCount[COLOR_NB];
71 Bitboard pinnedPieces[COLOR_NB];
76 enum Terms { // First 8 entries are for PieceType
77 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERMS_NB
80 Score scores[COLOR_NB][TERMS_NB];
84 double to_cp(Value v);
85 void write(int idx, Color c, Score s);
86 void write(int idx, Score w, Score b = SCORE_ZERO);
87 void print(std::stringstream& ss, const char* name, int idx);
88 std::string do_trace(const Position& pos);
91 // Evaluation weights, indexed by evaluation term
92 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
93 const struct Weight { int mg, eg; } Weights[] = {
94 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {318, 0}
98 #define S(mg, eg) make_score(mg, eg)
100 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
101 // game, indexed by piece type and number of attacked squares not occupied by
103 const Score MobilityBonus[][32] = {
105 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
106 S( 37, 28), S( 42, 31), S(44, 33) },
107 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
108 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
109 S( 84, 79), S( 86, 81) },
110 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
111 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
112 S( 35,122), S( 36,123), S(37,124) },
113 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
114 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
115 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
116 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
117 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
120 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
121 // indexed by piece type and square (from white's point of view).
122 const Value Outpost[][SQUARE_NB] = {
124 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
125 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
126 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
127 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
128 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
129 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
134 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
135 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
136 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
139 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
140 // bonuses according to which piece type attacks which one.
141 const Score Threat[][2][PIECE_TYPE_NB] = {
142 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
143 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
144 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
145 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
148 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
149 // type is attacked by an enemy pawn.
150 const Score ThreatenedByPawn[] = {
151 S(0, 0), S(0, 0), S(87, 118), S(84, 122), S(114, 203), S(121, 217)
154 // Assorted bonuses and penalties used by evaluation
155 const Score KingOnOne = S( 2, 58);
156 const Score KingOnMany = S( 6,125);
157 const Score RookOnPawn = S( 7, 27);
158 const Score RookOpenFile = S(43, 21);
159 const Score RookSemiOpenFile = S(19, 10);
160 const Score BishopPawns = S( 8, 12);
161 const Score MinorBehindPawn = S(16, 0);
162 const Score TrappedRook = S(92, 0);
163 const Score Unstoppable = S( 0, 20);
164 const Score Hanging = S(31, 26);
166 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
167 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
168 // happen in Chess960 games.
169 const Score TrappedBishopA1H1 = S(50, 50);
173 // SpaceMask[Color] contains the area of the board which is considered
174 // by the space evaluation. In the middlegame, each side is given a bonus
175 // based on how many squares inside this area are safe and available for
176 // friendly minor pieces.
177 const Bitboard SpaceMask[] = {
178 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
179 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
182 // King danger constants and variables. The king danger scores are taken
183 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
184 // of the enemy attack are added up into an integer, which is used as an
185 // index to KingDanger[].
187 // KingAttackWeights[PieceType] contains king attack weights by piece type
188 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
190 // Bonuses for enemy's safe checks
191 const int QueenContactCheck = 24;
192 const int RookContactCheck = 16;
193 const int QueenCheck = 12;
194 const int RookCheck = 8;
195 const int BishopCheck = 2;
196 const int KnightCheck = 3;
198 // KingDanger[attackUnits] contains the actual king danger weighted
199 // scores, indexed by a calculated integer number.
200 Score KingDanger[128];
202 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
203 Score apply_weight(Score v, const Weight& w) {
204 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
208 // init_eval_info() initializes king bitboards for given color adding
209 // pawn attacks. To be done at the beginning of the evaluation.
212 void init_eval_info(const Position& pos, EvalInfo& ei) {
214 const Color Them = (Us == WHITE ? BLACK : WHITE);
215 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
217 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
219 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
220 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
222 // Init king safety tables only if we are going to use them
223 if (pos.non_pawn_material(Us) >= QueenValueMg)
225 ei.kingRing[Them] = b | shift_bb<Down>(b);
226 b &= ei.attackedBy[Us][PAWN];
227 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
228 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
231 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
235 // evaluate_outpost() evaluates bishop and knight outpost squares
237 template<PieceType Pt, Color Us>
238 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
240 const Color Them = (Us == WHITE ? BLACK : WHITE);
242 assert (Pt == BISHOP || Pt == KNIGHT);
244 // Initial bonus based on square
245 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
247 // Increase bonus if supported by pawn, especially if the opponent has
248 // no minor piece which can trade with the outpost piece.
249 if (bonus && (ei.attackedBy[Us][PAWN] & s))
251 if ( !pos.pieces(Them, KNIGHT)
252 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
253 bonus += bonus + bonus / 2;
258 return make_score(bonus * 2, bonus / 2);
262 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
264 template<PieceType Pt, Color Us, bool Trace>
265 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
269 Score score = SCORE_ZERO;
271 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
272 const Color Them = (Us == WHITE ? BLACK : WHITE);
273 const Square* pl = pos.list<Pt>(Us);
275 ei.attackedBy[Us][Pt] = 0;
277 while ((s = *pl++) != SQ_NONE)
279 // Find attacked squares, including x-ray attacks for bishops and rooks
280 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
281 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
282 : pos.attacks_from<Pt>(s);
284 if (ei.pinnedPieces[Us] & s)
285 b &= LineBB[pos.king_square(Us)][s];
287 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
289 if (b & ei.kingRing[Them])
291 ei.kingAttackersCount[Us]++;
292 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
293 Bitboard bb = b & ei.attackedBy[Them][KING];
295 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
299 b &= ~( ei.attackedBy[Them][KNIGHT]
300 | ei.attackedBy[Them][BISHOP]
301 | ei.attackedBy[Them][ROOK]);
303 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
304 : popcount<Full >(b & mobilityArea[Us]);
306 mobility[Us] += MobilityBonus[Pt][mob];
308 // Decrease score if we are attacked by an enemy pawn. The remaining part
309 // of threat evaluation must be done later when we have full attack info.
310 if (ei.attackedBy[Them][PAWN] & s)
311 score -= ThreatenedByPawn[Pt];
313 if (Pt == BISHOP || Pt == KNIGHT)
315 // Penalty for bishop with same colored pawns
317 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
319 // Bishop and knight outpost square
320 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
321 score += evaluate_outpost<Pt, Us>(pos, ei, s);
323 // Bishop or knight behind a pawn
324 if ( relative_rank(Us, s) < RANK_5
325 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
326 score += MinorBehindPawn;
331 // Rook piece attacking enemy pawns on the same rank/file
332 if (relative_rank(Us, s) >= RANK_5)
334 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
336 score += popcount<Max15>(pawns) * RookOnPawn;
339 // Give a bonus for a rook on a open or semi-open file
340 if (ei.pi->semiopen_file(Us, file_of(s)))
341 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiOpenFile;
343 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
346 Square ksq = pos.king_square(Us);
348 // Penalize rooks which are trapped by a king. Penalize more if the
349 // king has lost its castling capability.
350 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
351 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
352 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
353 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
356 // An important Chess960 pattern: A cornered bishop blocked by a friendly
357 // pawn diagonally in front of it is a very serious problem, especially
358 // when that pawn is also blocked.
361 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
363 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
364 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
365 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
366 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
372 Tracing::write(Pt, Us, score);
374 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
378 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
380 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
383 // evaluate_king() assigns bonuses and penalties to a king of a given color
385 template<Color Us, bool Trace>
386 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
388 const Color Them = (Us == WHITE ? BLACK : WHITE);
390 Bitboard undefended, b, b1, b2, safe;
392 const Square ksq = pos.king_square(Us);
394 // King shelter and enemy pawns storm
395 Score score = ei.pi->king_safety<Us>(pos, ksq);
397 // Main king safety evaluation
398 if (ei.kingAttackersCount[Them])
400 // Find the attacked squares around the king which have no defenders
401 // apart from the king itself
402 undefended = ei.attackedBy[Them][ALL_PIECES]
403 & ei.attackedBy[Us][KING]
404 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
405 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
406 | ei.attackedBy[Us][QUEEN]);
408 // Initialize the 'attackUnits' variable, which is used later on as an
409 // index to the KingDanger[] array. The initial value is based on the
410 // number and types of the enemy's attacking pieces, the number of
411 // attacked and undefended squares around our king and the quality of
412 // the pawn shelter (current 'score' value).
413 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
414 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
415 + 2 * (ei.pinnedPieces[Us] != 0)
416 - mg_value(score) / 32
417 - !pos.count<QUEEN>(Them) * 15;
419 // Analyse the enemy's safe queen contact checks. Firstly, find the
420 // undefended squares around the king that are attacked by the enemy's
422 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
425 // ...and then remove squares not supported by another enemy piece
426 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
427 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
430 attackUnits += QueenContactCheck * popcount<Max15>(b);
433 // Analyse the enemy's safe rook contact checks. Firstly, find the
434 // undefended squares around the king that are attacked by the enemy's
436 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
438 // Consider only squares where the enemy's rook gives check
439 b &= PseudoAttacks[ROOK][ksq];
443 // ...and then remove squares not supported by another enemy piece
444 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
445 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
448 attackUnits += RookContactCheck * popcount<Max15>(b);
451 // Analyse the enemy's safe distance checks for sliders and knights
452 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
454 b1 = pos.attacks_from<ROOK>(ksq) & safe;
455 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
457 // Enemy queen safe checks
458 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
460 attackUnits += QueenCheck * popcount<Max15>(b);
462 // Enemy rooks safe checks
463 b = b1 & ei.attackedBy[Them][ROOK];
465 attackUnits += RookCheck * popcount<Max15>(b);
467 // Enemy bishops safe checks
468 b = b2 & ei.attackedBy[Them][BISHOP];
470 attackUnits += BishopCheck * popcount<Max15>(b);
472 // Enemy knights safe checks
473 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
475 attackUnits += KnightCheck * popcount<Max15>(b);
477 // To index KingDanger[] attackUnits must be in [0, 99] range
478 attackUnits = std::min(99, std::max(0, attackUnits));
480 // Finally, extract the king danger score from the KingDanger[]
481 // array and subtract the score from evaluation.
482 score -= KingDanger[attackUnits];
486 Tracing::write(KING, Us, score);
492 // evaluate_threats() assigns bonuses according to the type of attacking piece
493 // and the type of attacked one.
495 template<Color Us, bool Trace>
496 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
498 const Color Them = (Us == WHITE ? BLACK : WHITE);
500 enum { Defended, Weak };
501 enum { Minor, Major };
503 Bitboard b, weak, defended;
504 Score score = SCORE_ZERO;
506 // Non-pawn enemies defended by a pawn
507 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
508 & ei.attackedBy[Them][PAWN];
510 // Add a bonus according to the kind of attacking pieces
513 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
515 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
517 b = defended & (ei.attackedBy[Us][ROOK]);
519 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
522 // Enemies not defended by a pawn and under our attack
523 weak = pos.pieces(Them)
524 & ~ei.attackedBy[Them][PAWN]
525 & ei.attackedBy[Us][ALL_PIECES];
527 // Add a bonus according to the kind of attacking pieces
530 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
532 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
534 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
536 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
538 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
540 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
542 b = weak & ei.attackedBy[Us][KING];
544 score += more_than_one(b) ? KingOnMany : KingOnOne;
548 Tracing::write(Tracing::THREAT, Us, score);
554 // evaluate_passed_pawns() evaluates the passed pawns of the given color
556 template<Color Us, bool Trace>
557 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
559 const Color Them = (Us == WHITE ? BLACK : WHITE);
561 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
562 Score score = SCORE_ZERO;
564 b = ei.pi->passed_pawns(Us);
568 Square s = pop_lsb(&b);
570 assert(pos.pawn_passed(Us, s));
572 int r = relative_rank(Us, s) - RANK_2;
573 int rr = r * (r - 1);
575 // Base bonus based on rank
576 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
580 Square blockSq = s + pawn_push(Us);
582 // Adjust bonus based on the king's proximity
583 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
584 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
586 // If blockSq is not the queening square then consider also a second push
587 if (relative_rank(Us, blockSq) != RANK_8)
588 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
590 // If the pawn is free to advance, then increase the bonus
591 if (pos.empty(blockSq))
593 // If there is a rook or queen attacking/defending the pawn from behind,
594 // consider all the squaresToQueen. Otherwise consider only the squares
595 // in the pawn's path attacked or occupied by the enemy.
596 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
598 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
600 if (!(pos.pieces(Us) & bb))
601 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
603 if (!(pos.pieces(Them) & bb))
604 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
606 // If there aren't any enemy attacks, assign a big bonus. Otherwise
607 // assign a smaller bonus if the block square isn't attacked.
608 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
610 // If the path to queen is fully defended, assign a big bonus.
611 // Otherwise assign a smaller bonus if the block square is defended.
612 if (defendedSquares == squaresToQueen)
615 else if (defendedSquares & blockSq)
618 mbonus += k * rr, ebonus += k * rr;
620 else if (pos.pieces(Us) & blockSq)
621 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
624 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
625 ebonus += ebonus / 4;
627 score += make_score(mbonus, ebonus);
631 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
633 // Add the scores to the middlegame and endgame eval
634 return apply_weight(score, Weights[PassedPawns]);
638 // evaluate_unstoppable_pawns() scores the most advanced passed pawn. In case
639 // both players have no pieces but pawns, this is somewhat related to the
640 // possibility that pawns are unstoppable.
642 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
644 Bitboard b = ei.pi->passed_pawns(us);
646 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
650 // evaluate_space() computes the space evaluation for a given side. The
651 // space evaluation is a simple bonus based on the number of safe squares
652 // available for minor pieces on the central four files on ranks 2--4. Safe
653 // squares one, two or three squares behind a friendly pawn are counted
654 // twice. Finally, the space bonus is scaled by a weight taken from the
655 // material hash table. The aim is to improve play on game opening.
657 int evaluate_space(const Position& pos, const EvalInfo& ei) {
659 const Color Them = (Us == WHITE ? BLACK : WHITE);
661 // Find the safe squares for our pieces inside the area defined by
662 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
663 // pawn, or if it is undefended and attacked by an enemy piece.
664 Bitboard safe = SpaceMask[Us]
665 & ~pos.pieces(Us, PAWN)
666 & ~ei.attackedBy[Them][PAWN]
667 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
669 // Find all squares which are at most three squares behind some friendly pawn
670 Bitboard behind = pos.pieces(Us, PAWN);
671 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
672 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
674 // Since SpaceMask[Us] is fully on our half of the board
675 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
677 // Count safe + (behind & safe) with a single popcount
678 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
682 // do_evaluate() is the evaluation entry point, called directly from evaluate()
685 Value do_evaluate(const Position& pos) {
687 assert(!pos.checkers());
690 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
691 Thread* thisThread = pos.this_thread();
693 // Initialize score by reading the incrementally updated scores included
694 // in the position object (material + piece square tables).
695 // Score is computed from the point of view of white.
696 score = pos.psq_score();
698 // Probe the material hash table
699 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
700 score += ei.mi->material_value();
702 // If we have a specialized evaluation function for the current material
703 // configuration, call it and return.
704 if (ei.mi->specialized_eval_exists())
705 return ei.mi->evaluate(pos) + Eval::Tempo;
707 // Probe the pawn hash table
708 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
709 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
711 // Initialize attack and king safety bitboards
712 init_eval_info<WHITE>(pos, ei);
713 init_eval_info<BLACK>(pos, ei);
715 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
716 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
718 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
719 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
720 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
722 // Evaluate pieces and mobility
723 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
724 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
726 // Evaluate kings after all other pieces because we need complete attack
727 // information when computing the king safety evaluation.
728 score += evaluate_king<WHITE, Trace>(pos, ei)
729 - evaluate_king<BLACK, Trace>(pos, ei);
731 // Evaluate tactical threats, we need full attack information including king
732 score += evaluate_threats<WHITE, Trace>(pos, ei)
733 - evaluate_threats<BLACK, Trace>(pos, ei);
735 // Evaluate passed pawns, we need full attack information including king
736 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
737 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
739 // If both sides have only pawns, score for potential unstoppable pawns
740 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
741 score += evaluate_unstoppable_pawns(WHITE, ei)
742 - evaluate_unstoppable_pawns(BLACK, ei);
744 // Evaluate space for both sides, only in middlegame
745 if (ei.mi->space_weight())
747 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
748 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
751 // Scale winning side if position is more drawish than it appears
752 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
753 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
755 // If we don't already have an unusual scale factor, check for certain
756 // types of endgames, and use a lower scale for those.
757 if ( ei.mi->game_phase() < PHASE_MIDGAME
758 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
760 if (pos.opposite_bishops())
762 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
763 // is almost a draw, in case of KBP vs KB is even more a draw.
764 if ( pos.non_pawn_material(WHITE) == BishopValueMg
765 && pos.non_pawn_material(BLACK) == BishopValueMg)
766 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
768 // Endgame with opposite-colored bishops, but also other pieces. Still
769 // a bit drawish, but not as drawish as with only the two bishops.
771 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
773 // Endings where weaker side can place his king in front of the opponent's
774 // pawns are drawish.
775 else if ( abs(eg_value(score)) <= BishopValueEg
776 && ei.pi->pawn_span(strongSide) <= 1
777 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
778 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
781 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
782 Value v = mg_value(score) * int(ei.mi->game_phase())
783 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
785 v /= int(PHASE_MIDGAME);
787 // In case of tracing add all single evaluation contributions for both white and black
790 Tracing::write(Tracing::MATERIAL, pos.psq_score());
791 Tracing::write(Tracing::IMBALANCE, ei.mi->material_value());
792 Tracing::write(PAWN, ei.pi->pawns_value());
793 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
794 , apply_weight(mobility[BLACK], Weights[Mobility]));
795 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
796 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
797 Tracing::write(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
798 Tracing::write(Tracing::TOTAL, score);
803 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
807 // Tracing function definitions
809 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
811 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
813 void Tracing::write(int idx, Score w, Score b) {
815 write(idx, WHITE, w);
816 write(idx, BLACK, b);
819 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
821 Score wScore = scores[WHITE][idx];
822 Score bScore = scores[BLACK][idx];
825 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
826 ss << std::setw(15) << name << " | --- --- | --- --- | "
827 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
828 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
831 ss << std::setw(15) << name << " | " << std::noshowpos
832 << std::setw(5) << to_cp(mg_value(wScore)) << " "
833 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
834 << std::setw(5) << to_cp(mg_value(bScore)) << " "
835 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
836 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
837 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
841 std::string Tracing::do_trace(const Position& pos) {
843 std::memset(scores, 0, sizeof(scores));
845 Value v = do_evaluate<true>(pos);
846 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
848 std::stringstream ss;
849 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
850 << " Eval term | White | Black | Total \n"
851 << " | MG EG | MG EG | MG EG \n"
852 << "----------------+-------------+-------------+-------------\n";
854 print(ss, "Material", MATERIAL);
855 print(ss, "Imbalance", IMBALANCE);
856 print(ss, "Pawns", PAWN);
857 print(ss, "Knights", KNIGHT);
858 print(ss, "Bishops", BISHOP);
859 print(ss, "Rooks", ROOK);
860 print(ss, "Queens", QUEEN);
861 print(ss, "Mobility", MOBILITY);
862 print(ss, "King safety", KING);
863 print(ss, "Threats", THREAT);
864 print(ss, "Passed pawns", PASSED);
865 print(ss, "Space", SPACE);
867 ss << "----------------+-------------+-------------+-------------\n";
868 print(ss, "Total", TOTAL);
870 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
880 /// evaluate() is the main evaluation function. It returns a static evaluation
881 /// of the position always from the point of view of the side to move.
883 Value evaluate(const Position& pos) {
884 return do_evaluate<false>(pos);
888 /// trace() is like evaluate(), but instead of returning a value, it returns
889 /// a string (suitable for outputting to stdout) that contains the detailed
890 /// descriptions and values of each evaluation term. It's mainly used for
892 std::string trace(const Position& pos) {
893 return Tracing::do_trace(pos);
897 /// init() computes evaluation weights.
901 const double MaxSlope = 30;
902 const double Peak = 1280;
904 for (int t = 0, i = 1; i < 100; ++i)
906 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
907 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);