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 RookOnOpenFile = S(43, 21);
159 const Score RookOnSemiOpenFile = 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);
174 // SpaceMask[Color] contains the area of the board which is considered
175 // by the space evaluation. In the middlegame, each side is given a bonus
176 // based on how many squares inside this area are safe and available for
177 // friendly minor pieces.
178 const Bitboard SpaceMask[] = {
179 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
180 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
183 // King danger constants and variables. The king danger scores are looked-up
184 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
185 // of the enemy attack are added up into an integer, which is used as an
186 // index to KingDanger[].
188 // KingAttackWeights[PieceType] contains king attack weights by piece type
189 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
191 // Bonuses for enemy's safe checks
192 const int QueenContactCheck = 24;
193 const int RookContactCheck = 16;
194 const int QueenCheck = 12;
195 const int RookCheck = 8;
196 const int BishopCheck = 2;
197 const int KnightCheck = 3;
199 // KingDanger[attackUnits] contains the actual king danger weighted
200 // scores, indexed by a calculated integer number.
201 Score KingDanger[128];
203 // apply_weight() weighs score 's' by weight 'w' trying to prevent overflow
204 Score apply_weight(Score s, const Weight& w) {
205 return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
209 // init_eval_info() initializes king bitboards for given color adding
210 // pawn attacks. To be done at the beginning of the evaluation.
213 void init_eval_info(const Position& pos, EvalInfo& ei) {
215 const Color Them = (Us == WHITE ? BLACK : WHITE);
216 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
218 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
220 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
221 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
223 // Init king safety tables only if we are going to use them
224 if (pos.non_pawn_material(Us) >= QueenValueMg)
226 ei.kingRing[Them] = b | shift_bb<Down>(b);
227 b &= ei.attackedBy[Us][PAWN];
228 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
229 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
232 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
236 // evaluate_outpost() evaluates bishop and knight outpost squares
238 template<PieceType Pt, Color Us>
239 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
241 const Color Them = (Us == WHITE ? BLACK : WHITE);
243 assert (Pt == BISHOP || Pt == KNIGHT);
245 // Initial bonus based on square
246 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
248 // Increase bonus if supported by pawn, especially if the opponent has
249 // no minor piece which can trade with the outpost piece.
250 if (bonus && (ei.attackedBy[Us][PAWN] & s))
252 if ( !pos.pieces(Them, KNIGHT)
253 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
254 bonus += bonus + bonus / 2;
259 return make_score(bonus * 2, bonus / 2);
263 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
265 template<PieceType Pt, Color Us, bool Trace>
266 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
270 Score score = SCORE_ZERO;
272 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
273 const Color Them = (Us == WHITE ? BLACK : WHITE);
274 const Square* pl = pos.list<Pt>(Us);
276 ei.attackedBy[Us][Pt] = 0;
278 while ((s = *pl++) != SQ_NONE)
280 // Find attacked squares, including x-ray attacks for bishops and rooks
281 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
282 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
283 : pos.attacks_from<Pt>(s);
285 if (ei.pinnedPieces[Us] & s)
286 b &= LineBB[pos.king_square(Us)][s];
288 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
290 if (b & ei.kingRing[Them])
292 ei.kingAttackersCount[Us]++;
293 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
294 Bitboard bb = b & ei.attackedBy[Them][KING];
296 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
300 b &= ~( ei.attackedBy[Them][KNIGHT]
301 | ei.attackedBy[Them][BISHOP]
302 | ei.attackedBy[Them][ROOK]);
304 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
305 : popcount<Full >(b & mobilityArea[Us]);
307 mobility[Us] += MobilityBonus[Pt][mob];
309 // Decrease score if we are attacked by an enemy pawn. The remaining part
310 // of threat evaluation must be done later when we have full attack info.
311 if (ei.attackedBy[Them][PAWN] & s)
312 score -= ThreatenedByPawn[Pt];
314 if (Pt == BISHOP || Pt == KNIGHT)
316 // Bonus for outpost square
317 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
318 score += evaluate_outpost<Pt, Us>(pos, ei, s);
320 // Bonus when behind a pawn
321 if ( relative_rank(Us, s) < RANK_5
322 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
323 score += MinorBehindPawn;
325 // Penalty for pawns on same color square of bishop
327 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
329 // An important Chess960 pattern: A cornered bishop blocked by a friendly
330 // pawn diagonally in front of it is a very serious problem, especially
331 // when that pawn is also blocked.
334 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
336 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
337 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
338 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
339 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
346 // Bonus for aligning with enemy pawns on the same rank/file
347 if (relative_rank(Us, s) >= RANK_5)
349 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
351 score += popcount<Max15>(alignedPawns) * RookOnPawn;
354 // Bonus when on an open or semi-open file
355 if (ei.pi->semiopen_file(Us, file_of(s)))
356 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
358 // Penalize when trapped by the king, even more if king cannot castle
359 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
361 Square ksq = pos.king_square(Us);
363 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
364 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
365 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
366 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
372 Tracing::write(Pt, Us, score);
374 // Recursively call evaluate_pieces() of next piece type until KING excluded
375 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
379 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
381 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
384 // evaluate_king() assigns bonuses and penalties to a king of a given color
386 template<Color Us, bool Trace>
387 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
389 const Color Them = (Us == WHITE ? BLACK : WHITE);
391 Bitboard undefended, b, b1, b2, safe;
393 const Square ksq = pos.king_square(Us);
395 // King shelter and enemy pawns storm
396 Score score = ei.pi->king_safety<Us>(pos, ksq);
398 // Main king safety evaluation
399 if (ei.kingAttackersCount[Them])
401 // Find the attacked squares around the king which have no defenders
402 // apart from the king itself
403 undefended = ei.attackedBy[Them][ALL_PIECES]
404 & ei.attackedBy[Us][KING]
405 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
406 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
407 | ei.attackedBy[Us][QUEEN]);
409 // Initialize the 'attackUnits' variable, which is used later on as an
410 // index into the KingDanger[] array. The initial value is based on the
411 // number and types of the enemy's attacking pieces, the number of
412 // attacked and undefended squares around our king and the quality of
413 // the pawn shelter (current 'score' value).
414 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
415 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
416 + 2 * (ei.pinnedPieces[Us] != 0)
417 - mg_value(score) / 32
418 - !pos.count<QUEEN>(Them) * 15;
420 // Analyse the enemy's safe queen contact checks. Firstly, find the
421 // undefended squares around the king reachable by the enemy queen...
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 reachable by the enemy rooks...
435 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
437 // Consider only squares where the enemy's rook gives check
438 b &= PseudoAttacks[ROOK][ksq];
442 // ...and then remove squares not supported by another enemy piece
443 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
444 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
447 attackUnits += RookContactCheck * popcount<Max15>(b);
450 // Analyse the enemy's safe distance checks for sliders and knights
451 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
453 b1 = pos.attacks_from<ROOK >(ksq) & safe;
454 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
456 // Enemy queen safe checks
457 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
459 attackUnits += QueenCheck * popcount<Max15>(b);
461 // Enemy rooks safe checks
462 b = b1 & ei.attackedBy[Them][ROOK];
464 attackUnits += RookCheck * popcount<Max15>(b);
466 // Enemy bishops safe checks
467 b = b2 & ei.attackedBy[Them][BISHOP];
469 attackUnits += BishopCheck * popcount<Max15>(b);
471 // Enemy knights safe checks
472 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
474 attackUnits += KnightCheck * popcount<Max15>(b);
476 // Finally, extract the king danger score from the KingDanger[]
477 // array and subtract the score from evaluation.
478 score -= KingDanger[std::max(std::min(attackUnits, 99), 0)];
482 Tracing::write(KING, Us, score);
488 // evaluate_threats() assigns bonuses according to the type of attacking piece
489 // and the type of attacked one.
491 template<Color Us, bool Trace>
492 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
494 const Color Them = (Us == WHITE ? BLACK : WHITE);
496 enum { Defended, Weak };
497 enum { Minor, Major };
499 Bitboard b, weak, defended;
500 Score score = SCORE_ZERO;
502 // Non-pawn enemies defended by a pawn
503 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN))
504 & ei.attackedBy[Them][PAWN];
506 // Add a bonus according to the kind of attacking pieces
509 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
511 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
513 b = defended & (ei.attackedBy[Us][ROOK]);
515 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
518 // Enemies not defended by a pawn and under our attack
519 weak = pos.pieces(Them)
520 & ~ei.attackedBy[Them][PAWN]
521 & ei.attackedBy[Us][ALL_PIECES];
523 // Add a bonus according to the kind of attacking pieces
526 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
528 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
530 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
532 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
534 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
536 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
538 b = weak & ei.attackedBy[Us][KING];
540 score += more_than_one(b) ? KingOnMany : KingOnOne;
544 Tracing::write(Tracing::THREAT, Us, score);
550 // evaluate_passed_pawns() evaluates the passed pawns of the given color
552 template<Color Us, bool Trace>
553 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
555 const Color Them = (Us == WHITE ? BLACK : WHITE);
557 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
558 Score score = SCORE_ZERO;
560 b = ei.pi->passed_pawns(Us);
564 Square s = pop_lsb(&b);
566 assert(pos.pawn_passed(Us, s));
568 int r = relative_rank(Us, s) - RANK_2;
569 int rr = r * (r - 1);
571 // Base bonus based on rank
572 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
576 Square blockSq = s + pawn_push(Us);
578 // Adjust bonus based on the king's proximity
579 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
580 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
582 // If blockSq is not the queening square then consider also a second push
583 if (relative_rank(Us, blockSq) != RANK_8)
584 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
586 // If the pawn is free to advance, then increase the bonus
587 if (pos.empty(blockSq))
589 // If there is a rook or queen attacking/defending the pawn from behind,
590 // consider all the squaresToQueen. Otherwise consider only the squares
591 // in the pawn's path attacked or occupied by the enemy.
592 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
594 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
596 if (!(pos.pieces(Us) & bb))
597 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
599 if (!(pos.pieces(Them) & bb))
600 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
602 // If there aren't any enemy attacks, assign a big bonus. Otherwise
603 // assign a smaller bonus if the block square isn't attacked.
604 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
606 // If the path to queen is fully defended, assign a big bonus.
607 // Otherwise assign a smaller bonus if the block square is defended.
608 if (defendedSquares == squaresToQueen)
611 else if (defendedSquares & blockSq)
614 mbonus += k * rr, ebonus += k * rr;
616 else if (pos.pieces(Us) & blockSq)
617 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
620 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
621 ebonus += ebonus / 4;
623 score += make_score(mbonus, ebonus);
627 Tracing::write(Tracing::PASSED, Us, apply_weight(score, Weights[PassedPawns]));
629 // Add the scores to the middlegame and endgame eval
630 return apply_weight(score, Weights[PassedPawns]);
634 // evaluate_space() computes the space evaluation for a given side. The
635 // space evaluation is a simple bonus based on the number of safe squares
636 // available for minor pieces on the central four files on ranks 2--4. Safe
637 // squares one, two or three squares behind a friendly pawn are counted
638 // twice. Finally, the space bonus is scaled by a weight taken from the
639 // material hash table. The aim is to improve play on game opening.
641 Score evaluate_space(const Position& pos, const EvalInfo& ei, Score weight) {
643 const Color Them = (Us == WHITE ? BLACK : WHITE);
645 // Find the safe squares for our pieces inside the area defined by
646 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
647 // pawn, or if it is undefended and attacked by an enemy piece.
648 Bitboard safe = SpaceMask[Us]
649 & ~pos.pieces(Us, PAWN)
650 & ~ei.attackedBy[Them][PAWN]
651 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
653 // Find all squares which are at most three squares behind some friendly pawn
654 Bitboard behind = pos.pieces(Us, PAWN);
655 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
656 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
658 // Since SpaceMask[Us] is fully on our half of the board
659 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
661 // Count safe + (behind & safe) with a single popcount
662 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe)) * weight;
666 // do_evaluate() is the evaluation entry point, called directly from evaluate()
669 Value do_evaluate(const Position& pos) {
671 assert(!pos.checkers());
674 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
675 Thread* thisThread = pos.this_thread();
677 // Initialize score by reading the incrementally updated scores included
678 // in the position object (material + piece square tables).
679 // Score is computed from the point of view of white.
680 score = pos.psq_score();
682 // Probe the material hash table
683 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
684 score += ei.mi->imbalance();
686 // If we have a specialized evaluation function for the current material
687 // configuration, call it and return.
688 if (ei.mi->specialized_eval_exists())
689 return ei.mi->evaluate(pos);
691 // Probe the pawn hash table
692 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
693 score += apply_weight(ei.pi->pawns_score(), Weights[PawnStructure]);
695 // Initialize attack and king safety bitboards
696 init_eval_info<WHITE>(pos, ei);
697 init_eval_info<BLACK>(pos, ei);
699 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
700 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
702 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
703 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
704 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
706 // Evaluate pieces and mobility
707 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
708 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
710 // Evaluate kings after all other pieces because we need complete attack
711 // information when computing the king safety evaluation.
712 score += evaluate_king<WHITE, Trace>(pos, ei)
713 - evaluate_king<BLACK, Trace>(pos, ei);
715 // Evaluate tactical threats, we need full attack information including king
716 score += evaluate_threats<WHITE, Trace>(pos, ei)
717 - evaluate_threats<BLACK, Trace>(pos, ei);
719 // Evaluate passed pawns, we need full attack information including king
720 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
721 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
723 // If both sides have only pawns, score for potential unstoppable pawns
724 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
727 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
728 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
730 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
731 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
734 // Evaluate space for both sides, only in middlegame
735 if (ei.mi->space_weight())
737 Score s = evaluate_space<WHITE>(pos, ei, ei.mi->space_weight())
738 - evaluate_space<BLACK>(pos, ei, ei.mi->space_weight());
740 score += apply_weight(s, Weights[Space]);
743 // Scale winning side if position is more drawish than it appears
744 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
745 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
747 // If we don't already have an unusual scale factor, check for certain
748 // types of endgames, and use a lower scale for those.
749 if ( ei.mi->game_phase() < PHASE_MIDGAME
750 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
752 if (pos.opposite_bishops())
754 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
755 // is almost a draw, in case of KBP vs KB is even more a draw.
756 if ( pos.non_pawn_material(WHITE) == BishopValueMg
757 && pos.non_pawn_material(BLACK) == BishopValueMg)
758 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
760 // Endgame with opposite-colored bishops, but also other pieces. Still
761 // a bit drawish, but not as drawish as with only the two bishops.
763 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
765 // Endings where weaker side can place his king in front of the opponent's
766 // pawns are drawish.
767 else if ( abs(eg_value(score)) <= BishopValueEg
768 && ei.pi->pawn_span(strongSide) <= 1
769 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
770 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
773 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
774 Value v = mg_value(score) * int(ei.mi->game_phase())
775 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
777 v /= int(PHASE_MIDGAME);
779 // In case of tracing add all single evaluation contributions for both white and black
782 Tracing::write(Tracing::MATERIAL, pos.psq_score());
783 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
784 Tracing::write(PAWN, ei.pi->pawns_score());
785 Tracing::write(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
786 , apply_weight(mobility[BLACK], Weights[Mobility]));
787 Score w = evaluate_space<WHITE>(pos, ei, ei.mi->space_weight());
788 Score b = evaluate_space<BLACK>(pos, ei, ei.mi->space_weight());
789 Tracing::write(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
790 Tracing::write(Tracing::TOTAL, score);
795 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo;
799 // Tracing function definitions
801 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
803 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
805 void Tracing::write(int idx, Score w, Score b) {
807 write(idx, WHITE, w);
808 write(idx, BLACK, b);
811 void Tracing::print(std::stringstream& ss, const char* name, int idx) {
813 Score wScore = scores[WHITE][idx];
814 Score bScore = scores[BLACK][idx];
817 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
818 ss << std::setw(15) << name << " | --- --- | --- --- | "
819 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
820 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
823 ss << std::setw(15) << name << " | " << std::noshowpos
824 << std::setw(5) << to_cp(mg_value(wScore)) << " "
825 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
826 << std::setw(5) << to_cp(mg_value(bScore)) << " "
827 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
828 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
829 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
833 std::string Tracing::do_trace(const Position& pos) {
835 std::memset(scores, 0, sizeof(scores));
837 Value v = do_evaluate<true>(pos);
838 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
840 std::stringstream ss;
841 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
842 << " Eval term | White | Black | Total \n"
843 << " | MG EG | MG EG | MG EG \n"
844 << "----------------+-------------+-------------+-------------\n";
846 print(ss, "Material", MATERIAL);
847 print(ss, "Imbalance", IMBALANCE);
848 print(ss, "Pawns", PAWN);
849 print(ss, "Knights", KNIGHT);
850 print(ss, "Bishops", BISHOP);
851 print(ss, "Rooks", ROOK);
852 print(ss, "Queens", QUEEN);
853 print(ss, "Mobility", MOBILITY);
854 print(ss, "King safety", KING);
855 print(ss, "Threats", THREAT);
856 print(ss, "Passed pawns", PASSED);
857 print(ss, "Space", SPACE);
859 ss << "----------------+-------------+-------------+-------------\n";
860 print(ss, "Total", TOTAL);
862 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
872 /// evaluate() is the main evaluation function. It returns a static evaluation
873 /// of the position always from the point of view of the side to move.
875 Value evaluate(const Position& pos) {
876 return do_evaluate<false>(pos);
880 /// trace() is like evaluate(), but instead of returning a value, it returns
881 /// a string (suitable for outputting to stdout) that contains the detailed
882 /// descriptions and values of each evaluation term. It's mainly used for
884 std::string trace(const Position& pos) {
885 return Tracing::do_trace(pos);
889 /// init() computes evaluation weights, usually at startup
893 const double MaxSlope = 30;
894 const double Peak = 1280;
896 for (int t = 0, i = 1; i < 100; ++i)
898 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
899 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);