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, indexed by evaluation term
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
94 const struct Weight { int mg, eg; } Weights[] = {
95 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {271, 0}, {307, 0}
99 #define S(mg, eg) make_score(mg, eg)
101 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
102 // game, indexed by piece type and number of attacked squares not occupied by
104 const Score MobilityBonus[][32] = {
106 { S(-65,-50), S(-42,-30), S(-9,-10), S( 3, 0), S(15, 10), S(27, 20), // Knights
107 S( 37, 28), S( 42, 31), S(44, 33) },
108 { S(-52,-47), S(-28,-23), S( 6, 1), S(20, 15), S(34, 29), S(48, 43), // Bishops
109 S( 60, 55), S( 68, 63), S(74, 68), S(77, 72), S(80, 75), S(82, 77),
110 S( 84, 79), S( 86, 81) },
111 { S(-47,-53), S(-31,-26), S(-5, 0), S( 1, 16), S( 7, 32), S(13, 48), // Rooks
112 S( 18, 64), S( 22, 80), S(26, 96), S(29,109), S(31,115), S(33,119),
113 S( 35,122), S( 36,123), S(37,124) },
114 { S(-42,-40), S(-28,-23), S(-5, -7), S( 0, 0), S( 6, 10), S(11, 19), // Queens
115 S( 13, 29), S( 18, 38), S(20, 40), S(21, 41), S(22, 41), S(22, 41),
116 S( 22, 41), S( 23, 41), S(24, 41), S(25, 41), S(25, 41), S(25, 41),
117 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41), S(25, 41), S(25, 41),
118 S( 25, 41), S( 25, 41), S(25, 41), S(25, 41) }
121 // Outpost[PieceType][Square] contains bonuses for knights and bishops outposts,
122 // indexed by piece type and square (from white's point of view).
123 const Value Outpost[][SQUARE_NB] = {
125 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
126 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
127 V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0),
128 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0),
129 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0),
130 V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0) },
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
133 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
134 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0),
135 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0),
136 V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0),
137 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0) }
140 // Threat[attacking][attacked] contains bonuses according to which piece
141 // type attacks which one.
142 const Score Threat[][PIECE_TYPE_NB] = {
143 { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
144 { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) } // Major
147 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
148 // type is attacked by an enemy pawn.
149 const Score ThreatenedByPawn[] = {
150 S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
153 // Hanging[side to move] contains a bonus for each enemy hanging piece
154 const Score Hanging[2] = { S(23, 20) , S(35, 45) };
158 const Score Tempo = make_score(24, 11);
159 const Score RookOnPawn = make_score(10, 28);
160 const Score RookOpenFile = make_score(43, 21);
161 const Score RookSemiopenFile = make_score(19, 10);
162 const Score BishopPawns = make_score( 8, 12);
163 const Score MinorBehindPawn = make_score(16, 0);
164 const Score TrappedRook = make_score(90, 0);
165 const Score Unstoppable = make_score( 0, 20);
167 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
168 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
169 // happen in Chess960 games.
170 const Score TrappedBishopA1H1 = make_score(50, 50);
172 // SpaceMask[Color] contains the area of the board which is considered
173 // by the space evaluation. In the middlegame, each side is given a bonus
174 // based on how many squares inside this area are safe and available for
175 // friendly minor pieces.
176 const Bitboard SpaceMask[] = {
177 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
178 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
181 // King danger constants and variables. The king danger scores are taken
182 // from KingDanger[]. Various little "meta-bonuses" measuring the strength
183 // of the enemy attack are added up into an integer, which is used as an
184 // index to KingDanger[].
186 // KingAttackWeights[PieceType] contains king attack weights by piece type
187 const int KingAttackWeights[] = { 0, 0, 2, 2, 3, 5 };
189 // Bonuses for enemy's safe checks
190 const int QueenContactCheck = 24;
191 const int RookContactCheck = 16;
192 const int QueenCheck = 12;
193 const int RookCheck = 8;
194 const int BishopCheck = 2;
195 const int KnightCheck = 3;
197 // KingDanger[Color][attackUnits] contains the actual king danger weighted
198 // scores, indexed by color and by a calculated integer number.
199 Score KingDanger[COLOR_NB][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.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
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_outposts() evaluates bishop and knight outpost squares
237 template<PieceType Pt, Color Us>
238 Score evaluate_outposts(const Position& pos, 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, bonus);
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 outposts squares
320 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
321 score += evaluate_outposts<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 * 8, 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::terms[Us][Pt] = 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;
418 // Analyse the enemy's safe queen contact checks. Firstly, find the
419 // undefended squares around the king that are attacked by the enemy's
421 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
424 // ...and then remove squares not supported by another enemy piece
425 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
426 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
429 attackUnits += QueenContactCheck
431 * (Them == pos.side_to_move() ? 2 : 1);
434 // Analyse the enemy's safe rook contact checks. Firstly, find the
435 // undefended squares around the king that are attacked by the enemy's
437 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
439 // Consider only squares where the enemy's rook gives check
440 b &= PseudoAttacks[ROOK][ksq];
444 // ...and then remove squares not supported by another enemy piece
445 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
446 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
449 attackUnits += RookContactCheck
451 * (Them == pos.side_to_move() ? 2 : 1);
454 // Analyse the enemy's safe distance checks for sliders and knights
455 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
457 b1 = pos.attacks_from<ROOK>(ksq) & safe;
458 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
460 // Enemy queen safe checks
461 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
463 attackUnits += QueenCheck * popcount<Max15>(b);
465 // Enemy rooks safe checks
466 b = b1 & ei.attackedBy[Them][ROOK];
468 attackUnits += RookCheck * popcount<Max15>(b);
470 // Enemy bishops safe checks
471 b = b2 & ei.attackedBy[Them][BISHOP];
473 attackUnits += BishopCheck * popcount<Max15>(b);
475 // Enemy knights safe checks
476 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
478 attackUnits += KnightCheck * popcount<Max15>(b);
480 // To index KingDanger[] attackUnits must be in [0, 99] range
481 attackUnits = std::min(99, std::max(0, attackUnits));
483 // Finally, extract the king danger score from the KingDanger[]
484 // array and subtract the score from evaluation.
485 score -= KingDanger[Us == Search::RootColor][attackUnits];
489 Tracing::terms[Us][KING] = score;
495 // evaluate_threats() assigns bonuses according to the type of attacking piece
496 // and the type of attacked one.
498 template<Color Us, bool Trace>
499 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
501 const Color Them = (Us == WHITE ? BLACK : WHITE);
503 Bitboard b, weakEnemies;
504 Score score = SCORE_ZERO;
506 // Enemies not defended by a pawn and under our attack
507 weakEnemies = pos.pieces(Them)
508 & ~ei.attackedBy[Them][PAWN]
509 & ei.attackedBy[Us][ALL_PIECES];
511 // Add a bonus according if the attacking pieces are minor or major
514 b = weakEnemies & (ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
516 score += Threat[0][type_of(pos.piece_on(lsb(b)))];
518 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
520 score += Threat[1][type_of(pos.piece_on(lsb(b)))];
522 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
524 score += more_than_one(b) ? Hanging[Us != pos.side_to_move()] * popcount<Max15>(b)
525 : Hanging[Us == pos.side_to_move()];
529 Tracing::terms[Us][Tracing::THREAT] = score;
535 // evaluate_passed_pawns() evaluates the passed pawns of the given color
537 template<Color Us, bool Trace>
538 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
540 const Color Them = (Us == WHITE ? BLACK : WHITE);
542 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
543 Score score = SCORE_ZERO;
545 b = ei.pi->passed_pawns(Us);
549 Square s = pop_lsb(&b);
551 assert(pos.pawn_passed(Us, s));
553 int r = relative_rank(Us, s) - RANK_2;
554 int rr = r * (r - 1);
556 // Base bonus based on rank
557 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
561 Square blockSq = s + pawn_push(Us);
563 // Adjust bonus based on the king's proximity
564 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
565 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
567 // If blockSq is not the queening square then consider also a second push
568 if (relative_rank(Us, blockSq) != RANK_8)
569 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
571 // If the pawn is free to advance, then increase the bonus
572 if (pos.empty(blockSq))
574 squaresToQueen = forward_bb(Us, s);
576 // If there is an enemy rook or queen attacking the pawn from behind,
577 // add all X-ray attacks by the rook or queen. Otherwise consider only
578 // the squares in the pawn's path attacked or occupied by the enemy.
579 if ( unlikely(forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN))
580 && (forward_bb(Them, s) & pos.pieces(Them, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
581 unsafeSquares = squaresToQueen;
583 unsafeSquares = squaresToQueen & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
585 if ( unlikely(forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN))
586 && (forward_bb(Them, s) & pos.pieces(Us, ROOK, QUEEN) & pos.attacks_from<ROOK>(s)))
587 defendedSquares = squaresToQueen;
589 defendedSquares = squaresToQueen & ei.attackedBy[Us][ALL_PIECES];
591 // If there aren't any enemy attacks, assign a big bonus. Otherwise
592 // assign a smaller bonus if the block square isn't attacked.
593 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
595 // If the path to queen is fully defended, assign a big bonus.
596 // Otherwise assign a smaller bonus if the block square is defended.
597 if (defendedSquares == squaresToQueen)
600 else if (defendedSquares & blockSq)
603 mbonus += k * rr, ebonus += k * rr;
607 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
608 ebonus += ebonus / 4;
610 score += make_score(mbonus, ebonus);
614 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
616 // Add the scores to the middlegame and endgame eval
617 return apply_weight(score, Weights[PassedPawns]);
621 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
622 // candidate pawns. In case opponent has no pieces but pawns, this is somewhat
623 // related to the possibility that pawns are unstoppable.
625 Score evaluate_unstoppable_pawns(const Position& pos, Color us, const EvalInfo& ei) {
627 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
629 if (!b || pos.non_pawn_material(~us))
632 return Unstoppable * int(relative_rank(us, frontmost_sq(us, b)));
636 // evaluate_space() computes the space evaluation for a given side. The
637 // space evaluation is a simple bonus based on the number of safe squares
638 // available for minor pieces on the central four files on ranks 2--4. Safe
639 // squares one, two or three squares behind a friendly pawn are counted
640 // twice. Finally, the space bonus is scaled by a weight taken from the
641 // material hash table. The aim is to improve play on game opening.
643 int evaluate_space(const Position& pos, const EvalInfo& ei) {
645 const Color Them = (Us == WHITE ? BLACK : WHITE);
647 // Find the safe squares for our pieces inside the area defined by
648 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
649 // pawn, or if it is undefended and attacked by an enemy piece.
650 Bitboard safe = SpaceMask[Us]
651 & ~pos.pieces(Us, PAWN)
652 & ~ei.attackedBy[Them][PAWN]
653 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
655 // Find all squares which are at most three squares behind some friendly pawn
656 Bitboard behind = pos.pieces(Us, PAWN);
657 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
658 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
660 // Since SpaceMask[Us] is fully on our half of the board
661 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
663 // Count safe + (behind & safe) with a single popcount
664 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
668 // do_evaluate() is the evaluation entry point, called directly from evaluate()
671 Value do_evaluate(const Position& pos) {
673 assert(!pos.checkers());
676 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
677 Thread* thisThread = pos.this_thread();
679 // Initialize score by reading the incrementally updated scores included
680 // in the position object (material + piece square tables) and adding a
681 // Tempo bonus. Score is computed from the point of view of white.
682 score = pos.psq_score() + (pos.side_to_move() == WHITE ? Tempo : -Tempo);
684 // Probe the material hash table
685 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
686 score += ei.mi->material_value();
688 // If we have a specialized evaluation function for the current material
689 // configuration, call it and return.
690 if (ei.mi->specialized_eval_exists())
691 return ei.mi->evaluate(pos);
693 // Probe the pawn hash table
694 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
695 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
697 // Initialize attack and king safety bitboards
698 init_eval_info<WHITE>(pos, ei);
699 init_eval_info<BLACK>(pos, ei);
701 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
702 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
704 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
705 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
706 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
708 // Evaluate pieces and mobility
709 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
710 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
712 // Evaluate kings after all other pieces because we need complete attack
713 // information when computing the king safety evaluation.
714 score += evaluate_king<WHITE, Trace>(pos, ei)
715 - evaluate_king<BLACK, Trace>(pos, ei);
717 // Evaluate tactical threats, we need full attack information including king
718 score += evaluate_threats<WHITE, Trace>(pos, ei)
719 - evaluate_threats<BLACK, Trace>(pos, ei);
721 // Evaluate passed pawns, we need full attack information including king
722 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
723 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
725 // If one side has only a king, score for potential unstoppable pawns
726 if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
727 score += evaluate_unstoppable_pawns(pos, WHITE, ei)
728 - evaluate_unstoppable_pawns(pos, BLACK, ei);
730 // Evaluate space for both sides, only in middlegame
731 if (ei.mi->space_weight())
733 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
734 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
737 // Scale winning side if position is more drawish than it appears
738 ScaleFactor sf = eg_value(score) > VALUE_DRAW ? ei.mi->scale_factor(pos, WHITE)
739 : ei.mi->scale_factor(pos, BLACK);
741 // If we don't already have an unusual scale factor, check for opposite
742 // colored bishop endgames, and use a lower scale for those.
743 if ( ei.mi->game_phase() < PHASE_MIDGAME
744 && pos.opposite_bishops()
745 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
747 // Ignoring any pawns, do both sides only have a single bishop and no
749 if ( pos.non_pawn_material(WHITE) == BishopValueMg
750 && pos.non_pawn_material(BLACK) == BishopValueMg)
752 // Check for KBP vs KB with only a single pawn that is almost
753 // certainly a draw or at least two pawns.
754 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
755 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
758 // Endgame with opposite-colored bishops, but also other pieces. Still
759 // a bit drawish, but not as drawish as with only the two bishops.
760 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
763 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
764 Value v = mg_value(score) * int(ei.mi->game_phase())
765 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
767 v /= int(PHASE_MIDGAME);
769 // In case of tracing add all single evaluation contributions for both white and black
772 Tracing::add_term(Tracing::PST, pos.psq_score());
773 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
774 Tracing::add_term(PAWN, ei.pi->pawns_value());
775 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
776 , apply_weight(mobility[BLACK], Weights[Mobility]));
777 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
778 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
779 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
780 Tracing::add_term(Tracing::TOTAL, score);
785 return pos.side_to_move() == WHITE ? v : -v;
789 // Tracing function definitions
791 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
793 void Tracing::add_term(int idx, Score wScore, Score bScore) {
795 terms[WHITE][idx] = wScore;
796 terms[BLACK][idx] = bScore;
799 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
801 Score wScore = terms[WHITE][idx];
802 Score bScore = terms[BLACK][idx];
805 case PST: case IMBALANCE: case PAWN: case TOTAL:
806 ss << std::setw(20) << name << " | --- --- | --- --- | "
807 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
808 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
811 ss << std::setw(20) << name << " | " << std::noshowpos
812 << std::setw(5) << to_cp(mg_value(wScore)) << " "
813 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
814 << std::setw(5) << to_cp(mg_value(bScore)) << " "
815 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
816 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
817 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
821 std::string Tracing::do_trace(const Position& pos) {
823 std::memset(terms, 0, sizeof(terms));
825 Value v = do_evaluate<true>(pos);
826 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
828 std::stringstream ss;
829 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
830 << " Eval term | White | Black | Total \n"
831 << " | MG EG | MG EG | MG EG \n"
832 << "---------------------+-------------+-------------+-------------\n";
834 format_row(ss, "Material, PST, Tempo", PST);
835 format_row(ss, "Material imbalance", IMBALANCE);
836 format_row(ss, "Pawns", PAWN);
837 format_row(ss, "Knights", KNIGHT);
838 format_row(ss, "Bishops", BISHOP);
839 format_row(ss, "Rooks", ROOK);
840 format_row(ss, "Queens", QUEEN);
841 format_row(ss, "Mobility", MOBILITY);
842 format_row(ss, "King safety", KING);
843 format_row(ss, "Threats", THREAT);
844 format_row(ss, "Passed pawns", PASSED);
845 format_row(ss, "Space", SPACE);
847 ss << "---------------------+-------------+-------------+-------------\n";
848 format_row(ss, "Total", TOTAL);
850 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
860 /// evaluate() is the main evaluation function. It returns a static evaluation
861 /// of the position always from the point of view of the side to move.
863 Value evaluate(const Position& pos) {
864 return do_evaluate<false>(pos);
868 /// trace() is like evaluate(), but instead of returning a value, it returns
869 /// a string (suitable for outputting to stdout) that contains the detailed
870 /// descriptions and values of each evaluation term. It's mainly used for
872 std::string trace(const Position& pos) {
873 return Tracing::do_trace(pos);
877 /// init() computes evaluation weights from the corresponding UCI parameters
878 /// and setup king tables.
882 const double MaxSlope = 30;
883 const double Peak = 1280;
885 for (int t = 0, i = 1; i < 100; ++i)
887 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
889 KingDanger[1][i] = apply_weight(make_score(t, 0), Weights[KingDangerUs]);
890 KingDanger[0][i] = apply_weight(make_score(t, 0), Weights[KingDangerThem]);