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 MATERIAL = 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, KingSafety };
94 const struct Weight { int mg, eg; } Weights[] = {
95 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {318, 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(80, 119), S(80, 119), S(117, 199), S(127, 218)
153 // Hanging contains a bonus for each enemy hanging piece
154 const Score Hanging = S(23, 20);
155 const Score KingPawnThreatOne = S(0, 64);
156 const Score KingPawnThreatMany = S(0, 128);
160 const Score RookOnPawn = make_score(10, 28);
161 const Score RookOpenFile = make_score(43, 21);
162 const Score RookSemiopenFile = make_score(19, 10);
163 const Score BishopPawns = make_score( 8, 12);
164 const Score MinorBehindPawn = make_score(16, 0);
165 const Score TrappedRook = make_score(92, 0);
166 const Score Unstoppable = make_score( 0, 20);
168 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
169 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
170 // happen in Chess960 games.
171 const Score TrappedBishopA1H1 = make_score(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 const int ScalePawnSpan[2] = { 38, 56 };
204 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
205 Score apply_weight(Score v, const Weight& w) {
206 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * w.eg / 256);
210 // init_eval_info() initializes king bitboards for given color adding
211 // pawn attacks. To be done at the beginning of the evaluation.
214 void init_eval_info(const Position& pos, EvalInfo& ei) {
216 const Color Them = (Us == WHITE ? BLACK : WHITE);
217 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
219 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
221 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
222 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
224 // Init king safety tables only if we are going to use them
225 if (pos.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
227 ei.kingRing[Them] = b | shift_bb<Down>(b);
228 b &= ei.attackedBy[Us][PAWN];
229 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
230 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
233 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
237 // evaluate_outpost() evaluates bishop and knight outpost squares
239 template<PieceType Pt, Color Us>
240 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
242 const Color Them = (Us == WHITE ? BLACK : WHITE);
244 assert (Pt == BISHOP || Pt == KNIGHT);
246 // Initial bonus based on square
247 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
249 // Increase bonus if supported by pawn, especially if the opponent has
250 // no minor piece which can trade with the outpost piece.
251 if (bonus && (ei.attackedBy[Us][PAWN] & s))
253 if ( !pos.pieces(Them, KNIGHT)
254 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
255 bonus += bonus + bonus / 2;
260 return make_score(bonus * 2, bonus / 2);
264 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
266 template<PieceType Pt, Color Us, bool Trace>
267 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
271 Score score = SCORE_ZERO;
273 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
274 const Color Them = (Us == WHITE ? BLACK : WHITE);
275 const Square* pl = pos.list<Pt>(Us);
277 ei.attackedBy[Us][Pt] = 0;
279 while ((s = *pl++) != SQ_NONE)
281 // Find attacked squares, including x-ray attacks for bishops and rooks
282 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
283 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
284 : pos.attacks_from<Pt>(s);
286 if (ei.pinnedPieces[Us] & s)
287 b &= LineBB[pos.king_square(Us)][s];
289 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
291 if (b & ei.kingRing[Them])
293 ei.kingAttackersCount[Us]++;
294 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
295 Bitboard bb = b & ei.attackedBy[Them][KING];
297 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
301 b &= ~( ei.attackedBy[Them][KNIGHT]
302 | ei.attackedBy[Them][BISHOP]
303 | ei.attackedBy[Them][ROOK]);
305 int mob = Pt != QUEEN ? popcount<Max15>(b & mobilityArea[Us])
306 : popcount<Full >(b & mobilityArea[Us]);
308 mobility[Us] += MobilityBonus[Pt][mob];
310 // Decrease score if we are attacked by an enemy pawn. The remaining part
311 // of threat evaluation must be done later when we have full attack info.
312 if (ei.attackedBy[Them][PAWN] & s)
313 score -= ThreatenedByPawn[Pt];
315 if (Pt == BISHOP || Pt == KNIGHT)
317 // Penalty for bishop with same colored pawns
319 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
321 // Bishop and knight outpost square
322 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
323 score += evaluate_outpost<Pt, Us>(pos, ei, s);
325 // Bishop or knight behind a pawn
326 if ( relative_rank(Us, s) < RANK_5
327 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
328 score += MinorBehindPawn;
333 // Rook piece attacking enemy pawns on the same rank/file
334 if (relative_rank(Us, s) >= RANK_5)
336 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
338 score += popcount<Max15>(pawns) * RookOnPawn;
341 // Give a bonus for a rook on a open or semi-open file
342 if (ei.pi->semiopen_file(Us, file_of(s)))
343 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
345 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
348 Square ksq = pos.king_square(Us);
350 // Penalize rooks which are trapped by a king. Penalize more if the
351 // king has lost its castling capability.
352 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
353 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
354 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
355 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
358 // An important Chess960 pattern: A cornered bishop blocked by a friendly
359 // pawn diagonally in front of it is a very serious problem, especially
360 // when that pawn is also blocked.
363 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
365 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
366 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
367 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
368 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
374 Tracing::terms[Us][Pt] = score;
376 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
380 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
382 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
385 // evaluate_king() assigns bonuses and penalties to a king of a given color
387 template<Color Us, bool Trace>
388 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
390 const Color Them = (Us == WHITE ? BLACK : WHITE);
392 Bitboard undefended, b, b1, b2, safe;
394 const Square ksq = pos.king_square(Us);
396 // King shelter and enemy pawns storm
397 Score score = ei.pi->king_safety<Us>(pos, ksq);
399 // Main king safety evaluation
400 if (ei.kingAttackersCount[Them])
402 // Find the attacked squares around the king which have no defenders
403 // apart from the king itself
404 undefended = ei.attackedBy[Them][ALL_PIECES]
405 & ei.attackedBy[Us][KING]
406 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
407 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
408 | ei.attackedBy[Us][QUEEN]);
410 // Initialize the 'attackUnits' variable, which is used later on as an
411 // index to the KingDanger[] array. The initial value is based on the
412 // number and types of the enemy's attacking pieces, the number of
413 // attacked and undefended squares around our king and the quality of
414 // the pawn shelter (current 'score' value).
415 attackUnits = std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
416 + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
417 + 2 * (ei.pinnedPieces[Us] != 0)
418 - mg_value(score) / 32;
420 // Analyse the enemy's safe queen contact checks. Firstly, find the
421 // undefended squares around the king that are attacked by the enemy's
423 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
426 // ...and then remove squares not supported by another enemy piece
427 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
428 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
431 attackUnits += QueenContactCheck * popcount<Max15>(b);
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 * popcount<Max15>(b);
452 // Analyse the enemy's safe distance checks for sliders and knights
453 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
455 b1 = pos.attacks_from<ROOK>(ksq) & safe;
456 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
458 // Enemy queen safe checks
459 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
461 attackUnits += QueenCheck * popcount<Max15>(b);
463 // Enemy rooks safe checks
464 b = b1 & ei.attackedBy[Them][ROOK];
466 attackUnits += RookCheck * popcount<Max15>(b);
468 // Enemy bishops safe checks
469 b = b2 & ei.attackedBy[Them][BISHOP];
471 attackUnits += BishopCheck * popcount<Max15>(b);
473 // Enemy knights safe checks
474 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
476 attackUnits += KnightCheck * popcount<Max15>(b);
478 // To index KingDanger[] attackUnits must be in [0, 99] range
479 attackUnits = std::min(99, std::max(0, attackUnits));
481 // Finally, extract the king danger score from the KingDanger[]
482 // array and subtract the score from evaluation.
483 score -= KingDanger[attackUnits];
487 Tracing::terms[Us][KING] = score;
493 // evaluate_threats() assigns bonuses according to the type of attacking piece
494 // and the type of attacked one.
496 template<Color Us, bool Trace>
497 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
499 const Color Them = (Us == WHITE ? BLACK : WHITE);
501 Bitboard b, weakEnemies, protectedEnemies;
502 Score score = SCORE_ZERO;
503 enum { Minor, Major };
506 protectedEnemies = (pos.pieces(Them) ^ pos.pieces(Them,PAWN))
507 & ei.attackedBy[Them][PAWN]
508 & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
511 score += Threat[Minor][type_of(pos.piece_on(lsb(protectedEnemies)))];
513 // Enemies not defended by a pawn and under our attack
514 weakEnemies = pos.pieces(Them)
515 & ~ei.attackedBy[Them][PAWN]
516 & ei.attackedBy[Us][ALL_PIECES];
518 // Add a bonus according if the attacking pieces are minor or major
521 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
523 score += Threat[Minor][type_of(pos.piece_on(lsb(b)))];
525 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
527 score += Threat[Major][type_of(pos.piece_on(lsb(b)))];
529 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
531 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
533 b = weakEnemies & pos.pieces(Them, PAWN) & ei.attackedBy[Us][KING];
535 score += more_than_one(b) ? KingPawnThreatMany : KingPawnThreatOne;
539 Tracing::terms[Us][Tracing::THREAT] = score;
545 // evaluate_passed_pawns() evaluates the passed pawns of the given color
547 template<Color Us, bool Trace>
548 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
550 const Color Them = (Us == WHITE ? BLACK : WHITE);
552 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
553 Score score = SCORE_ZERO;
555 b = ei.pi->passed_pawns(Us);
559 Square s = pop_lsb(&b);
561 assert(pos.pawn_passed(Us, s));
563 int r = relative_rank(Us, s) - RANK_2;
564 int rr = r * (r - 1);
566 // Base bonus based on rank
567 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
571 Square blockSq = s + pawn_push(Us);
573 // Adjust bonus based on the king's proximity
574 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
575 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
577 // If blockSq is not the queening square then consider also a second push
578 if (relative_rank(Us, blockSq) != RANK_8)
579 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
581 // If the pawn is free to advance, then increase the bonus
582 if (pos.empty(blockSq))
584 // If there is a rook or queen attacking/defending the pawn from behind,
585 // consider all the squaresToQueen. Otherwise consider only the squares
586 // in the pawn's path attacked or occupied by the enemy.
587 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
589 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
591 if (!(pos.pieces(Us) & bb))
592 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
594 if (!(pos.pieces(Them) & bb))
595 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
597 // If there aren't any enemy attacks, assign a big bonus. Otherwise
598 // assign a smaller bonus if the block square isn't attacked.
599 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
601 // If the path to queen is fully defended, assign a big bonus.
602 // Otherwise assign a smaller bonus if the block square is defended.
603 if (defendedSquares == squaresToQueen)
606 else if (defendedSquares & blockSq)
609 mbonus += k * rr, ebonus += k * rr;
611 else if(pos.pieces(Us) & blockSq)
612 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
615 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
616 ebonus += ebonus / 4;
618 score += make_score(mbonus, ebonus);
622 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
624 // Add the scores to the middlegame and endgame eval
625 return apply_weight(score, Weights[PassedPawns]);
629 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
630 // candidate pawns. In case both players have no pieces but pawns, this is
631 // somewhat related to the possibility that pawns are unstoppable.
633 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
635 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
637 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
641 // evaluate_space() computes the space evaluation for a given side. The
642 // space evaluation is a simple bonus based on the number of safe squares
643 // available for minor pieces on the central four files on ranks 2--4. Safe
644 // squares one, two or three squares behind a friendly pawn are counted
645 // twice. Finally, the space bonus is scaled by a weight taken from the
646 // material hash table. The aim is to improve play on game opening.
648 int evaluate_space(const Position& pos, const EvalInfo& ei) {
650 const Color Them = (Us == WHITE ? BLACK : WHITE);
652 // Find the safe squares for our pieces inside the area defined by
653 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
654 // pawn, or if it is undefended and attacked by an enemy piece.
655 Bitboard safe = SpaceMask[Us]
656 & ~pos.pieces(Us, PAWN)
657 & ~ei.attackedBy[Them][PAWN]
658 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
660 // Find all squares which are at most three squares behind some friendly pawn
661 Bitboard behind = pos.pieces(Us, PAWN);
662 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
663 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
665 // Since SpaceMask[Us] is fully on our half of the board
666 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
668 // Count safe + (behind & safe) with a single popcount
669 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
673 // do_evaluate() is the evaluation entry point, called directly from evaluate()
676 Value do_evaluate(const Position& pos) {
678 assert(!pos.checkers());
681 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
682 Thread* thisThread = pos.this_thread();
684 // Initialize score by reading the incrementally updated scores included
685 // in the position object (material + piece square tables).
686 // Score is computed from the point of view of white.
687 score = pos.psq_score();
689 // Probe the material hash table
690 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
691 score += ei.mi->material_value();
693 // If we have a specialized evaluation function for the current material
694 // configuration, call it and return.
695 if (ei.mi->specialized_eval_exists())
696 return ei.mi->evaluate(pos);
698 // Probe the pawn hash table
699 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
700 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
702 // Initialize attack and king safety bitboards
703 init_eval_info<WHITE>(pos, ei);
704 init_eval_info<BLACK>(pos, ei);
706 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
707 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
709 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
710 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
711 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
713 // Evaluate pieces and mobility
714 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
715 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
717 // Evaluate kings after all other pieces because we need complete attack
718 // information when computing the king safety evaluation.
719 score += evaluate_king<WHITE, Trace>(pos, ei)
720 - evaluate_king<BLACK, Trace>(pos, ei);
722 // Evaluate tactical threats, we need full attack information including king
723 score += evaluate_threats<WHITE, Trace>(pos, ei)
724 - evaluate_threats<BLACK, Trace>(pos, ei);
726 // Evaluate passed pawns, we need full attack information including king
727 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
728 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
730 // If both sides have only pawns, score for potential unstoppable pawns
731 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
732 score += evaluate_unstoppable_pawns(WHITE, ei)
733 - evaluate_unstoppable_pawns(BLACK, ei);
735 // Evaluate space for both sides, only in middlegame
736 if (ei.mi->space_weight())
738 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
739 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
742 // Scale winning side if position is more drawish than it appears
743 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
744 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
746 // If we don't already have an unusual scale factor, check for certain
747 // types of endgames, and use a lower scale for those.
748 if ( ei.mi->game_phase() < PHASE_MIDGAME
749 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
751 if (pos.opposite_bishops()) {
752 // Ignoring any pawns, do both sides only have a single bishop and no
754 if ( pos.non_pawn_material(WHITE) == BishopValueMg
755 && pos.non_pawn_material(BLACK) == BishopValueMg)
757 // Check for KBP vs KB with only a single pawn that is almost
758 // certainly a draw or at least two pawns.
759 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
760 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
763 // Endgame with opposite-colored bishops, but also other pieces. Still
764 // a bit drawish, but not as drawish as with only the two bishops.
765 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
766 } else if ( abs(eg_value(score)) <= BishopValueEg
767 && ei.pi->pawn_span(strongSide) <= 1
768 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide))) {
769 // Endings where weaker side can be place his king in front of the opponent's pawns are drawish.
770 sf = ScaleFactor(ScalePawnSpan[ei.pi->pawn_span(strongSide)]);
774 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
775 Value v = mg_value(score) * int(ei.mi->game_phase())
776 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
778 v /= int(PHASE_MIDGAME);
780 // In case of tracing add all single evaluation contributions for both white and black
783 Tracing::add_term(Tracing::MATERIAL, pos.psq_score());
784 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
785 Tracing::add_term(PAWN, ei.pi->pawns_value());
786 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
787 , apply_weight(mobility[BLACK], Weights[Mobility]));
788 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
789 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
790 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
791 Tracing::add_term(Tracing::TOTAL, score);
796 return pos.side_to_move() == WHITE ? v : -v;
800 // Tracing function definitions
802 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
804 void Tracing::add_term(int idx, Score wScore, Score bScore) {
806 terms[WHITE][idx] = wScore;
807 terms[BLACK][idx] = bScore;
810 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
812 Score wScore = terms[WHITE][idx];
813 Score bScore = terms[BLACK][idx];
816 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
817 ss << std::setw(15) << name << " | --- --- | --- --- | "
818 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
819 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
822 ss << std::setw(15) << name << " | " << std::noshowpos
823 << std::setw(5) << to_cp(mg_value(wScore)) << " "
824 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
825 << std::setw(5) << to_cp(mg_value(bScore)) << " "
826 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
827 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
828 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
832 std::string Tracing::do_trace(const Position& pos) {
834 std::memset(terms, 0, sizeof(terms));
836 Value v = do_evaluate<true>(pos);
837 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
839 std::stringstream ss;
840 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
841 << " Eval term | White | Black | Total \n"
842 << " | MG EG | MG EG | MG EG \n"
843 << "----------------+-------------+-------------+-------------\n";
845 format_row(ss, "Material", MATERIAL);
846 format_row(ss, "Imbalance", IMBALANCE);
847 format_row(ss, "Pawns", PAWN);
848 format_row(ss, "Knights", KNIGHT);
849 format_row(ss, "Bishops", BISHOP);
850 format_row(ss, "Rooks", ROOK);
851 format_row(ss, "Queens", QUEEN);
852 format_row(ss, "Mobility", MOBILITY);
853 format_row(ss, "King safety", KING);
854 format_row(ss, "Threats", THREAT);
855 format_row(ss, "Passed pawns", PASSED);
856 format_row(ss, "Space", SPACE);
858 ss << "----------------+-------------+-------------+-------------\n";
859 format_row(ss, "Total", TOTAL);
861 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
871 /// evaluate() is the main evaluation function. It returns a static evaluation
872 /// of the position always from the point of view of the side to move.
874 Value evaluate(const Position& pos) {
875 return do_evaluate<false>(pos) + Tempo;
879 /// trace() is like evaluate(), but instead of returning a value, it returns
880 /// a string (suitable for outputting to stdout) that contains the detailed
881 /// descriptions and values of each evaluation term. It's mainly used for
883 std::string trace(const Position& pos) {
884 return Tracing::do_trace(pos);
888 /// init() computes evaluation weights from the corresponding UCI parameters
889 /// and setup king tables.
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]);