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 // Assorted bonuses and penalties used by evaluation
154 const Score KingOnPawnOne = S(0 , 64);
155 const Score KingOnPawnMany = S(0 ,128);
156 const Score RookOnPawn = S(10, 28);
157 const Score RookOpenFile = S(43, 21);
158 const Score RookSemiOpenFile = S(19, 10);
159 const Score BishopPawns = S( 8, 12);
160 const Score MinorBehindPawn = S(16, 0);
161 const Score TrappedRook = S(92, 0);
162 const Score Unstoppable = S( 0, 20);
163 const Score Hanging = S(23, 20);
165 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
166 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
167 // happen in Chess960 games.
168 const Score TrappedBishopA1H1 = S(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[attackUnits] contains the actual king danger weighted
198 // scores, indexed by a calculated integer number.
199 Score KingDanger[128];
201 const int ScalePawnSpan[2] = { 38, 56 };
203 // apply_weight() weighs score 'v' by weight 'w' trying to prevent overflow
204 Score apply_weight(Score v, const Weight& w) {
205 return make_score(mg_value(v) * w.mg / 256, eg_value(v) * 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.count<QUEEN>(Us) && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
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 // Penalty for bishop with same colored pawns
318 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
320 // Bishop and knight outpost square
321 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
322 score += evaluate_outpost<Pt, Us>(pos, ei, s);
324 // Bishop or knight behind a pawn
325 if ( relative_rank(Us, s) < RANK_5
326 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
327 score += MinorBehindPawn;
332 // Rook piece attacking enemy pawns on the same rank/file
333 if (relative_rank(Us, s) >= RANK_5)
335 Bitboard pawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
337 score += popcount<Max15>(pawns) * RookOnPawn;
340 // Give a bonus for a rook on a open or semi-open file
341 if (ei.pi->semiopen_file(Us, file_of(s)))
342 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiOpenFile;
344 if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
347 Square ksq = pos.king_square(Us);
349 // Penalize rooks which are trapped by a king. Penalize more if the
350 // king has lost its castling capability.
351 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
352 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
353 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
354 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
357 // An important Chess960 pattern: A cornered bishop blocked by a friendly
358 // pawn diagonally in front of it is a very serious problem, especially
359 // when that pawn is also blocked.
362 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
364 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
365 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
366 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
367 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
373 Tracing::terms[Us][Pt] = score;
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 to 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;
419 // Analyse the enemy's safe queen contact checks. Firstly, find the
420 // undefended squares around the king that are attacked by the enemy's
422 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
425 // ...and then remove squares not supported by another enemy piece
426 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
427 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]);
430 attackUnits += QueenContactCheck * popcount<Max15>(b);
433 // Analyse the enemy's safe rook contact checks. Firstly, find the
434 // undefended squares around the king that are attacked by the enemy's
436 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
438 // Consider only squares where the enemy's rook gives check
439 b &= PseudoAttacks[ROOK][ksq];
443 // ...and then remove squares not supported by another enemy piece
444 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
445 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
448 attackUnits += RookContactCheck * popcount<Max15>(b);
451 // Analyse the enemy's safe distance checks for sliders and knights
452 safe = ~(pos.pieces(Them) | ei.attackedBy[Us][ALL_PIECES]);
454 b1 = pos.attacks_from<ROOK>(ksq) & safe;
455 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
457 // Enemy queen safe checks
458 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
460 attackUnits += QueenCheck * popcount<Max15>(b);
462 // Enemy rooks safe checks
463 b = b1 & ei.attackedBy[Them][ROOK];
465 attackUnits += RookCheck * popcount<Max15>(b);
467 // Enemy bishops safe checks
468 b = b2 & ei.attackedBy[Them][BISHOP];
470 attackUnits += BishopCheck * popcount<Max15>(b);
472 // Enemy knights safe checks
473 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
475 attackUnits += KnightCheck * popcount<Max15>(b);
477 // To index KingDanger[] attackUnits must be in [0, 99] range
478 attackUnits = std::min(99, std::max(0, attackUnits));
480 // Finally, extract the king danger score from the KingDanger[]
481 // array and subtract the score from evaluation.
482 score -= KingDanger[attackUnits];
486 Tracing::terms[Us][KING] = score;
492 // evaluate_threats() assigns bonuses according to the type of attacking piece
493 // and the type of attacked one.
495 template<Color Us, bool Trace>
496 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
498 const Color Them = (Us == WHITE ? BLACK : WHITE);
500 Bitboard b, weakEnemies, protectedEnemies;
501 Score score = SCORE_ZERO;
502 enum { Minor, Major };
505 protectedEnemies = (pos.pieces(Them) ^ pos.pieces(Them,PAWN))
506 & ei.attackedBy[Them][PAWN]
507 & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
510 score += Threat[Minor][type_of(pos.piece_on(lsb(protectedEnemies)))];
512 // Enemies not defended by a pawn and under our attack
513 weakEnemies = pos.pieces(Them)
514 & ~ei.attackedBy[Them][PAWN]
515 & ei.attackedBy[Us][ALL_PIECES];
517 // Add a bonus according if the attacking pieces are minor or major
520 b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
522 score += Threat[Minor][type_of(pos.piece_on(lsb(b)))];
524 b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
526 score += Threat[Major][type_of(pos.piece_on(lsb(b)))];
528 b = weakEnemies & ~ei.attackedBy[Them][ALL_PIECES];
530 score += more_than_one(b) ? Hanging * popcount<Max15>(b) : Hanging;
532 b = weakEnemies & pos.pieces(Them, PAWN) & ei.attackedBy[Us][KING];
534 score += more_than_one(b) ? KingOnPawnMany : KingOnPawnOne;
538 Tracing::terms[Us][Tracing::THREAT] = score;
544 // evaluate_passed_pawns() evaluates the passed pawns of the given color
546 template<Color Us, bool Trace>
547 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
549 const Color Them = (Us == WHITE ? BLACK : WHITE);
551 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
552 Score score = SCORE_ZERO;
554 b = ei.pi->passed_pawns(Us);
558 Square s = pop_lsb(&b);
560 assert(pos.pawn_passed(Us, s));
562 int r = relative_rank(Us, s) - RANK_2;
563 int rr = r * (r - 1);
565 // Base bonus based on rank
566 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
570 Square blockSq = s + pawn_push(Us);
572 // Adjust bonus based on the king's proximity
573 ebonus += square_distance(pos.king_square(Them), blockSq) * 5 * rr
574 - square_distance(pos.king_square(Us ), blockSq) * 2 * rr;
576 // If blockSq is not the queening square then consider also a second push
577 if (relative_rank(Us, blockSq) != RANK_8)
578 ebonus -= square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
580 // If the pawn is free to advance, then increase the bonus
581 if (pos.empty(blockSq))
583 // If there is a rook or queen attacking/defending the pawn from behind,
584 // consider all the squaresToQueen. Otherwise consider only the squares
585 // in the pawn's path attacked or occupied by the enemy.
586 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
588 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
590 if (!(pos.pieces(Us) & bb))
591 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
593 if (!(pos.pieces(Them) & bb))
594 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
596 // If there aren't any enemy attacks, assign a big bonus. Otherwise
597 // assign a smaller bonus if the block square isn't attacked.
598 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
600 // If the path to queen is fully defended, assign a big bonus.
601 // Otherwise assign a smaller bonus if the block square is defended.
602 if (defendedSquares == squaresToQueen)
605 else if (defendedSquares & blockSq)
608 mbonus += k * rr, ebonus += k * rr;
610 else if(pos.pieces(Us) & blockSq)
611 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
614 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
615 ebonus += ebonus / 4;
617 score += make_score(mbonus, ebonus);
621 Tracing::terms[Us][Tracing::PASSED] = apply_weight(score, Weights[PassedPawns]);
623 // Add the scores to the middlegame and endgame eval
624 return apply_weight(score, Weights[PassedPawns]);
628 // evaluate_unstoppable_pawns() scores the most advanced among the passed and
629 // candidate pawns. In case both players have no pieces but pawns, this is
630 // somewhat related to the possibility that pawns are unstoppable.
632 Score evaluate_unstoppable_pawns(Color us, const EvalInfo& ei) {
634 Bitboard b = ei.pi->passed_pawns(us) | ei.pi->candidate_pawns(us);
636 return b ? Unstoppable * int(relative_rank(us, frontmost_sq(us, b))) : SCORE_ZERO;
640 // evaluate_space() computes the space evaluation for a given side. The
641 // space evaluation is a simple bonus based on the number of safe squares
642 // available for minor pieces on the central four files on ranks 2--4. Safe
643 // squares one, two or three squares behind a friendly pawn are counted
644 // twice. Finally, the space bonus is scaled by a weight taken from the
645 // material hash table. The aim is to improve play on game opening.
647 int evaluate_space(const Position& pos, const EvalInfo& ei) {
649 const Color Them = (Us == WHITE ? BLACK : WHITE);
651 // Find the safe squares for our pieces inside the area defined by
652 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
653 // pawn, or if it is undefended and attacked by an enemy piece.
654 Bitboard safe = SpaceMask[Us]
655 & ~pos.pieces(Us, PAWN)
656 & ~ei.attackedBy[Them][PAWN]
657 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
659 // Find all squares which are at most three squares behind some friendly pawn
660 Bitboard behind = pos.pieces(Us, PAWN);
661 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
662 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
664 // Since SpaceMask[Us] is fully on our half of the board
665 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
667 // Count safe + (behind & safe) with a single popcount
668 return popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
672 // do_evaluate() is the evaluation entry point, called directly from evaluate()
675 Value do_evaluate(const Position& pos) {
677 assert(!pos.checkers());
680 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
681 Thread* thisThread = pos.this_thread();
683 // Initialize score by reading the incrementally updated scores included
684 // in the position object (material + piece square tables).
685 // Score is computed from the point of view of white.
686 score = pos.psq_score();
688 // Probe the material hash table
689 ei.mi = Material::probe(pos, thisThread->materialTable, thisThread->endgames);
690 score += ei.mi->material_value();
692 // If we have a specialized evaluation function for the current material
693 // configuration, call it and return.
694 if (ei.mi->specialized_eval_exists())
695 return ei.mi->evaluate(pos);
697 // Probe the pawn hash table
698 ei.pi = Pawns::probe(pos, thisThread->pawnsTable);
699 score += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
701 // Initialize attack and king safety bitboards
702 init_eval_info<WHITE>(pos, ei);
703 init_eval_info<BLACK>(pos, ei);
705 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
706 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
708 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
709 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
710 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
712 // Evaluate pieces and mobility
713 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
714 score += apply_weight(mobility[WHITE] - mobility[BLACK], Weights[Mobility]);
716 // Evaluate kings after all other pieces because we need complete attack
717 // information when computing the king safety evaluation.
718 score += evaluate_king<WHITE, Trace>(pos, ei)
719 - evaluate_king<BLACK, Trace>(pos, ei);
721 // Evaluate tactical threats, we need full attack information including king
722 score += evaluate_threats<WHITE, Trace>(pos, ei)
723 - evaluate_threats<BLACK, Trace>(pos, ei);
725 // Evaluate passed pawns, we need full attack information including king
726 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
727 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
729 // If both sides have only pawns, score for potential unstoppable pawns
730 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
731 score += evaluate_unstoppable_pawns(WHITE, ei)
732 - evaluate_unstoppable_pawns(BLACK, ei);
734 // Evaluate space for both sides, only in middlegame
735 if (ei.mi->space_weight())
737 int s = evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei);
738 score += apply_weight(s * ei.mi->space_weight(), Weights[Space]);
741 // Scale winning side if position is more drawish than it appears
742 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
743 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
745 // If we don't already have an unusual scale factor, check for certain
746 // types of endgames, and use a lower scale for those.
747 if ( ei.mi->game_phase() < PHASE_MIDGAME
748 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
750 if (pos.opposite_bishops()) {
751 // Ignoring any pawns, do both sides only have a single bishop and no
753 if ( pos.non_pawn_material(WHITE) == BishopValueMg
754 && pos.non_pawn_material(BLACK) == BishopValueMg)
756 // Check for KBP vs KB with only a single pawn that is almost
757 // certainly a draw or at least two pawns.
758 bool one_pawn = (pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK) == 1);
759 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
762 // Endgame with opposite-colored bishops, but also other pieces. Still
763 // a bit drawish, but not as drawish as with only the two bishops.
764 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
765 } else if ( abs(eg_value(score)) <= BishopValueEg
766 && ei.pi->pawn_span(strongSide) <= 1
767 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide))) {
768 // Endings where weaker side can be place his king in front of the opponent's pawns are drawish.
769 sf = ScaleFactor(ScalePawnSpan[ei.pi->pawn_span(strongSide)]);
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::add_term(Tracing::MATERIAL, pos.psq_score());
783 Tracing::add_term(Tracing::IMBALANCE, ei.mi->material_value());
784 Tracing::add_term(PAWN, ei.pi->pawns_value());
785 Tracing::add_term(Tracing::MOBILITY, apply_weight(mobility[WHITE], Weights[Mobility])
786 , apply_weight(mobility[BLACK], Weights[Mobility]));
787 Score w = ei.mi->space_weight() * evaluate_space<WHITE>(pos, ei);
788 Score b = ei.mi->space_weight() * evaluate_space<BLACK>(pos, ei);
789 Tracing::add_term(Tracing::SPACE, apply_weight(w, Weights[Space]), apply_weight(b, Weights[Space]));
790 Tracing::add_term(Tracing::TOTAL, score);
795 return pos.side_to_move() == WHITE ? v : -v;
799 // Tracing function definitions
801 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
803 void Tracing::add_term(int idx, Score wScore, Score bScore) {
805 terms[WHITE][idx] = wScore;
806 terms[BLACK][idx] = bScore;
809 void Tracing::format_row(std::stringstream& ss, const char* name, int idx) {
811 Score wScore = terms[WHITE][idx];
812 Score bScore = terms[BLACK][idx];
815 case MATERIAL: case IMBALANCE: case PAWN: case TOTAL:
816 ss << std::setw(15) << name << " | --- --- | --- --- | "
817 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
818 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
821 ss << std::setw(15) << name << " | " << std::noshowpos
822 << std::setw(5) << to_cp(mg_value(wScore)) << " "
823 << std::setw(5) << to_cp(eg_value(wScore)) << " | "
824 << std::setw(5) << to_cp(mg_value(bScore)) << " "
825 << std::setw(5) << to_cp(eg_value(bScore)) << " | "
826 << std::setw(5) << to_cp(mg_value(wScore - bScore)) << " "
827 << std::setw(5) << to_cp(eg_value(wScore - bScore)) << " \n";
831 std::string Tracing::do_trace(const Position& pos) {
833 std::memset(terms, 0, sizeof(terms));
835 Value v = do_evaluate<true>(pos);
836 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
838 std::stringstream ss;
839 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
840 << " Eval term | White | Black | Total \n"
841 << " | MG EG | MG EG | MG EG \n"
842 << "----------------+-------------+-------------+-------------\n";
844 format_row(ss, "Material", MATERIAL);
845 format_row(ss, "Imbalance", IMBALANCE);
846 format_row(ss, "Pawns", PAWN);
847 format_row(ss, "Knights", KNIGHT);
848 format_row(ss, "Bishops", BISHOP);
849 format_row(ss, "Rooks", ROOK);
850 format_row(ss, "Queens", QUEEN);
851 format_row(ss, "Mobility", MOBILITY);
852 format_row(ss, "King safety", KING);
853 format_row(ss, "Threats", THREAT);
854 format_row(ss, "Passed pawns", PASSED);
855 format_row(ss, "Space", SPACE);
857 ss << "----------------+-------------+-------------+-------------\n";
858 format_row(ss, "Total", TOTAL);
860 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
870 /// evaluate() is the main evaluation function. It returns a static evaluation
871 /// of the position always from the point of view of the side to move.
873 Value evaluate(const Position& pos) {
874 return do_evaluate<false>(pos) + Tempo;
878 /// trace() is like evaluate(), but instead of returning a value, it returns
879 /// a string (suitable for outputting to stdout) that contains the detailed
880 /// descriptions and values of each evaluation term. It's mainly used for
882 std::string trace(const Position& pos) {
883 return Tracing::do_trace(pos);
887 /// init() computes evaluation weights from the corresponding UCI parameters
888 /// and setup king tables.
892 const double MaxSlope = 30;
893 const double Peak = 1280;
895 for (int t = 0, i = 1; i < 100; ++i)
897 t = int(std::min(Peak, std::min(0.4 * i * i, t + MaxSlope)));
898 KingDanger[i] = apply_weight(make_score(t, 0), Weights[KingSafety]);