2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 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/>.
22 #include <cstring> // For std::memset
35 enum Term { // First 8 entries are for PieceType
36 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
39 Score scores[COLOR_NB][TERM_NB];
41 std::ostream& operator<<(std::ostream& os, Term idx);
43 double to_cp(Value v);
44 void write(int idx, Color c, Score s);
45 void write(int idx, Score w, Score b = SCORE_ZERO);
46 std::string do_trace(const Position& pos);
50 // Struct EvalInfo contains various information computed and collected
51 // by the evaluation functions.
54 // Pointers to material and pawn hash table entries
58 // attackedBy[color][piece type] is a bitboard representing all squares
59 // attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
60 // contains all squares attacked by the given color.
61 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
63 // kingRing[color] is the zone around the king which is considered
64 // by the king safety evaluation. This consists of the squares directly
65 // adjacent to the king, and the three (or two, for a king on an edge file)
66 // squares two ranks in front of the king. For instance, if black's king
67 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
68 // f7, g7, h7, f6, g6 and h6.
69 Bitboard kingRing[COLOR_NB];
71 // kingAttackersCount[color] is the number of pieces of the given color
72 // which attack a square in the kingRing of the enemy king.
73 int kingAttackersCount[COLOR_NB];
75 // kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
76 // given color which attack a square in the kingRing of the enemy king. The
77 // weights of the individual piece types are given by the elements in the
78 // KingAttackWeights array.
79 int kingAttackersWeight[COLOR_NB];
81 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
82 // color to squares directly adjacent to the enemy king. Pieces which attack
83 // more than one square are counted multiple times. For instance, if there is
84 // a white knight on g5 and black's king is on g8, this white knight adds 2
85 // to kingAdjacentZoneAttacksCount[WHITE].
86 int kingAdjacentZoneAttacksCount[COLOR_NB];
88 Bitboard pinnedPieces[COLOR_NB];
92 // Evaluation weights, indexed by the corresponding evaluation term
93 enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
95 const struct Weight { int mg, eg; } Weights[] = {
96 {289, 344}, {233, 201}, {221, 273}, {46, 0}, {322, 0}
99 Score operator*(Score s, const Weight& w) {
100 return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
104 #define V(v) Value(v)
105 #define S(mg, eg) make_score(mg, eg)
107 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
108 // game, indexed by piece type and number of attacked squares not occupied by
110 const Score MobilityBonus[][32] = {
112 { S(-68,-49), S(-46,-33), S(-3,-12), S( 5, -4), S( 9, 11), S(15, 16), // Knights
113 S( 23, 27), S( 33, 28), S(37, 29) },
114 { S(-49,-44), S(-23,-16), S(16, 1), S(29, 16), S(40, 25), S(51, 34), // Bishops
115 S( 55, 43), S( 61, 49), S(64, 51), S(68, 52), S(73, 55), S(75, 60),
116 S( 80, 65), S( 86, 66) },
117 { S(-50,-57), S(-28,-22), S(-11, 7), S(-1, 29), S( 0, 39), S( 1, 46), // Rooks
118 S( 10, 66), S( 16, 79), S(22, 86), S(23,103), S(30,109), S(33,111),
119 S( 37,115), S( 38,119), S(48,124) },
120 { S(-43,-30), S(-27,-15), S( 1, -5), S( 2, -3), S(14, 10), S(18, 24), // Queens
121 S( 20, 27), S( 33, 37), S(33, 38), S(34, 43), S(40, 46), S(43, 56),
122 S( 46, 61), S( 52, 63), S(52, 63), S(57, 65), S(60, 70), S(61, 74),
123 S( 67, 80), S( 76, 82), S(77, 88), S(82, 94), S(86, 95), S(90, 96),
124 S( 94, 99), S( 96,100), S(99,111), S(99,112) }
127 // Outpost[Bishop/Knight][Square] contains bonuses for knights and bishops
128 // outposts, indexed by piece type and square (from white's point of view).
129 const Value Outpost[][SQUARE_NB] = {
131 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
132 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
133 V(0), V(0), V(3), V(9), V(9), V(3), V(0), V(0),
134 V(0), V(4),V(18),V(25),V(25),V(18), V(4), V(0),
135 V(4), V(9),V(29),V(38),V(38),V(29), V(9), V(4),
136 V(2), V(9),V(19),V(15),V(15),V(19), V(9), V(2) },
138 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
139 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
140 V(2), V(4), V(3), V(8), V(8), V(3), V(4), V(2),
141 V(1), V(9), V(9),V(13),V(13), V(9), V(9), V(1),
142 V(2), V(8),V(21),V(24),V(24),V(21), V(8), V(2),
143 V(0), V(4), V(6), V(6), V(6), V(6), V(4), V(0) }
146 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
147 // bonuses according to which piece type attacks which one.
148 const Score Threat[][2][PIECE_TYPE_NB] = {
149 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
150 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
151 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
152 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
155 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
156 // type is attacked by an enemy pawn.
157 const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
158 S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
161 // Assorted bonuses and penalties used by evaluation
162 const Score KingOnOne = S( 2, 58);
163 const Score KingOnMany = S( 6,125);
164 const Score RookOnPawn = S( 7, 27);
165 const Score RookOnOpenFile = S(43, 21);
166 const Score RookOnSemiOpenFile = S(19, 10);
167 const Score BishopPawns = S( 8, 12);
168 const Score MinorBehindPawn = S(16, 0);
169 const Score TrappedRook = S(92, 0);
170 const Score Unstoppable = S( 0, 20);
171 const Score Hanging = S(31, 26);
172 const Score PawnAttackThreat = S(20, 20);
173 const Score PawnSafePush = S( 5, 5);
175 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
176 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
177 // happen in Chess960 games.
178 const Score TrappedBishopA1H1 = S(50, 50);
183 // SpaceMask[Color] contains the area of the board which is considered
184 // by the space evaluation. In the middlegame, each side is given a bonus
185 // based on how many squares inside this area are safe and available for
186 // friendly minor pieces.
187 const Bitboard SpaceMask[COLOR_NB] = {
188 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
189 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
192 // King danger constants and variables. The king danger scores are looked-up
193 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
194 // of the enemy attack are added up into an integer, which is used as an
195 // index to KingDanger[].
196 Score KingDanger[512];
198 // KingAttackWeights[PieceType] contains king attack weights by piece type
199 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
201 // Penalties for enemy's safe checks
202 const int QueenContactCheck = 89;
203 const int RookContactCheck = 71;
204 const int QueenCheck = 50;
205 const int RookCheck = 37;
206 const int BishopCheck = 6;
207 const int KnightCheck = 14;
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);
220 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
221 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
223 // Init king safety tables only if we are going to use them
224 if (pos.non_pawn_material(Us) >= QueenValueMg)
226 ei.kingRing[Them] = b | shift_bb<Down>(b);
227 b &= ei.attackedBy[Us][PAWN];
228 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
229 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
232 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
236 // evaluate_outpost() evaluates bishop and knight outpost squares
238 template<PieceType Pt, Color Us>
239 Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
241 const Color Them = (Us == WHITE ? BLACK : WHITE);
243 assert (Pt == BISHOP || Pt == KNIGHT);
245 // Initial bonus based on square
246 Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
248 // Increase bonus if supported by pawn, especially if the opponent has
249 // no minor piece which can trade with the outpost piece.
250 if (bonus && (ei.attackedBy[Us][PAWN] & s))
252 if ( !pos.pieces(Them, KNIGHT)
253 && !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
254 bonus += bonus + bonus / 2;
259 return make_score(bonus * 2, bonus / 2);
263 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
265 template<PieceType Pt, Color Us, bool Trace>
266 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
270 Score score = SCORE_ZERO;
272 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
273 const Color Them = (Us == WHITE ? BLACK : WHITE);
274 const Square* pl = pos.list<Pt>(Us);
276 ei.attackedBy[Us][Pt] = 0;
278 while ((s = *pl++) != SQ_NONE)
280 // Find attacked squares, including x-ray attacks for bishops and rooks
281 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
282 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
283 : pos.attacks_from<Pt>(s);
285 if (ei.pinnedPieces[Us] & s)
286 b &= LineBB[pos.king_square(Us)][s];
288 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
290 if (b & ei.kingRing[Them])
292 ei.kingAttackersCount[Us]++;
293 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
294 Bitboard bb = b & ei.attackedBy[Them][KING];
296 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
300 b &= ~( ei.attackedBy[Them][KNIGHT]
301 | ei.attackedBy[Them][BISHOP]
302 | ei.attackedBy[Them][ROOK]);
304 int mob = popcount<Pt == QUEEN ? Full : Max15>(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 // Bonus for outpost square
316 if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
317 score += evaluate_outpost<Pt, Us>(pos, ei, s);
319 // Bonus when behind a pawn
320 if ( relative_rank(Us, s) < RANK_5
321 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
322 score += MinorBehindPawn;
324 // Penalty for pawns on same color square of bishop
326 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
328 // An important Chess960 pattern: A cornered bishop blocked by a friendly
329 // pawn diagonally in front of it is a very serious problem, especially
330 // when that pawn is also blocked.
333 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
335 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
336 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
337 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
338 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
345 // Bonus for aligning with enemy pawns on the same rank/file
346 if (relative_rank(Us, s) >= RANK_5)
348 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
350 score += popcount<Max15>(alignedPawns) * RookOnPawn;
353 // Bonus when on an open or semi-open file
354 if (ei.pi->semiopen_file(Us, file_of(s)))
355 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
357 // Penalize when trapped by the king, even more if king cannot castle
358 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
360 Square ksq = pos.king_square(Us);
362 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
363 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
364 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
365 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
371 Tracing::write(Pt, Us, score);
373 // Recursively call evaluate_pieces() of next piece type until KING excluded
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 into 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(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
414 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
415 + 25 * popcount<Max15>(undefended)
416 + 11 * (ei.pinnedPieces[Us] != 0)
417 - mg_value(score) / 8
418 - !pos.count<QUEEN>(Them) * 60;
420 // Analyse the enemy's safe queen contact checks. Firstly, find the
421 // undefended squares around the king reachable by the enemy queen...
422 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
425 // ...and then remove squares not supported by another enemy piece
426 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
427 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
430 attackUnits += QueenContactCheck * popcount<Max15>(b);
433 // Analyse the enemy's safe rook contact checks. Firstly, find the
434 // undefended squares around the king reachable by the enemy rooks...
435 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
437 // Consider only squares where the enemy's rook gives check
438 b &= PseudoAttacks[ROOK][ksq];
442 // ...and then remove squares not supported by another enemy piece
443 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
444 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
447 attackUnits += RookContactCheck * popcount<Max15>(b);
450 // Analyse the enemy's safe distance checks for sliders and knights
451 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
453 b1 = pos.attacks_from<ROOK >(ksq) & safe;
454 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
456 // Enemy queen safe checks
457 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
459 attackUnits += QueenCheck * popcount<Max15>(b);
461 // Enemy rooks safe checks
462 b = b1 & ei.attackedBy[Them][ROOK];
464 attackUnits += RookCheck * popcount<Max15>(b);
466 // Enemy bishops safe checks
467 b = b2 & ei.attackedBy[Them][BISHOP];
469 attackUnits += BishopCheck * popcount<Max15>(b);
471 // Enemy knights safe checks
472 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
474 attackUnits += KnightCheck * popcount<Max15>(b);
476 // Finally, extract the king danger score from the KingDanger[]
477 // array and subtract the score from evaluation.
478 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
482 Tracing::write(KING, Us, score);
488 // evaluate_threats() assigns bonuses according to the type of attacking piece
489 // and the type of attacked one.
491 template<Color Us, bool Trace>
492 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
494 const Color Them = (Us == WHITE ? BLACK : WHITE);
495 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
496 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
497 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
498 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
499 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
501 enum { Defended, Weak };
502 enum { Minor, Major };
504 Bitboard b, weak, defended;
505 Score score = SCORE_ZERO;
507 // Non-pawn enemies defended by a pawn
508 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
510 // Add a bonus according to the kind of attacking pieces
513 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
515 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
517 b = defended & (ei.attackedBy[Us][ROOK]);
519 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
522 // Enemies not defended by a pawn and under our attack
523 weak = pos.pieces(Them)
524 & ~ei.attackedBy[Them][PAWN]
525 & ei.attackedBy[Us][ALL_PIECES];
527 // Add a bonus according to the kind of attacking pieces
530 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
532 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
534 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
536 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
538 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
540 score += Hanging * popcount<Max15>(b);
542 b = weak & ei.attackedBy[Us][KING];
544 score += more_than_one(b) ? KingOnMany : KingOnOne;
547 // Add a small bonus for safe pawn pushes
548 b = pos.pieces(Us, PAWN) & ~TRank7BB;
549 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
552 & ~ei.attackedBy[Them][PAWN]
553 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
556 score += popcount<Full>(b) * PawnSafePush;
558 // Add another bonus if the pawn push attacks an enemy piece
559 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
561 & ~ei.attackedBy[Us][PAWN];
564 score += popcount<Max15>(b) * PawnAttackThreat;
567 Tracing::write(Tracing::THREAT, Us, score);
573 // evaluate_passed_pawns() evaluates the passed pawns of the given color
575 template<Color Us, bool Trace>
576 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
578 const Color Them = (Us == WHITE ? BLACK : WHITE);
580 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
581 Score score = SCORE_ZERO;
583 b = ei.pi->passed_pawns(Us);
587 Square s = pop_lsb(&b);
589 assert(pos.pawn_passed(Us, s));
591 int r = relative_rank(Us, s) - RANK_2;
592 int rr = r * (r - 1);
594 // Base bonus based on rank
595 Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
599 Square blockSq = s + pawn_push(Us);
601 // Adjust bonus based on the king's proximity
602 ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
603 - distance(pos.king_square(Us ), blockSq) * 2 * rr;
605 // If blockSq is not the queening square then consider also a second push
606 if (relative_rank(Us, blockSq) != RANK_8)
607 ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
609 // If the pawn is free to advance, then increase the bonus
610 if (pos.empty(blockSq))
612 // If there is a rook or queen attacking/defending the pawn from behind,
613 // consider all the squaresToQueen. Otherwise consider only the squares
614 // in the pawn's path attacked or occupied by the enemy.
615 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
617 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
619 if (!(pos.pieces(Us) & bb))
620 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
622 if (!(pos.pieces(Them) & bb))
623 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
625 // If there aren't any enemy attacks, assign a big bonus. Otherwise
626 // assign a smaller bonus if the block square isn't attacked.
627 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
629 // If the path to queen is fully defended, assign a big bonus.
630 // Otherwise assign a smaller bonus if the block square is defended.
631 if (defendedSquares == squaresToQueen)
634 else if (defendedSquares & blockSq)
637 mbonus += k * rr, ebonus += k * rr;
639 else if (pos.pieces(Us) & blockSq)
640 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
643 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
644 ebonus += ebonus / 4;
646 score += make_score(mbonus, ebonus);
650 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
652 // Add the scores to the middlegame and endgame eval
653 return score * Weights[PassedPawns];
657 // evaluate_space() computes the space evaluation for a given side. The
658 // space evaluation is a simple bonus based on the number of safe squares
659 // available for minor pieces on the central four files on ranks 2--4. Safe
660 // squares one, two or three squares behind a friendly pawn are counted
661 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
662 // improve play on game opening.
664 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
666 const Color Them = (Us == WHITE ? BLACK : WHITE);
668 // Find the safe squares for our pieces inside the area defined by
669 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
670 // pawn, or if it is undefended and attacked by an enemy piece.
671 Bitboard safe = SpaceMask[Us]
672 & ~pos.pieces(Us, PAWN)
673 & ~ei.attackedBy[Them][PAWN]
674 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
676 // Find all squares which are at most three squares behind some friendly pawn
677 Bitboard behind = pos.pieces(Us, PAWN);
678 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
679 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
681 // Since SpaceMask[Us] is fully on our half of the board
682 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
684 // Count safe + (behind & safe) with a single popcount
685 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
686 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
687 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
689 return make_score(bonus * weight * weight, 0);
693 // do_evaluate() is the evaluation entry point, called directly from evaluate()
696 Value do_evaluate(const Position& pos) {
698 assert(!pos.checkers());
701 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
703 // Initialize score by reading the incrementally updated scores included
704 // in the position object (material + piece square tables).
705 // Score is computed from the point of view of white.
706 score = pos.psq_score();
708 // Probe the material hash table
709 ei.mi = Material::probe(pos);
710 score += ei.mi->imbalance();
712 // If we have a specialized evaluation function for the current material
713 // configuration, call it and return.
714 if (ei.mi->specialized_eval_exists())
715 return ei.mi->evaluate(pos);
717 // Probe the pawn hash table
718 ei.pi = Pawns::probe(pos);
719 score += ei.pi->pawns_score() * Weights[PawnStructure];
721 // Initialize attack and king safety bitboards
722 init_eval_info<WHITE>(pos, ei);
723 init_eval_info<BLACK>(pos, ei);
725 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
726 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
728 // Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
729 Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
730 ~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
732 // Evaluate pieces and mobility
733 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
734 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
736 // Evaluate kings after all other pieces because we need complete attack
737 // information when computing the king safety evaluation.
738 score += evaluate_king<WHITE, Trace>(pos, ei)
739 - evaluate_king<BLACK, Trace>(pos, ei);
741 // Evaluate tactical threats, we need full attack information including king
742 score += evaluate_threats<WHITE, Trace>(pos, ei)
743 - evaluate_threats<BLACK, Trace>(pos, ei);
745 // Evaluate passed pawns, we need full attack information including king
746 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
747 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
749 // If both sides have only pawns, score for potential unstoppable pawns
750 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
753 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
754 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
756 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
757 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
760 // Evaluate space for both sides, only during opening
761 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
762 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
764 // Scale winning side if position is more drawish than it appears
765 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
766 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
768 // If we don't already have an unusual scale factor, check for certain
769 // types of endgames, and use a lower scale for those.
770 if ( ei.mi->game_phase() < PHASE_MIDGAME
771 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
773 if (pos.opposite_bishops())
775 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
776 // is almost a draw, in case of KBP vs KB is even more a draw.
777 if ( pos.non_pawn_material(WHITE) == BishopValueMg
778 && pos.non_pawn_material(BLACK) == BishopValueMg)
779 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
781 // Endgame with opposite-colored bishops, but also other pieces. Still
782 // a bit drawish, but not as drawish as with only the two bishops.
784 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
786 // Endings where weaker side can place his king in front of the opponent's
787 // pawns are drawish.
788 else if ( abs(eg_value(score)) <= BishopValueEg
789 && ei.pi->pawn_span(strongSide) <= 1
790 && !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
791 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
794 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
795 Value v = mg_value(score) * int(ei.mi->game_phase())
796 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
798 v /= int(PHASE_MIDGAME);
800 // In case of tracing add all single evaluation terms for both white and black
803 Tracing::write(Tracing::MATERIAL, pos.psq_score());
804 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
805 Tracing::write(PAWN, ei.pi->pawns_score());
806 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
807 , mobility[BLACK] * Weights[Mobility]);
808 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
809 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
810 Tracing::write(Tracing::TOTAL, score);
813 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
819 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
821 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
823 void Tracing::write(int idx, Score w, Score b) {
824 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
827 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
829 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
830 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
832 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
833 os << " --- --- | --- --- | ";
835 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
836 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
838 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
839 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
844 std::string Tracing::do_trace(const Position& pos) {
846 std::memset(scores, 0, sizeof(scores));
848 Value v = do_evaluate<true>(pos);
849 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
851 std::stringstream ss;
852 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
853 << " Eval term | White | Black | Total \n"
854 << " | MG EG | MG EG | MG EG \n"
855 << "----------------+-------------+-------------+-------------\n"
856 << " Material | " << Term(MATERIAL)
857 << " Imbalance | " << Term(IMBALANCE)
858 << " Pawns | " << Term(PAWN)
859 << " Knights | " << Term(KNIGHT)
860 << " Bishop | " << Term(BISHOP)
861 << " Rooks | " << Term(ROOK)
862 << " Queens | " << Term(QUEEN)
863 << " Mobility | " << Term(MOBILITY)
864 << " King safety | " << Term(KING)
865 << " Threats | " << Term(THREAT)
866 << " Passed pawns | " << Term(PASSED)
867 << " Space | " << Term(SPACE)
868 << "----------------+-------------+-------------+-------------\n"
869 << " Total | " << Term(TOTAL);
871 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
881 /// evaluate() is the main evaluation function. It returns a static evaluation
882 /// of the position always from the point of view of the side to move.
884 Value evaluate(const Position& pos) {
885 return do_evaluate<false>(pos);
889 /// trace() is like evaluate(), but instead of returning a value, it returns
890 /// a string (suitable for outputting to stdout) that contains the detailed
891 /// descriptions and values of each evaluation term. It's mainly used for
893 std::string trace(const Position& pos) {
894 return Tracing::do_trace(pos);
898 /// init() computes evaluation weights, usually at startup
902 const int MaxSlope = 8700;
903 const int Peak = 1280000;
906 for (int i = 0; i < 400; ++i)
908 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
909 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];