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[knight/bishop][supported by pawn] contains bonuses for knights and bishops
128 // outposts, bigger if outpost piece is supported by a pawn.
129 const Score Outpost[][2] = {
130 { S(28, 7), S(42,11) }, // Knights
131 { S(12, 3), S(18, 5) } // Bishops
134 // Threat[defended/weak][minor/major attacking][attacked PieceType] contains
135 // bonuses according to which piece type attacks which one.
136 const Score Threat[][2][PIECE_TYPE_NB] = {
137 { { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
138 { S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
139 { { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
140 { S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
143 // ThreatenedByPawn[PieceType] contains a penalty according to which piece
144 // type is attacked by an enemy pawn.
145 const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
146 S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
149 // PassedPawnsBonusMg[Rank] and PassedPawnsBonusEg[Rank]
150 //contains bonuses for midgame and endgame for passed pawns according to
151 //the rank of the pawn.
152 const Value PassedPawnsBonusMg[6] = {
153 V(0), V(1), V(34), V(90), V(214), V(328)
156 const Value PassedPawnsBonusEg[6] = {
157 V(7), V(14), V(37), V(63), V(134), V(189)
160 const Score ThreatenedByHangingPawn = S(40, 60);
162 // Assorted bonuses and penalties used by evaluation
163 const Score KingOnOne = S( 2, 58);
164 const Score KingOnMany = S( 6,125);
165 const Score RookOnPawn = S( 7, 27);
166 const Score RookOnOpenFile = S(43, 21);
167 const Score RookOnSemiOpenFile = S(19, 10);
168 const Score BishopPawns = S( 8, 12);
169 const Score MinorBehindPawn = S(16, 0);
170 const Score TrappedRook = S(92, 0);
171 const Score Unstoppable = S( 0, 20);
172 const Score Hanging = S(31, 26);
173 const Score PawnAttackThreat = S(20, 20);
174 const Score PawnSafePush = S( 5, 5);
176 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
177 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
178 // happen in Chess960 games.
179 const Score TrappedBishopA1H1 = S(50, 50);
184 // SpaceMask[Color] contains the area of the board which is considered
185 // by the space evaluation. In the middlegame, each side is given a bonus
186 // based on how many squares inside this area are safe and available for
187 // friendly minor pieces.
188 const Bitboard SpaceMask[COLOR_NB] = {
189 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
190 (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
193 // King danger constants and variables. The king danger scores are looked-up
194 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
195 // of the enemy attack are added up into an integer, which is used as an
196 // index to KingDanger[].
197 Score KingDanger[512];
199 // KingAttackWeights[PieceType] contains king attack weights by piece type
200 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
202 // Penalties for enemy's safe checks
203 const int QueenContactCheck = 89;
204 const int RookContactCheck = 71;
205 const int QueenCheck = 50;
206 const int RookCheck = 37;
207 const int BishopCheck = 6;
208 const int KnightCheck = 14;
211 // init_eval_info() initializes king bitboards for given color adding
212 // pawn attacks. To be done at the beginning of the evaluation.
215 void init_eval_info(const Position& pos, EvalInfo& ei) {
217 const Color Them = (Us == WHITE ? BLACK : WHITE);
218 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
220 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
221 ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
222 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
224 // Init king safety tables only if we are going to use them
225 if (pos.non_pawn_material(Us) >= QueenValueMg)
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_pieces() assigns bonuses and penalties to the pieces of a given color
239 template<PieceType Pt, Color Us, bool Trace>
240 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
244 Score score = SCORE_ZERO;
246 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
247 const Color Them = (Us == WHITE ? BLACK : WHITE);
248 const Square* pl = pos.squares<Pt>(Us);
250 ei.attackedBy[Us][Pt] = 0;
252 while ((s = *pl++) != SQ_NONE)
254 // Find attacked squares, including x-ray attacks for bishops and rooks
255 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
256 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
257 : pos.attacks_from<Pt>(s);
259 if (ei.pinnedPieces[Us] & s)
260 b &= LineBB[pos.square<KING>(Us)][s];
262 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
264 if (b & ei.kingRing[Them])
266 ei.kingAttackersCount[Us]++;
267 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
268 Bitboard bb = b & ei.attackedBy[Them][KING];
270 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
274 b &= ~( ei.attackedBy[Them][KNIGHT]
275 | ei.attackedBy[Them][BISHOP]
276 | ei.attackedBy[Them][ROOK]);
278 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
280 mobility[Us] += MobilityBonus[Pt][mob];
282 if (Pt == BISHOP || Pt == KNIGHT)
284 // Bonus for outpost square
285 if ( relative_rank(Us, s) >= RANK_4
286 && !(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
287 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
289 // Bonus when behind a pawn
290 if ( relative_rank(Us, s) < RANK_5
291 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
292 score += MinorBehindPawn;
294 // Penalty for pawns on same color square of bishop
296 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
298 // An important Chess960 pattern: A cornered bishop blocked by a friendly
299 // pawn diagonally in front of it is a very serious problem, especially
300 // when that pawn is also blocked.
303 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
305 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
306 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
307 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
308 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
315 // Bonus for aligning with enemy pawns on the same rank/file
316 if (relative_rank(Us, s) >= RANK_5)
318 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
320 score += popcount<Max15>(alignedPawns) * RookOnPawn;
323 // Bonus when on an open or semi-open file
324 if (ei.pi->semiopen_file(Us, file_of(s)))
325 score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
327 // Penalize when trapped by the king, even more if king cannot castle
328 if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
330 Square ksq = pos.square<KING>(Us);
332 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
333 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
334 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
335 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
341 Tracing::write(Pt, Us, score);
343 // Recursively call evaluate_pieces() of next piece type until KING excluded
344 return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
348 Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
350 Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
353 // evaluate_king() assigns bonuses and penalties to a king of a given color
355 template<Color Us, bool Trace>
356 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
358 const Color Them = (Us == WHITE ? BLACK : WHITE);
360 Bitboard undefended, b, b1, b2, safe;
362 const Square ksq = pos.square<KING>(Us);
364 // King shelter and enemy pawns storm
365 Score score = ei.pi->king_safety<Us>(pos, ksq);
367 // Main king safety evaluation
368 if (ei.kingAttackersCount[Them])
370 // Find the attacked squares around the king which have no defenders
371 // apart from the king itself
372 undefended = ei.attackedBy[Them][ALL_PIECES]
373 & ei.attackedBy[Us][KING]
374 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
375 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
376 | ei.attackedBy[Us][QUEEN]);
378 // Initialize the 'attackUnits' variable, which is used later on as an
379 // index into the KingDanger[] array. The initial value is based on the
380 // number and types of the enemy's attacking pieces, the number of
381 // attacked and undefended squares around our king and the quality of
382 // the pawn shelter (current 'score' value).
383 attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
384 + 8 * ei.kingAdjacentZoneAttacksCount[Them]
385 + 25 * popcount<Max15>(undefended)
386 + 11 * (ei.pinnedPieces[Us] != 0)
387 - mg_value(score) / 8
388 - !pos.count<QUEEN>(Them) * 60;
390 // Analyse the enemy's safe queen contact checks. Firstly, find the
391 // undefended squares around the king reachable by the enemy queen...
392 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
395 // ...and then remove squares not supported by another enemy piece
396 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
397 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
400 attackUnits += QueenContactCheck * popcount<Max15>(b);
403 // Analyse the enemy's safe rook contact checks. Firstly, find the
404 // undefended squares around the king reachable by the enemy rooks...
405 b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
407 // Consider only squares where the enemy's rook gives check
408 b &= PseudoAttacks[ROOK][ksq];
412 // ...and then remove squares not supported by another enemy piece
413 b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
414 | ei.attackedBy[Them][BISHOP]);
417 attackUnits += RookContactCheck * popcount<Max15>(b);
420 // Analyse the enemy's safe distance checks for sliders and knights
421 safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
423 b1 = pos.attacks_from<ROOK >(ksq) & safe;
424 b2 = pos.attacks_from<BISHOP>(ksq) & safe;
426 // Enemy queen safe checks
427 b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
429 attackUnits += QueenCheck * popcount<Max15>(b);
431 // Enemy rooks safe checks
432 b = b1 & ei.attackedBy[Them][ROOK];
434 attackUnits += RookCheck * popcount<Max15>(b);
436 // Enemy bishops safe checks
437 b = b2 & ei.attackedBy[Them][BISHOP];
439 attackUnits += BishopCheck * popcount<Max15>(b);
441 // Enemy knights safe checks
442 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
444 attackUnits += KnightCheck * popcount<Max15>(b);
446 // Finally, extract the king danger score from the KingDanger[]
447 // array and subtract the score from evaluation.
448 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
452 Tracing::write(KING, Us, score);
458 // evaluate_threats() assigns bonuses according to the type of attacking piece
459 // and the type of attacked one.
461 template<Color Us, bool Trace>
462 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
464 const Color Them = (Us == WHITE ? BLACK : WHITE);
465 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
466 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
467 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
468 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
469 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
471 enum { Defended, Weak };
472 enum { Minor, Major };
474 Bitboard b, weak, defended, safeThreats;
475 Score score = SCORE_ZERO;
477 // Non-pawn enemies attacked by a pawn
478 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
482 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
483 | ei.attackedBy[Us][ALL_PIECES]);
485 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
487 if (weak ^ safeThreats)
488 score += ThreatenedByHangingPawn;
491 score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
494 // Non-pawn enemies defended by a pawn
495 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
497 // Add a bonus according to the kind of attacking pieces
500 b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
502 score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
504 b = defended & (ei.attackedBy[Us][ROOK]);
506 score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
509 // Enemies not defended by a pawn and under our attack
510 weak = pos.pieces(Them)
511 & ~ei.attackedBy[Them][PAWN]
512 & ei.attackedBy[Us][ALL_PIECES];
514 // Add a bonus according to the kind of attacking pieces
517 b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
519 score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
521 b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
523 score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
525 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
527 score += Hanging * popcount<Max15>(b);
529 b = weak & ei.attackedBy[Us][KING];
531 score += more_than_one(b) ? KingOnMany : KingOnOne;
534 // Add a small bonus for safe pawn pushes
535 b = pos.pieces(Us, PAWN) & ~TRank7BB;
536 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
539 & ~ei.attackedBy[Them][PAWN]
540 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
543 score += popcount<Full>(b) * PawnSafePush;
545 // Add another bonus if the pawn push attacks an enemy piece
546 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
548 & ~ei.attackedBy[Us][PAWN];
551 score += popcount<Max15>(b) * PawnAttackThreat;
554 Tracing::write(Tracing::THREAT, Us, score);
560 // evaluate_passed_pawns() evaluates the passed pawns of the given color
562 template<Color Us, bool Trace>
563 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
565 const Color Them = (Us == WHITE ? BLACK : WHITE);
567 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
568 Score score = SCORE_ZERO;
570 b = ei.pi->passed_pawns(Us);
574 Square s = pop_lsb(&b);
576 assert(pos.pawn_passed(Us, s));
578 int r = relative_rank(Us, s) - RANK_2;
579 int rr = r * (r - 1);
581 Value mbonus = PassedPawnsBonusMg[r],
582 ebonus = PassedPawnsBonusEg[r];
586 Square blockSq = s + pawn_push(Us);
588 // Adjust bonus based on the king's proximity
589 ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
590 - distance(pos.square<KING>(Us ), blockSq) * 2 * rr;
592 // If blockSq is not the queening square then consider also a second push
593 if (relative_rank(Us, blockSq) != RANK_8)
594 ebonus -= distance(pos.square<KING>(Us), blockSq + pawn_push(Us)) * rr;
596 // If the pawn is free to advance, then increase the bonus
597 if (pos.empty(blockSq))
599 // If there is a rook or queen attacking/defending the pawn from behind,
600 // consider all the squaresToQueen. Otherwise consider only the squares
601 // in the pawn's path attacked or occupied by the enemy.
602 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
604 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
606 if (!(pos.pieces(Us) & bb))
607 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
609 if (!(pos.pieces(Them) & bb))
610 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
612 // If there aren't any enemy attacks, assign a big bonus. Otherwise
613 // assign a smaller bonus if the block square isn't attacked.
614 int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
616 // If the path to queen is fully defended, assign a big bonus.
617 // Otherwise assign a smaller bonus if the block square is defended.
618 if (defendedSquares == squaresToQueen)
621 else if (defendedSquares & blockSq)
624 mbonus += k * rr, ebonus += k * rr;
626 else if (pos.pieces(Us) & blockSq)
627 mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
630 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
631 ebonus += ebonus / 4;
633 score += make_score(mbonus, ebonus);
637 Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
639 // Add the scores to the middlegame and endgame eval
640 return score * Weights[PassedPawns];
644 // evaluate_space() computes the space evaluation for a given side. The
645 // space evaluation is a simple bonus based on the number of safe squares
646 // available for minor pieces on the central four files on ranks 2--4. Safe
647 // squares one, two or three squares behind a friendly pawn are counted
648 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
649 // improve play on game opening.
651 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
653 const Color Them = (Us == WHITE ? BLACK : WHITE);
655 // Find the safe squares for our pieces inside the area defined by
656 // SpaceMask[]. A square is unsafe if it is attacked by an enemy
657 // pawn, or if it is undefended and attacked by an enemy piece.
658 Bitboard safe = SpaceMask[Us]
659 & ~pos.pieces(Us, PAWN)
660 & ~ei.attackedBy[Them][PAWN]
661 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
663 // Find all squares which are at most three squares behind some friendly pawn
664 Bitboard behind = pos.pieces(Us, PAWN);
665 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
666 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
668 // Since SpaceMask[Us] is fully on our half of the board
669 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
671 // Count safe + (behind & safe) with a single popcount
672 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
673 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
674 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
676 return make_score(bonus * weight * weight, 0);
680 // do_evaluate() is the evaluation entry point, called directly from evaluate()
683 Value do_evaluate(const Position& pos) {
685 assert(!pos.checkers());
688 Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
690 // Initialize score by reading the incrementally updated scores included
691 // in the position object (material + piece square tables).
692 // Score is computed from the point of view of white.
693 score = pos.psq_score();
695 // Probe the material hash table
696 ei.mi = Material::probe(pos);
697 score += ei.mi->imbalance();
699 // If we have a specialized evaluation function for the current material
700 // configuration, call it and return.
701 if (ei.mi->specialized_eval_exists())
702 return ei.mi->evaluate(pos);
704 // Probe the pawn hash table
705 ei.pi = Pawns::probe(pos);
706 score += ei.pi->pawns_score() * Weights[PawnStructure];
708 // Initialize attack and king safety bitboards
709 init_eval_info<WHITE>(pos, ei);
710 init_eval_info<BLACK>(pos, ei);
712 ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
713 ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
715 // Pawns blocked or on ranks 2 and 3. Will be excluded from the mobility area
716 Bitboard blockedPawns[] = {
717 pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
718 pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
721 // Do not include in mobility squares protected by enemy pawns, or occupied
722 // by our blocked pawns or king.
723 Bitboard mobilityArea[] = {
724 ~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
725 ~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
728 // Evaluate pieces and mobility
729 score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
730 score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
732 // Evaluate kings after all other pieces because we need complete attack
733 // information when computing the king safety evaluation.
734 score += evaluate_king<WHITE, Trace>(pos, ei)
735 - evaluate_king<BLACK, Trace>(pos, ei);
737 // Evaluate tactical threats, we need full attack information including king
738 score += evaluate_threats<WHITE, Trace>(pos, ei)
739 - evaluate_threats<BLACK, Trace>(pos, ei);
741 // Evaluate passed pawns, we need full attack information including king
742 score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
743 - evaluate_passed_pawns<BLACK, Trace>(pos, ei);
745 // If both sides have only pawns, score for potential unstoppable pawns
746 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
749 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
750 score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
752 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
753 score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
756 // Evaluate space for both sides, only during opening
757 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
758 score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
760 // Scale winning side if position is more drawish than it appears
761 Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
762 ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
764 // If we don't already have an unusual scale factor, check for certain
765 // types of endgames, and use a lower scale for those.
766 if ( ei.mi->game_phase() < PHASE_MIDGAME
767 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
769 if (pos.opposite_bishops())
771 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
772 // is almost a draw, in case of KBP vs KB is even more a draw.
773 if ( pos.non_pawn_material(WHITE) == BishopValueMg
774 && pos.non_pawn_material(BLACK) == BishopValueMg)
775 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
777 // Endgame with opposite-colored bishops, but also other pieces. Still
778 // a bit drawish, but not as drawish as with only the two bishops.
780 sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
782 // Endings where weaker side can place his king in front of the opponent's
783 // pawns are drawish.
784 else if ( abs(eg_value(score)) <= BishopValueEg
785 && ei.pi->pawn_span(strongSide) <= 1
786 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
787 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
790 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
791 Value v = mg_value(score) * int(ei.mi->game_phase())
792 + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
794 v /= int(PHASE_MIDGAME);
796 // In case of tracing add all single evaluation terms for both white and black
799 Tracing::write(Tracing::MATERIAL, pos.psq_score());
800 Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
801 Tracing::write(PAWN, ei.pi->pawns_score());
802 Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
803 , mobility[BLACK] * Weights[Mobility]);
804 Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
805 , evaluate_space<BLACK>(pos, ei) * Weights[Space]);
806 Tracing::write(Tracing::TOTAL, score);
809 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
815 double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
817 void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
819 void Tracing::write(int idx, Score w, Score b) {
820 scores[WHITE][idx] = w, scores[BLACK][idx] = b;
823 std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
825 double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
826 double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
828 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
829 os << " --- --- | --- --- | ";
831 os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
832 << std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
834 os << std::setw(5) << wScore[MG] - bScore[MG] << " "
835 << std::setw(5) << wScore[EG] - bScore[EG] << " \n";
840 std::string Tracing::do_trace(const Position& pos) {
842 std::memset(scores, 0, sizeof(scores));
844 Value v = do_evaluate<true>(pos);
845 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
847 std::stringstream ss;
848 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
849 << " Eval term | White | Black | Total \n"
850 << " | MG EG | MG EG | MG EG \n"
851 << "----------------+-------------+-------------+-------------\n"
852 << " Material | " << Term(MATERIAL)
853 << " Imbalance | " << Term(IMBALANCE)
854 << " Pawns | " << Term(PAWN)
855 << " Knights | " << Term(KNIGHT)
856 << " Bishop | " << Term(BISHOP)
857 << " Rooks | " << Term(ROOK)
858 << " Queens | " << Term(QUEEN)
859 << " Mobility | " << Term(MOBILITY)
860 << " King safety | " << Term(KING)
861 << " Threats | " << Term(THREAT)
862 << " Passed pawns | " << Term(PASSED)
863 << " Space | " << Term(SPACE)
864 << "----------------+-------------+-------------+-------------\n"
865 << " Total | " << Term(TOTAL);
867 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
877 /// evaluate() is the main evaluation function. It returns a static evaluation
878 /// of the position always from the point of view of the side to move.
880 Value evaluate(const Position& pos) {
881 return do_evaluate<false>(pos);
885 /// trace() is like evaluate(), but instead of returning a value, it returns
886 /// a string (suitable for outputting to stdout) that contains the detailed
887 /// descriptions and values of each evaluation term. It's mainly used for
889 std::string trace(const Position& pos) {
890 return Tracing::do_trace(pos);
894 /// init() computes evaluation weights, usually at startup
898 const int MaxSlope = 8700;
899 const int Peak = 1280000;
902 for (int i = 0; i < 400; ++i)
904 t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
905 KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];