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
5 Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
23 #include <cstring> // For std::memset
36 enum Term { // The first 8 entries are for PieceType
37 MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
40 double scores[TERM_NB][COLOR_NB][PHASE_NB];
42 double to_cp(Value v) { return double(v) / PawnValueEg; }
44 void add(int idx, Color c, Score s) {
45 scores[idx][c][MG] = to_cp(mg_value(s));
46 scores[idx][c][EG] = to_cp(eg_value(s));
49 void add(int idx, Score w, Score b = SCORE_ZERO) {
50 add(idx, WHITE, w); add(idx, BLACK, b);
53 std::ostream& operator<<(std::ostream& os, Term t) {
55 if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
56 os << " --- --- | --- --- | ";
58 os << std::setw(5) << scores[t][WHITE][MG] << " "
59 << std::setw(5) << scores[t][WHITE][EG] << " | "
60 << std::setw(5) << scores[t][BLACK][MG] << " "
61 << std::setw(5) << scores[t][BLACK][EG] << " | ";
63 os << std::setw(5) << scores[t][WHITE][MG] - scores[t][BLACK][MG] << " "
64 << std::setw(5) << scores[t][WHITE][EG] - scores[t][BLACK][EG] << " \n";
70 using namespace Trace;
72 // Struct EvalInfo contains various information computed and collected
73 // by the evaluation functions.
76 // attackedBy[color][piece type] is a bitboard representing all squares
77 // attacked by a given color and piece type (can be also ALL_PIECES).
78 Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
80 // kingRing[color] is the zone around the king which is considered
81 // by the king safety evaluation. This consists of the squares directly
82 // adjacent to the king, and the three (or two, for a king on an edge file)
83 // squares two ranks in front of the king. For instance, if black's king
84 // is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
85 // f7, g7, h7, f6, g6 and h6.
86 Bitboard kingRing[COLOR_NB];
88 // kingAttackersCount[color] is the number of pieces of the given color
89 // which attack a square in the kingRing of the enemy king.
90 int kingAttackersCount[COLOR_NB];
92 // kingAttackersWeight[color] is the sum of the "weights" of the pieces of the
93 // given color which attack a square in the kingRing of the enemy king. The
94 // weights of the individual piece types are given by the elements in the
95 // KingAttackWeights array.
96 int kingAttackersWeight[COLOR_NB];
98 // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
99 // color to squares directly adjacent to the enemy king. Pieces which attack
100 // more than one square are counted multiple times. For instance, if there is
101 // a white knight on g5 and black's king is on g8, this white knight adds 2
102 // to kingAdjacentZoneAttacksCount[WHITE].
103 int kingAdjacentZoneAttacksCount[COLOR_NB];
105 Bitboard pinnedPieces[COLOR_NB];
110 #define V(v) Value(v)
111 #define S(mg, eg) make_score(mg, eg)
113 // MobilityBonus[PieceType][attacked] contains bonuses for middle and end
114 // game, indexed by piece type and number of attacked squares in the MobilityArea.
115 const Score MobilityBonus[][32] = {
117 { S(-75,-76), S(-56,-54), S(- 9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
118 S( 22, 26), S( 30, 28), S( 36, 29) },
119 { S(-48,-58), S(-21,-19), S( 16, -2), S( 26, 12), S( 37, 22), S( 51, 42), // Bishops
120 S( 54, 54), S( 63, 58), S( 65, 63), S( 71, 70), S( 79, 74), S( 81, 86),
121 S( 92, 90), S( 97, 94) },
122 { S(-56,-78), S(-25,-18), S(-11, 26), S( -5, 55), S( -4, 70), S( -1, 81), // Rooks
123 S( 8,109), S( 14,120), S( 21,128), S( 23,143), S( 31,154), S( 32,160),
124 S( 43,165), S( 49,168), S( 59,169) },
125 { S(-40,-35), S(-25,-12), S( 2, 7), S( 4, 19), S( 14, 37), S( 24, 55), // Queens
126 S( 25, 62), S( 40, 76), S( 43, 79), S( 47, 87), S( 54, 94), S( 56,102),
127 S( 60,111), S( 70,116), S( 72,118), S( 73,122), S( 75,128), S( 77,130),
128 S( 85,133), S( 94,136), S( 99,140), S(108,157), S(112,158), S(113,161),
129 S(118,174), S(119,177), S(123,191), S(128,199) }
132 // Outpost[knight/bishop][supported by pawn] contains bonuses for knights and
133 // bishops outposts, bigger if outpost piece is supported by a pawn.
134 const Score Outpost[][2] = {
135 { S(42,11), S(63,17) }, // Knights
136 { S(18, 5), S(27, 8) } // Bishops
139 // ReachableOutpost[knight/bishop][supported by pawn] contains bonuses for
140 // knights and bishops which can reach an outpost square in one move, bigger
141 // if outpost square is supported by a pawn.
142 const Score ReachableOutpost[][2] = {
143 { S(21, 5), S(31, 8) }, // Knights
144 { S( 8, 2), S(13, 4) } // Bishops
147 // RookOnFile[semiopen/open] contains bonuses for each rook when there is no
148 // friendly pawn on the rook file.
149 const Score RookOnFile[2] = { S(19, 10), S(43, 21) };
151 // ThreatBySafePawn[PieceType] contains bonuses according to which piece
152 // type is attacked by a pawn which is protected or is not attacked.
153 const Score ThreatBySafePawn[PIECE_TYPE_NB] = {
154 S(0, 0), S(0, 0), S(176, 139), S(131, 127), S(217, 218), S(203, 215) };
156 // Threat[by minor/by rook][attacked PieceType] contains
157 // bonuses according to which piece type attacks which one.
158 // Attacks on lesser pieces which are pawn-defended are not considered.
159 const Score Threat[][PIECE_TYPE_NB] = {
160 { S(0, 0), S(0, 33), S(45, 43), S(46, 47), S(72,107), S(48,118) }, // by Minor
161 { S(0, 0), S(0, 25), S(40, 62), S(40, 59), S( 0, 34), S(35, 48) } // by Rook
164 // ThreatByKing[on one/on many] contains bonuses for King attacks on
165 // pawns or pieces which are not pawn-defended.
166 const Score ThreatByKing[2] = { S(3, 62), S(9, 138) };
168 // Passed[mg/eg][Rank] contains midgame and endgame bonuses for passed pawns.
169 // We don't use a Score because we process the two components independently.
170 const Value Passed[][RANK_NB] = {
171 { V(5), V( 5), V(31), V(73), V(166), V(252) },
172 { V(7), V(14), V(38), V(64), V(137), V(193) }
175 // PassedFile[File] contains a bonus according to the file of a passed pawn
176 const Score PassedFile[FILE_NB] = {
177 S( 9, 10), S( 2, 10), S( 1, -8), S(-20,-12),
178 S(-20,-12), S( 1, -8), S( 2, 10), S( 9, 10)
181 // Assorted bonuses and penalties used by evaluation
182 const Score MinorBehindPawn = S(16, 0);
183 const Score BishopPawns = S( 8, 12);
184 const Score RookOnPawn = S( 7, 27);
185 const Score TrappedRook = S(92, 0);
186 const Score Checked = S(20, 20);
187 const Score ThreatByHangingPawn = S(70, 63);
188 const Score Hanging = S(48, 28);
189 const Score ThreatByPawnPush = S(31, 19);
190 const Score Unstoppable = S( 0, 20);
192 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
193 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
194 // happen in Chess960 games.
195 const Score TrappedBishopA1H1 = S(50, 50);
200 // King danger constants and variables. The king danger scores are looked-up
201 // in KingDanger[]. Various little "meta-bonuses" measuring the strength
202 // of the enemy attack are added up into an integer, which is used as an
203 // index to KingDanger[].
204 Score KingDanger[512];
206 // KingAttackWeights[PieceType] contains king attack weights by piece type
207 const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
209 // Penalties for enemy's safe checks
210 const int QueenContactCheck = 89;
211 const int QueenCheck = 50;
212 const int RookCheck = 45;
213 const int BishopCheck = 6;
214 const int KnightCheck = 14;
217 // eval_init() initializes king and attack bitboards for a given color
218 // adding pawn attacks. To be done at the beginning of the evaluation.
221 void eval_init(const Position& pos, EvalInfo& ei) {
223 const Color Them = (Us == WHITE ? BLACK : WHITE);
224 const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
226 ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
227 Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
228 ei.attackedBy[Them][ALL_PIECES] |= b;
229 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
231 // Init king safety tables only if we are going to use them
232 if (pos.non_pawn_material(Us) >= QueenValueMg)
234 ei.kingRing[Them] = b | shift_bb<Down>(b);
235 b &= ei.attackedBy[Us][PAWN];
236 ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
237 ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
240 ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
244 // evaluate_pieces() assigns bonuses and penalties to the pieces of a given
247 template<bool DoTrace, Color Us = WHITE, PieceType Pt = KNIGHT>
248 Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility,
249 const Bitboard* mobilityArea) {
252 Score score = SCORE_ZERO;
254 const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
255 const Color Them = (Us == WHITE ? BLACK : WHITE);
256 const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
257 : Rank5BB | Rank4BB | Rank3BB);
258 const Square* pl = pos.squares<Pt>(Us);
260 ei.attackedBy[Us][Pt] = 0;
262 while ((s = *pl++) != SQ_NONE)
264 // Find attacked squares, including x-ray attacks for bishops and rooks
265 b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
266 : Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
267 : pos.attacks_from<Pt>(s);
269 if (ei.pinnedPieces[Us] & s)
270 b &= LineBB[pos.square<KING>(Us)][s];
272 ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
274 if (b & ei.kingRing[Them])
276 ei.kingAttackersCount[Us]++;
277 ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
278 bb = b & ei.attackedBy[Them][KING];
280 ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
284 b &= ~( ei.attackedBy[Them][KNIGHT]
285 | ei.attackedBy[Them][BISHOP]
286 | ei.attackedBy[Them][ROOK]);
288 int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
290 mobility[Us] += MobilityBonus[Pt][mob];
292 if (Pt == BISHOP || Pt == KNIGHT)
294 // Bonus for outpost squares
295 bb = OutpostRanks & ~ei.pi->pawn_attacks_span(Them);
297 score += Outpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & s)];
300 bb &= b & ~pos.pieces(Us);
302 score += ReachableOutpost[Pt == BISHOP][!!(ei.attackedBy[Us][PAWN] & bb)];
305 // Bonus when behind a pawn
306 if ( relative_rank(Us, s) < RANK_5
307 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
308 score += MinorBehindPawn;
310 // Penalty for pawns on the same color square as the bishop
312 score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
314 // An important Chess960 pattern: A cornered bishop blocked by a friendly
315 // pawn diagonally in front of it is a very serious problem, especially
316 // when that pawn is also blocked.
319 && (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
321 Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
322 if (pos.piece_on(s + d) == make_piece(Us, PAWN))
323 score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
324 : pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
331 // Bonus for aligning with enemy pawns on the same rank/file
332 if (relative_rank(Us, s) >= RANK_5)
334 Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
336 score += RookOnPawn * popcount<Max15>(alignedPawns);
339 // Bonus when on an open or semi-open file
340 if (ei.pi->semiopen_file(Us, file_of(s)))
341 score += RookOnFile[!!ei.pi->semiopen_file(Them, file_of(s))];
343 // Penalize when trapped by the king, even more if the king cannot castle
346 Square ksq = pos.square<KING>(Us);
348 if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
349 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
350 && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
351 score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
357 Trace::add(Pt, Us, score);
359 // Recursively call evaluate_pieces() of next piece type until KING is excluded
360 return score - evaluate_pieces<DoTrace, Them, NextPt>(pos, ei, mobility, mobilityArea);
364 Score evaluate_pieces<false, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
366 Score evaluate_pieces< true, WHITE, KING>(const Position&, EvalInfo&, Score*, const Bitboard*) { return SCORE_ZERO; }
369 // evaluate_king() assigns bonuses and penalties to a king of a given color
371 template<Color Us, bool DoTrace>
372 Score evaluate_king(const Position& pos, const EvalInfo& ei) {
374 const Color Them = (Us == WHITE ? BLACK : WHITE);
376 Bitboard undefended, b, b1, b2, safe;
378 const Square ksq = pos.square<KING>(Us);
380 // King shelter and enemy pawns storm
381 Score score = ei.pi->king_safety<Us>(pos, ksq);
383 // Main king safety evaluation
384 if (ei.kingAttackersCount[Them])
386 // Find the attacked squares around the king which have no defenders
387 // apart from the king itself.
388 undefended = ei.attackedBy[Them][ALL_PIECES]
389 & ei.attackedBy[Us][KING]
390 & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
391 | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
392 | ei.attackedBy[Us][QUEEN]);
394 // Initialize the 'attackUnits' variable, which is used later on as an
395 // index into the KingDanger[] array. The initial value is based on the
396 // number and types of the enemy's attacking pieces, the number of
397 // attacked and undefended squares around our king and the quality of
398 // the pawn shelter (current 'score' value).
399 attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
400 + 9 * ei.kingAdjacentZoneAttacksCount[Them]
401 + 27 * popcount<Max15>(undefended)
402 + 11 * !!ei.pinnedPieces[Us]
403 - 64 * !pos.count<QUEEN>(Them)
404 - mg_value(score) / 8;
406 // Analyse the enemy's safe queen contact checks. Firstly, find the
407 // undefended squares around the king reachable by the enemy queen...
408 b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
411 // ...and then remove squares not supported by another enemy piece
412 b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
413 | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]
414 | ei.attackedBy[Them][KING];
417 attackUnits += QueenContactCheck * 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];
430 attackUnits += QueenCheck * popcount<Max15>(b);
434 // Enemy rooks safe checks
435 b = b1 & ei.attackedBy[Them][ROOK];
438 attackUnits += RookCheck * popcount<Max15>(b);
442 // Enemy bishops safe checks
443 b = b2 & ei.attackedBy[Them][BISHOP];
446 attackUnits += BishopCheck * popcount<Max15>(b);
450 // Enemy knights safe checks
451 b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
454 attackUnits += KnightCheck * popcount<Max15>(b);
458 // Finally, extract the king danger score from the KingDanger[]
459 // array and subtract the score from the evaluation.
460 score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
464 Trace::add(KING, Us, score);
470 // evaluate_threats() assigns bonuses according to the types of the attacking
471 // and the attacked pieces.
473 template<Color Us, bool DoTrace>
474 Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
476 const Color Them = (Us == WHITE ? BLACK : WHITE);
477 const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
478 const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
479 const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
480 const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
481 const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
483 enum { Minor, Rook };
485 Bitboard b, weak, defended, safeThreats;
486 Score score = SCORE_ZERO;
488 // Non-pawn enemies attacked by a pawn
489 weak = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Us][PAWN];
493 b = pos.pieces(Us, PAWN) & ( ~ei.attackedBy[Them][ALL_PIECES]
494 | ei.attackedBy[Us][ALL_PIECES]);
496 safeThreats = (shift_bb<Right>(b) | shift_bb<Left>(b)) & weak;
498 if (weak ^ safeThreats)
499 score += ThreatByHangingPawn;
502 score += ThreatBySafePawn[type_of(pos.piece_on(pop_lsb(&safeThreats)))];
505 // Non-pawn enemies defended by a pawn
506 defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
508 // Enemies not defended by a pawn and under our attack
509 weak = pos.pieces(Them)
510 & ~ei.attackedBy[Them][PAWN]
511 & ei.attackedBy[Us][ALL_PIECES];
513 // Add a bonus according to the kind of attacking pieces
516 b = (defended | weak) & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
518 score += Threat[Minor][type_of(pos.piece_on(pop_lsb(&b)))];
520 b = (pos.pieces(Them, QUEEN) | weak) & ei.attackedBy[Us][ROOK];
522 score += Threat[Rook ][type_of(pos.piece_on(pop_lsb(&b)))];
524 b = weak & ~ei.attackedBy[Them][ALL_PIECES];
526 score += Hanging * popcount<Max15>(b);
528 b = weak & ei.attackedBy[Us][KING];
530 score += ThreatByKing[more_than_one(b)];
533 // Bonus if some pawns can safely push and attack an enemy piece
534 b = pos.pieces(Us, PAWN) & ~TRank7BB;
535 b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
538 & ~ei.attackedBy[Them][PAWN]
539 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
541 b = (shift_bb<Left>(b) | shift_bb<Right>(b))
543 & ~ei.attackedBy[Us][PAWN];
546 score += ThreatByPawnPush * popcount<Max15>(b);
549 Trace::add(THREAT, Us, score);
555 // evaluate_passed_pawns() evaluates the passed pawns of the given color
557 template<Color Us, bool DoTrace>
558 Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
560 const Color Them = (Us == WHITE ? BLACK : WHITE);
562 Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
563 Score score = SCORE_ZERO;
565 b = ei.pi->passed_pawns(Us);
569 Square s = pop_lsb(&b);
571 assert(pos.pawn_passed(Us, s));
573 int r = relative_rank(Us, s) - RANK_2;
574 int rr = r * (r - 1);
576 Value mbonus = Passed[MG][r], ebonus = Passed[EG][r];
580 Square blockSq = s + pawn_push(Us);
582 // Adjust bonus based on the king's proximity
583 ebonus += distance(pos.square<KING>(Them), blockSq) * 5 * rr
584 - distance(pos.square<KING>(Us ), blockSq) * 2 * rr;
586 // If blockSq is not the queening square then consider also a second push
587 if (relative_rank(Us, blockSq) != RANK_8)
588 ebonus -= distance(pos.square<KING>(Us), blockSq + pawn_push(Us)) * rr;
590 // If the pawn is free to advance, then increase the bonus
591 if (pos.empty(blockSq))
593 // If there is a rook or queen attacking/defending the pawn from behind,
594 // consider all the squaresToQueen. Otherwise consider only the squares
595 // in the pawn's path attacked or occupied by the enemy.
596 defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
598 Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
600 if (!(pos.pieces(Us) & bb))
601 defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
603 if (!(pos.pieces(Them) & bb))
604 unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
606 // If there aren't any enemy attacks, assign a big bonus. Otherwise
607 // assign a smaller bonus if the block square isn't attacked.
608 int k = !unsafeSquares ? 18 : !(unsafeSquares & blockSq) ? 8 : 0;
610 // If the path to the queen is fully defended, assign a big bonus.
611 // Otherwise assign a smaller bonus if the block square is defended.
612 if (defendedSquares == squaresToQueen)
615 else if (defendedSquares & blockSq)
618 mbonus += k * rr, ebonus += k * rr;
620 else if (pos.pieces(Us) & blockSq)
621 mbonus += rr + r * 2, ebonus += rr + r * 2;
624 if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
625 ebonus += ebonus / 4;
627 score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
631 Trace::add(PASSED, Us, score);
633 // Add the scores to the middlegame and endgame eval
638 // evaluate_space() computes the space evaluation for a given side. The
639 // space evaluation is a simple bonus based on the number of safe squares
640 // available for minor pieces on the central four files on ranks 2--4. Safe
641 // squares one, two or three squares behind a friendly pawn are counted
642 // twice. Finally, the space bonus is multiplied by a weight. The aim is to
643 // improve play on game opening.
645 Score evaluate_space(const Position& pos, const EvalInfo& ei) {
647 const Color Them = (Us == WHITE ? BLACK : WHITE);
648 const Bitboard SpaceMask =
649 Us == WHITE ? (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB)
650 : (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB);
652 // Find the safe squares for our pieces inside the area defined by
653 // SpaceMask. A square is unsafe if it is attacked by an enemy
654 // pawn, or if it is undefended and attacked by an enemy piece.
655 Bitboard safe = SpaceMask
656 & ~pos.pieces(Us, PAWN)
657 & ~ei.attackedBy[Them][PAWN]
658 & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
660 // Find all squares which are at most three squares behind some friendly pawn
661 Bitboard behind = pos.pieces(Us, PAWN);
662 behind |= (Us == WHITE ? behind >> 8 : behind << 8);
663 behind |= (Us == WHITE ? behind >> 16 : behind << 16);
665 // Since SpaceMask[Us] is fully on our half of the board...
666 assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
668 // ...count safe + (behind & safe) with a single popcount
669 int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
670 int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
671 + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
673 return make_score(bonus * weight * weight * 2 / 11, 0);
677 // evaluate_initiative() computes the initiative correction value for the
678 // position, i.e., second order bonus/malus based on the known attacking/defending
679 // status of the players.
680 Score evaluate_initiative(const Position& pos, int asymmetry, Value eg) {
682 int kingDistance = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
683 - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
684 int pawns = pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK);
686 // Compute the initiative bonus for the attacking side
687 int initiative = 8 * (asymmetry + kingDistance - 15) + 12 * pawns;
689 // Now apply the bonus: note that we find the attacking side by extracting
690 // the sign of the endgame value, and that we carefully cap the bonus so
691 // that the endgame score will never be divided by more than two.
692 int value = ((eg > 0) - (eg < 0)) * std::max(initiative, -abs(eg / 2));
694 return make_score(0, value);
698 // evaluate_scale_factor() computes the scale factor for the winning side
699 ScaleFactor evaluate_scale_factor(const Position& pos, const EvalInfo& ei, Value eg) {
701 Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
702 ScaleFactor sf = ei.me->scale_factor(pos, strongSide);
704 // If we don't already have an unusual scale factor, check for certain
705 // types of endgames, and use a lower scale for those.
706 if ( ei.me->game_phase() < PHASE_MIDGAME
707 && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
709 if (pos.opposite_bishops())
711 // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
712 // is almost a draw, in case of KBP vs KB, it is even more a draw.
713 if ( pos.non_pawn_material(WHITE) == BishopValueMg
714 && pos.non_pawn_material(BLACK) == BishopValueMg)
715 sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(31) : ScaleFactor(9);
717 // Endgame with opposite-colored bishops, but also other pieces. Still
718 // a bit drawish, but not as drawish as with only the two bishops.
720 sf = ScaleFactor(46 * sf / SCALE_FACTOR_NORMAL);
722 // Endings where weaker side can place his king in front of the opponent's
723 // pawns are drawish.
724 else if ( abs(eg) <= BishopValueEg
725 && ei.pi->pawn_span(strongSide) <= 1
726 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
727 sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(51) : ScaleFactor(37);
736 /// evaluate() is the main evaluation function. It returns a static evaluation
737 /// of the position from the point of view of the side to move.
739 template<bool DoTrace>
740 Value Eval::evaluate(const Position& pos) {
742 assert(!pos.checkers());
745 Score score, mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
747 // Initialize score by reading the incrementally updated scores included in
748 // the position object (material + piece square tables). Score is computed
749 // internally from the white point of view.
750 score = pos.psq_score();
752 // Probe the material hash table
753 ei.me = Material::probe(pos);
754 score += ei.me->imbalance();
756 // If we have a specialized evaluation function for the current material
757 // configuration, call it and return.
758 if (ei.me->specialized_eval_exists())
759 return ei.me->evaluate(pos);
761 // Probe the pawn hash table
762 ei.pi = Pawns::probe(pos);
763 score += ei.pi->pawns_score();
765 // Initialize attack and king safety bitboards
766 ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[BLACK][ALL_PIECES] = 0;
767 eval_init<WHITE>(pos, ei);
768 eval_init<BLACK>(pos, ei);
770 // Pawns blocked or on ranks 2 and 3 will be excluded from the mobility area
771 Bitboard blockedPawns[] = {
772 pos.pieces(WHITE, PAWN) & (shift_bb<DELTA_S>(pos.pieces()) | Rank2BB | Rank3BB),
773 pos.pieces(BLACK, PAWN) & (shift_bb<DELTA_N>(pos.pieces()) | Rank7BB | Rank6BB)
776 // Do not include in mobility area squares protected by enemy pawns, or occupied
777 // by our blocked pawns or king.
778 Bitboard mobilityArea[] = {
779 ~(ei.attackedBy[BLACK][PAWN] | blockedPawns[WHITE] | pos.square<KING>(WHITE)),
780 ~(ei.attackedBy[WHITE][PAWN] | blockedPawns[BLACK] | pos.square<KING>(BLACK))
783 // Evaluate all pieces but king and pawns
784 score += evaluate_pieces<DoTrace>(pos, ei, mobility, mobilityArea);
785 score += mobility[WHITE] - mobility[BLACK];
787 // Evaluate kings after all other pieces because we need full attack
788 // information when computing the king safety evaluation.
789 score += evaluate_king<WHITE, DoTrace>(pos, ei)
790 - evaluate_king<BLACK, DoTrace>(pos, ei);
792 // Evaluate tactical threats, we need full attack information including king
793 score += evaluate_threats<WHITE, DoTrace>(pos, ei)
794 - evaluate_threats<BLACK, DoTrace>(pos, ei);
796 // Evaluate passed pawns, we need full attack information including king
797 score += evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
798 - evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
800 // If both sides have only pawns, score for potential unstoppable pawns
801 if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
804 if ((b = ei.pi->passed_pawns(WHITE)) != 0)
805 score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
807 if ((b = ei.pi->passed_pawns(BLACK)) != 0)
808 score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
811 // Evaluate space for both sides, only during opening
812 if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
813 score += evaluate_space<WHITE>(pos, ei)
814 - evaluate_space<BLACK>(pos, ei);
816 // Evaluate position potential for the winning side
817 score += evaluate_initiative(pos, ei.pi->pawn_asymmetry(), eg_value(score));
819 // Evaluate scale factor for the winning side
820 ScaleFactor sf = evaluate_scale_factor(pos, ei, eg_value(score));
822 // Interpolate between a middlegame and a (scaled by 'sf') endgame score
823 Value v = mg_value(score) * int(ei.me->game_phase())
824 + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
826 v /= int(PHASE_MIDGAME);
828 // In case of tracing add all remaining individual evaluation terms
831 Trace::add(MATERIAL, pos.psq_score());
832 Trace::add(IMBALANCE, ei.me->imbalance());
833 Trace::add(PAWN, ei.pi->pawns_score());
834 Trace::add(MOBILITY, mobility[WHITE], mobility[BLACK]);
835 Trace::add(SPACE, evaluate_space<WHITE>(pos, ei)
836 , evaluate_space<BLACK>(pos, ei));
837 Trace::add(TOTAL, score);
840 return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
843 // Explicit template instantiations
844 template Value Eval::evaluate<true >(const Position&);
845 template Value Eval::evaluate<false>(const Position&);
848 /// trace() is like evaluate(), but instead of returning a value, it returns
849 /// a string (suitable for outputting to stdout) that contains the detailed
850 /// descriptions and values of each evaluation term. Useful for debugging.
852 std::string Eval::trace(const Position& pos) {
854 std::memset(scores, 0, sizeof(scores));
856 Value v = evaluate<true>(pos);
857 v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
859 std::stringstream ss;
860 ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
861 << " Eval term | White | Black | Total \n"
862 << " | MG EG | MG EG | MG EG \n"
863 << "----------------+-------------+-------------+-------------\n"
864 << " Material | " << Term(MATERIAL)
865 << " Imbalance | " << Term(IMBALANCE)
866 << " Pawns | " << Term(PAWN)
867 << " Knights | " << Term(KNIGHT)
868 << " Bishop | " << Term(BISHOP)
869 << " Rooks | " << Term(ROOK)
870 << " Queens | " << Term(QUEEN)
871 << " Mobility | " << Term(MOBILITY)
872 << " King safety | " << Term(KING)
873 << " Threats | " << Term(THREAT)
874 << " Passed pawns | " << Term(PASSED)
875 << " Space | " << Term(SPACE)
876 << "----------------+-------------+-------------+-------------\n"
877 << " Total | " << Term(TOTAL);
879 ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
885 /// init() computes evaluation weights, usually at startup
889 const int MaxSlope = 322;
890 const int Peak = 47410;
893 for (int i = 0; i < 400; ++i)
895 t = std::min(Peak, std::min(i * i - 16, t + MaxSlope));
896 KingDanger[i] = make_score(t * 268 / 7700, 0);