2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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/>.
33 #include "ucioption.h"
37 //// Local definitions
42 const int Sign[2] = {1, -1};
44 // Evaluation grain size, must be a power of 2.
45 const int GrainSize = 4;
47 // Evaluation weights, initialized from UCI options
48 int WeightMobilityMidgame, WeightMobilityEndgame;
49 int WeightPawnStructureMidgame, WeightPawnStructureEndgame;
50 int WeightPassedPawnsMidgame, WeightPassedPawnsEndgame;
51 int WeightKingSafety[2];
54 // Internal evaluation weights. These are applied on top of the evaluation
55 // weights read from UCI parameters. The purpose is to be able to change
56 // the evaluation weights while keeping the default values of the UCI
57 // parameters at 100, which looks prettier.
59 // Values modified by Joona Kiiski
60 const int WeightMobilityMidgameInternal = 0x0FA;
61 const int WeightMobilityEndgameInternal = 0x10A;
62 const int WeightPawnStructureMidgameInternal = 0x0EC;
63 const int WeightPawnStructureEndgameInternal = 0x0CD;
64 const int WeightPassedPawnsMidgameInternal = 0x108;
65 const int WeightPassedPawnsEndgameInternal = 0x109;
66 const int WeightKingSafetyInternal = 0x0F7;
67 const int WeightKingOppSafetyInternal = 0x101;
68 const int WeightSpaceInternal = 0x02F;
70 // Visually better to define tables constants
73 // Knight mobility bonus in middle game and endgame, indexed by the number
74 // of attacked squares not occupied by friendly piecess.
75 const Value MidgameKnightMobilityBonus[] = {
77 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
80 const Value EndgameKnightMobilityBonus[] = {
82 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
85 // Bishop mobility bonus in middle game and endgame, indexed by the number
86 // of attacked squares not occupied by friendly pieces. X-ray attacks through
87 // queens are also included.
88 const Value MidgameBishopMobilityBonus[] = {
90 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
91 // 8 9 10 11 12 13 14 15
92 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
95 const Value EndgameBishopMobilityBonus[] = {
97 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
98 // 8 9 10 11 12 13 14 15
99 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
102 // Rook mobility bonus in middle game and endgame, indexed by the number
103 // of attacked squares not occupied by friendly pieces. X-ray attacks through
104 // queens and rooks are also included.
105 const Value MidgameRookMobilityBonus[] = {
107 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
108 // 8 9 10 11 12 13 14 15
109 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
112 const Value EndgameRookMobilityBonus[] = {
114 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
115 // 8 9 10 11 12 13 14 15
116 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
119 // Queen mobility bonus in middle game and endgame, indexed by the number
120 // of attacked squares not occupied by friendly pieces.
121 const Value MidgameQueenMobilityBonus[] = {
123 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
124 // 8 9 10 11 12 13 14 15
125 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
126 // 16 17 18 19 20 21 22 23
127 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
128 // 24 25 26 27 28 29 30 31
129 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
132 const Value EndgameQueenMobilityBonus[] = {
134 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
135 // 8 9 10 11 12 13 14 15
136 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
137 // 16 17 18 19 20 21 22 23
138 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
139 // 24 25 26 27 28 29 30 31
140 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
143 // Outpost bonuses for knights and bishops, indexed by square (from white's
145 const Value KnightOutpostBonus[64] = {
147 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
148 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
149 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
150 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
151 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
152 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
153 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
154 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
157 const Value BishopOutpostBonus[64] = {
159 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
160 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
161 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
162 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
163 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
164 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
165 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
166 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
169 // Bonus for unstoppable passed pawns
170 const Value UnstoppablePawnValue = Value(0x500);
172 // Rooks and queens on the 7th rank
173 const Value MidgameRookOn7thBonus = Value(47);
174 const Value EndgameRookOn7thBonus = Value(98);
175 const Value MidgameQueenOn7thBonus = Value(27);
176 const Value EndgameQueenOn7thBonus = Value(54);
179 // Rooks on open files
180 const Value RookOpenFileBonus = Value(43);
181 const Value RookHalfOpenFileBonus = Value(19);
183 // Penalty for rooks trapped inside a friendly king which has lost the
185 const Value TrappedRookPenalty = Value(180);
187 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
189 const Value TrappedBishopA7H7Penalty = Value(300);
191 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
192 const Bitboard MaskA7H7[2] = {
193 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
194 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
197 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
198 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
199 // happen in Chess960 games.
200 const Value TrappedBishopA1H1Penalty = Value(100);
202 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
203 const Bitboard MaskA1H1[2] = {
204 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
205 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
208 // The SpaceMask[color] contains area of the board which is consdered by
209 // the space evaluation. In the middle game, each side is given a bonus
210 // based on how many squares inside this area are safe and available for
211 // friendly minor pieces.
212 const Bitboard SpaceMask[2] = {
213 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
214 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
215 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
216 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
217 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
218 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
221 /// King safety constants and variables. The king safety scores are taken
222 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
223 /// the strength of the attack are added up into an integer, which is used
224 /// as an index to SafetyTable[].
226 // Attack weights for each piece type.
227 const int QueenAttackWeight = 5;
228 const int RookAttackWeight = 3;
229 const int BishopAttackWeight = 2;
230 const int KnightAttackWeight = 2;
232 // Bonuses for safe checks, initialized from UCI options
233 int QueenContactCheckBonus, DiscoveredCheckBonus;
234 int QueenCheckBonus, RookCheckBonus, BishopCheckBonus, KnightCheckBonus;
236 // Scan for queen contact mates?
237 const bool QueenContactMates = true;
239 // Bonus for having a mate threat, initialized from UCI options
242 // InitKingDanger[] contains bonuses based on the position of the defending
244 const int InitKingDanger[64] = {
245 2, 0, 2, 5, 5, 2, 0, 2,
246 2, 2, 4, 8, 8, 4, 2, 2,
247 7, 10, 12, 12, 12, 12, 10, 7,
248 15, 15, 15, 15, 15, 15, 15, 15,
249 15, 15, 15, 15, 15, 15, 15, 15,
250 15, 15, 15, 15, 15, 15, 15, 15,
251 15, 15, 15, 15, 15, 15, 15, 15,
252 15, 15, 15, 15, 15, 15, 15, 15
255 // SafetyTable[] contains the actual king safety scores. It is initialized
257 Value SafetyTable[100];
259 // Pawn and material hash tables, indexed by the current thread id
260 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
261 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
263 // Sizes of pawn and material hash tables
264 const int PawnTableSize = 16384;
265 const int MaterialTableSize = 1024;
267 // Array which gives the number of nonzero bits in an 8-bit integer:
268 uint8_t BitCount8Bit[256];
270 // Function prototypes
271 template<PieceType Piece>
272 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
275 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
277 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
278 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
280 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
283 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
284 inline Value apply_weight(Value v, int w);
285 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
287 int count_1s_8bit(Bitboard b);
289 int compute_weight(int uciWeight, int internalWeight);
290 int weight_option(const std::string& opt, int weight);
300 /// evaluate() is the main evaluation function. It always computes two
301 /// values, an endgame score and a middle game score, and interpolates
302 /// between them based on the remaining material.
304 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
307 assert(threadID >= 0 && threadID < THREAD_MAX);
309 memset(&ei, 0, sizeof(EvalInfo));
311 // Initialize by reading the incrementally updated scores included in the
312 // position object (material + piece square tables)
313 ei.mgValue = pos.mg_value();
314 ei.egValue = pos.eg_value();
316 // Probe the material hash table
317 ei.mi = MaterialTable[threadID]->get_material_info(pos);
318 ei.mgValue += ei.mi->mg_value();
319 ei.egValue += ei.mi->eg_value();
321 // If we have a specialized evaluation function for the current material
322 // configuration, call it and return
323 if (ei.mi->specialized_eval_exists())
324 return ei.mi->evaluate(pos);
326 // After get_material_info() call that modifies them
327 ScaleFactor factor[2];
328 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
329 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
331 // Probe the pawn hash table
332 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
333 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
334 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
336 // Initialize king attack bitboards and king attack zones for both sides
337 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
338 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
339 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
340 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
342 // Initialize pawn attack bitboards for both sides
343 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
344 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
345 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
346 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
349 for (Color c = WHITE; c <= BLACK; c++)
351 evaluate_pieces<KNIGHT>(pos, c, ei);
352 evaluate_pieces<BISHOP>(pos, c, ei);
353 evaluate_pieces<ROOK>(pos, c, ei);
354 evaluate_pieces<QUEEN>(pos, c, ei);
356 // Sum up all attacked squares
357 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
358 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
359 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
362 // Kings. Kings are evaluated after all other pieces for both sides,
363 // because we need complete attack information for all pieces when computing
364 // the king safety evaluation.
365 for (Color c = WHITE; c <= BLACK; c++)
366 evaluate_pieces<KING>(pos, c, ei);
368 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
369 // because we need to know which side promotes first in positions where
370 // both sides have an unstoppable passed pawn.
371 if (ei.pi->passed_pawns())
372 evaluate_passed_pawns(pos, ei);
374 Phase phase = pos.game_phase();
376 // Middle-game specific evaluation terms
377 if (phase > PHASE_ENDGAME)
379 // Pawn storms in positions with opposite castling.
380 if ( square_file(pos.king_square(WHITE)) >= FILE_E
381 && square_file(pos.king_square(BLACK)) <= FILE_D)
383 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
384 - ei.pi->kingside_storm_value(BLACK);
386 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
387 && square_file(pos.king_square(BLACK)) >= FILE_E)
389 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
390 - ei.pi->queenside_storm_value(BLACK);
392 // Evaluate space for both sides
393 if (ei.mi->space_weight() > 0)
395 evaluate_space(pos, WHITE, ei);
396 evaluate_space(pos, BLACK, ei);
401 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
402 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
404 // If we don't already have an unusual scale factor, check for opposite
405 // colored bishop endgames, and use a lower scale for those
406 if ( phase < PHASE_MIDGAME
407 && pos.opposite_colored_bishops()
408 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
409 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
413 // Only the two bishops ?
414 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
415 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
417 // Check for KBP vs KB with only a single pawn that is almost
418 // certainly a draw or at least two pawns.
419 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
420 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
423 // Endgame with opposite-colored bishops, but also other pieces. Still
424 // a bit drawish, but not as drawish as with only the two bishops.
425 sf = ScaleFactor(50);
427 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
429 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
433 // Interpolate between the middle game and the endgame score, and
435 Color stm = pos.side_to_move();
437 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
439 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
443 /// quick_evaluate() does a very approximate evaluation of the current position.
444 /// It currently considers only material and piece square table scores. Perhaps
445 /// we should add scores from the pawn and material hash tables?
447 Value quick_evaluate(const Position &pos) {
452 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
454 Value mgv = pos.mg_value();
455 Value egv = pos.eg_value();
456 Phase ph = pos.game_phase();
457 Color stm = pos.side_to_move();
459 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
463 /// init_eval() initializes various tables used by the evaluation function.
465 void init_eval(int threads) {
467 assert(threads <= THREAD_MAX);
469 for (int i = 0; i < THREAD_MAX; i++)
474 delete MaterialTable[i];
476 MaterialTable[i] = NULL;
480 PawnTable[i] = new PawnInfoTable(PawnTableSize);
481 if (!MaterialTable[i])
482 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
485 for (Bitboard b = 0ULL; b < 256ULL; b++)
487 assert(count_1s(b) == int(uint8_t(count_1s(b))));
488 BitCount8Bit[b] = (uint8_t)count_1s(b);
493 /// quit_eval() releases heap-allocated memory at program termination.
497 for (int i = 0; i < THREAD_MAX; i++)
500 delete MaterialTable[i];
502 MaterialTable[i] = NULL;
507 /// read_weights() reads evaluation weights from the corresponding UCI
510 void read_weights(Color us) {
512 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
513 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
514 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
515 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
516 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
517 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
519 Color them = opposite_color(us);
521 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
522 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
523 WeightSpace = weight_option("Space", WeightSpaceInternal);
531 // evaluate_common() computes terms common to all pieces attack
533 template<PieceType Piece>
534 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
536 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
537 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
538 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
539 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
541 Color them = opposite_color(us);
543 // Update attack info
544 ei.attackedBy[us][Piece] |= b;
547 if (b & ei.kingZone[us])
549 ei.kingAttackersCount[us]++;
550 ei.kingAttackersWeight[us] += AttackWeight[Piece];
551 Bitboard bb = (b & ei.attackedBy[them][KING]);
553 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
556 // Remove squares protected by enemy pawns
557 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
560 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
561 : count_1s(bb & ~p.pieces_of_color(us)));
563 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
564 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
566 // Bishop and Knight outposts
567 if ( (Piece == BISHOP || Piece == KNIGHT) // compile time condition
568 && p.square_is_weak(s, them))
570 // Initial bonus based on square
572 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
574 // Increase bonus if supported by pawn, especially if the opponent has
575 // no minor piece which can exchange the outpost piece
576 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
579 if ( p.piece_count(them, KNIGHT) == 0
580 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
583 ei.mgValue += Sign[us] * bonus;
584 ei.egValue += Sign[us] * bonus;
590 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
593 template<PieceType Piece>
594 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
602 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
604 s = pos.piece_list(us, Piece, i);
606 if (Piece == KNIGHT || Piece == QUEEN)
607 b = pos.piece_attacks<Piece>(s);
608 else if (Piece == BISHOP)
609 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
610 else if (Piece == ROOK)
611 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
613 // Attacks, mobility and outposts
614 mob = evaluate_common<Piece>(pos, b, us, ei, s);
616 // Special patterns: trapped bishops on a7/h7/a2/h2
617 // and trapped bishops on a1/h1/a8/h8 in Chess960.
620 if (bit_is_set(MaskA7H7[us], s))
621 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
623 if (Chess960 && bit_is_set(MaskA1H1[us], s))
624 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
627 if (Piece == ROOK || Piece == QUEEN)
629 // Queen or rook on 7th rank
630 them = opposite_color(us);
632 if ( relative_rank(us, s) == RANK_7
633 && relative_rank(us, pos.king_square(them)) == RANK_8)
635 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
636 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
640 // Special extra evaluation for rooks
643 // Open and half-open files
645 if (ei.pi->file_is_half_open(us, f))
647 if (ei.pi->file_is_half_open(them, f))
649 ei.mgValue += Sign[us] * RookOpenFileBonus;
650 ei.egValue += Sign[us] * RookOpenFileBonus;
654 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
655 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
659 // Penalize rooks which are trapped inside a king. Penalize more if
660 // king has lost right to castle.
661 if (mob > 6 || ei.pi->file_is_half_open(us, f))
664 ksq = pos.king_square(us);
666 if ( square_file(ksq) >= FILE_E
667 && square_file(s) > square_file(ksq)
668 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
670 // Is there a half-open file between the king and the edge of the board?
671 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
672 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
673 : Sign[us] * (TrappedRookPenalty - mob * 16);
675 else if ( square_file(ksq) <= FILE_D
676 && square_file(s) < square_file(ksq)
677 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
679 // Is there a half-open file between the king and the edge of the board?
680 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
681 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
682 : Sign[us] * (TrappedRookPenalty - mob * 16);
688 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
690 return b >> (num << 3);
693 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
697 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
699 int shelter = 0, sign = Sign[us];
700 Square s = p.king_square(us);
703 if (relative_rank(us, s) <= RANK_4)
705 // Shelter cache lookup
706 shelter = ei.pi->kingShelter(us, s);
710 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
711 Rank r = square_rank(s);
712 for (int i = 1; i < 4; i++)
713 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
715 // Cache shelter value in pawn info
716 ei.pi->setKingShelter(us, s, shelter);
718 ei.mgValue += sign * Value(shelter);
721 // King safety. This is quite complicated, and is almost certainly far
722 // from optimally tuned.
723 Color them = opposite_color(us);
725 if ( p.piece_count(them, QUEEN) >= 1
726 && ei.kingAttackersCount[them] >= 2
727 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
728 && ei.kingAdjacentZoneAttacksCount[them])
730 // Is it the attackers turn to move?
731 bool sente = (them == p.side_to_move());
733 // Find the attacked squares around the king which has no defenders
734 // apart from the king itself
735 Bitboard undefended =
736 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
737 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
738 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
739 & ei.attacked_by(us, KING);
741 Bitboard occ = p.occupied_squares(), b, b2;
743 // Initialize the 'attackUnits' variable, which is used later on as an
744 // index to the SafetyTable[] array. The initial value is based on the
745 // number and types of the attacking pieces, the number of attacked and
746 // undefended squares around the king, the square of the king, and the
747 // quality of the pawn shelter.
749 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
750 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
751 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
753 // Analyse safe queen contact checks
754 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
757 Bitboard attackedByOthers =
758 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
759 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
761 b &= attackedByOthers;
764 // The bitboard b now contains the squares available for safe queen
766 int count = count_1s_max_15(b);
767 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
769 // Is there a mate threat?
770 if (QueenContactMates && !p.is_check())
772 Bitboard escapeSquares =
773 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
777 Square from, to = pop_1st_bit(&b);
778 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
780 // We have a mate, unless the queen is pinned or there
781 // is an X-ray attack through the queen.
782 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
784 from = p.piece_list(them, QUEEN, i);
785 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
786 && !bit_is_set(p.pinned_pieces(them), from)
787 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
788 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
790 ei.mateThreat[them] = make_move(from, to);
798 // Analyse safe distance checks
799 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
801 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
804 b2 = b & ei.attacked_by(them, QUEEN);
806 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
809 b2 = b & ei.attacked_by(them, ROOK);
811 attackUnits += RookCheckBonus * count_1s_max_15(b2);
813 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
815 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
818 b2 = b & ei.attacked_by(them, QUEEN);
820 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
823 b2 = b & ei.attacked_by(them, BISHOP);
825 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
827 if (KnightCheckBonus > 0)
829 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
832 b2 = b & ei.attacked_by(them, KNIGHT);
834 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
837 // Analyse discovered checks (only for non-pawns right now, consider
838 // adding pawns later).
839 if (DiscoveredCheckBonus)
841 b = p.discovered_check_candidates(them) & ~p.pawns();
843 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
846 // Has a mate threat been found? We don't do anything here if the
847 // side with the mating move is the side to move, because in that
848 // case the mating side will get a huge bonus at the end of the main
849 // evaluation function instead.
850 if (ei.mateThreat[them] != MOVE_NONE)
851 attackUnits += MateThreatBonus;
853 // Ensure that attackUnits is between 0 and 99, in order to avoid array
854 // out of bounds errors:
858 if (attackUnits >= 100)
861 // Finally, extract the king safety score from the SafetyTable[] array.
862 // Add the score to the evaluation, and also to ei.futilityMargin. The
863 // reason for adding the king safety score to the futility margin is
864 // that the king safety scores can sometimes be very big, and that
865 // capturing a single attacking piece can therefore result in a score
866 // change far bigger than the value of the captured piece.
867 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
869 ei.mgValue -= sign * v;
871 if (us == p.side_to_move())
872 ei.futilityMargin += v;
877 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
879 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
881 bool hasUnstoppable[2] = {false, false};
882 int movesToGo[2] = {100, 100};
884 for (Color us = WHITE; us <= BLACK; us++)
886 Color them = opposite_color(us);
887 Square ourKingSq = pos.king_square(us);
888 Square theirKingSq = pos.king_square(them);
889 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
893 Square s = pop_1st_bit(&b);
895 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
896 assert(pos.pawn_is_passed(us, s));
898 int r = int(relative_rank(us, s) - RANK_2);
899 int tr = Max(0, r * (r - 1));
900 Square blockSq = s + pawn_push(us);
902 // Base bonus based on rank
903 Value mbonus = Value(20 * tr);
904 Value ebonus = Value(10 + r * r * 10);
906 // Adjust bonus based on king proximity
909 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
910 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
911 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
913 // If the pawn is free to advance, increase bonus
914 if (pos.square_is_empty(blockSq))
916 b2 = squares_in_front_of(us, s);
917 b3 = b2 & ei.attacked_by(them);
918 b4 = b2 & ei.attacked_by(us);
920 // If there is an enemy rook or queen attacking the pawn from behind,
921 // add all X-ray attacks by the rook or queen.
922 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
923 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
926 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
928 // There are no enemy pieces in the pawn's path! Are any of the
929 // squares in the pawn's path attacked by the enemy?
930 if (b3 == EmptyBoardBB)
931 // No enemy attacks, huge bonus!
932 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
934 // OK, there are enemy attacks. Are those squares which are
935 // attacked by the enemy also attacked by us? If yes, big bonus
936 // (but smaller than when there are no enemy attacks), if no,
937 // somewhat smaller bonus.
938 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
942 // There are some enemy pieces in the pawn's path. While this is
943 // sad, we still assign a moderate bonus if all squares in the path
944 // which are either occupied by or attacked by enemy pieces are
945 // also attacked by us.
946 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
947 ebonus += Value(tr * 6);
949 // At last, add a small bonus when there are no *friendly* pieces
950 // in the pawn's path.
951 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
956 // If the pawn is supported by a friendly pawn, increase bonus
957 b2 = pos.pawns(us) & neighboring_files_bb(s);
959 ebonus += Value(r * 20);
960 else if (pos.pawn_attacks(them, s) & b2)
961 ebonus += Value(r * 12);
963 // If the other side has only a king, check whether the pawn is
965 if (pos.non_pawn_material(them) == Value(0))
970 qsq = relative_square(us, make_square(square_file(s), RANK_8));
971 d = square_distance(s, qsq)
972 - square_distance(theirKingSq, qsq)
973 + (us != pos.side_to_move());
977 int mtg = RANK_8 - relative_rank(us, s);
978 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
983 hasUnstoppable[us] = true;
984 movesToGo[us] = Min(movesToGo[us], mtg);
988 // Rook pawns are a special case: They are sometimes worse, and
989 // sometimes better than other passed pawns. It is difficult to find
990 // good rules for determining whether they are good or bad. For now,
991 // we try the following: Increase the value for rook pawns if the
992 // other side has no pieces apart from a knight, and decrease the
993 // value if the other side has a rook or queen.
994 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
996 if( pos.non_pawn_material(them) <= KnightValueMidgame
997 && pos.piece_count(them, KNIGHT) <= 1)
998 ebonus += ebonus / 4;
999 else if(pos.rooks_and_queens(them))
1000 ebonus -= ebonus / 4;
1003 // Add the scores for this pawn to the middle game and endgame eval.
1004 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1005 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1009 // Does either side have an unstoppable passed pawn?
1010 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1011 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1012 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1013 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1014 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1016 // Both sides have unstoppable pawns! Try to find out who queens
1017 // first. We begin by transforming 'movesToGo' to the number of
1018 // plies until the pawn queens for both sides.
1019 movesToGo[WHITE] *= 2;
1020 movesToGo[BLACK] *= 2;
1021 movesToGo[pos.side_to_move()]--;
1023 // If one side queens at least three plies before the other, that
1025 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1026 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1027 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1028 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1030 // We could also add some rules about the situation when one side
1031 // queens exactly one ply before the other: Does the first queen
1032 // check the opponent's king, or attack the opponent's queening square?
1033 // This is slightly tricky to get right, because it is possible that
1034 // the opponent's king has moved somewhere before the first pawn queens.
1039 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1040 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1043 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1045 assert(square_is_ok(s));
1046 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1048 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1049 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1051 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1052 && pos.see(s, b6) < 0
1053 && pos.see(s, b8) < 0)
1055 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1056 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1061 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1062 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1063 // black), and assigns a penalty if it is. This pattern can obviously
1064 // only occur in Chess960 games.
1066 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1068 Piece pawn = piece_of_color_and_type(us, PAWN);
1072 assert(square_is_ok(s));
1073 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1075 if (square_file(s) == FILE_A)
1077 b2 = relative_square(us, SQ_B2);
1078 b3 = relative_square(us, SQ_B3);
1079 c3 = relative_square(us, SQ_C3);
1083 b2 = relative_square(us, SQ_G2);
1084 b3 = relative_square(us, SQ_G3);
1085 c3 = relative_square(us, SQ_F3);
1088 if (pos.piece_on(b2) == pawn)
1092 if (!pos.square_is_empty(b3))
1093 penalty = 2*TrappedBishopA1H1Penalty;
1094 else if (pos.piece_on(c3) == pawn)
1095 penalty = TrappedBishopA1H1Penalty;
1097 penalty = TrappedBishopA1H1Penalty / 2;
1099 ei.mgValue -= Sign[us] * penalty;
1100 ei.egValue -= Sign[us] * penalty;
1105 // evaluate_space() computes the space evaluation for a given side. The
1106 // space evaluation is a simple bonus based on the number of safe squares
1107 // available for minor pieces on the central four files on ranks 2--4. Safe
1108 // squares one, two or three squares behind a friendly pawn are counted
1109 // twice. Finally, the space bonus is scaled by a weight taken from the
1110 // material hash table.
1112 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1114 Color them = opposite_color(us);
1116 // Find the safe squares for our pieces inside the area defined by
1117 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1118 // pawn, or if it is undefended and attacked by an enemy piece.
1120 Bitboard safeSquares = SpaceMask[us]
1122 & ~ei.attacked_by(them, PAWN)
1123 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1125 // Find all squares which are at most three squares behind some friendly
1127 Bitboard behindFriendlyPawns = pos.pawns(us);
1130 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1131 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1135 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1136 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1139 int space = count_1s_max_15(safeSquares)
1140 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1142 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1146 // apply_weight() applies an evaluation weight to a value
1148 inline Value apply_weight(Value v, int w) {
1149 return (v*w) / 0x100;
1153 // scale_by_game_phase() interpolates between a middle game and an endgame
1154 // score, based on game phase. It also scales the return value by a
1155 // ScaleFactor array.
1157 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1159 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1160 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1161 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1163 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1165 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1166 return Value(int(result) & ~(GrainSize - 1));
1170 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1171 // significant bits of a Bitboard. This function is used by the king
1172 // shield evaluation.
1174 int count_1s_8bit(Bitboard b) {
1175 return int(BitCount8Bit[b & 0xFF]);
1179 // compute_weight() computes the value of an evaluation weight, by combining
1180 // an UCI-configurable weight with an internal weight.
1182 int compute_weight(int uciWeight, int internalWeight) {
1184 uciWeight = (uciWeight * 0x100) / 100;
1185 return (uciWeight * internalWeight) / 0x100;
1189 // helper used in read_weights()
1190 int weight_option(const std::string& opt, int weight) {
1192 return compute_weight(get_option_value_int(opt), weight);
1196 // init_safety() initizes the king safety evaluation, based on UCI
1197 // parameters. It is called from read_weights().
1199 void init_safety() {
1201 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1202 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1203 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1204 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1205 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1206 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1207 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1209 int maxSlope = get_option_value_int("King Safety Max Slope");
1210 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1211 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1212 double b = get_option_value_int("King Safety X Intercept");
1213 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1214 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1216 for (int i = 0; i < 100; i++)
1219 SafetyTable[i] = Value(0);
1221 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1223 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1226 for (int i = 0; i < 100; i++)
1228 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1229 for (int j = i + 1; j < 100; j++)
1230 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1232 if (SafetyTable[i] > Value(peak))
1233 SafetyTable[i] = Value(peak);