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);
178 // Rooks on open files
179 const Value RookOpenFileBonus = Value(43);
180 const Value RookHalfOpenFileBonus = Value(19);
182 // Penalty for rooks trapped inside a friendly king which has lost the
184 const Value TrappedRookPenalty = Value(180);
186 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
188 const Value TrappedBishopA7H7Penalty = Value(300);
190 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
191 const Bitboard MaskA7H7[2] = {
192 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
193 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
196 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
197 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
198 // happen in Chess960 games.
199 const Value TrappedBishopA1H1Penalty = Value(100);
201 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
202 const Bitboard MaskA1H1[2] = {
203 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
204 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
207 // The SpaceMask[color] contains area of the board which is consdered by
208 // the space evaluation. In the middle game, each side is given a bonus
209 // based on how many squares inside this area are safe and available for
210 // friendly minor pieces.
211 const Bitboard SpaceMask[2] = {
212 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
213 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
214 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
215 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
216 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
217 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
220 /// King safety constants and variables. The king safety scores are taken
221 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
222 /// the strength of the attack are added up into an integer, which is used
223 /// as an index to SafetyTable[].
225 // Attack weights for each piece type
226 const int QueenAttackWeight = 5;
227 const int RookAttackWeight = 3;
228 const int BishopAttackWeight = 2;
229 const int KnightAttackWeight = 2;
231 // Bonuses for safe checks, initialized from UCI options
232 int QueenContactCheckBonus, DiscoveredCheckBonus;
233 int QueenCheckBonus, RookCheckBonus, BishopCheckBonus, KnightCheckBonus;
235 // Scan for queen contact mates?
236 const bool QueenContactMates = true;
238 // Bonus for having a mate threat, initialized from UCI options
241 // InitKingDanger[] contains bonuses based on the position of the defending
243 const int InitKingDanger[64] = {
244 2, 0, 2, 5, 5, 2, 0, 2,
245 2, 2, 4, 8, 8, 4, 2, 2,
246 7, 10, 12, 12, 12, 12, 10, 7,
247 15, 15, 15, 15, 15, 15, 15, 15,
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
254 // SafetyTable[] contains the actual king safety scores. It is initialized
256 Value SafetyTable[100];
258 // Pawn and material hash tables, indexed by the current thread id
259 PawnInfoTable* PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
260 MaterialInfoTable* MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
262 // Sizes of pawn and material hash tables
263 const int PawnTableSize = 16384;
264 const int MaterialTableSize = 1024;
266 // Array which gives the number of nonzero bits in an 8-bit integer
267 uint8_t BitCount8Bit[256];
269 // Function prototypes
270 template<PieceType Piece>
271 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
274 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
276 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
277 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
279 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
282 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
283 inline Value apply_weight(Value v, int w);
284 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
286 int compute_weight(int uciWeight, int internalWeight);
287 int weight_option(const std::string& opt, int weight);
297 /// evaluate() is the main evaluation function. It always computes two
298 /// values, an endgame score and a middle game score, and interpolates
299 /// between them based on the remaining material.
301 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
304 assert(threadID >= 0 && threadID < THREAD_MAX);
306 memset(&ei, 0, sizeof(EvalInfo));
308 // Initialize by reading the incrementally updated scores included in the
309 // position object (material + piece square tables)
310 ei.mgValue = pos.mg_value();
311 ei.egValue = pos.eg_value();
313 // Probe the material hash table
314 ei.mi = MaterialTable[threadID]->get_material_info(pos);
315 ei.mgValue += ei.mi->mg_value();
316 ei.egValue += ei.mi->eg_value();
318 // If we have a specialized evaluation function for the current material
319 // configuration, call it and return
320 if (ei.mi->specialized_eval_exists())
321 return ei.mi->evaluate(pos);
323 // After get_material_info() call that modifies them
324 ScaleFactor factor[2];
325 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
326 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
328 // Probe the pawn hash table
329 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
330 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
331 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
333 // Initialize king attack bitboards and king attack zones for both sides
334 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
335 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
336 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
337 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
339 // Initialize pawn attack bitboards for both sides
340 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
341 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
342 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
343 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
346 for (Color c = WHITE; c <= BLACK; c++)
348 evaluate_pieces<KNIGHT>(pos, c, ei);
349 evaluate_pieces<BISHOP>(pos, c, ei);
350 evaluate_pieces<ROOK>(pos, c, ei);
351 evaluate_pieces<QUEEN>(pos, c, ei);
353 // Sum up all attacked squares
354 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
355 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
356 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
359 // Kings. Kings are evaluated after all other pieces for both sides,
360 // because we need complete attack information for all pieces when computing
361 // the king safety evaluation.
362 for (Color c = WHITE; c <= BLACK; c++)
363 evaluate_pieces<KING>(pos, c, ei);
365 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
366 // because we need to know which side promotes first in positions where
367 // both sides have an unstoppable passed pawn.
368 if (ei.pi->passed_pawns())
369 evaluate_passed_pawns(pos, ei);
371 Phase phase = pos.game_phase();
373 // Middle-game specific evaluation terms
374 if (phase > PHASE_ENDGAME)
376 // Pawn storms in positions with opposite castling.
377 if ( square_file(pos.king_square(WHITE)) >= FILE_E
378 && square_file(pos.king_square(BLACK)) <= FILE_D)
380 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
381 - ei.pi->kingside_storm_value(BLACK);
383 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
384 && square_file(pos.king_square(BLACK)) >= FILE_E)
386 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
387 - ei.pi->queenside_storm_value(BLACK);
389 // Evaluate space for both sides
390 if (ei.mi->space_weight() > 0)
392 evaluate_space(pos, WHITE, ei);
393 evaluate_space(pos, BLACK, ei);
398 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
399 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
401 // If we don't already have an unusual scale factor, check for opposite
402 // colored bishop endgames, and use a lower scale for those
403 if ( phase < PHASE_MIDGAME
404 && pos.opposite_colored_bishops()
405 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
406 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
410 // Only the two bishops ?
411 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
412 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
414 // Check for KBP vs KB with only a single pawn that is almost
415 // certainly a draw or at least two pawns.
416 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
417 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
420 // Endgame with opposite-colored bishops, but also other pieces. Still
421 // a bit drawish, but not as drawish as with only the two bishops.
422 sf = ScaleFactor(50);
424 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
426 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
430 // Interpolate between the middle game and the endgame score, and
432 Color stm = pos.side_to_move();
434 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
436 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
440 /// quick_evaluate() does a very approximate evaluation of the current position.
441 /// It currently considers only material and piece square table scores. Perhaps
442 /// we should add scores from the pawn and material hash tables?
444 Value quick_evaluate(const Position &pos) {
449 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
451 Value mgv = pos.mg_value();
452 Value egv = pos.eg_value();
453 Phase ph = pos.game_phase();
454 Color stm = pos.side_to_move();
456 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
460 /// init_eval() initializes various tables used by the evaluation function.
462 void init_eval(int threads) {
464 assert(threads <= THREAD_MAX);
466 for (int i = 0; i < THREAD_MAX; i++)
471 delete MaterialTable[i];
473 MaterialTable[i] = NULL;
477 PawnTable[i] = new PawnInfoTable(PawnTableSize);
478 if (!MaterialTable[i])
479 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
482 for (Bitboard b = 0ULL; b < 256ULL; b++)
484 assert(count_1s(b) == int(uint8_t(count_1s(b))));
485 BitCount8Bit[b] = (uint8_t)count_1s(b);
490 /// quit_eval() releases heap-allocated memory at program termination.
494 for (int i = 0; i < THREAD_MAX; i++)
497 delete MaterialTable[i];
499 MaterialTable[i] = NULL;
504 /// read_weights() reads evaluation weights from the corresponding UCI
507 void read_weights(Color us) {
509 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
510 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
511 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
512 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
513 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
514 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
516 Color them = opposite_color(us);
518 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
519 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
520 WeightSpace = weight_option("Space", WeightSpaceInternal);
528 // evaluate_common() computes terms common to all pieces attack
530 template<PieceType Piece>
531 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
533 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
534 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
535 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
536 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
538 Color them = opposite_color(us);
540 // Update attack info
541 ei.attackedBy[us][Piece] |= b;
544 if (b & ei.kingZone[us])
546 ei.kingAttackersCount[us]++;
547 ei.kingAttackersWeight[us] += AttackWeight[Piece];
548 Bitboard bb = (b & ei.attackedBy[them][KING]);
550 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
553 // Remove squares protected by enemy pawns
554 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
557 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
558 : count_1s(bb & ~p.pieces_of_color(us)));
560 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
561 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
563 // Bishop and Knight outposts
564 if ( (Piece == BISHOP || Piece == KNIGHT) // compile time condition
565 && p.square_is_weak(s, them))
567 // Initial bonus based on square
569 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
571 // Increase bonus if supported by pawn, especially if the opponent has
572 // no minor piece which can exchange the outpost piece
573 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
576 if ( p.piece_count(them, KNIGHT) == 0
577 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
580 ei.mgValue += Sign[us] * bonus;
581 ei.egValue += Sign[us] * bonus;
587 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
590 template<PieceType Piece>
591 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
599 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
601 s = pos.piece_list(us, Piece, i);
603 if (Piece == KNIGHT || Piece == QUEEN)
604 b = pos.piece_attacks<Piece>(s);
605 else if (Piece == BISHOP)
606 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
607 else if (Piece == ROOK)
608 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
610 // Attacks, mobility and outposts
611 mob = evaluate_common<Piece>(pos, b, us, ei, s);
613 // Special patterns: trapped bishops on a7/h7/a2/h2
614 // and trapped bishops on a1/h1/a8/h8 in Chess960.
617 if (bit_is_set(MaskA7H7[us], s))
618 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
620 if (Chess960 && bit_is_set(MaskA1H1[us], s))
621 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
624 if (Piece == ROOK || Piece == QUEEN)
626 // Queen or rook on 7th rank
627 them = opposite_color(us);
629 if ( relative_rank(us, s) == RANK_7
630 && relative_rank(us, pos.king_square(them)) == RANK_8)
632 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
633 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
637 // Special extra evaluation for rooks
640 // Open and half-open files
642 if (ei.pi->file_is_half_open(us, f))
644 if (ei.pi->file_is_half_open(them, f))
646 ei.mgValue += Sign[us] * RookOpenFileBonus;
647 ei.egValue += Sign[us] * RookOpenFileBonus;
651 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
652 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
656 // Penalize rooks which are trapped inside a king. Penalize more if
657 // king has lost right to castle.
658 if (mob > 6 || ei.pi->file_is_half_open(us, f))
661 ksq = pos.king_square(us);
663 if ( square_file(ksq) >= FILE_E
664 && square_file(s) > square_file(ksq)
665 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
667 // Is there a half-open file between the king and the edge of the board?
668 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
669 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
670 : Sign[us] * (TrappedRookPenalty - mob * 16);
672 else if ( square_file(ksq) <= FILE_D
673 && square_file(s) < square_file(ksq)
674 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
676 // Is there a half-open file between the king and the edge of the board?
677 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
678 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
679 : Sign[us] * (TrappedRookPenalty - mob * 16);
685 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
687 return b >> (num << 3);
690 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
694 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
696 int shelter = 0, sign = Sign[us];
697 Square s = p.king_square(us);
700 if (relative_rank(us, s) <= RANK_4)
702 // Shelter cache lookup
703 shelter = ei.pi->kingShelter(us, s);
707 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
708 Rank r = square_rank(s);
709 for (int i = 1; i < 4; i++)
710 shelter += BitCount8Bit[shiftRowsDown(pawns, r+i*sign) & 0xFF] * (128 >> i);
712 // Cache shelter value in pawn info
713 ei.pi->setKingShelter(us, s, shelter);
715 ei.mgValue += sign * Value(shelter);
718 // King safety. This is quite complicated, and is almost certainly far
719 // from optimally tuned.
720 Color them = opposite_color(us);
722 if ( p.piece_count(them, QUEEN) >= 1
723 && ei.kingAttackersCount[them] >= 2
724 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
725 && ei.kingAdjacentZoneAttacksCount[them])
727 // Is it the attackers turn to move?
728 bool sente = (them == p.side_to_move());
730 // Find the attacked squares around the king which has no defenders
731 // apart from the king itself
732 Bitboard undefended =
733 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
734 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
735 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
736 & ei.attacked_by(us, KING);
738 Bitboard occ = p.occupied_squares(), b, b2;
740 // Initialize the 'attackUnits' variable, which is used later on as an
741 // index to the SafetyTable[] array. The initial value is based on the
742 // number and types of the attacking pieces, the number of attacked and
743 // undefended squares around the king, the square of the king, and the
744 // quality of the pawn shelter.
746 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
747 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
748 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
750 // Analyse safe queen contact checks
751 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
754 Bitboard attackedByOthers =
755 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
756 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
758 b &= attackedByOthers;
761 // The bitboard b now contains the squares available for safe queen
763 int count = count_1s_max_15(b);
764 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
766 // Is there a mate threat?
767 if (QueenContactMates && !p.is_check())
769 Bitboard escapeSquares =
770 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
774 Square from, to = pop_1st_bit(&b);
775 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
777 // We have a mate, unless the queen is pinned or there
778 // is an X-ray attack through the queen.
779 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
781 from = p.piece_list(them, QUEEN, i);
782 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
783 && !bit_is_set(p.pinned_pieces(them), from)
784 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
785 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
787 ei.mateThreat[them] = make_move(from, to);
795 // Analyse safe distance checks
796 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
798 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
801 b2 = b & ei.attacked_by(them, QUEEN);
803 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
806 b2 = b & ei.attacked_by(them, ROOK);
808 attackUnits += RookCheckBonus * count_1s_max_15(b2);
810 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
812 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
815 b2 = b & ei.attacked_by(them, QUEEN);
817 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
820 b2 = b & ei.attacked_by(them, BISHOP);
822 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
824 if (KnightCheckBonus > 0)
826 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
829 b2 = b & ei.attacked_by(them, KNIGHT);
831 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
834 // Analyse discovered checks (only for non-pawns right now, consider
835 // adding pawns later).
836 if (DiscoveredCheckBonus)
838 b = p.discovered_check_candidates(them) & ~p.pawns();
840 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
843 // Has a mate threat been found? We don't do anything here if the
844 // side with the mating move is the side to move, because in that
845 // case the mating side will get a huge bonus at the end of the main
846 // evaluation function instead.
847 if (ei.mateThreat[them] != MOVE_NONE)
848 attackUnits += MateThreatBonus;
850 // Ensure that attackUnits is between 0 and 99, in order to avoid array
851 // out of bounds errors:
855 if (attackUnits >= 100)
858 // Finally, extract the king safety score from the SafetyTable[] array.
859 // Add the score to the evaluation, and also to ei.futilityMargin. The
860 // reason for adding the king safety score to the futility margin is
861 // that the king safety scores can sometimes be very big, and that
862 // capturing a single attacking piece can therefore result in a score
863 // change far bigger than the value of the captured piece.
864 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
866 ei.mgValue -= sign * v;
868 if (us == p.side_to_move())
869 ei.futilityMargin += v;
874 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
876 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
878 bool hasUnstoppable[2] = {false, false};
879 int movesToGo[2] = {100, 100};
881 for (Color us = WHITE; us <= BLACK; us++)
883 Color them = opposite_color(us);
884 Square ourKingSq = pos.king_square(us);
885 Square theirKingSq = pos.king_square(them);
886 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
890 Square s = pop_1st_bit(&b);
892 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
893 assert(pos.pawn_is_passed(us, s));
895 int r = int(relative_rank(us, s) - RANK_2);
896 int tr = Max(0, r * (r - 1));
897 Square blockSq = s + pawn_push(us);
899 // Base bonus based on rank
900 Value mbonus = Value(20 * tr);
901 Value ebonus = Value(10 + r * r * 10);
903 // Adjust bonus based on king proximity
906 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
907 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
908 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
910 // If the pawn is free to advance, increase bonus
911 if (pos.square_is_empty(blockSq))
913 b2 = squares_in_front_of(us, s);
914 b3 = b2 & ei.attacked_by(them);
915 b4 = b2 & ei.attacked_by(us);
917 // If there is an enemy rook or queen attacking the pawn from behind,
918 // add all X-ray attacks by the rook or queen.
919 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
920 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
923 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
925 // There are no enemy pieces in the pawn's path! Are any of the
926 // squares in the pawn's path attacked by the enemy?
927 if (b3 == EmptyBoardBB)
928 // No enemy attacks, huge bonus!
929 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
931 // OK, there are enemy attacks. Are those squares which are
932 // attacked by the enemy also attacked by us? If yes, big bonus
933 // (but smaller than when there are no enemy attacks), if no,
934 // somewhat smaller bonus.
935 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
939 // There are some enemy pieces in the pawn's path. While this is
940 // sad, we still assign a moderate bonus if all squares in the path
941 // which are either occupied by or attacked by enemy pieces are
942 // also attacked by us.
943 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
944 ebonus += Value(tr * 6);
946 // At last, add a small bonus when there are no *friendly* pieces
947 // in the pawn's path.
948 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
953 // If the pawn is supported by a friendly pawn, increase bonus
954 b2 = pos.pawns(us) & neighboring_files_bb(s);
956 ebonus += Value(r * 20);
957 else if (pos.pawn_attacks(them, s) & b2)
958 ebonus += Value(r * 12);
960 // If the other side has only a king, check whether the pawn is
962 if (pos.non_pawn_material(them) == Value(0))
967 qsq = relative_square(us, make_square(square_file(s), RANK_8));
968 d = square_distance(s, qsq)
969 - square_distance(theirKingSq, qsq)
970 + (us != pos.side_to_move());
974 int mtg = RANK_8 - relative_rank(us, s);
975 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
980 hasUnstoppable[us] = true;
981 movesToGo[us] = Min(movesToGo[us], mtg);
985 // Rook pawns are a special case: They are sometimes worse, and
986 // sometimes better than other passed pawns. It is difficult to find
987 // good rules for determining whether they are good or bad. For now,
988 // we try the following: Increase the value for rook pawns if the
989 // other side has no pieces apart from a knight, and decrease the
990 // value if the other side has a rook or queen.
991 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
993 if( pos.non_pawn_material(them) <= KnightValueMidgame
994 && pos.piece_count(them, KNIGHT) <= 1)
995 ebonus += ebonus / 4;
996 else if(pos.rooks_and_queens(them))
997 ebonus -= ebonus / 4;
1000 // Add the scores for this pawn to the middle game and endgame eval.
1001 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1002 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1006 // Does either side have an unstoppable passed pawn?
1007 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1008 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1009 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1010 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1011 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1013 // Both sides have unstoppable pawns! Try to find out who queens
1014 // first. We begin by transforming 'movesToGo' to the number of
1015 // plies until the pawn queens for both sides.
1016 movesToGo[WHITE] *= 2;
1017 movesToGo[BLACK] *= 2;
1018 movesToGo[pos.side_to_move()]--;
1020 // If one side queens at least three plies before the other, that
1022 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1023 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1024 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1025 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1027 // We could also add some rules about the situation when one side
1028 // queens exactly one ply before the other: Does the first queen
1029 // check the opponent's king, or attack the opponent's queening square?
1030 // This is slightly tricky to get right, because it is possible that
1031 // the opponent's king has moved somewhere before the first pawn queens.
1036 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1037 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1040 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1042 assert(square_is_ok(s));
1043 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1045 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1046 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1048 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1049 && pos.see(s, b6) < 0
1050 && pos.see(s, b8) < 0)
1052 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1053 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1058 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1059 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1060 // black), and assigns a penalty if it is. This pattern can obviously
1061 // only occur in Chess960 games.
1063 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1065 Piece pawn = piece_of_color_and_type(us, PAWN);
1069 assert(square_is_ok(s));
1070 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1072 if (square_file(s) == FILE_A)
1074 b2 = relative_square(us, SQ_B2);
1075 b3 = relative_square(us, SQ_B3);
1076 c3 = relative_square(us, SQ_C3);
1080 b2 = relative_square(us, SQ_G2);
1081 b3 = relative_square(us, SQ_G3);
1082 c3 = relative_square(us, SQ_F3);
1085 if (pos.piece_on(b2) == pawn)
1089 if (!pos.square_is_empty(b3))
1090 penalty = 2*TrappedBishopA1H1Penalty;
1091 else if (pos.piece_on(c3) == pawn)
1092 penalty = TrappedBishopA1H1Penalty;
1094 penalty = TrappedBishopA1H1Penalty / 2;
1096 ei.mgValue -= Sign[us] * penalty;
1097 ei.egValue -= Sign[us] * penalty;
1102 // evaluate_space() computes the space evaluation for a given side. The
1103 // space evaluation is a simple bonus based on the number of safe squares
1104 // available for minor pieces on the central four files on ranks 2--4. Safe
1105 // squares one, two or three squares behind a friendly pawn are counted
1106 // twice. Finally, the space bonus is scaled by a weight taken from the
1107 // material hash table.
1109 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1111 Color them = opposite_color(us);
1113 // Find the safe squares for our pieces inside the area defined by
1114 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1115 // pawn, or if it is undefended and attacked by an enemy piece.
1117 Bitboard safeSquares = SpaceMask[us]
1119 & ~ei.attacked_by(them, PAWN)
1120 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1122 // Find all squares which are at most three squares behind some friendly
1124 Bitboard behindFriendlyPawns = pos.pawns(us);
1127 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1128 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1132 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1133 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1136 int space = count_1s_max_15(safeSquares)
1137 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1139 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1143 // apply_weight() applies an evaluation weight to a value
1145 inline Value apply_weight(Value v, int w) {
1146 return (v*w) / 0x100;
1150 // scale_by_game_phase() interpolates between a middle game and an endgame
1151 // score, based on game phase. It also scales the return value by a
1152 // ScaleFactor array.
1154 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1156 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1157 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1158 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1160 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1162 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1163 return Value(int(result) & ~(GrainSize - 1));
1167 // compute_weight() computes the value of an evaluation weight, by combining
1168 // an UCI-configurable weight with an internal weight.
1170 int compute_weight(int uciWeight, int internalWeight) {
1172 uciWeight = (uciWeight * 0x100) / 100;
1173 return (uciWeight * internalWeight) / 0x100;
1177 // helper used in read_weights()
1178 int weight_option(const std::string& opt, int weight) {
1180 return compute_weight(get_option_value_int(opt), weight);
1184 // init_safety() initizes the king safety evaluation, based on UCI
1185 // parameters. It is called from read_weights().
1187 void init_safety() {
1189 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1190 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1191 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1192 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1193 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1194 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1195 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1197 int maxSlope = get_option_value_int("King Safety Max Slope");
1198 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1199 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1200 double b = get_option_value_int("King Safety X Intercept");
1201 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1202 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1204 for (int i = 0; i < 100; i++)
1207 SafetyTable[i] = Value(0);
1209 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1211 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1214 for (int i = 0; i < 100; i++)
1216 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1217 for (int j = i + 1; j < 100; j++)
1218 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1220 if (SafetyTable[i] > Value(peak))
1221 SafetyTable[i] = Value(peak);