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/>.
34 #include "ucioption.h"
38 //// Local definitions
43 const int Sign[2] = { 1, -1 };
45 // Evaluation grain size, must be a power of 2
46 const int GrainSize = 4;
48 // Evaluation weights, initialized from UCI options
49 int WeightMobilityMidgame, WeightMobilityEndgame;
50 int WeightPawnStructureMidgame, WeightPawnStructureEndgame;
51 int WeightPassedPawnsMidgame, WeightPassedPawnsEndgame;
52 int WeightKingSafety[2];
55 // Internal evaluation weights. These are applied on top of the evaluation
56 // weights read from UCI parameters. The purpose is to be able to change
57 // the evaluation weights while keeping the default values of the UCI
58 // parameters at 100, which looks prettier.
60 // Values modified by Joona Kiiski
61 const int WeightMobilityMidgameInternal = 0x0FA;
62 const int WeightMobilityEndgameInternal = 0x10A;
63 const int WeightPawnStructureMidgameInternal = 0x0EC;
64 const int WeightPawnStructureEndgameInternal = 0x0CD;
65 const int WeightPassedPawnsMidgameInternal = 0x108;
66 const int WeightPassedPawnsEndgameInternal = 0x109;
67 const int WeightKingSafetyInternal = 0x0F7;
68 const int WeightKingOppSafetyInternal = 0x101;
69 const int WeightSpaceInternal = 0x02F;
71 // Visually better to define tables constants
74 // Knight mobility bonus in middle game and endgame, indexed by the number
75 // of attacked squares not occupied by friendly piecess.
76 const Value MidgameKnightMobilityBonus[] = {
78 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
81 const Value EndgameKnightMobilityBonus[] = {
83 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
86 // Bishop mobility bonus in middle game and endgame, indexed by the number
87 // of attacked squares not occupied by friendly pieces. X-ray attacks through
88 // queens are also included.
89 const Value MidgameBishopMobilityBonus[] = {
91 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
92 // 8 9 10 11 12 13 14 15
93 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
96 const Value EndgameBishopMobilityBonus[] = {
98 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
99 // 8 9 10 11 12 13 14 15
100 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
103 // Rook mobility bonus in middle game and endgame, indexed by the number
104 // of attacked squares not occupied by friendly pieces. X-ray attacks through
105 // queens and rooks are also included.
106 const Value MidgameRookMobilityBonus[] = {
108 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
109 // 8 9 10 11 12 13 14 15
110 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
113 const Value EndgameRookMobilityBonus[] = {
115 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
116 // 8 9 10 11 12 13 14 15
117 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
120 // Queen mobility bonus in middle game and endgame, indexed by the number
121 // of attacked squares not occupied by friendly pieces.
122 const Value MidgameQueenMobilityBonus[] = {
124 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
125 // 8 9 10 11 12 13 14 15
126 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
127 // 16 17 18 19 20 21 22 23
128 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
129 // 24 25 26 27 28 29 30 31
130 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
133 const Value EndgameQueenMobilityBonus[] = {
135 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
136 // 8 9 10 11 12 13 14 15
137 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
138 // 16 17 18 19 20 21 22 23
139 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
140 // 24 25 26 27 28 29 30 31
141 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
144 // Outpost bonuses for knights and bishops, indexed by square (from white's
146 const Value KnightOutpostBonus[64] = {
148 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
149 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
150 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
151 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
152 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
153 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
154 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
155 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
158 const Value BishopOutpostBonus[64] = {
160 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
161 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
162 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
163 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
164 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
165 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
166 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
167 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
170 // Bonus for unstoppable passed pawns
171 const Value UnstoppablePawnValue = Value(0x500);
173 // Rooks and queens on the 7th rank (modified by Joona Kiiski)
174 const Value MidgameRookOn7thBonus = Value(47);
175 const Value EndgameRookOn7thBonus = Value(98);
176 const Value MidgameQueenOn7thBonus = Value(27);
177 const Value EndgameQueenOn7thBonus = Value(54);
179 // Rooks on open files (modified by Joona Kiiski)
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<bool HasPopCnt>
272 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID);
274 template<PieceType Piece, bool HasPopCnt>
275 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
277 template<bool HasPopCnt>
278 void evaluate_king(const Position& p, Color us, EvalInfo &ei);
280 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
281 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
283 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
286 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
287 inline Value apply_weight(Value v, int w);
288 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
290 int compute_weight(int uciWeight, int internalWeight);
291 int weight_option(const std::string& opt, int weight);
301 /// evaluate() is the main evaluation function. It always computes two
302 /// values, an endgame score and a middle game score, and interpolates
303 /// between them based on the remaining material.
304 Value evaluate(const Position& pos, EvalInfo& ei, int threadID) {
306 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei, threadID)
307 : do_evaluate<false>(pos, ei, threadID);
312 template<bool HasPopCnt>
313 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
316 assert(threadID >= 0 && threadID < THREAD_MAX);
318 memset(&ei, 0, sizeof(EvalInfo));
320 // Initialize by reading the incrementally updated scores included in the
321 // position object (material + piece square tables)
322 ei.mgValue = pos.mg_value();
323 ei.egValue = pos.eg_value();
325 // Probe the material hash table
326 ei.mi = MaterialTable[threadID]->get_material_info(pos);
327 ei.mgValue += ei.mi->mg_value();
328 ei.egValue += ei.mi->eg_value();
330 // If we have a specialized evaluation function for the current material
331 // configuration, call it and return
332 if (ei.mi->specialized_eval_exists())
333 return ei.mi->evaluate(pos);
335 // After get_material_info() call that modifies them
336 ScaleFactor factor[2];
337 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
338 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
340 // Probe the pawn hash table
341 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
342 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
343 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
345 // Initialize king attack bitboards and king attack zones for both sides
346 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
347 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
348 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
349 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
351 // Initialize pawn attack bitboards for both sides
352 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
353 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
354 ei.kingAttackersCount[WHITE] = count_1s_max_15<HasPopCnt>(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
355 ei.kingAttackersCount[BLACK] = count_1s_max_15<HasPopCnt>(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
358 for (Color c = WHITE; c <= BLACK; c++)
360 evaluate_pieces<KNIGHT, HasPopCnt>(pos, c, ei);
361 evaluate_pieces<BISHOP, HasPopCnt>(pos, c, ei);
362 evaluate_pieces<ROOK, HasPopCnt>(pos, c, ei);
363 evaluate_pieces<QUEEN, HasPopCnt>(pos, c, ei);
365 // Sum up all attacked squares
366 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
367 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
368 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
371 // Kings. Kings are evaluated after all other pieces for both sides,
372 // because we need complete attack information for all pieces when computing
373 // the king safety evaluation.
374 for (Color c = WHITE; c <= BLACK; c++)
375 evaluate_king<HasPopCnt>(pos, c, ei);
377 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
378 // because we need to know which side promotes first in positions where
379 // both sides have an unstoppable passed pawn.
380 if (ei.pi->passed_pawns())
381 evaluate_passed_pawns(pos, ei);
383 Phase phase = pos.game_phase();
385 // Middle-game specific evaluation terms
386 if (phase > PHASE_ENDGAME)
388 // Pawn storms in positions with opposite castling.
389 if ( square_file(pos.king_square(WHITE)) >= FILE_E
390 && square_file(pos.king_square(BLACK)) <= FILE_D)
392 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
393 - ei.pi->kingside_storm_value(BLACK);
395 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
396 && square_file(pos.king_square(BLACK)) >= FILE_E)
398 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
399 - ei.pi->queenside_storm_value(BLACK);
401 // Evaluate space for both sides
402 if (ei.mi->space_weight() > 0)
404 evaluate_space(pos, WHITE, ei);
405 evaluate_space(pos, BLACK, ei);
410 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
411 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
413 // If we don't already have an unusual scale factor, check for opposite
414 // colored bishop endgames, and use a lower scale for those
415 if ( phase < PHASE_MIDGAME
416 && pos.opposite_colored_bishops()
417 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
418 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
422 // Only the two bishops ?
423 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
424 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
426 // Check for KBP vs KB with only a single pawn that is almost
427 // certainly a draw or at least two pawns.
428 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
429 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
432 // Endgame with opposite-colored bishops, but also other pieces. Still
433 // a bit drawish, but not as drawish as with only the two bishops.
434 sf = ScaleFactor(50);
436 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
438 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
442 // Interpolate between the middle game and the endgame score, and
444 Color stm = pos.side_to_move();
446 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
448 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
453 /// quick_evaluate() does a very approximate evaluation of the current position.
454 /// It currently considers only material and piece square table scores. Perhaps
455 /// we should add scores from the pawn and material hash tables?
457 Value quick_evaluate(const Position &pos) {
462 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
464 Value mgv = pos.mg_value();
465 Value egv = pos.eg_value();
466 Phase ph = pos.game_phase();
467 Color stm = pos.side_to_move();
469 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
473 /// init_eval() initializes various tables used by the evaluation function.
475 void init_eval(int threads) {
477 assert(threads <= THREAD_MAX);
479 for (int i = 0; i < THREAD_MAX; i++)
484 delete MaterialTable[i];
486 MaterialTable[i] = NULL;
490 PawnTable[i] = new PawnInfoTable(PawnTableSize);
491 if (!MaterialTable[i])
492 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
495 for (Bitboard b = 0ULL; b < 256ULL; b++)
497 assert(count_1s(b) == int(uint8_t(count_1s(b))));
498 BitCount8Bit[b] = (uint8_t)count_1s(b);
503 /// quit_eval() releases heap-allocated memory at program termination.
507 for (int i = 0; i < THREAD_MAX; i++)
510 delete MaterialTable[i];
512 MaterialTable[i] = NULL;
517 /// read_weights() reads evaluation weights from the corresponding UCI
520 void read_weights(Color us) {
522 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
523 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
524 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
525 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
526 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
527 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
529 Color them = opposite_color(us);
531 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
532 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
533 WeightSpace = weight_option("Space", WeightSpaceInternal);
541 // evaluate_mobility() computes mobility and attacks for every piece
543 template<PieceType Piece, bool HasPopCnt>
544 int evaluate_mobility(const Position& p, const Bitboard& b, Color us, Color them, EvalInfo& ei) {
546 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
547 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
548 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
550 // Update attack info
551 ei.attackedBy[us][Piece] |= b;
554 if (b & ei.kingZone[us])
556 ei.kingAttackersCount[us]++;
557 ei.kingAttackersWeight[us] += AttackWeight[Piece];
558 Bitboard bb = (b & ei.attackedBy[them][KING]);
560 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15<HasPopCnt>(bb);
563 // Remove squares protected by enemy pawns
564 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
567 int mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(bb & ~p.pieces_of_color(us))
568 : count_1s<HasPopCnt>(bb & ~p.pieces_of_color(us)));
570 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
571 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
576 // evaluate_outposts() evaluates bishop and knight outposts squares
578 template<PieceType Piece>
579 void evaluate_outposts(const Position& p, Color us, Color them, EvalInfo& ei, Square s) {
581 // Initial bonus based on square
582 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(us, s)]
583 : KnightOutpostBonus[relative_square(us, s)]);
585 // Increase bonus if supported by pawn, especially if the opponent has
586 // no minor piece which can exchange the outpost piece
587 if (bonus && (p.pawn_attacks(them, s) & p.pawns(us)))
589 if ( p.knights(them) == EmptyBoardBB
590 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
591 bonus += bonus + bonus / 2;
595 ei.mgValue += Sign[us] * bonus;
596 ei.egValue += Sign[us] * bonus;
600 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
603 template<PieceType Piece, bool HasPopCnt>
604 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
610 Color them = opposite_color(us);
612 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
614 s = pos.piece_list(us, Piece, i);
616 if (Piece == KNIGHT || Piece == QUEEN)
617 b = pos.piece_attacks<Piece>(s);
618 else if (Piece == BISHOP)
619 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
620 else if (Piece == ROOK)
621 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
625 // Attacks and mobility
626 mob = evaluate_mobility<Piece, HasPopCnt>(pos, b, us, them, ei);
628 // Bishop and knight outposts squares
629 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, them))
630 evaluate_outposts<Piece>(pos, us, them, ei, s);
632 // Special patterns: trapped bishops on a7/h7/a2/h2
633 // and trapped bishops on a1/h1/a8/h8 in Chess960.
636 if (bit_is_set(MaskA7H7[us], s))
637 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
639 if (Chess960 && bit_is_set(MaskA1H1[us], s))
640 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
643 if (Piece == ROOK || Piece == QUEEN)
645 // Queen or rook on 7th rank
646 if ( relative_rank(us, s) == RANK_7
647 && relative_rank(us, pos.king_square(them)) == RANK_8)
649 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
650 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
654 // Special extra evaluation for rooks
657 // Open and half-open files
659 if (ei.pi->file_is_half_open(us, f))
661 if (ei.pi->file_is_half_open(them, f))
663 ei.mgValue += Sign[us] * RookOpenFileBonus;
664 ei.egValue += Sign[us] * RookOpenFileBonus;
668 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
669 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
673 // Penalize rooks which are trapped inside a king. Penalize more if
674 // king has lost right to castle.
675 if (mob > 6 || ei.pi->file_is_half_open(us, f))
678 ksq = pos.king_square(us);
680 if ( square_file(ksq) >= FILE_E
681 && square_file(s) > square_file(ksq)
682 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
684 // Is there a half-open file between the king and the edge of the board?
685 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
686 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
687 : Sign[us] * (TrappedRookPenalty - mob * 16);
689 else if ( square_file(ksq) <= FILE_D
690 && square_file(s) < square_file(ksq)
691 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
693 // Is there a half-open file between the king and the edge of the board?
694 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
695 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
696 : Sign[us] * (TrappedRookPenalty - mob * 16);
702 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
704 return b >> (num << 3);
707 // evaluate_king<>() assigns bonuses and penalties to a king of a given color.
709 template<bool HasPopCnt>
710 void evaluate_king(const Position& p, Color us, EvalInfo& ei) {
712 int shelter = 0, sign = Sign[us];
713 Square s = p.king_square(us);
716 if (relative_rank(us, s) <= RANK_4)
718 // Shelter cache lookup
719 shelter = ei.pi->kingShelter(us, s);
723 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
724 Rank r = square_rank(s);
725 for (int i = 1; i < 4; i++)
726 shelter += BitCount8Bit[shiftRowsDown(pawns, r+i*sign) & 0xFF] * (128 >> i);
728 // Cache shelter value in pawn info
729 ei.pi->setKingShelter(us, s, shelter);
731 ei.mgValue += sign * Value(shelter);
734 // King safety. This is quite complicated, and is almost certainly far
735 // from optimally tuned.
736 Color them = opposite_color(us);
738 if ( p.piece_count(them, QUEEN) >= 1
739 && ei.kingAttackersCount[them] >= 2
740 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
741 && ei.kingAdjacentZoneAttacksCount[them])
743 // Is it the attackers turn to move?
744 bool sente = (them == p.side_to_move());
746 // Find the attacked squares around the king which has no defenders
747 // apart from the king itself
748 Bitboard undefended =
749 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
750 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
751 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
752 & ei.attacked_by(us, KING);
754 Bitboard occ = p.occupied_squares(), b, b2;
756 // Initialize the 'attackUnits' variable, which is used later on as an
757 // index to the SafetyTable[] array. The initial value is based on the
758 // number and types of the attacking pieces, the number of attacked and
759 // undefended squares around the king, the square of the king, and the
760 // quality of the pawn shelter.
762 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
763 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15<HasPopCnt>(undefended)) * 3
764 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
766 // Analyse safe queen contact checks
767 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
770 Bitboard attackedByOthers =
771 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
772 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
774 b &= attackedByOthers;
777 // The bitboard b now contains the squares available for safe queen
779 int count = count_1s_max_15<HasPopCnt>(b);
780 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
782 // Is there a mate threat?
783 if (QueenContactMates && !p.is_check())
785 Bitboard escapeSquares =
786 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
790 Square from, to = pop_1st_bit(&b);
791 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
793 // We have a mate, unless the queen is pinned or there
794 // is an X-ray attack through the queen.
795 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
797 from = p.piece_list(them, QUEEN, i);
798 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
799 && !bit_is_set(p.pinned_pieces(them), from)
800 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
801 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
803 ei.mateThreat[them] = make_move(from, to);
811 // Analyse safe distance checks
812 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
814 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
817 b2 = b & ei.attacked_by(them, QUEEN);
819 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
822 b2 = b & ei.attacked_by(them, ROOK);
824 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b2);
826 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
828 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
831 b2 = b & ei.attacked_by(them, QUEEN);
833 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
836 b2 = b & ei.attacked_by(them, BISHOP);
838 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b2);
840 if (KnightCheckBonus > 0)
842 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
845 b2 = b & ei.attacked_by(them, KNIGHT);
847 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b2);
850 // Analyse discovered checks (only for non-pawns right now, consider
851 // adding pawns later).
852 if (DiscoveredCheckBonus)
854 b = p.discovered_check_candidates(them) & ~p.pawns();
856 attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente? 2 : 1);
859 // Has a mate threat been found? We don't do anything here if the
860 // side with the mating move is the side to move, because in that
861 // case the mating side will get a huge bonus at the end of the main
862 // evaluation function instead.
863 if (ei.mateThreat[them] != MOVE_NONE)
864 attackUnits += MateThreatBonus;
866 // Ensure that attackUnits is between 0 and 99, in order to avoid array
867 // out of bounds errors:
871 if (attackUnits >= 100)
874 // Finally, extract the king safety score from the SafetyTable[] array.
875 // Add the score to the evaluation, and also to ei.futilityMargin. The
876 // reason for adding the king safety score to the futility margin is
877 // that the king safety scores can sometimes be very big, and that
878 // capturing a single attacking piece can therefore result in a score
879 // change far bigger than the value of the captured piece.
880 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
882 ei.mgValue -= sign * v;
884 if (us == p.side_to_move())
885 ei.futilityMargin += v;
890 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
892 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
894 bool hasUnstoppable[2] = {false, false};
895 int movesToGo[2] = {100, 100};
897 for (Color us = WHITE; us <= BLACK; us++)
899 Color them = opposite_color(us);
900 Square ourKingSq = pos.king_square(us);
901 Square theirKingSq = pos.king_square(them);
902 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
906 Square s = pop_1st_bit(&b);
908 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
909 assert(pos.pawn_is_passed(us, s));
911 int r = int(relative_rank(us, s) - RANK_2);
912 int tr = Max(0, r * (r - 1));
913 Square blockSq = s + pawn_push(us);
915 // Base bonus based on rank
916 Value mbonus = Value(20 * tr);
917 Value ebonus = Value(10 + r * r * 10);
919 // Adjust bonus based on king proximity
922 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
923 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
924 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
926 // If the pawn is free to advance, increase bonus
927 if (pos.square_is_empty(blockSq))
929 b2 = squares_in_front_of(us, s);
930 b3 = b2 & ei.attacked_by(them);
931 b4 = b2 & ei.attacked_by(us);
933 // If there is an enemy rook or queen attacking the pawn from behind,
934 // add all X-ray attacks by the rook or queen.
935 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
936 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
939 // Squares attacked or occupied by enemy pieces
940 b3 |= (b2 & pos.pieces_of_color(them));
942 // There are no enemy pawns in the pawn's path
943 assert((b2 & pos.pieces_of_color_and_type(them, PAWN)) == EmptyBoardBB);
945 // Are any of the squares in the pawn's path attacked or occupied by the enemy?
946 if (b3 == EmptyBoardBB)
947 // No enemy attacks or pieces, huge bonus!
948 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
950 // OK, there are enemy attacks or pieces (but not pawns). Are those
951 // squares which are attacked by the enemy also attacked by us?
952 // If yes, big bonus (but smaller than when there are no enemy attacks),
953 // if no, somewhat smaller bonus.
954 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
956 // At last, add a small bonus when there are no *friendly* pieces
957 // in the pawn's path.
958 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
963 // If the pawn is supported by a friendly pawn, increase bonus
964 b2 = pos.pawns(us) & neighboring_files_bb(s);
966 ebonus += Value(r * 20);
967 else if (pos.pawn_attacks(them, s) & b2)
968 ebonus += Value(r * 12);
970 // If the other side has only a king, check whether the pawn is
972 if (pos.non_pawn_material(them) == Value(0))
977 qsq = relative_square(us, make_square(square_file(s), RANK_8));
978 d = square_distance(s, qsq)
979 - square_distance(theirKingSq, qsq)
980 + (us != pos.side_to_move());
984 int mtg = RANK_8 - relative_rank(us, s);
985 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
990 hasUnstoppable[us] = true;
991 movesToGo[us] = Min(movesToGo[us], mtg);
995 // Rook pawns are a special case: They are sometimes worse, and
996 // sometimes better than other passed pawns. It is difficult to find
997 // good rules for determining whether they are good or bad. For now,
998 // we try the following: Increase the value for rook pawns if the
999 // other side has no pieces apart from a knight, and decrease the
1000 // value if the other side has a rook or queen.
1001 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
1003 if ( pos.non_pawn_material(them) <= KnightValueMidgame
1004 && pos.piece_count(them, KNIGHT) <= 1)
1005 ebonus += ebonus / 4;
1006 else if (pos.rooks_and_queens(them))
1007 ebonus -= ebonus / 4;
1010 // Add the scores for this pawn to the middle game and endgame eval.
1011 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1012 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1016 // Does either side have an unstoppable passed pawn?
1017 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1018 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1019 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1020 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1021 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1023 // Both sides have unstoppable pawns! Try to find out who queens
1024 // first. We begin by transforming 'movesToGo' to the number of
1025 // plies until the pawn queens for both sides.
1026 movesToGo[WHITE] *= 2;
1027 movesToGo[BLACK] *= 2;
1028 movesToGo[pos.side_to_move()]--;
1030 // If one side queens at least three plies before the other, that
1032 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1033 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1034 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1035 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1037 // We could also add some rules about the situation when one side
1038 // queens exactly one ply before the other: Does the first queen
1039 // check the opponent's king, or attack the opponent's queening square?
1040 // This is slightly tricky to get right, because it is possible that
1041 // the opponent's king has moved somewhere before the first pawn queens.
1046 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1047 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1050 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1052 assert(square_is_ok(s));
1053 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1055 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1056 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1058 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1059 && pos.see(s, b6) < 0
1060 && pos.see(s, b8) < 0)
1062 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1063 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1068 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1069 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1070 // black), and assigns a penalty if it is. This pattern can obviously
1071 // only occur in Chess960 games.
1073 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1075 Piece pawn = piece_of_color_and_type(us, PAWN);
1079 assert(square_is_ok(s));
1080 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1082 if (square_file(s) == FILE_A)
1084 b2 = relative_square(us, SQ_B2);
1085 b3 = relative_square(us, SQ_B3);
1086 c3 = relative_square(us, SQ_C3);
1090 b2 = relative_square(us, SQ_G2);
1091 b3 = relative_square(us, SQ_G3);
1092 c3 = relative_square(us, SQ_F3);
1095 if (pos.piece_on(b2) == pawn)
1099 if (!pos.square_is_empty(b3))
1100 penalty = 2*TrappedBishopA1H1Penalty;
1101 else if (pos.piece_on(c3) == pawn)
1102 penalty = TrappedBishopA1H1Penalty;
1104 penalty = TrappedBishopA1H1Penalty / 2;
1106 ei.mgValue -= Sign[us] * penalty;
1107 ei.egValue -= Sign[us] * penalty;
1112 // evaluate_space() computes the space evaluation for a given side. The
1113 // space evaluation is a simple bonus based on the number of safe squares
1114 // available for minor pieces on the central four files on ranks 2--4. Safe
1115 // squares one, two or three squares behind a friendly pawn are counted
1116 // twice. Finally, the space bonus is scaled by a weight taken from the
1117 // material hash table.
1119 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1121 Color them = opposite_color(us);
1123 // Find the safe squares for our pieces inside the area defined by
1124 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1125 // pawn, or if it is undefended and attacked by an enemy piece.
1127 Bitboard safeSquares = SpaceMask[us]
1129 & ~ei.attacked_by(them, PAWN)
1130 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1132 // Find all squares which are at most three squares behind some friendly
1134 Bitboard behindFriendlyPawns = pos.pawns(us);
1137 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1138 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1142 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1143 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1146 int space = count_1s_max_15(safeSquares)
1147 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1149 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1153 // apply_weight() applies an evaluation weight to a value
1155 inline Value apply_weight(Value v, int w) {
1156 return (v*w) / 0x100;
1160 // scale_by_game_phase() interpolates between a middle game and an endgame
1161 // score, based on game phase. It also scales the return value by a
1162 // ScaleFactor array.
1164 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1166 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1167 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1168 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1170 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1172 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1173 return Value(int(result) & ~(GrainSize - 1));
1177 // compute_weight() computes the value of an evaluation weight, by combining
1178 // an UCI-configurable weight with an internal weight.
1180 int compute_weight(int uciWeight, int internalWeight) {
1182 uciWeight = (uciWeight * 0x100) / 100;
1183 return (uciWeight * internalWeight) / 0x100;
1187 // helper used in read_weights()
1188 int weight_option(const std::string& opt, int weight) {
1190 return compute_weight(get_option_value_int(opt), weight);
1194 // init_safety() initizes the king safety evaluation, based on UCI
1195 // parameters. It is called from read_weights().
1197 void init_safety() {
1199 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1200 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1201 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1202 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1203 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1204 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1205 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1207 int maxSlope = get_option_value_int("King Safety Max Slope");
1208 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1209 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1210 double b = get_option_value_int("King Safety X Intercept");
1211 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1212 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1214 for (int i = 0; i < 100; i++)
1217 SafetyTable[i] = Value(0);
1219 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1221 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1224 for (int i = 0; i < 100; i++)
1226 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1227 for (int j = i + 1; j < 100; j++)
1228 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1230 if (SafetyTable[i] > Value(peak))
1231 SafetyTable[i] = Value(peak);