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
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
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);
278 void evaluate_pieces<KING, false>(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_pieces<KING, false>(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_common() computes terms common to all pieces attack
543 template<PieceType Piece, bool HasPopCnt>
544 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
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 };
549 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
551 Color them = opposite_color(us);
553 // Update attack info
554 ei.attackedBy[us][Piece] |= b;
557 if (b & ei.kingZone[us])
559 ei.kingAttackersCount[us]++;
560 ei.kingAttackersWeight[us] += AttackWeight[Piece];
561 Bitboard bb = (b & ei.attackedBy[them][KING]);
563 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15<HasPopCnt>(bb);
566 // Remove squares protected by enemy pawns
567 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
570 int mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(bb & ~p.pieces_of_color(us))
571 : count_1s<HasPopCnt>(bb & ~p.pieces_of_color(us)));
573 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
574 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
576 // Bishop and Knight outposts
577 if ( (Piece == BISHOP || Piece == KNIGHT) // compile time condition
578 && p.square_is_weak(s, them))
580 // Initial bonus based on square
582 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
584 // Increase bonus if supported by pawn, especially if the opponent has
585 // no minor piece which can exchange the outpost piece
586 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
589 if ( p.piece_count(them, KNIGHT) == 0
590 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
593 ei.mgValue += Sign[us] * bonus;
594 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) {
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));
623 // Attacks, mobility and outposts
624 mob = evaluate_common<Piece, HasPopCnt>(pos, b, us, ei, s);
626 // Special patterns: trapped bishops on a7/h7/a2/h2
627 // and trapped bishops on a1/h1/a8/h8 in Chess960.
630 if (bit_is_set(MaskA7H7[us], s))
631 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
633 if (Chess960 && bit_is_set(MaskA1H1[us], s))
634 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
637 if (Piece == ROOK || Piece == QUEEN)
639 // Queen or rook on 7th rank
640 them = opposite_color(us);
642 if ( relative_rank(us, s) == RANK_7
643 && relative_rank(us, pos.king_square(them)) == RANK_8)
645 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
646 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
650 // Special extra evaluation for rooks
653 // Open and half-open files
655 if (ei.pi->file_is_half_open(us, f))
657 if (ei.pi->file_is_half_open(them, f))
659 ei.mgValue += Sign[us] * RookOpenFileBonus;
660 ei.egValue += Sign[us] * RookOpenFileBonus;
664 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
665 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
669 // Penalize rooks which are trapped inside a king. Penalize more if
670 // king has lost right to castle.
671 if (mob > 6 || ei.pi->file_is_half_open(us, f))
674 ksq = pos.king_square(us);
676 if ( square_file(ksq) >= FILE_E
677 && square_file(s) > square_file(ksq)
678 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
680 // Is there a half-open file between the king and the edge of the board?
681 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
682 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
683 : Sign[us] * (TrappedRookPenalty - mob * 16);
685 else if ( square_file(ksq) <= FILE_D
686 && square_file(s) < square_file(ksq)
687 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
689 // Is there a half-open file between the king and the edge of the board?
690 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
691 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
692 : Sign[us] * (TrappedRookPenalty - mob * 16);
698 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
700 return b >> (num << 3);
703 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
707 void evaluate_pieces<KING, false>(const Position& p, Color us, EvalInfo& ei) {
709 int shelter = 0, sign = Sign[us];
710 Square s = p.king_square(us);
713 if (relative_rank(us, s) <= RANK_4)
715 // Shelter cache lookup
716 shelter = ei.pi->kingShelter(us, s);
720 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
721 Rank r = square_rank(s);
722 for (int i = 1; i < 4; i++)
723 shelter += BitCount8Bit[shiftRowsDown(pawns, r+i*sign) & 0xFF] * (128 >> i);
725 // Cache shelter value in pawn info
726 ei.pi->setKingShelter(us, s, shelter);
728 ei.mgValue += sign * Value(shelter);
731 // King safety. This is quite complicated, and is almost certainly far
732 // from optimally tuned.
733 Color them = opposite_color(us);
735 if ( p.piece_count(them, QUEEN) >= 1
736 && ei.kingAttackersCount[them] >= 2
737 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
738 && ei.kingAdjacentZoneAttacksCount[them])
740 // Is it the attackers turn to move?
741 bool sente = (them == p.side_to_move());
743 // Find the attacked squares around the king which has no defenders
744 // apart from the king itself
745 Bitboard undefended =
746 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
747 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
748 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
749 & ei.attacked_by(us, KING);
751 Bitboard occ = p.occupied_squares(), b, b2;
753 // Initialize the 'attackUnits' variable, which is used later on as an
754 // index to the SafetyTable[] array. The initial value is based on the
755 // number and types of the attacking pieces, the number of attacked and
756 // undefended squares around the king, the square of the king, and the
757 // quality of the pawn shelter.
759 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
760 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
761 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
763 // Analyse safe queen contact checks
764 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
767 Bitboard attackedByOthers =
768 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
769 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
771 b &= attackedByOthers;
774 // The bitboard b now contains the squares available for safe queen
776 int count = count_1s_max_15(b);
777 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
779 // Is there a mate threat?
780 if (QueenContactMates && !p.is_check())
782 Bitboard escapeSquares =
783 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
787 Square from, to = pop_1st_bit(&b);
788 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
790 // We have a mate, unless the queen is pinned or there
791 // is an X-ray attack through the queen.
792 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
794 from = p.piece_list(them, QUEEN, i);
795 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
796 && !bit_is_set(p.pinned_pieces(them), from)
797 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
798 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
800 ei.mateThreat[them] = make_move(from, to);
808 // Analyse safe distance checks
809 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
811 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
814 b2 = b & ei.attacked_by(them, QUEEN);
816 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
819 b2 = b & ei.attacked_by(them, ROOK);
821 attackUnits += RookCheckBonus * count_1s_max_15(b2);
823 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
825 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
828 b2 = b & ei.attacked_by(them, QUEEN);
830 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
833 b2 = b & ei.attacked_by(them, BISHOP);
835 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
837 if (KnightCheckBonus > 0)
839 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
842 b2 = b & ei.attacked_by(them, KNIGHT);
844 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
847 // Analyse discovered checks (only for non-pawns right now, consider
848 // adding pawns later).
849 if (DiscoveredCheckBonus)
851 b = p.discovered_check_candidates(them) & ~p.pawns();
853 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
856 // Has a mate threat been found? We don't do anything here if the
857 // side with the mating move is the side to move, because in that
858 // case the mating side will get a huge bonus at the end of the main
859 // evaluation function instead.
860 if (ei.mateThreat[them] != MOVE_NONE)
861 attackUnits += MateThreatBonus;
863 // Ensure that attackUnits is between 0 and 99, in order to avoid array
864 // out of bounds errors:
868 if (attackUnits >= 100)
871 // Finally, extract the king safety score from the SafetyTable[] array.
872 // Add the score to the evaluation, and also to ei.futilityMargin. The
873 // reason for adding the king safety score to the futility margin is
874 // that the king safety scores can sometimes be very big, and that
875 // capturing a single attacking piece can therefore result in a score
876 // change far bigger than the value of the captured piece.
877 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
879 ei.mgValue -= sign * v;
881 if (us == p.side_to_move())
882 ei.futilityMargin += v;
887 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
889 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
891 bool hasUnstoppable[2] = {false, false};
892 int movesToGo[2] = {100, 100};
894 for (Color us = WHITE; us <= BLACK; us++)
896 Color them = opposite_color(us);
897 Square ourKingSq = pos.king_square(us);
898 Square theirKingSq = pos.king_square(them);
899 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
903 Square s = pop_1st_bit(&b);
905 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
906 assert(pos.pawn_is_passed(us, s));
908 int r = int(relative_rank(us, s) - RANK_2);
909 int tr = Max(0, r * (r - 1));
910 Square blockSq = s + pawn_push(us);
912 // Base bonus based on rank
913 Value mbonus = Value(20 * tr);
914 Value ebonus = Value(10 + r * r * 10);
916 // Adjust bonus based on king proximity
919 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
920 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
921 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
923 // If the pawn is free to advance, increase bonus
924 if (pos.square_is_empty(blockSq))
926 b2 = squares_in_front_of(us, s);
927 b3 = b2 & ei.attacked_by(them);
928 b4 = b2 & ei.attacked_by(us);
930 // If there is an enemy rook or queen attacking the pawn from behind,
931 // add all X-ray attacks by the rook or queen.
932 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
933 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
936 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
938 // There are no enemy pieces in the pawn's path! Are any of the
939 // squares in the pawn's path attacked by the enemy?
940 if (b3 == EmptyBoardBB)
941 // No enemy attacks, huge bonus!
942 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
944 // OK, there are enemy attacks. Are those squares which are
945 // attacked by the enemy also attacked by us? If yes, big bonus
946 // (but smaller than when there are no enemy attacks), if no,
947 // somewhat smaller bonus.
948 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
952 // There are some enemy pieces in the pawn's path. While this is
953 // sad, we still assign a moderate bonus if all squares in the path
954 // which are either occupied by or attacked by enemy pieces are
955 // also attacked by us.
956 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
957 ebonus += Value(tr * 6);
959 // At last, add a small bonus when there are no *friendly* pieces
960 // in the pawn's path.
961 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
966 // If the pawn is supported by a friendly pawn, increase bonus
967 b2 = pos.pawns(us) & neighboring_files_bb(s);
969 ebonus += Value(r * 20);
970 else if (pos.pawn_attacks(them, s) & b2)
971 ebonus += Value(r * 12);
973 // If the other side has only a king, check whether the pawn is
975 if (pos.non_pawn_material(them) == Value(0))
980 qsq = relative_square(us, make_square(square_file(s), RANK_8));
981 d = square_distance(s, qsq)
982 - square_distance(theirKingSq, qsq)
983 + (us != pos.side_to_move());
987 int mtg = RANK_8 - relative_rank(us, s);
988 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
993 hasUnstoppable[us] = true;
994 movesToGo[us] = Min(movesToGo[us], mtg);
998 // Rook pawns are a special case: They are sometimes worse, and
999 // sometimes better than other passed pawns. It is difficult to find
1000 // good rules for determining whether they are good or bad. For now,
1001 // we try the following: Increase the value for rook pawns if the
1002 // other side has no pieces apart from a knight, and decrease the
1003 // value if the other side has a rook or queen.
1004 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
1006 if( pos.non_pawn_material(them) <= KnightValueMidgame
1007 && pos.piece_count(them, KNIGHT) <= 1)
1008 ebonus += ebonus / 4;
1009 else if(pos.rooks_and_queens(them))
1010 ebonus -= ebonus / 4;
1013 // Add the scores for this pawn to the middle game and endgame eval.
1014 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1015 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1019 // Does either side have an unstoppable passed pawn?
1020 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1021 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1022 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1023 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1024 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1026 // Both sides have unstoppable pawns! Try to find out who queens
1027 // first. We begin by transforming 'movesToGo' to the number of
1028 // plies until the pawn queens for both sides.
1029 movesToGo[WHITE] *= 2;
1030 movesToGo[BLACK] *= 2;
1031 movesToGo[pos.side_to_move()]--;
1033 // If one side queens at least three plies before the other, that
1035 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1036 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1037 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1038 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1040 // We could also add some rules about the situation when one side
1041 // queens exactly one ply before the other: Does the first queen
1042 // check the opponent's king, or attack the opponent's queening square?
1043 // This is slightly tricky to get right, because it is possible that
1044 // the opponent's king has moved somewhere before the first pawn queens.
1049 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1050 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1053 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1055 assert(square_is_ok(s));
1056 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1058 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1059 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1061 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1062 && pos.see(s, b6) < 0
1063 && pos.see(s, b8) < 0)
1065 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1066 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1071 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1072 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1073 // black), and assigns a penalty if it is. This pattern can obviously
1074 // only occur in Chess960 games.
1076 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1078 Piece pawn = piece_of_color_and_type(us, PAWN);
1082 assert(square_is_ok(s));
1083 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1085 if (square_file(s) == FILE_A)
1087 b2 = relative_square(us, SQ_B2);
1088 b3 = relative_square(us, SQ_B3);
1089 c3 = relative_square(us, SQ_C3);
1093 b2 = relative_square(us, SQ_G2);
1094 b3 = relative_square(us, SQ_G3);
1095 c3 = relative_square(us, SQ_F3);
1098 if (pos.piece_on(b2) == pawn)
1102 if (!pos.square_is_empty(b3))
1103 penalty = 2*TrappedBishopA1H1Penalty;
1104 else if (pos.piece_on(c3) == pawn)
1105 penalty = TrappedBishopA1H1Penalty;
1107 penalty = TrappedBishopA1H1Penalty / 2;
1109 ei.mgValue -= Sign[us] * penalty;
1110 ei.egValue -= Sign[us] * penalty;
1115 // evaluate_space() computes the space evaluation for a given side. The
1116 // space evaluation is a simple bonus based on the number of safe squares
1117 // available for minor pieces on the central four files on ranks 2--4. Safe
1118 // squares one, two or three squares behind a friendly pawn are counted
1119 // twice. Finally, the space bonus is scaled by a weight taken from the
1120 // material hash table.
1122 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1124 Color them = opposite_color(us);
1126 // Find the safe squares for our pieces inside the area defined by
1127 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1128 // pawn, or if it is undefended and attacked by an enemy piece.
1130 Bitboard safeSquares = SpaceMask[us]
1132 & ~ei.attacked_by(them, PAWN)
1133 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1135 // Find all squares which are at most three squares behind some friendly
1137 Bitboard behindFriendlyPawns = pos.pawns(us);
1140 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1141 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1145 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1146 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1149 int space = count_1s_max_15(safeSquares)
1150 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1152 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1156 // apply_weight() applies an evaluation weight to a value
1158 inline Value apply_weight(Value v, int w) {
1159 return (v*w) / 0x100;
1163 // scale_by_game_phase() interpolates between a middle game and an endgame
1164 // score, based on game phase. It also scales the return value by a
1165 // ScaleFactor array.
1167 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1169 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1170 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1171 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1173 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1175 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1176 return Value(int(result) & ~(GrainSize - 1));
1180 // compute_weight() computes the value of an evaluation weight, by combining
1181 // an UCI-configurable weight with an internal weight.
1183 int compute_weight(int uciWeight, int internalWeight) {
1185 uciWeight = (uciWeight * 0x100) / 100;
1186 return (uciWeight * internalWeight) / 0x100;
1190 // helper used in read_weights()
1191 int weight_option(const std::string& opt, int weight) {
1193 return compute_weight(get_option_value_int(opt), weight);
1197 // init_safety() initizes the king safety evaluation, based on UCI
1198 // parameters. It is called from read_weights().
1200 void init_safety() {
1202 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1203 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1204 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1205 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1206 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1207 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1208 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1210 int maxSlope = get_option_value_int("King Safety Max Slope");
1211 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1212 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1213 double b = get_option_value_int("King Safety X Intercept");
1214 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1215 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1217 for (int i = 0; i < 100; i++)
1220 SafetyTable[i] = Value(0);
1222 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1224 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1227 for (int i = 0; i < 100; i++)
1229 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1230 for (int j = i + 1; j < 100; j++)
1231 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1233 if (SafetyTable[i] > Value(peak))
1234 SafetyTable[i] = Value(peak);