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 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;
48 int WeightMobilityMidgame = 0x100;
49 int WeightMobilityEndgame = 0x100;
50 int WeightPawnStructureMidgame = 0x100;
51 int WeightPawnStructureEndgame = 0x100;
52 int WeightPassedPawnsMidgame = 0x100;
53 int WeightPassedPawnsEndgame = 0x100;
54 int WeightKingSafety[2] = { 0x100, 0x100 };
57 // Internal evaluation weights. These are applied on top of the evaluation
58 // weights read from UCI parameters. The purpose is to be able to change
59 // the evaluation weights while keeping the default values of the UCI
60 // parameters at 100, which looks prettier.
61 const int WeightMobilityMidgameInternal = 0x100;
62 const int WeightMobilityEndgameInternal = 0x100;
63 const int WeightPawnStructureMidgameInternal = 0x100;
64 const int WeightPawnStructureEndgameInternal = 0x100;
65 const int WeightPassedPawnsMidgameInternal = 0x100;
66 const int WeightPassedPawnsEndgameInternal = 0x100;
67 const int WeightKingSafetyInternal = 0x110;
68 const int WeightKingOppSafetyInternal = 0x110;
69 const int WeightSpaceInternal = 0x30;
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(50);
175 const Value EndgameRookOn7thBonus = Value(100);
176 const Value MidgameQueenOn7thBonus = Value(25);
177 const Value EndgameQueenOn7thBonus = Value(50);
179 // Rooks on open files:
180 const Value RookOpenFileBonus = Value(40);
181 const Value RookHalfOpenFileBonus = Value(20);
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 for each piece type.
233 int QueenContactCheckBonus = 3;
234 int QueenCheckBonus = 2;
235 int RookCheckBonus = 1;
236 int BishopCheckBonus = 1;
237 int KnightCheckBonus = 1;
238 int DiscoveredCheckBonus = 3;
240 // Scan for queen contact mates?
241 const bool QueenContactMates = true;
243 // Bonus for having a mate threat.
244 int MateThreatBonus = 3;
246 // InitKingDanger[] contains bonuses based on the position of the defending
248 const int InitKingDanger[64] = {
249 2, 0, 2, 5, 5, 2, 0, 2,
250 2, 2, 4, 8, 8, 4, 2, 2,
251 7, 10, 12, 12, 12, 12, 10, 7,
252 15, 15, 15, 15, 15, 15, 15, 15,
253 15, 15, 15, 15, 15, 15, 15, 15,
254 15, 15, 15, 15, 15, 15, 15, 15,
255 15, 15, 15, 15, 15, 15, 15, 15,
256 15, 15, 15, 15, 15, 15, 15, 15
259 // SafetyTable[] contains the actual king safety scores. It is initialized
261 Value SafetyTable[100];
263 // Pawn and material hash tables, indexed by the current thread id
264 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
265 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
267 // Sizes of pawn and material hash tables
268 const int PawnTableSize = 16384;
269 const int MaterialTableSize = 1024;
271 // Array which gives the number of nonzero bits in an 8-bit integer:
272 uint8_t BitCount8Bit[256];
274 // Function prototypes
275 template<PieceType Piece>
276 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
279 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
281 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
282 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
284 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
287 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
288 inline Value apply_weight(Value v, int w);
289 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
291 int count_1s_8bit(Bitboard b);
293 int compute_weight(int uciWeight, int internalWeight);
294 int weight_option(const std::string& opt, int weight);
304 /// evaluate() is the main evaluation function. It always computes two
305 /// values, an endgame score and a middle game score, and interpolates
306 /// between them based on the remaining material.
308 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
311 assert(threadID >= 0 && threadID < THREAD_MAX);
313 memset(&ei, 0, sizeof(EvalInfo));
315 // Initialize by reading the incrementally updated scores included in the
316 // position object (material + piece square tables)
317 ei.mgValue = pos.mg_value();
318 ei.egValue = pos.eg_value();
320 // Probe the material hash table
321 ei.mi = MaterialTable[threadID]->get_material_info(pos);
322 ei.mgValue += ei.mi->mg_value();
323 ei.egValue += ei.mi->eg_value();
325 // If we have a specialized evaluation function for the current material
326 // configuration, call it and return
327 if (ei.mi->specialized_eval_exists())
328 return ei.mi->evaluate(pos);
330 // After get_material_info() call that modifies them
331 ScaleFactor factor[2];
332 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
333 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
335 // Probe the pawn hash table
336 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
337 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
338 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
340 // Initialize king attack bitboards and king attack zones for both sides
341 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
342 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
343 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
344 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
346 // Initialize pawn attack bitboards for both sides
347 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
348 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
349 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
350 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
353 for (Color c = WHITE; c <= BLACK; c++)
355 evaluate_pieces<KNIGHT>(pos, c, ei);
356 evaluate_pieces<BISHOP>(pos, c, ei);
357 evaluate_pieces<ROOK>(pos, c, ei);
358 evaluate_pieces<QUEEN>(pos, c, ei);
360 // Sum up all attacked squares
361 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
362 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
363 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
366 // Kings. Kings are evaluated after all other pieces for both sides,
367 // because we need complete attack information for all pieces when computing
368 // the king safety evaluation.
369 for (Color c = WHITE; c <= BLACK; c++)
370 evaluate_pieces<KING>(pos, c, ei);
372 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
373 // because we need to know which side promotes first in positions where
374 // both sides have an unstoppable passed pawn.
375 if (ei.pi->passed_pawns())
376 evaluate_passed_pawns(pos, ei);
378 Phase phase = pos.game_phase();
380 // Middle-game specific evaluation terms
381 if (phase > PHASE_ENDGAME)
383 // Pawn storms in positions with opposite castling.
384 if ( square_file(pos.king_square(WHITE)) >= FILE_E
385 && square_file(pos.king_square(BLACK)) <= FILE_D)
387 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
388 - ei.pi->kingside_storm_value(BLACK);
390 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
391 && square_file(pos.king_square(BLACK)) >= FILE_E)
393 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
394 - ei.pi->queenside_storm_value(BLACK);
396 // Evaluate space for both sides
397 if (ei.mi->space_weight() > 0)
399 evaluate_space(pos, WHITE, ei);
400 evaluate_space(pos, BLACK, ei);
405 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
406 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
408 // If we don't already have an unusual scale factor, check for opposite
409 // colored bishop endgames, and use a lower scale for those
410 if ( phase < PHASE_MIDGAME
411 && pos.opposite_colored_bishops()
412 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
413 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
417 // Only the two bishops ?
418 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
419 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
421 // Check for KBP vs KB with only a single pawn that is almost
422 // certainly a draw or at least two pawns.
423 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
424 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
427 // Endgame with opposite-colored bishops, but also other pieces. Still
428 // a bit drawish, but not as drawish as with only the two bishops.
429 sf = ScaleFactor(50);
431 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
433 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
437 // Interpolate between the middle game and the endgame score, and
439 Color stm = pos.side_to_move();
441 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
443 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
447 /// quick_evaluate() does a very approximate evaluation of the current position.
448 /// It currently considers only material and piece square table scores. Perhaps
449 /// we should add scores from the pawn and material hash tables?
451 Value quick_evaluate(const Position &pos) {
456 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
458 Value mgv = pos.mg_value();
459 Value egv = pos.eg_value();
460 Phase ph = pos.game_phase();
461 Color stm = pos.side_to_move();
463 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
467 /// init_eval() initializes various tables used by the evaluation function.
469 void init_eval(int threads) {
471 assert(threads <= THREAD_MAX);
473 for (int i = 0; i < THREAD_MAX; i++)
478 delete MaterialTable[i];
480 MaterialTable[i] = NULL;
484 PawnTable[i] = new PawnInfoTable(PawnTableSize);
485 if (!MaterialTable[i])
486 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
489 for (Bitboard b = 0ULL; b < 256ULL; b++)
490 BitCount8Bit[b] = count_1s(b);
494 /// quit_eval() releases heap-allocated memory at program termination.
498 for (int i = 0; i < THREAD_MAX; i++)
501 delete MaterialTable[i];
506 /// read_weights() reads evaluation weights from the corresponding UCI
509 void read_weights(Color us) {
511 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
512 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
513 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
514 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
515 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
516 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
518 Color them = opposite_color(us);
520 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
521 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
522 WeightSpace = weight_option("Space", WeightSpaceInternal);
530 // evaluate_common() computes terms common to all pieces attack
532 template<PieceType Piece>
533 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
535 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
536 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
537 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
538 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
540 Color them = opposite_color(us);
542 // Update attack info
543 ei.attackedBy[us][Piece] |= b;
546 if (b & ei.kingZone[us])
548 ei.kingAttackersCount[us]++;
549 ei.kingAttackersWeight[us] += AttackWeight[Piece];
550 Bitboard bb = (b & ei.attackedBy[them][KING]);
552 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
555 // Remove squares protected by enemy pawns
556 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
559 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
560 : count_1s(bb & ~p.pieces_of_color(us)));
562 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
563 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
565 // Bishop and Knight outposts
566 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
567 || !p.square_is_weak(s, them))
570 // Initial bonus based on square
572 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
574 // Increase bonus if supported by pawn, especially if the opponent has
575 // no minor piece which can exchange the outpost piece
576 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
579 if ( p.piece_count(them, KNIGHT) == 0
580 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
583 ei.mgValue += Sign[us] * bonus;
584 ei.egValue += Sign[us] * bonus;
589 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
592 template<PieceType Piece>
593 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
601 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
603 s = pos.piece_list(us, Piece, i);
605 if (Piece == KNIGHT || Piece == QUEEN)
606 b = pos.piece_attacks<Piece>(s);
607 else if (Piece == BISHOP)
608 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
609 else if (Piece == ROOK)
610 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
612 // Attacks, mobility and outposts
613 mob = evaluate_common<Piece>(pos, b, us, ei, s);
615 // Special patterns: trapped bishops on a7/h7/a2/h2
616 // and trapped bishops on a1/h1/a8/h8 in Chess960.
619 if (bit_is_set(MaskA7H7[us], s))
620 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
622 if (Chess960 && bit_is_set(MaskA1H1[us], s))
623 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
626 if (Piece != ROOK && Piece != QUEEN)
629 // Queen or rook on 7th rank
630 them = opposite_color(us);
632 if ( relative_rank(us, s) == RANK_7
633 && relative_rank(us, pos.king_square(them)) == RANK_8)
635 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
636 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
639 // Special extra evaluation for rooks
643 // Open and half-open files
645 if (ei.pi->file_is_half_open(us, f))
647 if (ei.pi->file_is_half_open(them, f))
649 ei.mgValue += Sign[us] * RookOpenFileBonus;
650 ei.egValue += Sign[us] * RookOpenFileBonus;
654 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
655 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
659 // Penalize rooks which are trapped inside a king. Penalize more if
660 // king has lost right to castle.
661 if (mob > 6 || ei.pi->file_is_half_open(us, f))
664 ksq = pos.king_square(us);
666 if ( square_file(ksq) >= FILE_E
667 && square_file(s) > square_file(ksq)
668 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
670 // Is there a half-open file between the king and the edge of the board?
671 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
672 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
673 : Sign[us] * (TrappedRookPenalty - mob * 16);
675 else if ( square_file(ksq) <= FILE_D
676 && square_file(s) < square_file(ksq)
677 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
679 // Is there a half-open file between the king and the edge of the board?
680 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
681 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
682 : Sign[us] * (TrappedRookPenalty - mob * 16);
687 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
689 return b >> (num << 3);
692 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
696 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
698 int shelter = 0, sign = Sign[us];
699 Square s = p.king_square(us);
702 if (relative_rank(us, s) <= RANK_4)
704 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
705 Rank r = square_rank(s);
706 for (int i = 1; i < 4; i++)
707 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
709 ei.mgValue += sign * Value(shelter);
712 // King safety. This is quite complicated, and is almost certainly far
713 // from optimally tuned.
714 Color them = opposite_color(us);
716 if ( p.piece_count(them, QUEEN) >= 1
717 && ei.kingAttackersCount[them] >= 2
718 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
719 && ei.kingAdjacentZoneAttacksCount[them])
721 // Is it the attackers turn to move?
722 bool sente = (them == p.side_to_move());
724 // Find the attacked squares around the king which has no defenders
725 // apart from the king itself
726 Bitboard undefended =
727 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
728 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
729 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
730 & ei.attacked_by(us, KING);
732 Bitboard occ = p.occupied_squares(), b, b2;
734 // Initialize the 'attackUnits' variable, which is used later on as an
735 // index to the SafetyTable[] array. The initial value is based on the
736 // number and types of the attacking pieces, the number of attacked and
737 // undefended squares around the king, the square of the king, and the
738 // quality of the pawn shelter.
740 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
741 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
742 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
744 // Analyse safe queen contact checks
745 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
748 Bitboard attackedByOthers =
749 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
750 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
752 b &= attackedByOthers;
755 // The bitboard b now contains the squares available for safe queen
757 int count = count_1s_max_15(b);
758 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
760 // Is there a mate threat?
761 if (QueenContactMates && !p.is_check())
763 Bitboard escapeSquares =
764 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
768 Square from, to = pop_1st_bit(&b);
769 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
771 // We have a mate, unless the queen is pinned or there
772 // is an X-ray attack through the queen.
773 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
775 from = p.piece_list(them, QUEEN, i);
776 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
777 && !bit_is_set(p.pinned_pieces(them), from)
778 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
779 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
781 ei.mateThreat[them] = make_move(from, to);
789 // Analyse safe distance checks
790 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
792 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
795 b2 = b & ei.attacked_by(them, QUEEN);
797 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
800 b2 = b & ei.attacked_by(them, ROOK);
802 attackUnits += RookCheckBonus * count_1s_max_15(b2);
804 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
806 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
809 b2 = b & ei.attacked_by(them, QUEEN);
811 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
814 b2 = b & ei.attacked_by(them, BISHOP);
816 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
818 if (KnightCheckBonus > 0)
820 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
823 b2 = b & ei.attacked_by(them, KNIGHT);
825 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
828 // Analyse discovered checks (only for non-pawns right now, consider
829 // adding pawns later).
830 if (DiscoveredCheckBonus)
832 b = p.discovered_check_candidates(them) & ~p.pawns();
834 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
837 // Has a mate threat been found? We don't do anything here if the
838 // side with the mating move is the side to move, because in that
839 // case the mating side will get a huge bonus at the end of the main
840 // evaluation function instead.
841 if (ei.mateThreat[them] != MOVE_NONE)
842 attackUnits += MateThreatBonus;
844 // Ensure that attackUnits is between 0 and 99, in order to avoid array
845 // out of bounds errors:
849 if (attackUnits >= 100)
852 // Finally, extract the king safety score from the SafetyTable[] array.
853 // Add the score to the evaluation, and also to ei.futilityMargin. The
854 // reason for adding the king safety score to the futility margin is
855 // that the king safety scores can sometimes be very big, and that
856 // capturing a single attacking piece can therefore result in a score
857 // change far bigger than the value of the captured piece.
858 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
860 ei.mgValue -= sign * v;
862 if (us == p.side_to_move())
863 ei.futilityMargin += v;
868 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
870 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
872 bool hasUnstoppable[2] = {false, false};
873 int movesToGo[2] = {100, 100};
875 for (Color us = WHITE; us <= BLACK; us++)
877 Color them = opposite_color(us);
878 Square ourKingSq = pos.king_square(us);
879 Square theirKingSq = pos.king_square(them);
880 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
884 Square s = pop_1st_bit(&b);
886 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
887 assert(pos.pawn_is_passed(us, s));
889 int r = int(relative_rank(us, s) - RANK_2);
890 int tr = Max(0, r * (r - 1));
891 Square blockSq = s + pawn_push(us);
893 // Base bonus based on rank
894 Value mbonus = Value(20 * tr);
895 Value ebonus = Value(10 + r * r * 10);
897 // Adjust bonus based on king proximity
900 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
901 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
902 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
904 // If the pawn is free to advance, increase bonus
905 if (pos.square_is_empty(blockSq))
907 b2 = squares_in_front_of(us, s);
908 b3 = b2 & ei.attacked_by(them);
909 b4 = b2 & ei.attacked_by(us);
911 // If there is an enemy rook or queen attacking the pawn from behind,
912 // add all X-ray attacks by the rook or queen.
913 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
914 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
917 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
919 // There are no enemy pieces in the pawn's path! Are any of the
920 // squares in the pawn's path attacked by the enemy?
921 if (b3 == EmptyBoardBB)
922 // No enemy attacks, huge bonus!
923 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
925 // OK, there are enemy attacks. Are those squares which are
926 // attacked by the enemy also attacked by us? If yes, big bonus
927 // (but smaller than when there are no enemy attacks), if no,
928 // somewhat smaller bonus.
929 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
933 // There are some enemy pieces in the pawn's path. While this is
934 // sad, we still assign a moderate bonus if all squares in the path
935 // which are either occupied by or attacked by enemy pieces are
936 // also attacked by us.
937 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
938 ebonus += Value(tr * 6);
940 // At last, add a small bonus when there are no *friendly* pieces
941 // in the pawn's path.
942 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
947 // If the pawn is supported by a friendly pawn, increase bonus
948 b2 = pos.pawns(us) & neighboring_files_bb(s);
950 ebonus += Value(r * 20);
951 else if (pos.pawn_attacks(them, s) & b2)
952 ebonus += Value(r * 12);
954 // If the other side has only a king, check whether the pawn is
956 if (pos.non_pawn_material(them) == Value(0))
961 qsq = relative_square(us, make_square(square_file(s), RANK_8));
962 d = square_distance(s, qsq)
963 - square_distance(theirKingSq, qsq)
964 + (us != pos.side_to_move());
968 int mtg = RANK_8 - relative_rank(us, s);
969 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
974 hasUnstoppable[us] = true;
975 movesToGo[us] = Min(movesToGo[us], mtg);
979 // Rook pawns are a special case: They are sometimes worse, and
980 // sometimes better than other passed pawns. It is difficult to find
981 // good rules for determining whether they are good or bad. For now,
982 // we try the following: Increase the value for rook pawns if the
983 // other side has no pieces apart from a knight, and decrease the
984 // value if the other side has a rook or queen.
985 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
987 if( pos.non_pawn_material(them) <= KnightValueMidgame
988 && pos.piece_count(them, KNIGHT) <= 1)
989 ebonus += ebonus / 4;
990 else if(pos.rooks_and_queens(them))
991 ebonus -= ebonus / 4;
994 // Add the scores for this pawn to the middle game and endgame eval.
995 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
996 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1000 // Does either side have an unstoppable passed pawn?
1001 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1002 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1003 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1004 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1005 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1007 // Both sides have unstoppable pawns! Try to find out who queens
1008 // first. We begin by transforming 'movesToGo' to the number of
1009 // plies until the pawn queens for both sides.
1010 movesToGo[WHITE] *= 2;
1011 movesToGo[BLACK] *= 2;
1012 movesToGo[pos.side_to_move()]--;
1014 // If one side queens at least three plies before the other, that
1016 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1017 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1018 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1019 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1021 // We could also add some rules about the situation when one side
1022 // queens exactly one ply before the other: Does the first queen
1023 // check the opponent's king, or attack the opponent's queening square?
1024 // This is slightly tricky to get right, because it is possible that
1025 // the opponent's king has moved somewhere before the first pawn queens.
1030 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1031 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1034 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1036 assert(square_is_ok(s));
1037 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1039 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1040 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1042 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1043 && pos.see(s, b6) < 0
1044 && pos.see(s, b8) < 0)
1046 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1047 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1052 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1053 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1054 // black), and assigns a penalty if it is. This pattern can obviously
1055 // only occur in Chess960 games.
1057 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1059 Piece pawn = piece_of_color_and_type(us, PAWN);
1063 assert(square_is_ok(s));
1064 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1066 if (square_file(s) == FILE_A)
1068 b2 = relative_square(us, SQ_B2);
1069 b3 = relative_square(us, SQ_B3);
1070 c3 = relative_square(us, SQ_C3);
1074 b2 = relative_square(us, SQ_G2);
1075 b3 = relative_square(us, SQ_G3);
1076 c3 = relative_square(us, SQ_F3);
1079 if (pos.piece_on(b2) == pawn)
1083 if (!pos.square_is_empty(b3))
1084 penalty = 2*TrappedBishopA1H1Penalty;
1085 else if (pos.piece_on(c3) == pawn)
1086 penalty = TrappedBishopA1H1Penalty;
1088 penalty = TrappedBishopA1H1Penalty / 2;
1090 ei.mgValue -= Sign[us] * penalty;
1091 ei.egValue -= Sign[us] * penalty;
1096 // evaluate_space() computes the space evaluation for a given side. The
1097 // space evaluation is a simple bonus based on the number of safe squares
1098 // available for minor pieces on the central four files on ranks 2--4. Safe
1099 // squares one, two or three squares behind a friendly pawn are counted
1100 // twice. Finally, the space bonus is scaled by a weight taken from the
1101 // material hash table.
1103 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1105 Color them = opposite_color(us);
1107 // Find the safe squares for our pieces inside the area defined by
1108 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1109 // pawn, or if it is undefended and attacked by an enemy piece.
1111 Bitboard safeSquares = SpaceMask[us]
1113 & ~ei.attacked_by(them, PAWN)
1114 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1116 // Find all squares which are at most three squares behind some friendly
1118 Bitboard behindFriendlyPawns = pos.pawns(us);
1121 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1122 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1126 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1127 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1130 int space = count_1s_max_15(safeSquares)
1131 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1133 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1137 // apply_weight() applies an evaluation weight to a value
1139 inline Value apply_weight(Value v, int w) {
1140 return (v*w) / 0x100;
1144 // scale_by_game_phase() interpolates between a middle game and an endgame
1145 // score, based on game phase. It also scales the return value by a
1146 // ScaleFactor array.
1148 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1150 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1151 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1152 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1154 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1156 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1157 return Value(int(result) & ~(GrainSize - 1));
1161 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1162 // significant bits of a Bitboard. This function is used by the king
1163 // shield evaluation.
1165 int count_1s_8bit(Bitboard b) {
1166 return int(BitCount8Bit[b & 0xFF]);
1170 // compute_weight() computes the value of an evaluation weight, by combining
1171 // an UCI-configurable weight with an internal weight.
1173 int compute_weight(int uciWeight, int internalWeight) {
1175 uciWeight = (uciWeight * 0x100) / 100;
1176 return (uciWeight * internalWeight) / 0x100;
1180 // helper used in read_weights()
1181 int weight_option(const std::string& opt, int weight) {
1183 return compute_weight(get_option_value_int(opt), weight);
1187 // init_safety() initizes the king safety evaluation, based on UCI
1188 // parameters. It is called from read_weights().
1190 void init_safety() {
1192 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1193 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1194 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1195 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1196 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1197 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1198 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1200 int maxSlope = get_option_value_int("King Safety Max Slope");
1201 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1202 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1203 double b = get_option_value_int("King Safety X Intercept");
1204 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1205 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1207 for (int i = 0; i < 100; i++)
1210 SafetyTable[i] = Value(0);
1212 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1214 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1217 for (int i = 0; i < 100; i++)
1219 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1220 for (int j = i + 1; j < 100; j++)
1221 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1223 if (SafetyTable[i] > Value(peak))
1224 SafetyTable[i] = Value(peak);