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.
62 // Values modified by Joona Kiiski
63 const int WeightMobilityMidgameInternal = 0x0FA;
64 const int WeightMobilityEndgameInternal = 0x10A;
65 const int WeightPawnStructureMidgameInternal = 0x0EC;
66 const int WeightPawnStructureEndgameInternal = 0x0CD;
67 const int WeightPassedPawnsMidgameInternal = 0x108;
68 const int WeightPassedPawnsEndgameInternal = 0x109;
69 const int WeightKingSafetyInternal = 0x0F7;
70 const int WeightKingOppSafetyInternal = 0x101;
71 const int WeightSpaceInternal = 0x02F;
73 // Visually better to define tables constants
76 // Knight mobility bonus in middle game and endgame, indexed by the number
77 // of attacked squares not occupied by friendly piecess.
78 const Value MidgameKnightMobilityBonus[] = {
80 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
83 const Value EndgameKnightMobilityBonus[] = {
85 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
88 // Bishop mobility bonus in middle game and endgame, indexed by the number
89 // of attacked squares not occupied by friendly pieces. X-ray attacks through
90 // queens are also included.
91 const Value MidgameBishopMobilityBonus[] = {
93 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
94 // 8 9 10 11 12 13 14 15
95 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
98 const Value EndgameBishopMobilityBonus[] = {
100 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
101 // 8 9 10 11 12 13 14 15
102 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
105 // Rook mobility bonus in middle game and endgame, indexed by the number
106 // of attacked squares not occupied by friendly pieces. X-ray attacks through
107 // queens and rooks are also included.
108 const Value MidgameRookMobilityBonus[] = {
110 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
111 // 8 9 10 11 12 13 14 15
112 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
115 const Value EndgameRookMobilityBonus[] = {
117 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
118 // 8 9 10 11 12 13 14 15
119 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
122 // Queen mobility bonus in middle game and endgame, indexed by the number
123 // of attacked squares not occupied by friendly pieces.
124 const Value MidgameQueenMobilityBonus[] = {
126 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
127 // 8 9 10 11 12 13 14 15
128 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
129 // 16 17 18 19 20 21 22 23
130 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
131 // 24 25 26 27 28 29 30 31
132 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
135 const Value EndgameQueenMobilityBonus[] = {
137 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
138 // 8 9 10 11 12 13 14 15
139 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
140 // 16 17 18 19 20 21 22 23
141 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
142 // 24 25 26 27 28 29 30 31
143 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
146 // Outpost bonuses for knights and bishops, indexed by square (from white's
148 const Value KnightOutpostBonus[64] = {
150 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
152 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
153 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
154 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
155 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
156 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
160 const Value BishopOutpostBonus[64] = {
162 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
164 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
165 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
166 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
167 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
168 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
169 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
172 // Bonus for unstoppable passed pawns
173 const Value UnstoppablePawnValue = Value(0x500);
175 // Rooks and queens on the 7th rank
176 const Value MidgameRookOn7thBonus = Value(47);
177 const Value EndgameRookOn7thBonus = Value(98);
178 const Value MidgameQueenOn7thBonus = Value(27);
179 const Value EndgameQueenOn7thBonus = Value(54);
182 // Rooks on open files
183 const Value RookOpenFileBonus = Value(43);
184 const Value RookHalfOpenFileBonus = Value(19);
186 // Penalty for rooks trapped inside a friendly king which has lost the
188 const Value TrappedRookPenalty = Value(180);
190 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
192 const Value TrappedBishopA7H7Penalty = Value(300);
194 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
195 const Bitboard MaskA7H7[2] = {
196 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
197 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
200 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
201 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
202 // happen in Chess960 games.
203 const Value TrappedBishopA1H1Penalty = Value(100);
205 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
206 const Bitboard MaskA1H1[2] = {
207 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
208 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
211 // The SpaceMask[color] contains area of the board which is consdered by
212 // the space evaluation. In the middle game, each side is given a bonus
213 // based on how many squares inside this area are safe and available for
214 // friendly minor pieces.
215 const Bitboard SpaceMask[2] = {
216 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
217 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
218 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
219 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
220 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
221 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
224 /// King safety constants and variables. The king safety scores are taken
225 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
226 /// the strength of the attack are added up into an integer, which is used
227 /// as an index to SafetyTable[].
229 // Attack weights for each piece type.
230 const int QueenAttackWeight = 5;
231 const int RookAttackWeight = 3;
232 const int BishopAttackWeight = 2;
233 const int KnightAttackWeight = 2;
235 // Bonuses for safe checks for each piece type.
236 int QueenContactCheckBonus = 3;
237 int QueenCheckBonus = 2;
238 int RookCheckBonus = 1;
239 int BishopCheckBonus = 1;
240 int KnightCheckBonus = 1;
241 int DiscoveredCheckBonus = 3;
243 // Scan for queen contact mates?
244 const bool QueenContactMates = true;
246 // Bonus for having a mate threat.
247 int MateThreatBonus = 3;
249 // InitKingDanger[] contains bonuses based on the position of the defending
251 const int InitKingDanger[64] = {
252 2, 0, 2, 5, 5, 2, 0, 2,
253 2, 2, 4, 8, 8, 4, 2, 2,
254 7, 10, 12, 12, 12, 12, 10, 7,
255 15, 15, 15, 15, 15, 15, 15, 15,
256 15, 15, 15, 15, 15, 15, 15, 15,
257 15, 15, 15, 15, 15, 15, 15, 15,
258 15, 15, 15, 15, 15, 15, 15, 15,
259 15, 15, 15, 15, 15, 15, 15, 15
262 // SafetyTable[] contains the actual king safety scores. It is initialized
264 Value SafetyTable[100];
266 // Pawn and material hash tables, indexed by the current thread id
267 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
268 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
270 // Sizes of pawn and material hash tables
271 const int PawnTableSize = 16384;
272 const int MaterialTableSize = 1024;
274 // Array which gives the number of nonzero bits in an 8-bit integer:
275 uint8_t BitCount8Bit[256];
277 // Function prototypes
278 template<PieceType Piece>
279 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
282 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
284 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
285 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
287 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
290 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
291 inline Value apply_weight(Value v, int w);
292 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
294 int count_1s_8bit(Bitboard b);
296 int compute_weight(int uciWeight, int internalWeight);
297 int weight_option(const std::string& opt, int weight);
307 /// evaluate() is the main evaluation function. It always computes two
308 /// values, an endgame score and a middle game score, and interpolates
309 /// between them based on the remaining material.
311 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
314 assert(threadID >= 0 && threadID < THREAD_MAX);
316 memset(&ei, 0, sizeof(EvalInfo));
318 // Initialize by reading the incrementally updated scores included in the
319 // position object (material + piece square tables)
320 ei.mgValue = pos.mg_value();
321 ei.egValue = pos.eg_value();
323 // Probe the material hash table
324 ei.mi = MaterialTable[threadID]->get_material_info(pos);
325 ei.mgValue += ei.mi->mg_value();
326 ei.egValue += ei.mi->eg_value();
328 // If we have a specialized evaluation function for the current material
329 // configuration, call it and return
330 if (ei.mi->specialized_eval_exists())
331 return ei.mi->evaluate(pos);
333 // After get_material_info() call that modifies them
334 ScaleFactor factor[2];
335 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
336 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
338 // Probe the pawn hash table
339 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
340 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
341 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
343 // Initialize king attack bitboards and king attack zones for both sides
344 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
345 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
346 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
347 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
349 // Initialize pawn attack bitboards for both sides
350 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
351 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
352 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
353 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
356 for (Color c = WHITE; c <= BLACK; c++)
358 evaluate_pieces<KNIGHT>(pos, c, ei);
359 evaluate_pieces<BISHOP>(pos, c, ei);
360 evaluate_pieces<ROOK>(pos, c, ei);
361 evaluate_pieces<QUEEN>(pos, c, ei);
363 // Sum up all attacked squares
364 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
365 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
366 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
369 // Kings. Kings are evaluated after all other pieces for both sides,
370 // because we need complete attack information for all pieces when computing
371 // the king safety evaluation.
372 for (Color c = WHITE; c <= BLACK; c++)
373 evaluate_pieces<KING>(pos, c, ei);
375 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
376 // because we need to know which side promotes first in positions where
377 // both sides have an unstoppable passed pawn.
378 if (ei.pi->passed_pawns())
379 evaluate_passed_pawns(pos, ei);
381 Phase phase = pos.game_phase();
383 // Middle-game specific evaluation terms
384 if (phase > PHASE_ENDGAME)
386 // Pawn storms in positions with opposite castling.
387 if ( square_file(pos.king_square(WHITE)) >= FILE_E
388 && square_file(pos.king_square(BLACK)) <= FILE_D)
390 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
391 - ei.pi->kingside_storm_value(BLACK);
393 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
394 && square_file(pos.king_square(BLACK)) >= FILE_E)
396 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
397 - ei.pi->queenside_storm_value(BLACK);
399 // Evaluate space for both sides
400 if (ei.mi->space_weight() > 0)
402 evaluate_space(pos, WHITE, ei);
403 evaluate_space(pos, BLACK, ei);
408 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
409 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
411 // If we don't already have an unusual scale factor, check for opposite
412 // colored bishop endgames, and use a lower scale for those
413 if ( phase < PHASE_MIDGAME
414 && pos.opposite_colored_bishops()
415 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
416 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
420 // Only the two bishops ?
421 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
422 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
424 // Check for KBP vs KB with only a single pawn that is almost
425 // certainly a draw or at least two pawns.
426 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
427 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
430 // Endgame with opposite-colored bishops, but also other pieces. Still
431 // a bit drawish, but not as drawish as with only the two bishops.
432 sf = ScaleFactor(50);
434 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
436 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
440 // Interpolate between the middle game and the endgame score, and
442 Color stm = pos.side_to_move();
444 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
446 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
450 /// quick_evaluate() does a very approximate evaluation of the current position.
451 /// It currently considers only material and piece square table scores. Perhaps
452 /// we should add scores from the pawn and material hash tables?
454 Value quick_evaluate(const Position &pos) {
459 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
461 Value mgv = pos.mg_value();
462 Value egv = pos.eg_value();
463 Phase ph = pos.game_phase();
464 Color stm = pos.side_to_move();
466 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
470 /// init_eval() initializes various tables used by the evaluation function.
472 void init_eval(int threads) {
474 assert(threads <= THREAD_MAX);
476 for (int i = 0; i < THREAD_MAX; i++)
481 delete MaterialTable[i];
483 MaterialTable[i] = NULL;
487 PawnTable[i] = new PawnInfoTable(PawnTableSize);
488 if (!MaterialTable[i])
489 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
492 for (Bitboard b = 0ULL; b < 256ULL; b++)
494 assert(count_1s(b) == int(uint8_t(count_1s(b))));
495 BitCount8Bit[b] = (uint8_t)count_1s(b);
500 /// quit_eval() releases heap-allocated memory at program termination.
504 for (int i = 0; i < THREAD_MAX; i++)
507 delete MaterialTable[i];
512 /// read_weights() reads evaluation weights from the corresponding UCI
515 void read_weights(Color us) {
517 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
518 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
519 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
520 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
521 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
522 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
524 Color them = opposite_color(us);
526 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
527 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
528 WeightSpace = weight_option("Space", WeightSpaceInternal);
536 // evaluate_common() computes terms common to all pieces attack
538 template<PieceType Piece>
539 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
541 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
542 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
543 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
544 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
546 Color them = opposite_color(us);
548 // Update attack info
549 ei.attackedBy[us][Piece] |= b;
552 if (b & ei.kingZone[us])
554 ei.kingAttackersCount[us]++;
555 ei.kingAttackersWeight[us] += AttackWeight[Piece];
556 Bitboard bb = (b & ei.attackedBy[them][KING]);
558 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
561 // Remove squares protected by enemy pawns
562 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
565 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
566 : count_1s(bb & ~p.pieces_of_color(us)));
568 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
569 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
571 // Bishop and Knight outposts
572 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
573 || !p.square_is_weak(s, them))
576 // Initial bonus based on square
578 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
580 // Increase bonus if supported by pawn, especially if the opponent has
581 // no minor piece which can exchange the outpost piece
582 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
585 if ( p.piece_count(them, KNIGHT) == 0
586 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
589 ei.mgValue += Sign[us] * bonus;
590 ei.egValue += Sign[us] * bonus;
595 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
598 template<PieceType Piece>
599 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
607 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
609 s = pos.piece_list(us, Piece, i);
611 if (Piece == KNIGHT || Piece == QUEEN)
612 b = pos.piece_attacks<Piece>(s);
613 else if (Piece == BISHOP)
614 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
615 else if (Piece == ROOK)
616 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
618 // Attacks, mobility and outposts
619 mob = evaluate_common<Piece>(pos, b, us, ei, s);
621 // Special patterns: trapped bishops on a7/h7/a2/h2
622 // and trapped bishops on a1/h1/a8/h8 in Chess960.
625 if (bit_is_set(MaskA7H7[us], s))
626 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
628 if (Chess960 && bit_is_set(MaskA1H1[us], s))
629 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
632 if (Piece == ROOK || Piece == QUEEN)
634 // Queen or rook on 7th rank
635 them = opposite_color(us);
637 if ( relative_rank(us, s) == RANK_7
638 && relative_rank(us, pos.king_square(them)) == RANK_8)
640 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
641 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
645 // Special extra evaluation for rooks
648 // Open and half-open files
650 if (ei.pi->file_is_half_open(us, f))
652 if (ei.pi->file_is_half_open(them, f))
654 ei.mgValue += Sign[us] * RookOpenFileBonus;
655 ei.egValue += Sign[us] * RookOpenFileBonus;
659 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
660 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
664 // Penalize rooks which are trapped inside a king. Penalize more if
665 // king has lost right to castle.
666 if (mob > 6 || ei.pi->file_is_half_open(us, f))
669 ksq = pos.king_square(us);
671 if ( square_file(ksq) >= FILE_E
672 && square_file(s) > square_file(ksq)
673 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
675 // Is there a half-open file between the king and the edge of the board?
676 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
677 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
678 : Sign[us] * (TrappedRookPenalty - mob * 16);
680 else if ( square_file(ksq) <= FILE_D
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_left(us, square_file(ksq)))
686 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
687 : Sign[us] * (TrappedRookPenalty - mob * 16);
693 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
695 return b >> (num << 3);
698 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
702 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
704 int shelter = 0, sign = Sign[us];
705 Square s = p.king_square(us);
708 if (relative_rank(us, s) <= RANK_4)
710 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
711 Rank r = square_rank(s);
712 for (int i = 1; i < 4; i++)
713 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
715 ei.mgValue += sign * Value(shelter);
718 // King safety. This is quite complicated, and is almost certainly far
719 // from optimally tuned.
720 Color them = opposite_color(us);
722 if ( p.piece_count(them, QUEEN) >= 1
723 && ei.kingAttackersCount[them] >= 2
724 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
725 && ei.kingAdjacentZoneAttacksCount[them])
727 // Is it the attackers turn to move?
728 bool sente = (them == p.side_to_move());
730 // Find the attacked squares around the king which has no defenders
731 // apart from the king itself
732 Bitboard undefended =
733 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
734 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
735 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
736 & ei.attacked_by(us, KING);
738 Bitboard occ = p.occupied_squares(), b, b2;
740 // Initialize the 'attackUnits' variable, which is used later on as an
741 // index to the SafetyTable[] array. The initial value is based on the
742 // number and types of the attacking pieces, the number of attacked and
743 // undefended squares around the king, the square of the king, and the
744 // quality of the pawn shelter.
746 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
747 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
748 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
750 // Analyse safe queen contact checks
751 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
754 Bitboard attackedByOthers =
755 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
756 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
758 b &= attackedByOthers;
761 // The bitboard b now contains the squares available for safe queen
763 int count = count_1s_max_15(b);
764 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
766 // Is there a mate threat?
767 if (QueenContactMates && !p.is_check())
769 Bitboard escapeSquares =
770 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
774 Square from, to = pop_1st_bit(&b);
775 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
777 // We have a mate, unless the queen is pinned or there
778 // is an X-ray attack through the queen.
779 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
781 from = p.piece_list(them, QUEEN, i);
782 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
783 && !bit_is_set(p.pinned_pieces(them), from)
784 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
785 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
787 ei.mateThreat[them] = make_move(from, to);
795 // Analyse safe distance checks
796 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
798 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
801 b2 = b & ei.attacked_by(them, QUEEN);
803 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
806 b2 = b & ei.attacked_by(them, ROOK);
808 attackUnits += RookCheckBonus * count_1s_max_15(b2);
810 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
812 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
815 b2 = b & ei.attacked_by(them, QUEEN);
817 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
820 b2 = b & ei.attacked_by(them, BISHOP);
822 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
824 if (KnightCheckBonus > 0)
826 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
829 b2 = b & ei.attacked_by(them, KNIGHT);
831 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
834 // Analyse discovered checks (only for non-pawns right now, consider
835 // adding pawns later).
836 if (DiscoveredCheckBonus)
838 b = p.discovered_check_candidates(them) & ~p.pawns();
840 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
843 // Has a mate threat been found? We don't do anything here if the
844 // side with the mating move is the side to move, because in that
845 // case the mating side will get a huge bonus at the end of the main
846 // evaluation function instead.
847 if (ei.mateThreat[them] != MOVE_NONE)
848 attackUnits += MateThreatBonus;
850 // Ensure that attackUnits is between 0 and 99, in order to avoid array
851 // out of bounds errors:
855 if (attackUnits >= 100)
858 // Finally, extract the king safety score from the SafetyTable[] array.
859 // Add the score to the evaluation, and also to ei.futilityMargin. The
860 // reason for adding the king safety score to the futility margin is
861 // that the king safety scores can sometimes be very big, and that
862 // capturing a single attacking piece can therefore result in a score
863 // change far bigger than the value of the captured piece.
864 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
866 ei.mgValue -= sign * v;
868 if (us == p.side_to_move())
869 ei.futilityMargin += v;
874 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
876 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
878 bool hasUnstoppable[2] = {false, false};
879 int movesToGo[2] = {100, 100};
881 for (Color us = WHITE; us <= BLACK; us++)
883 Color them = opposite_color(us);
884 Square ourKingSq = pos.king_square(us);
885 Square theirKingSq = pos.king_square(them);
886 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
890 Square s = pop_1st_bit(&b);
892 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
893 assert(pos.pawn_is_passed(us, s));
895 int r = int(relative_rank(us, s) - RANK_2);
896 int tr = Max(0, r * (r - 1));
897 Square blockSq = s + pawn_push(us);
899 // Base bonus based on rank
900 Value mbonus = Value(20 * tr);
901 Value ebonus = Value(10 + r * r * 10);
903 // Adjust bonus based on king proximity
906 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
907 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
908 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
910 // If the pawn is free to advance, increase bonus
911 if (pos.square_is_empty(blockSq))
913 b2 = squares_in_front_of(us, s);
914 b3 = b2 & ei.attacked_by(them);
915 b4 = b2 & ei.attacked_by(us);
917 // If there is an enemy rook or queen attacking the pawn from behind,
918 // add all X-ray attacks by the rook or queen.
919 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
920 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
923 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
925 // There are no enemy pieces in the pawn's path! Are any of the
926 // squares in the pawn's path attacked by the enemy?
927 if (b3 == EmptyBoardBB)
928 // No enemy attacks, huge bonus!
929 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
931 // OK, there are enemy attacks. Are those squares which are
932 // attacked by the enemy also attacked by us? If yes, big bonus
933 // (but smaller than when there are no enemy attacks), if no,
934 // somewhat smaller bonus.
935 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
939 // There are some enemy pieces in the pawn's path. While this is
940 // sad, we still assign a moderate bonus if all squares in the path
941 // which are either occupied by or attacked by enemy pieces are
942 // also attacked by us.
943 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
944 ebonus += Value(tr * 6);
946 // At last, add a small bonus when there are no *friendly* pieces
947 // in the pawn's path.
948 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
953 // If the pawn is supported by a friendly pawn, increase bonus
954 b2 = pos.pawns(us) & neighboring_files_bb(s);
956 ebonus += Value(r * 20);
957 else if (pos.pawn_attacks(them, s) & b2)
958 ebonus += Value(r * 12);
960 // If the other side has only a king, check whether the pawn is
962 if (pos.non_pawn_material(them) == Value(0))
967 qsq = relative_square(us, make_square(square_file(s), RANK_8));
968 d = square_distance(s, qsq)
969 - square_distance(theirKingSq, qsq)
970 + (us != pos.side_to_move());
974 int mtg = RANK_8 - relative_rank(us, s);
975 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
980 hasUnstoppable[us] = true;
981 movesToGo[us] = Min(movesToGo[us], mtg);
985 // Rook pawns are a special case: They are sometimes worse, and
986 // sometimes better than other passed pawns. It is difficult to find
987 // good rules for determining whether they are good or bad. For now,
988 // we try the following: Increase the value for rook pawns if the
989 // other side has no pieces apart from a knight, and decrease the
990 // value if the other side has a rook or queen.
991 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
993 if( pos.non_pawn_material(them) <= KnightValueMidgame
994 && pos.piece_count(them, KNIGHT) <= 1)
995 ebonus += ebonus / 4;
996 else if(pos.rooks_and_queens(them))
997 ebonus -= ebonus / 4;
1000 // Add the scores for this pawn to the middle game and endgame eval.
1001 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1002 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1006 // Does either side have an unstoppable passed pawn?
1007 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1008 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1009 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1010 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1011 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1013 // Both sides have unstoppable pawns! Try to find out who queens
1014 // first. We begin by transforming 'movesToGo' to the number of
1015 // plies until the pawn queens for both sides.
1016 movesToGo[WHITE] *= 2;
1017 movesToGo[BLACK] *= 2;
1018 movesToGo[pos.side_to_move()]--;
1020 // If one side queens at least three plies before the other, that
1022 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1023 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1024 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1025 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1027 // We could also add some rules about the situation when one side
1028 // queens exactly one ply before the other: Does the first queen
1029 // check the opponent's king, or attack the opponent's queening square?
1030 // This is slightly tricky to get right, because it is possible that
1031 // the opponent's king has moved somewhere before the first pawn queens.
1036 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1037 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1040 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1042 assert(square_is_ok(s));
1043 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1045 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1046 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1048 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1049 && pos.see(s, b6) < 0
1050 && pos.see(s, b8) < 0)
1052 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1053 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1058 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1059 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1060 // black), and assigns a penalty if it is. This pattern can obviously
1061 // only occur in Chess960 games.
1063 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1065 Piece pawn = piece_of_color_and_type(us, PAWN);
1069 assert(square_is_ok(s));
1070 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1072 if (square_file(s) == FILE_A)
1074 b2 = relative_square(us, SQ_B2);
1075 b3 = relative_square(us, SQ_B3);
1076 c3 = relative_square(us, SQ_C3);
1080 b2 = relative_square(us, SQ_G2);
1081 b3 = relative_square(us, SQ_G3);
1082 c3 = relative_square(us, SQ_F3);
1085 if (pos.piece_on(b2) == pawn)
1089 if (!pos.square_is_empty(b3))
1090 penalty = 2*TrappedBishopA1H1Penalty;
1091 else if (pos.piece_on(c3) == pawn)
1092 penalty = TrappedBishopA1H1Penalty;
1094 penalty = TrappedBishopA1H1Penalty / 2;
1096 ei.mgValue -= Sign[us] * penalty;
1097 ei.egValue -= Sign[us] * penalty;
1102 // evaluate_space() computes the space evaluation for a given side. The
1103 // space evaluation is a simple bonus based on the number of safe squares
1104 // available for minor pieces on the central four files on ranks 2--4. Safe
1105 // squares one, two or three squares behind a friendly pawn are counted
1106 // twice. Finally, the space bonus is scaled by a weight taken from the
1107 // material hash table.
1109 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1111 Color them = opposite_color(us);
1113 // Find the safe squares for our pieces inside the area defined by
1114 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1115 // pawn, or if it is undefended and attacked by an enemy piece.
1117 Bitboard safeSquares = SpaceMask[us]
1119 & ~ei.attacked_by(them, PAWN)
1120 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1122 // Find all squares which are at most three squares behind some friendly
1124 Bitboard behindFriendlyPawns = pos.pawns(us);
1127 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1128 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1132 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1133 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1136 int space = count_1s_max_15(safeSquares)
1137 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1139 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1143 // apply_weight() applies an evaluation weight to a value
1145 inline Value apply_weight(Value v, int w) {
1146 return (v*w) / 0x100;
1150 // scale_by_game_phase() interpolates between a middle game and an endgame
1151 // score, based on game phase. It also scales the return value by a
1152 // ScaleFactor array.
1154 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1156 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1157 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1158 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1160 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1162 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1163 return Value(int(result) & ~(GrainSize - 1));
1167 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1168 // significant bits of a Bitboard. This function is used by the king
1169 // shield evaluation.
1171 int count_1s_8bit(Bitboard b) {
1172 return int(BitCount8Bit[b & 0xFF]);
1176 // compute_weight() computes the value of an evaluation weight, by combining
1177 // an UCI-configurable weight with an internal weight.
1179 int compute_weight(int uciWeight, int internalWeight) {
1181 uciWeight = (uciWeight * 0x100) / 100;
1182 return (uciWeight * internalWeight) / 0x100;
1186 // helper used in read_weights()
1187 int weight_option(const std::string& opt, int weight) {
1189 return compute_weight(get_option_value_int(opt), weight);
1193 // init_safety() initizes the king safety evaluation, based on UCI
1194 // parameters. It is called from read_weights().
1196 void init_safety() {
1198 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1199 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1200 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1201 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1202 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1203 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1204 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1206 int maxSlope = get_option_value_int("King Safety Max Slope");
1207 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1208 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1209 double b = get_option_value_int("King Safety X Intercept");
1210 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1211 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1213 for (int i = 0; i < 100; i++)
1216 SafetyTable[i] = Value(0);
1218 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1220 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1223 for (int i = 0; i < 100; i++)
1225 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1226 for (int j = i + 1; j < 100; j++)
1227 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1229 if (SafetyTable[i] > Value(peak))
1230 SafetyTable[i] = Value(peak);