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++)
493 BitCount8Bit[b] = (uint8_t)count_1s(b);
497 /// quit_eval() releases heap-allocated memory at program termination.
501 for (int i = 0; i < THREAD_MAX; i++)
504 delete MaterialTable[i];
509 /// read_weights() reads evaluation weights from the corresponding UCI
512 void read_weights(Color us) {
514 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
515 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
516 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
517 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
518 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
519 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
521 Color them = opposite_color(us);
523 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
524 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
525 WeightSpace = weight_option("Space", WeightSpaceInternal);
533 // evaluate_common() computes terms common to all pieces attack
535 template<PieceType Piece>
536 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
538 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
539 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
540 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
541 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
543 Color them = opposite_color(us);
545 // Update attack info
546 ei.attackedBy[us][Piece] |= b;
549 if (b & ei.kingZone[us])
551 ei.kingAttackersCount[us]++;
552 ei.kingAttackersWeight[us] += AttackWeight[Piece];
553 Bitboard bb = (b & ei.attackedBy[them][KING]);
555 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
558 // Remove squares protected by enemy pawns
559 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
562 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
563 : count_1s(bb & ~p.pieces_of_color(us)));
565 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
566 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
568 // Bishop and Knight outposts
569 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
570 || !p.square_is_weak(s, them))
573 // Initial bonus based on square
575 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
577 // Increase bonus if supported by pawn, especially if the opponent has
578 // no minor piece which can exchange the outpost piece
579 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
582 if ( p.piece_count(them, KNIGHT) == 0
583 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
586 ei.mgValue += Sign[us] * bonus;
587 ei.egValue += Sign[us] * bonus;
592 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
595 template<PieceType Piece>
596 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
604 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
606 s = pos.piece_list(us, Piece, i);
608 if (Piece == KNIGHT || Piece == QUEEN)
609 b = pos.piece_attacks<Piece>(s);
610 else if (Piece == BISHOP)
611 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
612 else if (Piece == ROOK)
613 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
615 // Attacks, mobility and outposts
616 mob = evaluate_common<Piece>(pos, b, us, ei, s);
618 // Special patterns: trapped bishops on a7/h7/a2/h2
619 // and trapped bishops on a1/h1/a8/h8 in Chess960.
622 if (bit_is_set(MaskA7H7[us], s))
623 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
625 if (Chess960 && bit_is_set(MaskA1H1[us], s))
626 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
629 if (Piece == ROOK || Piece == QUEEN)
631 // Queen or rook on 7th rank
632 them = opposite_color(us);
634 if ( relative_rank(us, s) == RANK_7
635 && relative_rank(us, pos.king_square(them)) == RANK_8)
637 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
638 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
642 // Special extra evaluation for rooks
645 // Open and half-open files
647 if (ei.pi->file_is_half_open(us, f))
649 if (ei.pi->file_is_half_open(them, f))
651 ei.mgValue += Sign[us] * RookOpenFileBonus;
652 ei.egValue += Sign[us] * RookOpenFileBonus;
656 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
657 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
661 // Penalize rooks which are trapped inside a king. Penalize more if
662 // king has lost right to castle.
663 if (mob > 6 || ei.pi->file_is_half_open(us, f))
666 ksq = pos.king_square(us);
668 if ( square_file(ksq) >= FILE_E
669 && square_file(s) > square_file(ksq)
670 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
672 // Is there a half-open file between the king and the edge of the board?
673 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
674 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
675 : Sign[us] * (TrappedRookPenalty - mob * 16);
677 else if ( square_file(ksq) <= FILE_D
678 && square_file(s) < square_file(ksq)
679 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
681 // Is there a half-open file between the king and the edge of the board?
682 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
683 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
684 : Sign[us] * (TrappedRookPenalty - mob * 16);
690 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
692 return b >> (num << 3);
695 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
699 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
701 int shelter = 0, sign = Sign[us];
702 Square s = p.king_square(us);
705 if (relative_rank(us, s) <= RANK_4)
707 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
708 Rank r = square_rank(s);
709 for (int i = 1; i < 4; i++)
710 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
712 ei.mgValue += sign * Value(shelter);
715 // King safety. This is quite complicated, and is almost certainly far
716 // from optimally tuned.
717 Color them = opposite_color(us);
719 if ( p.piece_count(them, QUEEN) >= 1
720 && ei.kingAttackersCount[them] >= 2
721 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
722 && ei.kingAdjacentZoneAttacksCount[them])
724 // Is it the attackers turn to move?
725 bool sente = (them == p.side_to_move());
727 // Find the attacked squares around the king which has no defenders
728 // apart from the king itself
729 Bitboard undefended =
730 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
731 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
732 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
733 & ei.attacked_by(us, KING);
735 Bitboard occ = p.occupied_squares(), b, b2;
737 // Initialize the 'attackUnits' variable, which is used later on as an
738 // index to the SafetyTable[] array. The initial value is based on the
739 // number and types of the attacking pieces, the number of attacked and
740 // undefended squares around the king, the square of the king, and the
741 // quality of the pawn shelter.
743 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
744 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
745 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
747 // Analyse safe queen contact checks
748 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
751 Bitboard attackedByOthers =
752 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
753 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
755 b &= attackedByOthers;
758 // The bitboard b now contains the squares available for safe queen
760 int count = count_1s_max_15(b);
761 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
763 // Is there a mate threat?
764 if (QueenContactMates && !p.is_check())
766 Bitboard escapeSquares =
767 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
771 Square from, to = pop_1st_bit(&b);
772 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
774 // We have a mate, unless the queen is pinned or there
775 // is an X-ray attack through the queen.
776 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
778 from = p.piece_list(them, QUEEN, i);
779 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
780 && !bit_is_set(p.pinned_pieces(them), from)
781 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
782 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
784 ei.mateThreat[them] = make_move(from, to);
792 // Analyse safe distance checks
793 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
795 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
798 b2 = b & ei.attacked_by(them, QUEEN);
800 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
803 b2 = b & ei.attacked_by(them, ROOK);
805 attackUnits += RookCheckBonus * count_1s_max_15(b2);
807 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
809 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
812 b2 = b & ei.attacked_by(them, QUEEN);
814 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
817 b2 = b & ei.attacked_by(them, BISHOP);
819 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
821 if (KnightCheckBonus > 0)
823 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
826 b2 = b & ei.attacked_by(them, KNIGHT);
828 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
831 // Analyse discovered checks (only for non-pawns right now, consider
832 // adding pawns later).
833 if (DiscoveredCheckBonus)
835 b = p.discovered_check_candidates(them) & ~p.pawns();
837 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
840 // Has a mate threat been found? We don't do anything here if the
841 // side with the mating move is the side to move, because in that
842 // case the mating side will get a huge bonus at the end of the main
843 // evaluation function instead.
844 if (ei.mateThreat[them] != MOVE_NONE)
845 attackUnits += MateThreatBonus;
847 // Ensure that attackUnits is between 0 and 99, in order to avoid array
848 // out of bounds errors:
852 if (attackUnits >= 100)
855 // Finally, extract the king safety score from the SafetyTable[] array.
856 // Add the score to the evaluation, and also to ei.futilityMargin. The
857 // reason for adding the king safety score to the futility margin is
858 // that the king safety scores can sometimes be very big, and that
859 // capturing a single attacking piece can therefore result in a score
860 // change far bigger than the value of the captured piece.
861 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
863 ei.mgValue -= sign * v;
865 if (us == p.side_to_move())
866 ei.futilityMargin += v;
871 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
873 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
875 bool hasUnstoppable[2] = {false, false};
876 int movesToGo[2] = {100, 100};
878 for (Color us = WHITE; us <= BLACK; us++)
880 Color them = opposite_color(us);
881 Square ourKingSq = pos.king_square(us);
882 Square theirKingSq = pos.king_square(them);
883 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
887 Square s = pop_1st_bit(&b);
889 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
890 assert(pos.pawn_is_passed(us, s));
892 int r = int(relative_rank(us, s) - RANK_2);
893 int tr = Max(0, r * (r - 1));
894 Square blockSq = s + pawn_push(us);
896 // Base bonus based on rank
897 Value mbonus = Value(20 * tr);
898 Value ebonus = Value(10 + r * r * 10);
900 // Adjust bonus based on king proximity
903 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
904 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
905 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
907 // If the pawn is free to advance, increase bonus
908 if (pos.square_is_empty(blockSq))
910 b2 = squares_in_front_of(us, s);
911 b3 = b2 & ei.attacked_by(them);
912 b4 = b2 & ei.attacked_by(us);
914 // If there is an enemy rook or queen attacking the pawn from behind,
915 // add all X-ray attacks by the rook or queen.
916 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
917 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
920 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
922 // There are no enemy pieces in the pawn's path! Are any of the
923 // squares in the pawn's path attacked by the enemy?
924 if (b3 == EmptyBoardBB)
925 // No enemy attacks, huge bonus!
926 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
928 // OK, there are enemy attacks. Are those squares which are
929 // attacked by the enemy also attacked by us? If yes, big bonus
930 // (but smaller than when there are no enemy attacks), if no,
931 // somewhat smaller bonus.
932 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
936 // There are some enemy pieces in the pawn's path. While this is
937 // sad, we still assign a moderate bonus if all squares in the path
938 // which are either occupied by or attacked by enemy pieces are
939 // also attacked by us.
940 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
941 ebonus += Value(tr * 6);
943 // At last, add a small bonus when there are no *friendly* pieces
944 // in the pawn's path.
945 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
950 // If the pawn is supported by a friendly pawn, increase bonus
951 b2 = pos.pawns(us) & neighboring_files_bb(s);
953 ebonus += Value(r * 20);
954 else if (pos.pawn_attacks(them, s) & b2)
955 ebonus += Value(r * 12);
957 // If the other side has only a king, check whether the pawn is
959 if (pos.non_pawn_material(them) == Value(0))
964 qsq = relative_square(us, make_square(square_file(s), RANK_8));
965 d = square_distance(s, qsq)
966 - square_distance(theirKingSq, qsq)
967 + (us != pos.side_to_move());
971 int mtg = RANK_8 - relative_rank(us, s);
972 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
977 hasUnstoppable[us] = true;
978 movesToGo[us] = Min(movesToGo[us], mtg);
982 // Rook pawns are a special case: They are sometimes worse, and
983 // sometimes better than other passed pawns. It is difficult to find
984 // good rules for determining whether they are good or bad. For now,
985 // we try the following: Increase the value for rook pawns if the
986 // other side has no pieces apart from a knight, and decrease the
987 // value if the other side has a rook or queen.
988 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
990 if( pos.non_pawn_material(them) <= KnightValueMidgame
991 && pos.piece_count(them, KNIGHT) <= 1)
992 ebonus += ebonus / 4;
993 else if(pos.rooks_and_queens(them))
994 ebonus -= ebonus / 4;
997 // Add the scores for this pawn to the middle game and endgame eval.
998 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
999 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1003 // Does either side have an unstoppable passed pawn?
1004 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1005 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1006 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1007 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1008 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1010 // Both sides have unstoppable pawns! Try to find out who queens
1011 // first. We begin by transforming 'movesToGo' to the number of
1012 // plies until the pawn queens for both sides.
1013 movesToGo[WHITE] *= 2;
1014 movesToGo[BLACK] *= 2;
1015 movesToGo[pos.side_to_move()]--;
1017 // If one side queens at least three plies before the other, that
1019 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1020 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1021 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1022 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1024 // We could also add some rules about the situation when one side
1025 // queens exactly one ply before the other: Does the first queen
1026 // check the opponent's king, or attack the opponent's queening square?
1027 // This is slightly tricky to get right, because it is possible that
1028 // the opponent's king has moved somewhere before the first pawn queens.
1033 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1034 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1037 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1039 assert(square_is_ok(s));
1040 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1042 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1043 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1045 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1046 && pos.see(s, b6) < 0
1047 && pos.see(s, b8) < 0)
1049 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1050 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1055 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1056 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1057 // black), and assigns a penalty if it is. This pattern can obviously
1058 // only occur in Chess960 games.
1060 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1062 Piece pawn = piece_of_color_and_type(us, PAWN);
1066 assert(square_is_ok(s));
1067 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1069 if (square_file(s) == FILE_A)
1071 b2 = relative_square(us, SQ_B2);
1072 b3 = relative_square(us, SQ_B3);
1073 c3 = relative_square(us, SQ_C3);
1077 b2 = relative_square(us, SQ_G2);
1078 b3 = relative_square(us, SQ_G3);
1079 c3 = relative_square(us, SQ_F3);
1082 if (pos.piece_on(b2) == pawn)
1086 if (!pos.square_is_empty(b3))
1087 penalty = 2*TrappedBishopA1H1Penalty;
1088 else if (pos.piece_on(c3) == pawn)
1089 penalty = TrappedBishopA1H1Penalty;
1091 penalty = TrappedBishopA1H1Penalty / 2;
1093 ei.mgValue -= Sign[us] * penalty;
1094 ei.egValue -= Sign[us] * penalty;
1099 // evaluate_space() computes the space evaluation for a given side. The
1100 // space evaluation is a simple bonus based on the number of safe squares
1101 // available for minor pieces on the central four files on ranks 2--4. Safe
1102 // squares one, two or three squares behind a friendly pawn are counted
1103 // twice. Finally, the space bonus is scaled by a weight taken from the
1104 // material hash table.
1106 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1108 Color them = opposite_color(us);
1110 // Find the safe squares for our pieces inside the area defined by
1111 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1112 // pawn, or if it is undefended and attacked by an enemy piece.
1114 Bitboard safeSquares = SpaceMask[us]
1116 & ~ei.attacked_by(them, PAWN)
1117 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1119 // Find all squares which are at most three squares behind some friendly
1121 Bitboard behindFriendlyPawns = pos.pawns(us);
1124 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1125 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1129 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1130 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1133 int space = count_1s_max_15(safeSquares)
1134 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1136 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1140 // apply_weight() applies an evaluation weight to a value
1142 inline Value apply_weight(Value v, int w) {
1143 return (v*w) / 0x100;
1147 // scale_by_game_phase() interpolates between a middle game and an endgame
1148 // score, based on game phase. It also scales the return value by a
1149 // ScaleFactor array.
1151 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1153 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1154 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1155 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1157 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1159 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1160 return Value(int(result) & ~(GrainSize - 1));
1164 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1165 // significant bits of a Bitboard. This function is used by the king
1166 // shield evaluation.
1168 int count_1s_8bit(Bitboard b) {
1169 return int(BitCount8Bit[b & 0xFF]);
1173 // compute_weight() computes the value of an evaluation weight, by combining
1174 // an UCI-configurable weight with an internal weight.
1176 int compute_weight(int uciWeight, int internalWeight) {
1178 uciWeight = (uciWeight * 0x100) / 100;
1179 return (uciWeight * internalWeight) / 0x100;
1183 // helper used in read_weights()
1184 int weight_option(const std::string& opt, int weight) {
1186 return compute_weight(get_option_value_int(opt), weight);
1190 // init_safety() initizes the king safety evaluation, based on UCI
1191 // parameters. It is called from read_weights().
1193 void init_safety() {
1195 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1196 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1197 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1198 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1199 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1200 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1201 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1203 int maxSlope = get_option_value_int("King Safety Max Slope");
1204 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1205 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1206 double b = get_option_value_int("King Safety X Intercept");
1207 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1208 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1210 for (int i = 0; i < 100; i++)
1213 SafetyTable[i] = Value(0);
1215 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1217 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1220 for (int i = 0; i < 100; i++)
1222 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1223 for (int j = i + 1; j < 100; j++)
1224 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1226 if (SafetyTable[i] > Value(peak))
1227 SafetyTable[i] = Value(peak);