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];
509 MaterialTable[i] = NULL;
514 /// read_weights() reads evaluation weights from the corresponding UCI
517 void read_weights(Color us) {
519 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
520 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
521 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
522 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
523 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
524 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
526 Color them = opposite_color(us);
528 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
529 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
530 WeightSpace = weight_option("Space", WeightSpaceInternal);
538 // evaluate_common() computes terms common to all pieces attack
540 template<PieceType Piece>
541 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
543 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
544 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
545 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
546 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
548 Color them = opposite_color(us);
550 // Update attack info
551 ei.attackedBy[us][Piece] |= b;
554 if (b & ei.kingZone[us])
556 ei.kingAttackersCount[us]++;
557 ei.kingAttackersWeight[us] += AttackWeight[Piece];
558 Bitboard bb = (b & ei.attackedBy[them][KING]);
560 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
563 // Remove squares protected by enemy pawns
564 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
567 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
568 : count_1s(bb & ~p.pieces_of_color(us)));
570 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
571 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
573 // Bishop and Knight outposts
574 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
575 || !p.square_is_weak(s, them))
578 // Initial bonus based on square
580 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
582 // Increase bonus if supported by pawn, especially if the opponent has
583 // no minor piece which can exchange the outpost piece
584 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
587 if ( p.piece_count(them, KNIGHT) == 0
588 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
591 ei.mgValue += Sign[us] * bonus;
592 ei.egValue += Sign[us] * bonus;
597 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
600 template<PieceType Piece>
601 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
609 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
611 s = pos.piece_list(us, Piece, i);
613 if (Piece == KNIGHT || Piece == QUEEN)
614 b = pos.piece_attacks<Piece>(s);
615 else if (Piece == BISHOP)
616 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
617 else if (Piece == ROOK)
618 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
620 // Attacks, mobility and outposts
621 mob = evaluate_common<Piece>(pos, b, us, ei, s);
623 // Special patterns: trapped bishops on a7/h7/a2/h2
624 // and trapped bishops on a1/h1/a8/h8 in Chess960.
627 if (bit_is_set(MaskA7H7[us], s))
628 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
630 if (Chess960 && bit_is_set(MaskA1H1[us], s))
631 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
634 if (Piece == ROOK || Piece == QUEEN)
636 // Queen or rook on 7th rank
637 them = opposite_color(us);
639 if ( relative_rank(us, s) == RANK_7
640 && relative_rank(us, pos.king_square(them)) == RANK_8)
642 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
643 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
647 // Special extra evaluation for rooks
650 // Open and half-open files
652 if (ei.pi->file_is_half_open(us, f))
654 if (ei.pi->file_is_half_open(them, f))
656 ei.mgValue += Sign[us] * RookOpenFileBonus;
657 ei.egValue += Sign[us] * RookOpenFileBonus;
661 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
662 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
666 // Penalize rooks which are trapped inside a king. Penalize more if
667 // king has lost right to castle.
668 if (mob > 6 || ei.pi->file_is_half_open(us, f))
671 ksq = pos.king_square(us);
673 if ( square_file(ksq) >= FILE_E
674 && square_file(s) > square_file(ksq)
675 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
677 // Is there a half-open file between the king and the edge of the board?
678 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
679 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
680 : Sign[us] * (TrappedRookPenalty - mob * 16);
682 else if ( square_file(ksq) <= FILE_D
683 && square_file(s) < square_file(ksq)
684 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
686 // Is there a half-open file between the king and the edge of the board?
687 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
688 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
689 : Sign[us] * (TrappedRookPenalty - mob * 16);
695 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
697 return b >> (num << 3);
700 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
704 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
706 int shelter = 0, sign = Sign[us];
707 Square s = p.king_square(us);
710 if (relative_rank(us, s) <= RANK_4)
712 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
713 Rank r = square_rank(s);
714 for (int i = 1; i < 4; i++)
715 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
717 ei.mgValue += sign * Value(shelter);
720 // King safety. This is quite complicated, and is almost certainly far
721 // from optimally tuned.
722 Color them = opposite_color(us);
724 if ( p.piece_count(them, QUEEN) >= 1
725 && ei.kingAttackersCount[them] >= 2
726 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
727 && ei.kingAdjacentZoneAttacksCount[them])
729 // Is it the attackers turn to move?
730 bool sente = (them == p.side_to_move());
732 // Find the attacked squares around the king which has no defenders
733 // apart from the king itself
734 Bitboard undefended =
735 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
736 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
737 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
738 & ei.attacked_by(us, KING);
740 Bitboard occ = p.occupied_squares(), b, b2;
742 // Initialize the 'attackUnits' variable, which is used later on as an
743 // index to the SafetyTable[] array. The initial value is based on the
744 // number and types of the attacking pieces, the number of attacked and
745 // undefended squares around the king, the square of the king, and the
746 // quality of the pawn shelter.
748 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
749 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
750 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
752 // Analyse safe queen contact checks
753 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
756 Bitboard attackedByOthers =
757 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
758 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
760 b &= attackedByOthers;
763 // The bitboard b now contains the squares available for safe queen
765 int count = count_1s_max_15(b);
766 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
768 // Is there a mate threat?
769 if (QueenContactMates && !p.is_check())
771 Bitboard escapeSquares =
772 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
776 Square from, to = pop_1st_bit(&b);
777 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
779 // We have a mate, unless the queen is pinned or there
780 // is an X-ray attack through the queen.
781 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
783 from = p.piece_list(them, QUEEN, i);
784 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
785 && !bit_is_set(p.pinned_pieces(them), from)
786 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
787 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
789 ei.mateThreat[them] = make_move(from, to);
797 // Analyse safe distance checks
798 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
800 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
803 b2 = b & ei.attacked_by(them, QUEEN);
805 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
808 b2 = b & ei.attacked_by(them, ROOK);
810 attackUnits += RookCheckBonus * count_1s_max_15(b2);
812 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
814 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
817 b2 = b & ei.attacked_by(them, QUEEN);
819 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
822 b2 = b & ei.attacked_by(them, BISHOP);
824 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
826 if (KnightCheckBonus > 0)
828 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
831 b2 = b & ei.attacked_by(them, KNIGHT);
833 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
836 // Analyse discovered checks (only for non-pawns right now, consider
837 // adding pawns later).
838 if (DiscoveredCheckBonus)
840 b = p.discovered_check_candidates(them) & ~p.pawns();
842 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
845 // Has a mate threat been found? We don't do anything here if the
846 // side with the mating move is the side to move, because in that
847 // case the mating side will get a huge bonus at the end of the main
848 // evaluation function instead.
849 if (ei.mateThreat[them] != MOVE_NONE)
850 attackUnits += MateThreatBonus;
852 // Ensure that attackUnits is between 0 and 99, in order to avoid array
853 // out of bounds errors:
857 if (attackUnits >= 100)
860 // Finally, extract the king safety score from the SafetyTable[] array.
861 // Add the score to the evaluation, and also to ei.futilityMargin. The
862 // reason for adding the king safety score to the futility margin is
863 // that the king safety scores can sometimes be very big, and that
864 // capturing a single attacking piece can therefore result in a score
865 // change far bigger than the value of the captured piece.
866 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
868 ei.mgValue -= sign * v;
870 if (us == p.side_to_move())
871 ei.futilityMargin += v;
876 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
878 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
880 bool hasUnstoppable[2] = {false, false};
881 int movesToGo[2] = {100, 100};
883 for (Color us = WHITE; us <= BLACK; us++)
885 Color them = opposite_color(us);
886 Square ourKingSq = pos.king_square(us);
887 Square theirKingSq = pos.king_square(them);
888 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
892 Square s = pop_1st_bit(&b);
894 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
895 assert(pos.pawn_is_passed(us, s));
897 int r = int(relative_rank(us, s) - RANK_2);
898 int tr = Max(0, r * (r - 1));
899 Square blockSq = s + pawn_push(us);
901 // Base bonus based on rank
902 Value mbonus = Value(20 * tr);
903 Value ebonus = Value(10 + r * r * 10);
905 // Adjust bonus based on king proximity
908 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
909 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
910 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
912 // If the pawn is free to advance, increase bonus
913 if (pos.square_is_empty(blockSq))
915 b2 = squares_in_front_of(us, s);
916 b3 = b2 & ei.attacked_by(them);
917 b4 = b2 & ei.attacked_by(us);
919 // If there is an enemy rook or queen attacking the pawn from behind,
920 // add all X-ray attacks by the rook or queen.
921 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
922 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
925 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
927 // There are no enemy pieces in the pawn's path! Are any of the
928 // squares in the pawn's path attacked by the enemy?
929 if (b3 == EmptyBoardBB)
930 // No enemy attacks, huge bonus!
931 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
933 // OK, there are enemy attacks. Are those squares which are
934 // attacked by the enemy also attacked by us? If yes, big bonus
935 // (but smaller than when there are no enemy attacks), if no,
936 // somewhat smaller bonus.
937 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
941 // There are some enemy pieces in the pawn's path. While this is
942 // sad, we still assign a moderate bonus if all squares in the path
943 // which are either occupied by or attacked by enemy pieces are
944 // also attacked by us.
945 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
946 ebonus += Value(tr * 6);
948 // At last, add a small bonus when there are no *friendly* pieces
949 // in the pawn's path.
950 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
955 // If the pawn is supported by a friendly pawn, increase bonus
956 b2 = pos.pawns(us) & neighboring_files_bb(s);
958 ebonus += Value(r * 20);
959 else if (pos.pawn_attacks(them, s) & b2)
960 ebonus += Value(r * 12);
962 // If the other side has only a king, check whether the pawn is
964 if (pos.non_pawn_material(them) == Value(0))
969 qsq = relative_square(us, make_square(square_file(s), RANK_8));
970 d = square_distance(s, qsq)
971 - square_distance(theirKingSq, qsq)
972 + (us != pos.side_to_move());
976 int mtg = RANK_8 - relative_rank(us, s);
977 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
982 hasUnstoppable[us] = true;
983 movesToGo[us] = Min(movesToGo[us], mtg);
987 // Rook pawns are a special case: They are sometimes worse, and
988 // sometimes better than other passed pawns. It is difficult to find
989 // good rules for determining whether they are good or bad. For now,
990 // we try the following: Increase the value for rook pawns if the
991 // other side has no pieces apart from a knight, and decrease the
992 // value if the other side has a rook or queen.
993 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
995 if( pos.non_pawn_material(them) <= KnightValueMidgame
996 && pos.piece_count(them, KNIGHT) <= 1)
997 ebonus += ebonus / 4;
998 else if(pos.rooks_and_queens(them))
999 ebonus -= ebonus / 4;
1002 // Add the scores for this pawn to the middle game and endgame eval.
1003 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1004 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1008 // Does either side have an unstoppable passed pawn?
1009 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1010 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1011 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1012 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1013 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1015 // Both sides have unstoppable pawns! Try to find out who queens
1016 // first. We begin by transforming 'movesToGo' to the number of
1017 // plies until the pawn queens for both sides.
1018 movesToGo[WHITE] *= 2;
1019 movesToGo[BLACK] *= 2;
1020 movesToGo[pos.side_to_move()]--;
1022 // If one side queens at least three plies before the other, that
1024 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1025 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1026 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1027 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1029 // We could also add some rules about the situation when one side
1030 // queens exactly one ply before the other: Does the first queen
1031 // check the opponent's king, or attack the opponent's queening square?
1032 // This is slightly tricky to get right, because it is possible that
1033 // the opponent's king has moved somewhere before the first pawn queens.
1038 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1039 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1042 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1044 assert(square_is_ok(s));
1045 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1047 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1048 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1050 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1051 && pos.see(s, b6) < 0
1052 && pos.see(s, b8) < 0)
1054 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1055 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1060 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1061 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1062 // black), and assigns a penalty if it is. This pattern can obviously
1063 // only occur in Chess960 games.
1065 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1067 Piece pawn = piece_of_color_and_type(us, PAWN);
1071 assert(square_is_ok(s));
1072 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1074 if (square_file(s) == FILE_A)
1076 b2 = relative_square(us, SQ_B2);
1077 b3 = relative_square(us, SQ_B3);
1078 c3 = relative_square(us, SQ_C3);
1082 b2 = relative_square(us, SQ_G2);
1083 b3 = relative_square(us, SQ_G3);
1084 c3 = relative_square(us, SQ_F3);
1087 if (pos.piece_on(b2) == pawn)
1091 if (!pos.square_is_empty(b3))
1092 penalty = 2*TrappedBishopA1H1Penalty;
1093 else if (pos.piece_on(c3) == pawn)
1094 penalty = TrappedBishopA1H1Penalty;
1096 penalty = TrappedBishopA1H1Penalty / 2;
1098 ei.mgValue -= Sign[us] * penalty;
1099 ei.egValue -= Sign[us] * penalty;
1104 // evaluate_space() computes the space evaluation for a given side. The
1105 // space evaluation is a simple bonus based on the number of safe squares
1106 // available for minor pieces on the central four files on ranks 2--4. Safe
1107 // squares one, two or three squares behind a friendly pawn are counted
1108 // twice. Finally, the space bonus is scaled by a weight taken from the
1109 // material hash table.
1111 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1113 Color them = opposite_color(us);
1115 // Find the safe squares for our pieces inside the area defined by
1116 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1117 // pawn, or if it is undefended and attacked by an enemy piece.
1119 Bitboard safeSquares = SpaceMask[us]
1121 & ~ei.attacked_by(them, PAWN)
1122 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1124 // Find all squares which are at most three squares behind some friendly
1126 Bitboard behindFriendlyPawns = pos.pawns(us);
1129 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1130 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1134 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1135 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1138 int space = count_1s_max_15(safeSquares)
1139 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1141 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1145 // apply_weight() applies an evaluation weight to a value
1147 inline Value apply_weight(Value v, int w) {
1148 return (v*w) / 0x100;
1152 // scale_by_game_phase() interpolates between a middle game and an endgame
1153 // score, based on game phase. It also scales the return value by a
1154 // ScaleFactor array.
1156 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1158 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1159 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1160 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1162 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1164 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1165 return Value(int(result) & ~(GrainSize - 1));
1169 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1170 // significant bits of a Bitboard. This function is used by the king
1171 // shield evaluation.
1173 int count_1s_8bit(Bitboard b) {
1174 return int(BitCount8Bit[b & 0xFF]);
1178 // compute_weight() computes the value of an evaluation weight, by combining
1179 // an UCI-configurable weight with an internal weight.
1181 int compute_weight(int uciWeight, int internalWeight) {
1183 uciWeight = (uciWeight * 0x100) / 100;
1184 return (uciWeight * internalWeight) / 0x100;
1188 // helper used in read_weights()
1189 int weight_option(const std::string& opt, int weight) {
1191 return compute_weight(get_option_value_int(opt), weight);
1195 // init_safety() initizes the king safety evaluation, based on UCI
1196 // parameters. It is called from read_weights().
1198 void init_safety() {
1200 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1201 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1202 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1203 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1204 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1205 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1206 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1208 int maxSlope = get_option_value_int("King Safety Max Slope");
1209 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1210 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1211 double b = get_option_value_int("King Safety X Intercept");
1212 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1213 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1215 for (int i = 0; i < 100; i++)
1218 SafetyTable[i] = Value(0);
1220 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1222 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1225 for (int i = 0; i < 100; i++)
1227 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1228 for (int j = i + 1; j < 100; j++)
1229 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1231 if (SafetyTable[i] > Value(peak))
1232 SafetyTable[i] = Value(peak);