2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
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))
577 // Initial bonus based on square
579 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
581 // Increase bonus if supported by pawn, especially if the opponent has
582 // no minor piece which can exchange the outpost piece
583 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
586 if ( p.piece_count(them, KNIGHT) == 0
587 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
590 ei.mgValue += Sign[us] * bonus;
591 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 // Shelter cache lookup
713 shelter = ei.pi->kingShelter(us, s);
717 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
718 Rank r = square_rank(s);
719 for (int i = 1; i < 4; i++)
720 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
722 // Cache shelter value in pawn info
723 ei.pi->setKingShelter(us, s, shelter);
725 ei.mgValue += sign * Value(shelter);
728 // King safety. This is quite complicated, and is almost certainly far
729 // from optimally tuned.
730 Color them = opposite_color(us);
732 if ( p.piece_count(them, QUEEN) >= 1
733 && ei.kingAttackersCount[them] >= 2
734 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
735 && ei.kingAdjacentZoneAttacksCount[them])
737 // Is it the attackers turn to move?
738 bool sente = (them == p.side_to_move());
740 // Find the attacked squares around the king which has no defenders
741 // apart from the king itself
742 Bitboard undefended =
743 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
744 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
745 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
746 & ei.attacked_by(us, KING);
748 Bitboard occ = p.occupied_squares(), b, b2;
750 // Initialize the 'attackUnits' variable, which is used later on as an
751 // index to the SafetyTable[] array. The initial value is based on the
752 // number and types of the attacking pieces, the number of attacked and
753 // undefended squares around the king, the square of the king, and the
754 // quality of the pawn shelter.
756 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
757 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
758 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
760 // Analyse safe queen contact checks
761 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
764 Bitboard attackedByOthers =
765 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
766 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
768 b &= attackedByOthers;
771 // The bitboard b now contains the squares available for safe queen
773 int count = count_1s_max_15(b);
774 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
776 // Is there a mate threat?
777 if (QueenContactMates && !p.is_check())
779 Bitboard escapeSquares =
780 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
784 Square from, to = pop_1st_bit(&b);
785 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
787 // We have a mate, unless the queen is pinned or there
788 // is an X-ray attack through the queen.
789 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
791 from = p.piece_list(them, QUEEN, i);
792 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
793 && !bit_is_set(p.pinned_pieces(them), from)
794 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
795 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
797 ei.mateThreat[them] = make_move(from, to);
805 // Analyse safe distance checks
806 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
808 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
811 b2 = b & ei.attacked_by(them, QUEEN);
813 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
816 b2 = b & ei.attacked_by(them, ROOK);
818 attackUnits += RookCheckBonus * count_1s_max_15(b2);
820 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
822 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
825 b2 = b & ei.attacked_by(them, QUEEN);
827 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
830 b2 = b & ei.attacked_by(them, BISHOP);
832 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
834 if (KnightCheckBonus > 0)
836 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
839 b2 = b & ei.attacked_by(them, KNIGHT);
841 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
844 // Analyse discovered checks (only for non-pawns right now, consider
845 // adding pawns later).
846 if (DiscoveredCheckBonus)
848 b = p.discovered_check_candidates(them) & ~p.pawns();
850 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
853 // Has a mate threat been found? We don't do anything here if the
854 // side with the mating move is the side to move, because in that
855 // case the mating side will get a huge bonus at the end of the main
856 // evaluation function instead.
857 if (ei.mateThreat[them] != MOVE_NONE)
858 attackUnits += MateThreatBonus;
860 // Ensure that attackUnits is between 0 and 99, in order to avoid array
861 // out of bounds errors:
865 if (attackUnits >= 100)
868 // Finally, extract the king safety score from the SafetyTable[] array.
869 // Add the score to the evaluation, and also to ei.futilityMargin. The
870 // reason for adding the king safety score to the futility margin is
871 // that the king safety scores can sometimes be very big, and that
872 // capturing a single attacking piece can therefore result in a score
873 // change far bigger than the value of the captured piece.
874 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
876 ei.mgValue -= sign * v;
878 if (us == p.side_to_move())
879 ei.futilityMargin += v;
884 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
886 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
888 bool hasUnstoppable[2] = {false, false};
889 int movesToGo[2] = {100, 100};
891 for (Color us = WHITE; us <= BLACK; us++)
893 Color them = opposite_color(us);
894 Square ourKingSq = pos.king_square(us);
895 Square theirKingSq = pos.king_square(them);
896 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
900 Square s = pop_1st_bit(&b);
902 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
903 assert(pos.pawn_is_passed(us, s));
905 int r = int(relative_rank(us, s) - RANK_2);
906 int tr = Max(0, r * (r - 1));
907 Square blockSq = s + pawn_push(us);
909 // Base bonus based on rank
910 Value mbonus = Value(20 * tr);
911 Value ebonus = Value(10 + r * r * 10);
913 // Adjust bonus based on king proximity
916 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
917 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
918 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
920 // If the pawn is free to advance, increase bonus
921 if (pos.square_is_empty(blockSq))
923 b2 = squares_in_front_of(us, s);
924 b3 = b2 & ei.attacked_by(them);
925 b4 = b2 & ei.attacked_by(us);
927 // If there is an enemy rook or queen attacking the pawn from behind,
928 // add all X-ray attacks by the rook or queen.
929 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
930 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
933 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
935 // There are no enemy pieces in the pawn's path! Are any of the
936 // squares in the pawn's path attacked by the enemy?
937 if (b3 == EmptyBoardBB)
938 // No enemy attacks, huge bonus!
939 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
941 // OK, there are enemy attacks. Are those squares which are
942 // attacked by the enemy also attacked by us? If yes, big bonus
943 // (but smaller than when there are no enemy attacks), if no,
944 // somewhat smaller bonus.
945 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
949 // There are some enemy pieces in the pawn's path. While this is
950 // sad, we still assign a moderate bonus if all squares in the path
951 // which are either occupied by or attacked by enemy pieces are
952 // also attacked by us.
953 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
954 ebonus += Value(tr * 6);
956 // At last, add a small bonus when there are no *friendly* pieces
957 // in the pawn's path.
958 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
963 // If the pawn is supported by a friendly pawn, increase bonus
964 b2 = pos.pawns(us) & neighboring_files_bb(s);
966 ebonus += Value(r * 20);
967 else if (pos.pawn_attacks(them, s) & b2)
968 ebonus += Value(r * 12);
970 // If the other side has only a king, check whether the pawn is
972 if (pos.non_pawn_material(them) == Value(0))
977 qsq = relative_square(us, make_square(square_file(s), RANK_8));
978 d = square_distance(s, qsq)
979 - square_distance(theirKingSq, qsq)
980 + (us != pos.side_to_move());
984 int mtg = RANK_8 - relative_rank(us, s);
985 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
990 hasUnstoppable[us] = true;
991 movesToGo[us] = Min(movesToGo[us], mtg);
995 // Rook pawns are a special case: They are sometimes worse, and
996 // sometimes better than other passed pawns. It is difficult to find
997 // good rules for determining whether they are good or bad. For now,
998 // we try the following: Increase the value for rook pawns if the
999 // other side has no pieces apart from a knight, and decrease the
1000 // value if the other side has a rook or queen.
1001 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
1003 if( pos.non_pawn_material(them) <= KnightValueMidgame
1004 && pos.piece_count(them, KNIGHT) <= 1)
1005 ebonus += ebonus / 4;
1006 else if(pos.rooks_and_queens(them))
1007 ebonus -= ebonus / 4;
1010 // Add the scores for this pawn to the middle game and endgame eval.
1011 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1012 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1016 // Does either side have an unstoppable passed pawn?
1017 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1018 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1019 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1020 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1021 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1023 // Both sides have unstoppable pawns! Try to find out who queens
1024 // first. We begin by transforming 'movesToGo' to the number of
1025 // plies until the pawn queens for both sides.
1026 movesToGo[WHITE] *= 2;
1027 movesToGo[BLACK] *= 2;
1028 movesToGo[pos.side_to_move()]--;
1030 // If one side queens at least three plies before the other, that
1032 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1033 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1034 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1035 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1037 // We could also add some rules about the situation when one side
1038 // queens exactly one ply before the other: Does the first queen
1039 // check the opponent's king, or attack the opponent's queening square?
1040 // This is slightly tricky to get right, because it is possible that
1041 // the opponent's king has moved somewhere before the first pawn queens.
1046 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1047 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1050 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1052 assert(square_is_ok(s));
1053 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1055 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1056 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1058 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1059 && pos.see(s, b6) < 0
1060 && pos.see(s, b8) < 0)
1062 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1063 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1068 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1069 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1070 // black), and assigns a penalty if it is. This pattern can obviously
1071 // only occur in Chess960 games.
1073 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1075 Piece pawn = piece_of_color_and_type(us, PAWN);
1079 assert(square_is_ok(s));
1080 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1082 if (square_file(s) == FILE_A)
1084 b2 = relative_square(us, SQ_B2);
1085 b3 = relative_square(us, SQ_B3);
1086 c3 = relative_square(us, SQ_C3);
1090 b2 = relative_square(us, SQ_G2);
1091 b3 = relative_square(us, SQ_G3);
1092 c3 = relative_square(us, SQ_F3);
1095 if (pos.piece_on(b2) == pawn)
1099 if (!pos.square_is_empty(b3))
1100 penalty = 2*TrappedBishopA1H1Penalty;
1101 else if (pos.piece_on(c3) == pawn)
1102 penalty = TrappedBishopA1H1Penalty;
1104 penalty = TrappedBishopA1H1Penalty / 2;
1106 ei.mgValue -= Sign[us] * penalty;
1107 ei.egValue -= Sign[us] * penalty;
1112 // evaluate_space() computes the space evaluation for a given side. The
1113 // space evaluation is a simple bonus based on the number of safe squares
1114 // available for minor pieces on the central four files on ranks 2--4. Safe
1115 // squares one, two or three squares behind a friendly pawn are counted
1116 // twice. Finally, the space bonus is scaled by a weight taken from the
1117 // material hash table.
1119 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1121 Color them = opposite_color(us);
1123 // Find the safe squares for our pieces inside the area defined by
1124 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1125 // pawn, or if it is undefended and attacked by an enemy piece.
1127 Bitboard safeSquares = SpaceMask[us]
1129 & ~ei.attacked_by(them, PAWN)
1130 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1132 // Find all squares which are at most three squares behind some friendly
1134 Bitboard behindFriendlyPawns = pos.pawns(us);
1137 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1138 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1142 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1143 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1146 int space = count_1s_max_15(safeSquares)
1147 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1149 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1153 // apply_weight() applies an evaluation weight to a value
1155 inline Value apply_weight(Value v, int w) {
1156 return (v*w) / 0x100;
1160 // scale_by_game_phase() interpolates between a middle game and an endgame
1161 // score, based on game phase. It also scales the return value by a
1162 // ScaleFactor array.
1164 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1166 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1167 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1168 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1170 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1172 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1173 return Value(int(result) & ~(GrainSize - 1));
1177 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1178 // significant bits of a Bitboard. This function is used by the king
1179 // shield evaluation.
1181 int count_1s_8bit(Bitboard b) {
1182 return int(BitCount8Bit[b & 0xFF]);
1186 // compute_weight() computes the value of an evaluation weight, by combining
1187 // an UCI-configurable weight with an internal weight.
1189 int compute_weight(int uciWeight, int internalWeight) {
1191 uciWeight = (uciWeight * 0x100) / 100;
1192 return (uciWeight * internalWeight) / 0x100;
1196 // helper used in read_weights()
1197 int weight_option(const std::string& opt, int weight) {
1199 return compute_weight(get_option_value_int(opt), weight);
1203 // init_safety() initizes the king safety evaluation, based on UCI
1204 // parameters. It is called from read_weights().
1206 void init_safety() {
1208 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1209 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1210 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1211 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1212 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1213 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1214 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1216 int maxSlope = get_option_value_int("King Safety Max Slope");
1217 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1218 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1219 double b = get_option_value_int("King Safety X Intercept");
1220 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1221 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1223 for (int i = 0; i < 100; i++)
1226 SafetyTable[i] = Value(0);
1228 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1230 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1233 for (int i = 0; i < 100; i++)
1235 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1236 for (int j = i + 1; j < 100; j++)
1237 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1239 if (SafetyTable[i] > Value(peak))
1240 SafetyTable[i] = Value(peak);