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);
293 int count_1s_8bit(Bitboard b);
295 int compute_weight(int uciWeight, int internalWeight);
296 int weight_option(const std::string& opt, int weight);
306 /// evaluate() is the main evaluation function. It always computes two
307 /// values, an endgame score and a middle game score, and interpolates
308 /// between them based on the remaining material.
310 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
313 assert(threadID >= 0 && threadID < THREAD_MAX);
315 memset(&ei, 0, sizeof(EvalInfo));
317 // Initialize by reading the incrementally updated scores included in the
318 // position object (material + piece square tables)
319 ei.mgValue = pos.mg_value();
320 ei.egValue = pos.eg_value();
322 // Probe the material hash table
323 ei.mi = MaterialTable[threadID]->get_material_info(pos);
324 ei.mgValue += ei.mi->mg_value();
325 ei.egValue += ei.mi->eg_value();
327 // If we have a specialized evaluation function for the current material
328 // configuration, call it and return
329 if (ei.mi->specialized_eval_exists())
330 return ei.mi->evaluate(pos);
332 // After get_material_info() call that modifies them
333 ScaleFactor factor[2];
334 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
335 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
337 // Probe the pawn hash table
338 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
339 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
340 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
342 // Initialize king attack bitboards and king attack zones for both sides
343 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
344 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
345 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
346 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
348 // Initialize pawn attack bitboards for both sides
349 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
350 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
351 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
352 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
355 for (Color c = WHITE; c <= BLACK; c++)
357 evaluate_pieces<KNIGHT>(pos, c, ei);
358 evaluate_pieces<BISHOP>(pos, c, ei);
359 evaluate_pieces<ROOK>(pos, c, ei);
360 evaluate_pieces<QUEEN>(pos, c, ei);
362 // Sum up all attacked squares
363 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
364 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
365 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
368 // Kings. Kings are evaluated after all other pieces for both sides,
369 // because we need complete attack information for all pieces when computing
370 // the king safety evaluation.
371 for (Color c = WHITE; c <= BLACK; c++)
372 evaluate_pieces<KING>(pos, c, ei);
374 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
375 // because we need to know which side promotes first in positions where
376 // both sides have an unstoppable passed pawn.
377 if (ei.pi->passed_pawns())
378 evaluate_passed_pawns(pos, ei);
380 Phase phase = pos.game_phase();
382 // Middle-game specific evaluation terms
383 if (phase > PHASE_ENDGAME)
385 // Pawn storms in positions with opposite castling.
386 if ( square_file(pos.king_square(WHITE)) >= FILE_E
387 && square_file(pos.king_square(BLACK)) <= FILE_D)
389 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
390 - ei.pi->kingside_storm_value(BLACK);
392 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
393 && square_file(pos.king_square(BLACK)) >= FILE_E)
395 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
396 - ei.pi->queenside_storm_value(BLACK);
398 // Evaluate space for both sides
399 if (ei.mi->space_weight() > 0)
401 evaluate_space(pos, WHITE, ei);
402 evaluate_space(pos, BLACK, ei);
407 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
408 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
410 // If we don't already have an unusual scale factor, check for opposite
411 // colored bishop endgames, and use a lower scale for those
412 if ( phase < PHASE_MIDGAME
413 && pos.opposite_colored_bishops()
414 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
415 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
419 // Only the two bishops ?
420 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
421 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
423 // Check for KBP vs KB with only a single pawn that is almost
424 // certainly a draw or at least two pawns.
425 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
426 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
429 // Endgame with opposite-colored bishops, but also other pieces. Still
430 // a bit drawish, but not as drawish as with only the two bishops.
431 sf = ScaleFactor(50);
433 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
435 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
439 // Interpolate between the middle game and the endgame score, and
441 Color stm = pos.side_to_move();
443 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
445 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
449 /// quick_evaluate() does a very approximate evaluation of the current position.
450 /// It currently considers only material and piece square table scores. Perhaps
451 /// we should add scores from the pawn and material hash tables?
453 Value quick_evaluate(const Position &pos) {
458 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
460 Value mgv = pos.mg_value();
461 Value egv = pos.eg_value();
462 Phase ph = pos.game_phase();
463 Color stm = pos.side_to_move();
465 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
469 /// init_eval() initializes various tables used by the evaluation function.
471 void init_eval(int threads) {
473 assert(threads <= THREAD_MAX);
475 for (int i = 0; i < THREAD_MAX; i++)
480 delete MaterialTable[i];
482 MaterialTable[i] = NULL;
486 PawnTable[i] = new PawnInfoTable(PawnTableSize);
487 if (!MaterialTable[i])
488 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
491 for (Bitboard b = 0ULL; b < 256ULL; b++)
492 BitCount8Bit[b] = count_1s(b);
496 /// quit_eval() releases heap-allocated memory at program termination.
500 for (int i = 0; i < THREAD_MAX; i++)
503 delete MaterialTable[i];
508 /// read_weights() reads evaluation weights from the corresponding UCI
511 void read_weights(Color us) {
513 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
514 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
515 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
516 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
517 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
518 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
520 Color them = opposite_color(us);
522 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
523 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
524 WeightSpace = weight_option("Space", WeightSpaceInternal);
530 /// scale_by_game_phase() interpolates between a middle game and an endgame
531 /// score, based on game phase. It also scales the return value by a
532 /// ScaleFactor array.
534 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
536 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
537 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
538 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
540 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
542 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
543 return Value(int(result) & ~(GrainSize - 1));
548 // evaluate_common() computes terms common to all pieces attack
550 template<PieceType Piece>
551 int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
553 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
554 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
555 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
556 static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
558 Color them = opposite_color(us);
560 // Update attack info
561 ei.attackedBy[us][Piece] |= b;
564 if (b & ei.kingZone[us])
566 ei.kingAttackersCount[us]++;
567 ei.kingAttackersWeight[us] += AttackWeight[Piece];
568 Bitboard bb = (b & ei.attackedBy[them][KING]);
570 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
573 // Remove squares protected by enemy pawns
574 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
577 int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
578 : count_1s(bb & ~p.pieces_of_color(us)));
580 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
581 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
583 // Bishop and Knight outposts
584 if ( (Piece != BISHOP && Piece != KNIGHT) // compile time condition
585 || !p.square_is_weak(s, them))
588 // Initial bonus based on square
590 v = bonus = OutpostBonus[Piece][relative_square(us, s)];
592 // Increase bonus if supported by pawn, especially if the opponent has
593 // no minor piece which can exchange the outpost piece
594 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
597 if ( p.piece_count(them, KNIGHT) == 0
598 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
601 ei.mgValue += Sign[us] * bonus;
602 ei.egValue += Sign[us] * bonus;
607 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
610 template<PieceType Piece>
611 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
619 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
621 s = pos.piece_list(us, Piece, i);
623 if (Piece == KNIGHT || Piece == QUEEN)
624 b = pos.piece_attacks<Piece>(s);
625 else if (Piece == BISHOP)
626 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
627 else if (Piece == ROOK)
628 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
630 // Attacks, mobility and outposts
631 mob = evaluate_common<Piece>(pos, b, us, ei, s);
633 // Special patterns: trapped bishops on a7/h7/a2/h2
634 // and trapped bishops on a1/h1/a8/h8 in Chess960.
637 if (bit_is_set(MaskA7H7[us], s))
638 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
640 if (Chess960 && bit_is_set(MaskA1H1[us], s))
641 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
644 if (Piece != ROOK && Piece != QUEEN)
647 // Queen or rook on 7th rank
648 them = opposite_color(us);
650 if ( relative_rank(us, s) == RANK_7
651 && relative_rank(us, pos.king_square(them)) == RANK_8)
653 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
654 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
657 // Special extra evaluation for rooks
661 // Open and half-open files
663 if (ei.pi->file_is_half_open(us, f))
665 if (ei.pi->file_is_half_open(them, f))
667 ei.mgValue += Sign[us] * RookOpenFileBonus;
668 ei.egValue += Sign[us] * RookOpenFileBonus;
672 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
673 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
677 // Penalize rooks which are trapped inside a king. Penalize more if
678 // king has lost right to castle.
679 if (mob > 6 || ei.pi->file_is_half_open(us, f))
682 ksq = pos.king_square(us);
684 if ( square_file(ksq) >= FILE_E
685 && square_file(s) > square_file(ksq)
686 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
688 // Is there a half-open file between the king and the edge of the board?
689 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
690 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
691 : Sign[us] * (TrappedRookPenalty - mob * 16);
693 else if ( square_file(ksq) <= FILE_D
694 && square_file(s) < square_file(ksq)
695 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
697 // Is there a half-open file between the king and the edge of the board?
698 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
699 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
700 : Sign[us] * (TrappedRookPenalty - mob * 16);
705 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
707 return b >> (num << 3);
710 // evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
714 void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
716 int shelter = 0, sign = Sign[us];
717 Square s = p.king_square(us);
720 if (relative_rank(us, s) <= RANK_4)
722 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
723 Rank r = square_rank(s);
724 for (int i = 1; i < 4; i++)
725 shelter += count_1s_8bit(shiftRowsDown(pawns, r+i*sign)) * (128>>i);
727 ei.mgValue += sign * Value(shelter);
730 // King safety. This is quite complicated, and is almost certainly far
731 // from optimally tuned.
732 Color them = opposite_color(us);
734 if ( p.piece_count(them, QUEEN) >= 1
735 && ei.kingAttackersCount[them] >= 2
736 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
737 && ei.kingAdjacentZoneAttacksCount[them])
739 // Is it the attackers turn to move?
740 bool sente = (them == p.side_to_move());
742 // Find the attacked squares around the king which has no defenders
743 // apart from the king itself
744 Bitboard undefended =
745 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
746 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
747 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
748 & ei.attacked_by(us, KING);
750 Bitboard occ = p.occupied_squares(), b, b2;
752 // Initialize the 'attackUnits' variable, which is used later on as an
753 // index to the SafetyTable[] array. The initial value is based on the
754 // number and types of the attacking pieces, the number of attacked and
755 // undefended squares around the king, the square of the king, and the
756 // quality of the pawn shelter.
758 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
759 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
760 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
762 // Analyse safe queen contact checks
763 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
766 Bitboard attackedByOthers =
767 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
768 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
770 b &= attackedByOthers;
773 // The bitboard b now contains the squares available for safe queen
775 int count = count_1s_max_15(b);
776 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
778 // Is there a mate threat?
779 if (QueenContactMates && !p.is_check())
781 Bitboard escapeSquares =
782 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
786 Square from, to = pop_1st_bit(&b);
787 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
789 // We have a mate, unless the queen is pinned or there
790 // is an X-ray attack through the queen.
791 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
793 from = p.piece_list(them, QUEEN, i);
794 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
795 && !bit_is_set(p.pinned_pieces(them), from)
796 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
797 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us)))
799 ei.mateThreat[them] = make_move(from, to);
807 // Analyse safe distance checks
808 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
810 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
813 b2 = b & ei.attacked_by(them, QUEEN);
815 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
818 b2 = b & ei.attacked_by(them, ROOK);
820 attackUnits += RookCheckBonus * count_1s_max_15(b2);
822 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
824 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
827 b2 = b & ei.attacked_by(them, QUEEN);
829 attackUnits += QueenCheckBonus * count_1s_max_15(b2);
832 b2 = b & ei.attacked_by(them, BISHOP);
834 attackUnits += BishopCheckBonus * count_1s_max_15(b2);
836 if (KnightCheckBonus > 0)
838 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
841 b2 = b & ei.attacked_by(them, KNIGHT);
843 attackUnits += KnightCheckBonus * count_1s_max_15(b2);
846 // Analyse discovered checks (only for non-pawns right now, consider
847 // adding pawns later).
848 if (DiscoveredCheckBonus)
850 b = p.discovered_check_candidates(them) & ~p.pawns();
852 attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
855 // Has a mate threat been found? We don't do anything here if the
856 // side with the mating move is the side to move, because in that
857 // case the mating side will get a huge bonus at the end of the main
858 // evaluation function instead.
859 if (ei.mateThreat[them] != MOVE_NONE)
860 attackUnits += MateThreatBonus;
862 // Ensure that attackUnits is between 0 and 99, in order to avoid array
863 // out of bounds errors:
867 if (attackUnits >= 100)
870 // Finally, extract the king safety score from the SafetyTable[] array.
871 // Add the score to the evaluation, and also to ei.futilityMargin. The
872 // reason for adding the king safety score to the futility margin is
873 // that the king safety scores can sometimes be very big, and that
874 // capturing a single attacking piece can therefore result in a score
875 // change far bigger than the value of the captured piece.
876 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
878 ei.mgValue -= sign * v;
880 if (us == p.side_to_move())
881 ei.futilityMargin += v;
886 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
888 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
890 bool hasUnstoppable[2] = {false, false};
891 int movesToGo[2] = {100, 100};
893 for (Color us = WHITE; us <= BLACK; us++)
895 Color them = opposite_color(us);
896 Square ourKingSq = pos.king_square(us);
897 Square theirKingSq = pos.king_square(them);
898 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
902 Square s = pop_1st_bit(&b);
904 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
905 assert(pos.pawn_is_passed(us, s));
907 int r = int(relative_rank(us, s) - RANK_2);
908 int tr = Max(0, r * (r - 1));
909 Square blockSq = s + pawn_push(us);
911 // Base bonus based on rank
912 Value mbonus = Value(20 * tr);
913 Value ebonus = Value(10 + r * r * 10);
915 // Adjust bonus based on king proximity
918 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
919 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
920 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
922 // If the pawn is free to advance, increase bonus
923 if (pos.square_is_empty(blockSq))
925 b2 = squares_in_front_of(us, s);
926 b3 = b2 & ei.attacked_by(them);
927 b4 = b2 & ei.attacked_by(us);
929 // If there is an enemy rook or queen attacking the pawn from behind,
930 // add all X-ray attacks by the rook or queen.
931 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
932 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
935 if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
937 // There are no enemy pieces in the pawn's path! Are any of the
938 // squares in the pawn's path attacked by the enemy?
939 if (b3 == EmptyBoardBB)
940 // No enemy attacks, huge bonus!
941 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
943 // OK, there are enemy attacks. Are those squares which are
944 // attacked by the enemy also attacked by us? If yes, big bonus
945 // (but smaller than when there are no enemy attacks), if no,
946 // somewhat smaller bonus.
947 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
951 // There are some enemy pieces in the pawn's path. While this is
952 // sad, we still assign a moderate bonus if all squares in the path
953 // which are either occupied by or attacked by enemy pieces are
954 // also attacked by us.
955 if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
956 ebonus += Value(tr * 6);
958 // At last, add a small bonus when there are no *friendly* pieces
959 // in the pawn's path.
960 if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
965 // If the pawn is supported by a friendly pawn, increase bonus
966 b2 = pos.pawns(us) & neighboring_files_bb(s);
968 ebonus += Value(r * 20);
969 else if (pos.pawn_attacks(them, s) & b2)
970 ebonus += Value(r * 12);
972 // If the other side has only a king, check whether the pawn is
974 if (pos.non_pawn_material(them) == Value(0))
979 qsq = relative_square(us, make_square(square_file(s), RANK_8));
980 d = square_distance(s, qsq)
981 - square_distance(theirKingSq, qsq)
982 + (us != pos.side_to_move());
986 int mtg = RANK_8 - relative_rank(us, s);
987 int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
992 hasUnstoppable[us] = true;
993 movesToGo[us] = Min(movesToGo[us], mtg);
997 // Rook pawns are a special case: They are sometimes worse, and
998 // sometimes better than other passed pawns. It is difficult to find
999 // good rules for determining whether they are good or bad. For now,
1000 // we try the following: Increase the value for rook pawns if the
1001 // other side has no pieces apart from a knight, and decrease the
1002 // value if the other side has a rook or queen.
1003 if (square_file(s) == FILE_A || square_file(s) == FILE_H)
1005 if( pos.non_pawn_material(them) <= KnightValueMidgame
1006 && pos.piece_count(them, KNIGHT) <= 1)
1007 ebonus += ebonus / 4;
1008 else if(pos.rooks_and_queens(them))
1009 ebonus -= ebonus / 4;
1012 // Add the scores for this pawn to the middle game and endgame eval.
1013 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
1014 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
1018 // Does either side have an unstoppable passed pawn?
1019 if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
1020 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
1021 else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
1022 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
1023 else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
1025 // Both sides have unstoppable pawns! Try to find out who queens
1026 // first. We begin by transforming 'movesToGo' to the number of
1027 // plies until the pawn queens for both sides.
1028 movesToGo[WHITE] *= 2;
1029 movesToGo[BLACK] *= 2;
1030 movesToGo[pos.side_to_move()]--;
1032 // If one side queens at least three plies before the other, that
1034 if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
1035 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
1036 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
1037 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
1039 // We could also add some rules about the situation when one side
1040 // queens exactly one ply before the other: Does the first queen
1041 // check the opponent's king, or attack the opponent's queening square?
1042 // This is slightly tricky to get right, because it is possible that
1043 // the opponent's king has moved somewhere before the first pawn queens.
1048 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1049 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1052 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1054 assert(square_is_ok(s));
1055 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1057 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1058 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1060 if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
1061 && pos.see(s, b6) < 0
1062 && pos.see(s, b8) < 0)
1064 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1065 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1070 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1071 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1072 // black), and assigns a penalty if it is. This pattern can obviously
1073 // only occur in Chess960 games.
1075 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1077 Piece pawn = piece_of_color_and_type(us, PAWN);
1081 assert(square_is_ok(s));
1082 assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
1084 if (square_file(s) == FILE_A)
1086 b2 = relative_square(us, SQ_B2);
1087 b3 = relative_square(us, SQ_B3);
1088 c3 = relative_square(us, SQ_C3);
1092 b2 = relative_square(us, SQ_G2);
1093 b3 = relative_square(us, SQ_G3);
1094 c3 = relative_square(us, SQ_F3);
1097 if (pos.piece_on(b2) == pawn)
1101 if (!pos.square_is_empty(b3))
1102 penalty = 2*TrappedBishopA1H1Penalty;
1103 else if (pos.piece_on(c3) == pawn)
1104 penalty = TrappedBishopA1H1Penalty;
1106 penalty = TrappedBishopA1H1Penalty / 2;
1108 ei.mgValue -= Sign[us] * penalty;
1109 ei.egValue -= Sign[us] * penalty;
1114 // evaluate_space() computes the space evaluation for a given side. The
1115 // space evaluation is a simple bonus based on the number of safe squares
1116 // available for minor pieces on the central four files on ranks 2--4. Safe
1117 // squares one, two or three squares behind a friendly pawn are counted
1118 // twice. Finally, the space bonus is scaled by a weight taken from the
1119 // material hash table.
1121 void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
1123 Color them = opposite_color(us);
1125 // Find the safe squares for our pieces inside the area defined by
1126 // SpaceMask[us]. A square is unsafe it is attacked by an enemy
1127 // pawn, or if it is undefended and attacked by an enemy piece.
1129 Bitboard safeSquares = SpaceMask[us]
1131 & ~ei.attacked_by(them, PAWN)
1132 & ~(~ei.attacked_by(us) & ei.attacked_by(them));
1134 // Find all squares which are at most three squares behind some friendly
1136 Bitboard behindFriendlyPawns = pos.pawns(us);
1139 behindFriendlyPawns |= (behindFriendlyPawns >> 8);
1140 behindFriendlyPawns |= (behindFriendlyPawns >> 16);
1144 behindFriendlyPawns |= (behindFriendlyPawns << 8);
1145 behindFriendlyPawns |= (behindFriendlyPawns << 16);
1148 int space = count_1s_max_15(safeSquares)
1149 + count_1s_max_15(behindFriendlyPawns & safeSquares);
1151 ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
1155 // apply_weight() applies an evaluation weight to a value
1157 inline Value apply_weight(Value v, int w) {
1158 return (v*w) / 0x100;
1162 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1163 // significant bits of a Bitboard. This function is used by the king
1164 // shield evaluation.
1166 int count_1s_8bit(Bitboard b) {
1167 return int(BitCount8Bit[b & 0xFF]);
1171 // compute_weight() computes the value of an evaluation weight, by combining
1172 // an UCI-configurable weight with an internal weight.
1174 int compute_weight(int uciWeight, int internalWeight) {
1176 uciWeight = (uciWeight * 0x100) / 100;
1177 return (uciWeight * internalWeight) / 0x100;
1181 // helper used in read_weights()
1182 int weight_option(const std::string& opt, int weight) {
1184 return compute_weight(get_option_value_int(opt), weight);
1188 // init_safety() initizes the king safety evaluation, based on UCI
1189 // parameters. It is called from read_weights().
1191 void init_safety() {
1193 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1194 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1195 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1196 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1197 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1198 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1199 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1201 int maxSlope = get_option_value_int("King Safety Max Slope");
1202 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1203 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1204 double b = get_option_value_int("King Safety X Intercept");
1205 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1206 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1208 for (int i = 0; i < 100; i++)
1211 SafetyTable[i] = Value(0);
1213 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1215 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1218 for (int i = 0; i < 100; i++)
1220 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1221 for (int j = i + 1; j < 100; j++)
1222 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1224 if (SafetyTable[i] > Value(peak))
1225 SafetyTable[i] = Value(peak);