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/>.
34 #include "ucioption.h"
38 //// Local definitions
43 const int Sign[2] = { 1, -1 };
45 // Evaluation grain size, must be a power of 2
46 const int GrainSize = 4;
48 // Evaluation weights, initialized from UCI options
49 int WeightMobilityMidgame, WeightMobilityEndgame;
50 int WeightPawnStructureMidgame, WeightPawnStructureEndgame;
51 int WeightPassedPawnsMidgame, WeightPassedPawnsEndgame;
52 int WeightKingSafety[2];
55 // Internal evaluation weights. These are applied on top of the evaluation
56 // weights read from UCI parameters. The purpose is to be able to change
57 // the evaluation weights while keeping the default values of the UCI
58 // parameters at 100, which looks prettier.
60 // Values modified by Joona Kiiski
61 const int WeightMobilityMidgameInternal = 248;
62 const int WeightMobilityEndgameInternal = 271;
63 const int WeightPawnStructureMidgameInternal = 233;
64 const int WeightPawnStructureEndgameInternal = 201;
65 const int WeightPassedPawnsMidgameInternal = 252;
66 const int WeightPassedPawnsEndgameInternal = 259;
67 const int WeightKingSafetyInternal = 247;
68 const int WeightKingOppSafetyInternal = 259;
69 const int WeightSpaceInternal = 46;
71 // Mobility and outposts bonus modified by Joona Kiiski
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(-38), V(-25),V(-12), V(0), V(12), V(25), V(31), V(38), V(38)
83 const Value EndgameKnightMobilityBonus[] = {
85 V(-33), V(-23),V(-13), V(-3), V(7), V(17), V(22), V(27), V(27)
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(-25), V(-11), V(3), V(17), V(31), V(45), V(57), V(65),
94 // 8 9 10 11 12 13 14 15
95 V( 71), V( 74), V(76), V(78), V(79), V(80), V(81), V(81)
98 const Value EndgameBishopMobilityBonus[] = {
100 V(-30), V(-16), V(-2), V(12), V(26), V(40), V(52), V(60),
101 // 8 9 10 11 12 13 14 15
102 V( 65), V( 69), V(71), V(73), V(74), V(75), V(76), V(76)
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(-20), V(-14), V(-8), V(-2), V(4), V(10), V(14), V(19),
111 // 8 9 10 11 12 13 14 15
112 V( 23), V( 26), V(27), V(28), V(29), V(30), V(31), V(32)
115 const Value EndgameRookMobilityBonus[] = {
117 V(-36), V(-19), V(-3), V(13), V(29), V(46), V(62), V(79),
118 // 8 9 10 11 12 13 14 15
119 V( 95), V(106),V(111),V(114),V(116),V(117),V(118),V(118)
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(-3), V(-1), V( 1), V( 3), V( 5),
127 // 8 9 10 11 12 13 14 15
128 V( 8), V(10), V(12), V(15), V(16), V(17), V(18), V(20),
129 // 16 17 18 19 20 21 22 23
130 V( 20), V(20), V(20), V(20), V(20), V(20), V(20), V(20),
131 // 24 25 26 27 28 29 30 31
132 V( 20), V(20), V(20), V(20), V(20), V(20), V(20), V(20)
135 const Value EndgameQueenMobilityBonus[] = {
137 V(-18),V(-13), V(-7), V(-2), V( 3), V (8), V(13), V(19),
138 // 8 9 10 11 12 13 14 15
139 V( 23), V(27), V(32), V(34), V(35), V(35), V(35), V(35),
140 // 16 17 18 19 20 21 22 23
141 V( 35), V(35), V(35), V(35), V(35), V(35), V(35), V(35),
142 // 24 25 26 27 28 29 30 31
143 V( 35), V(35), V(35), V(35), V(35), V(35), V(35), V(35)
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(4), V(8), V(8), V(4), V(0), V(0), // 3
153 V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
154 V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
155 V(0), V(4),V(17),V(17),V(17),V(17), V(4), 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(21),V(21),V(21),V(21),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 (modified by Joona Kiiski)
176 const Value MidgameRookOn7thBonus = Value(47);
177 const Value EndgameRookOn7thBonus = Value(98);
178 const Value MidgameQueenOn7thBonus = Value(27);
179 const Value EndgameQueenOn7thBonus = Value(54);
181 // Rooks on open files (modified by Joona Kiiski)
182 const Value RookOpenFileBonus = Value(43);
183 const Value RookHalfOpenFileBonus = Value(19);
185 // Penalty for rooks trapped inside a friendly king which has lost the
187 const Value TrappedRookPenalty = Value(180);
189 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
191 const Value TrappedBishopA7H7Penalty = Value(300);
193 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
194 const Bitboard MaskA7H7[2] = {
195 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
196 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
199 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
200 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
201 // happen in Chess960 games.
202 const Value TrappedBishopA1H1Penalty = Value(100);
204 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
205 const Bitboard MaskA1H1[2] = {
206 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
207 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
210 // The SpaceMask[color] contains area of the board which is consdered by
211 // the space evaluation. In the middle game, each side is given a bonus
212 // based on how many squares inside this area are safe and available for
213 // friendly minor pieces.
214 const Bitboard SpaceMask[2] = {
215 (1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
216 (1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
217 (1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
218 (1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
219 (1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
220 (1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
223 /// King safety constants and variables. The king safety scores are taken
224 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
225 /// the strength of the attack are added up into an integer, which is used
226 /// as an index to SafetyTable[].
228 // Attack weights for each piece type
229 const int QueenAttackWeight = 5;
230 const int RookAttackWeight = 3;
231 const int BishopAttackWeight = 2;
232 const int KnightAttackWeight = 2;
234 // Bonuses for safe checks, initialized from UCI options
235 int QueenContactCheckBonus, DiscoveredCheckBonus;
236 int QueenCheckBonus, RookCheckBonus, BishopCheckBonus, KnightCheckBonus;
238 // Scan for queen contact mates?
239 const bool QueenContactMates = true;
241 // Bonus for having a mate threat, initialized from UCI options
244 // InitKingDanger[] contains bonuses based on the position of the defending
246 const int InitKingDanger[64] = {
247 2, 0, 2, 5, 5, 2, 0, 2,
248 2, 2, 4, 8, 8, 4, 2, 2,
249 7, 10, 12, 12, 12, 12, 10, 7,
250 15, 15, 15, 15, 15, 15, 15, 15,
251 15, 15, 15, 15, 15, 15, 15, 15,
252 15, 15, 15, 15, 15, 15, 15, 15,
253 15, 15, 15, 15, 15, 15, 15, 15,
254 15, 15, 15, 15, 15, 15, 15, 15
257 // SafetyTable[] contains the actual king safety scores. It is initialized
259 Value SafetyTable[100];
261 // Pawn and material hash tables, indexed by the current thread id
262 PawnInfoTable* PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
263 MaterialInfoTable* MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
265 // Sizes of pawn and material hash tables
266 const int PawnTableSize = 16384;
267 const int MaterialTableSize = 1024;
269 // Array which gives the number of nonzero bits in an 8-bit integer
270 uint8_t BitCount8Bit[256];
272 // Function prototypes
273 template<bool HasPopCnt>
274 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID);
276 template<PieceType Piece, bool HasPopCnt>
277 void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
279 template<bool HasPopCnt>
280 void evaluate_king(const Position& p, Color us, EvalInfo &ei);
282 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
283 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
285 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
287 template<bool HasPopCnt>
288 void evaluate_space(const Position &p, Color us, EvalInfo &ei);
289 inline Value apply_weight(Value v, int w);
290 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
292 int compute_weight(int uciWeight, int internalWeight);
293 int weight_option(const std::string& opt, int weight);
303 /// evaluate() is the main evaluation function. It always computes two
304 /// values, an endgame score and a middle game score, and interpolates
305 /// between them based on the remaining material.
306 Value evaluate(const Position& pos, EvalInfo& ei, int threadID) {
308 return CpuHasPOPCNT ? do_evaluate<true>(pos, ei, threadID)
309 : do_evaluate<false>(pos, ei, threadID);
314 template<bool HasPopCnt>
315 Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
318 assert(threadID >= 0 && threadID < THREAD_MAX);
320 memset(&ei, 0, sizeof(EvalInfo));
322 // Initialize by reading the incrementally updated scores included in the
323 // position object (material + piece square tables)
324 ei.mgValue = pos.mg_value();
325 ei.egValue = pos.eg_value();
327 // Probe the material hash table
328 ei.mi = MaterialTable[threadID]->get_material_info(pos);
329 ei.mgValue += ei.mi->mg_value();
330 ei.egValue += ei.mi->eg_value();
332 // If we have a specialized evaluation function for the current material
333 // configuration, call it and return
334 if (ei.mi->specialized_eval_exists())
335 return ei.mi->evaluate(pos);
337 // After get_material_info() call that modifies them
338 ScaleFactor factor[2];
339 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
340 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
342 // Probe the pawn hash table
343 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
344 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
345 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
347 // Initialize king attack bitboards and king attack zones for both sides
348 ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
349 ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
350 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
351 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
353 // Initialize pawn attack bitboards for both sides
354 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
355 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
356 ei.kingAttackersCount[WHITE] = count_1s_max_15<HasPopCnt>(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
357 ei.kingAttackersCount[BLACK] = count_1s_max_15<HasPopCnt>(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
360 for (Color c = WHITE; c <= BLACK; c++)
362 evaluate_pieces<KNIGHT, HasPopCnt>(pos, c, ei);
363 evaluate_pieces<BISHOP, HasPopCnt>(pos, c, ei);
364 evaluate_pieces<ROOK, HasPopCnt>(pos, c, ei);
365 evaluate_pieces<QUEEN, HasPopCnt>(pos, c, ei);
367 // Sum up all attacked squares
368 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
369 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
370 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
373 // Kings. Kings are evaluated after all other pieces for both sides,
374 // because we need complete attack information for all pieces when computing
375 // the king safety evaluation.
376 for (Color c = WHITE; c <= BLACK; c++)
377 evaluate_king<HasPopCnt>(pos, c, ei);
379 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
380 // because we need to know which side promotes first in positions where
381 // both sides have an unstoppable passed pawn.
382 if (ei.pi->passed_pawns())
383 evaluate_passed_pawns(pos, ei);
385 Phase phase = pos.game_phase();
387 // Middle-game specific evaluation terms
388 if (phase > PHASE_ENDGAME)
390 // Pawn storms in positions with opposite castling.
391 if ( square_file(pos.king_square(WHITE)) >= FILE_E
392 && square_file(pos.king_square(BLACK)) <= FILE_D)
394 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
395 - ei.pi->kingside_storm_value(BLACK);
397 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
398 && square_file(pos.king_square(BLACK)) >= FILE_E)
400 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
401 - ei.pi->queenside_storm_value(BLACK);
403 // Evaluate space for both sides
404 if (ei.mi->space_weight() > 0)
406 evaluate_space<HasPopCnt>(pos, WHITE, ei);
407 evaluate_space<HasPopCnt>(pos, BLACK, ei);
412 ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
413 ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
415 // If we don't already have an unusual scale factor, check for opposite
416 // colored bishop endgames, and use a lower scale for those
417 if ( phase < PHASE_MIDGAME
418 && pos.opposite_colored_bishops()
419 && ( (factor[WHITE] == SCALE_FACTOR_NORMAL && ei.egValue > Value(0))
420 || (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < Value(0))))
424 // Only the two bishops ?
425 if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
426 && pos.non_pawn_material(BLACK) == BishopValueMidgame)
428 // Check for KBP vs KB with only a single pawn that is almost
429 // certainly a draw or at least two pawns.
430 bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
431 sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
434 // Endgame with opposite-colored bishops, but also other pieces. Still
435 // a bit drawish, but not as drawish as with only the two bishops.
436 sf = ScaleFactor(50);
438 if (factor[WHITE] == SCALE_FACTOR_NORMAL)
440 if (factor[BLACK] == SCALE_FACTOR_NORMAL)
444 // Interpolate between the middle game and the endgame score, and
446 Color stm = pos.side_to_move();
448 Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
450 return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
455 /// quick_evaluate() does a very approximate evaluation of the current position.
456 /// It currently considers only material and piece square table scores. Perhaps
457 /// we should add scores from the pawn and material hash tables?
459 Value quick_evaluate(const Position &pos) {
464 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
466 Value mgv = pos.mg_value();
467 Value egv = pos.eg_value();
468 Phase ph = pos.game_phase();
469 Color stm = pos.side_to_move();
471 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
475 /// init_eval() initializes various tables used by the evaluation function.
477 void init_eval(int threads) {
479 assert(threads <= THREAD_MAX);
481 for (int i = 0; i < THREAD_MAX; i++)
486 delete MaterialTable[i];
488 MaterialTable[i] = NULL;
492 PawnTable[i] = new PawnInfoTable(PawnTableSize);
493 if (!MaterialTable[i])
494 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
497 for (Bitboard b = 0ULL; b < 256ULL; b++)
499 assert(count_1s(b) == int(uint8_t(count_1s(b))));
500 BitCount8Bit[b] = (uint8_t)count_1s(b);
505 /// quit_eval() releases heap-allocated memory at program termination.
509 for (int i = 0; i < THREAD_MAX; i++)
512 delete MaterialTable[i];
514 MaterialTable[i] = NULL;
519 /// read_weights() reads evaluation weights from the corresponding UCI
522 void read_weights(Color us) {
524 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
525 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
526 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
527 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
528 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
529 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
531 Color them = opposite_color(us);
533 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
534 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
535 WeightSpace = weight_option("Space", WeightSpaceInternal);
543 // evaluate_mobility() computes mobility and attacks for every piece
545 template<PieceType Piece, bool HasPopCnt>
546 int evaluate_mobility(const Position& p, const Bitboard& b, Color us, Color them, EvalInfo& ei) {
548 static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
549 static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
550 static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
552 // Update attack info
553 ei.attackedBy[us][Piece] |= b;
556 if (b & ei.kingZone[us])
558 ei.kingAttackersCount[us]++;
559 ei.kingAttackersWeight[us] += AttackWeight[Piece];
560 Bitboard bb = (b & ei.attackedBy[them][KING]);
562 ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15<HasPopCnt>(bb);
565 // Remove squares protected by enemy pawns
566 Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
569 int mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(bb & ~p.pieces_of_color(us))
570 : count_1s<HasPopCnt>(bb & ~p.pieces_of_color(us)));
572 ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
573 ei.egMobility += Sign[us] * EgBonus[Piece][mob];
578 // evaluate_outposts() evaluates bishop and knight outposts squares
580 template<PieceType Piece>
581 void evaluate_outposts(const Position& p, Color us, Color them, EvalInfo& ei, Square s) {
583 // Initial bonus based on square
584 Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(us, s)]
585 : KnightOutpostBonus[relative_square(us, s)]);
587 // Increase bonus if supported by pawn, especially if the opponent has
588 // no minor piece which can exchange the outpost piece
589 if (bonus && (p.pawn_attacks(them, s) & p.pawns(us)))
591 if ( p.knights(them) == EmptyBoardBB
592 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
593 bonus += bonus + bonus / 2;
597 ei.mgValue += Sign[us] * bonus;
598 ei.egValue += Sign[us] * bonus;
602 // evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
605 template<PieceType Piece, bool HasPopCnt>
606 void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
612 Color them = opposite_color(us);
614 for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
616 s = pos.piece_list(us, Piece, i);
618 if (Piece == KNIGHT || Piece == QUEEN)
619 b = pos.piece_attacks<Piece>(s);
620 else if (Piece == BISHOP)
621 b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
622 else if (Piece == ROOK)
623 b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
627 // Attacks and mobility
628 mob = evaluate_mobility<Piece, HasPopCnt>(pos, b, us, them, ei);
630 // Bishop and knight outposts squares
631 if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, them))
632 evaluate_outposts<Piece>(pos, us, them, ei, s);
634 // Special patterns: trapped bishops on a7/h7/a2/h2
635 // and trapped bishops on a1/h1/a8/h8 in Chess960.
638 if (bit_is_set(MaskA7H7[us], s))
639 evaluate_trapped_bishop_a7h7(pos, s, us, ei);
641 if (Chess960 && bit_is_set(MaskA1H1[us], s))
642 evaluate_trapped_bishop_a1h1(pos, s, us, ei);
645 if (Piece == ROOK || Piece == QUEEN)
647 // Queen or rook on 7th rank
648 if ( relative_rank(us, s) == RANK_7
649 && relative_rank(us, pos.king_square(them)) == RANK_8)
651 ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
652 ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
656 // Special extra evaluation for rooks
659 // Open and half-open files
661 if (ei.pi->file_is_half_open(us, f))
663 if (ei.pi->file_is_half_open(them, f))
665 ei.mgValue += Sign[us] * RookOpenFileBonus;
666 ei.egValue += Sign[us] * RookOpenFileBonus;
670 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
671 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
675 // Penalize rooks which are trapped inside a king. Penalize more if
676 // king has lost right to castle.
677 if (mob > 6 || ei.pi->file_is_half_open(us, f))
680 ksq = pos.king_square(us);
682 if ( square_file(ksq) >= FILE_E
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_right(us, square_file(ksq)))
688 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
689 : Sign[us] * (TrappedRookPenalty - mob * 16);
691 else if ( square_file(ksq) <= FILE_D
692 && square_file(s) < square_file(ksq)
693 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
695 // Is there a half-open file between the king and the edge of the board?
696 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
697 ei.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
698 : Sign[us] * (TrappedRookPenalty - mob * 16);
704 inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
706 return b >> (num << 3);
709 // evaluate_king<>() assigns bonuses and penalties to a king of a given color.
711 template<bool HasPopCnt>
712 void evaluate_king(const Position& p, Color us, EvalInfo& ei) {
714 int shelter = 0, sign = Sign[us];
715 Square s = p.king_square(us);
718 if (relative_rank(us, s) <= RANK_4)
720 // Shelter cache lookup
721 shelter = ei.pi->kingShelter(us, s);
725 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
726 Rank r = square_rank(s);
727 for (int i = 1; i < 4; i++)
728 shelter += BitCount8Bit[shiftRowsDown(pawns, r+i*sign) & 0xFF] * (128 >> i);
730 // Cache shelter value in pawn info
731 ei.pi->setKingShelter(us, s, shelter);
733 ei.mgValue += sign * Value(shelter);
736 // King safety. This is quite complicated, and is almost certainly far
737 // from optimally tuned.
738 Color them = opposite_color(us);
740 if ( p.piece_count(them, QUEEN) >= 1
741 && ei.kingAttackersCount[them] >= 2
742 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
743 && ei.kingAdjacentZoneAttacksCount[them])
745 // Is it the attackers turn to move?
746 bool sente = (them == p.side_to_move());
748 // Find the attacked squares around the king which has no defenders
749 // apart from the king itself
750 Bitboard undefended =
751 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
752 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
753 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
754 & ei.attacked_by(us, KING);
756 Bitboard occ = p.occupied_squares(), b, b2;
758 // Initialize the 'attackUnits' variable, which is used later on as an
759 // index to the SafetyTable[] array. The initial value is based on the
760 // number and types of the attacking pieces, the number of attacked and
761 // undefended squares around the king, the square of the king, and the
762 // quality of the pawn shelter.
764 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
765 + (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15<HasPopCnt>(undefended)) * 3
766 + InitKingDanger[relative_square(us, s)] - (shelter >> 5);
768 // Analyse safe queen contact checks
769 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
772 Bitboard attackedByOthers =
773 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
774 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
776 b &= attackedByOthers;
779 // The bitboard b now contains the squares available for safe queen
781 int count = count_1s_max_15<HasPopCnt>(b);
782 attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
784 // Is there a mate threat?
785 if (QueenContactMates && !p.is_check())
787 Bitboard escapeSquares =
788 p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
792 Square from, to = pop_1st_bit(&b);
793 if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
795 // We have a mate, unless the queen is pinned or there
796 // is an X-ray attack through the queen.
797 for (int i = 0; i < p.piece_count(them, QUEEN); i++)
799 from = p.piece_list(them, QUEEN, i);
800 if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
801 && !bit_is_set(p.pinned_pieces(them), from)
802 && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
803 && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
805 ei.mateThreat[them] = make_move(from, to);
813 // Analyse safe distance checks
814 if (QueenCheckBonus > 0 || RookCheckBonus > 0)
816 b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
819 b2 = b & ei.attacked_by(them, QUEEN);
821 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
824 b2 = b & ei.attacked_by(them, ROOK);
826 attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b2);
828 if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
830 b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
833 b2 = b & ei.attacked_by(them, QUEEN);
835 attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b2);
838 b2 = b & ei.attacked_by(them, BISHOP);
840 attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b2);
842 if (KnightCheckBonus > 0)
844 b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
847 b2 = b & ei.attacked_by(them, KNIGHT);
849 attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b2);
852 // Analyse discovered checks (only for non-pawns right now, consider
853 // adding pawns later).
854 if (DiscoveredCheckBonus)
856 b = p.discovered_check_candidates(them) & ~p.pawns();
858 attackUnits += DiscoveredCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente? 2 : 1);
861 // Has a mate threat been found? We don't do anything here if the
862 // side with the mating move is the side to move, because in that
863 // case the mating side will get a huge bonus at the end of the main
864 // evaluation function instead.
865 if (ei.mateThreat[them] != MOVE_NONE)
866 attackUnits += MateThreatBonus;
868 // Ensure that attackUnits is between 0 and 99, in order to avoid array
869 // out of bounds errors:
873 if (attackUnits >= 100)
876 // Finally, extract the king safety score from the SafetyTable[] array.
877 // Add the score to the evaluation, and also to ei.futilityMargin. The
878 // reason for adding the king safety score to the futility margin is
879 // that the king safety scores can sometimes be very big, and that
880 // capturing a single attacking piece can therefore result in a score
881 // change far bigger than the value of the captured piece.
882 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
884 ei.mgValue -= sign * v;
886 if (us == p.side_to_move())
887 ei.futilityMargin += v;
892 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
894 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
896 bool hasUnstoppable[2] = {false, false};
897 int movesToGo[2] = {100, 100};
899 for (Color us = WHITE; us <= BLACK; us++)
901 Color them = opposite_color(us);
902 Square ourKingSq = pos.king_square(us);
903 Square theirKingSq = pos.king_square(them);
904 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
908 Square s = pop_1st_bit(&b);
910 assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
911 assert(pos.pawn_is_passed(us, s));
913 int r = int(relative_rank(us, s) - RANK_2);
914 int tr = Max(0, r * (r - 1));
915 Square blockSq = s + pawn_push(us);
917 // Base bonus based on rank
918 Value mbonus = Value(20 * tr);
919 Value ebonus = Value(10 + r * r * 10);
921 // Adjust bonus based on king proximity
924 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
925 ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
926 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
928 // If the pawn is free to advance, increase bonus
929 if (pos.square_is_empty(blockSq))
931 b2 = squares_in_front_of(us, s);
932 b3 = b2 & ei.attacked_by(them);
933 b4 = b2 & ei.attacked_by(us);
935 // If there is an enemy rook or queen attacking the pawn from behind,
936 // add all X-ray attacks by the rook or queen.
937 if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
938 && (squares_behind(us, s) & pos.rooks_and_queens(them)))
941 // Squares attacked or occupied by enemy pieces
942 b3 |= (b2 & pos.pieces_of_color(them));
944 // There are no enemy pawns in the pawn's path
945 assert((b2 & pos.pieces_of_color_and_type(them, PAWN)) == EmptyBoardBB);
947 // Are any of the squares in the pawn's path attacked or occupied by the enemy?
948 if (b3 == EmptyBoardBB)
949 // No enemy attacks or pieces, huge bonus!
950 ebonus += Value(tr * (b2 == b4 ? 17 : 15));
952 // OK, there are enemy attacks or pieces (but not pawns). Are those
953 // squares which are attacked by the enemy also attacked by us?
954 // If yes, big bonus (but smaller than when there are no enemy attacks),
955 // if no, somewhat smaller bonus.
956 ebonus += Value(tr * ((b3 & b4) == b3 ? 13 : 8));
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.
1120 template<bool HasPopCnt>
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<HasPopCnt>(safeSquares)
1149 + count_1s_max_15<HasPopCnt>(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 // scale_by_game_phase() interpolates between a middle game and an endgame
1163 // score, based on game phase. It also scales the return value by a
1164 // ScaleFactor array.
1166 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1168 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1169 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1170 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1172 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1174 Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
1175 return Value(int(result) & ~(GrainSize - 1));
1179 // compute_weight() computes the value of an evaluation weight, by combining
1180 // an UCI-configurable weight with an internal weight.
1182 int compute_weight(int uciWeight, int internalWeight) {
1184 uciWeight = (uciWeight * 0x100) / 100;
1185 return (uciWeight * internalWeight) / 0x100;
1189 // helper used in read_weights()
1190 int weight_option(const std::string& opt, int weight) {
1192 return compute_weight(get_option_value_int(opt), weight);
1196 // init_safety() initizes the king safety evaluation, based on UCI
1197 // parameters. It is called from read_weights().
1199 void init_safety() {
1201 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1202 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1203 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1204 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1205 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1206 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1207 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1209 int maxSlope = get_option_value_int("King Safety Max Slope");
1210 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1211 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1212 double b = get_option_value_int("King Safety X Intercept");
1213 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1214 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1216 for (int i = 0; i < 100; i++)
1219 SafetyTable[i] = Value(0);
1221 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1223 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1226 for (int i = 0; i < 100; i++)
1228 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1229 for (int j = i + 1; j < 100; j++)
1230 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1232 if (SafetyTable[i] > Value(peak))
1233 SafetyTable[i] = Value(peak);