2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
32 #include "ucioption.h"
36 //// Local definitions
41 const int Sign[2] = {1, -1};
43 // Evaluation grain size, must be a power of 2.
44 const int GrainSize = 4;
47 int WeightMobilityMidgame = 0x100;
48 int WeightMobilityEndgame = 0x100;
49 int WeightPawnStructureMidgame = 0x100;
50 int WeightPawnStructureEndgame = 0x100;
51 int WeightPassedPawnsMidgame = 0x100;
52 int WeightPassedPawnsEndgame = 0x100;
53 int WeightKingSafety[2] = { 0x100, 0x100 };
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.
59 const int WeightMobilityMidgameInternal = 0x100;
60 const int WeightMobilityEndgameInternal = 0x100;
61 const int WeightPawnStructureMidgameInternal = 0x100;
62 const int WeightPawnStructureEndgameInternal = 0x100;
63 const int WeightPassedPawnsMidgameInternal = 0x100;
64 const int WeightPassedPawnsEndgameInternal = 0x100;
65 const int WeightKingSafetyInternal = 0x100;
66 const int WeightKingOppSafetyInternal = 0x100;
68 // Visually better to define tables constants
71 // Knight mobility bonus in middle game and endgame, indexed by the number
72 // of attacked squares not occupied by friendly piecess.
73 const Value MidgameKnightMobilityBonus[] = {
75 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
78 const Value EndgameKnightMobilityBonus[] = {
80 V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
83 // Bishop mobility bonus in middle game and endgame, indexed by the number
84 // of attacked squares not occupied by friendly pieces. X-ray attacks through
85 // queens are also included.
86 const Value MidgameBishopMobilityBonus[] = {
88 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
89 // 8 9 10 11 12 13 14 15
90 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
93 const Value EndgameBishopMobilityBonus[] = {
95 V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
96 // 8 9 10 11 12 13 14 15
97 V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
100 // Rook mobility bonus in middle game and endgame, indexed by the number
101 // of attacked squares not occupied by friendly pieces. X-ray attacks through
102 // queens and rooks are also included.
103 const Value MidgameRookMobilityBonus[] = {
105 V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
106 // 8 9 10 11 12 13 14 15
107 V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
110 const Value EndgameRookMobilityBonus[] = {
112 V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
113 // 8 9 10 11 12 13 14 15
114 V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
117 // Queen mobility bonus in middle game and endgame, indexed by the number
118 // of attacked squares not occupied by friendly pieces.
119 const Value MidgameQueenMobilityBonus[] = {
121 V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
122 // 8 9 10 11 12 13 14 15
123 V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
124 // 16 17 18 19 20 21 22 23
125 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
126 // 24 25 26 27 28 29 30 31
127 V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
130 const Value EndgameQueenMobilityBonus[] = {
132 V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
133 // 8 9 10 11 12 13 14 15
134 V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
135 // 16 17 18 19 20 21 22 23
136 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
137 // 24 25 26 27 28 29 30 31
138 V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
141 // Outpost bonuses for knights and bishops, indexed by square (from white's
143 const Value KnightOutpostBonus[64] = {
145 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
146 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
147 V(0), V(0), V(5),V(10),V(10), V(5), V(0), V(0), // 3
148 V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
149 V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
150 V(0), V(5),V(20),V(20),V(20),V(20), V(5), V(0), // 6
151 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
152 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
155 const Value BishopOutpostBonus[64] = {
157 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
158 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
159 V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
160 V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
161 V(0),V(10),V(20),V(20),V(20),V(20),V(10), V(0), // 5
162 V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
163 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
164 V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
167 // Bonus for unstoppable passed pawns:
168 const Value UnstoppablePawnValue = Value(0x500);
170 // Rooks and queens on the 7th rank:
171 const Value MidgameRookOn7thBonus = Value(50);
172 const Value EndgameRookOn7thBonus = Value(100);
173 const Value MidgameQueenOn7thBonus = Value(25);
174 const Value EndgameQueenOn7thBonus = Value(50);
176 // Rooks on open files:
177 const Value RookOpenFileBonus = Value(40);
178 const Value RookHalfOpenFileBonus = Value(20);
180 // Penalty for rooks trapped inside a friendly king which has lost the
182 const Value TrappedRookPenalty = Value(180);
184 // Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
186 const Value TrappedBishopA7H7Penalty = Value(300);
188 // Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black):
189 const Bitboard MaskA7H7[2] = {
190 ((1ULL << SQ_A7) | (1ULL << SQ_H7)),
191 ((1ULL << SQ_A2) | (1ULL << SQ_H2))
194 // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
195 // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
196 // happen in Chess960 games.
197 const Value TrappedBishopA1H1Penalty = Value(100);
199 // Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black):
200 const Bitboard MaskA1H1[2] = {
201 ((1ULL << SQ_A1) | (1ULL << SQ_H1)),
202 ((1ULL << SQ_A8) | (1ULL << SQ_H8))
205 /// King safety constants and variables. The king safety scores are taken
206 /// from the array SafetyTable[]. Various little "meta-bonuses" measuring
207 /// the strength of the attack are added up into an integer, which is used
208 /// as an index to SafetyTable[].
210 // Attack weights for each piece type.
211 const int QueenAttackWeight = 5;
212 const int RookAttackWeight = 3;
213 const int BishopAttackWeight = 2;
214 const int KnightAttackWeight = 2;
216 // Bonuses for safe checks for each piece type.
217 int QueenContactCheckBonus = 4;
218 int RookContactCheckBonus = 2;
219 int QueenCheckBonus = 2;
220 int RookCheckBonus = 1;
221 int BishopCheckBonus = 1;
222 int KnightCheckBonus = 1;
223 int DiscoveredCheckBonus = 3;
225 // Scan for queen contact mates?
226 const bool QueenContactMates = true;
228 // Bonus for having a mate threat.
229 int MateThreatBonus = 3;
231 // InitKingDanger[] contains bonuses based on the position of the defending
233 const int InitKingDanger[64] = {
234 2, 0, 2, 5, 5, 2, 0, 2,
235 2, 2, 4, 8, 8, 4, 2, 2,
236 7, 10, 12, 12, 12, 12, 10, 7,
237 15, 15, 15, 15, 15, 15, 15, 15,
238 15, 15, 15, 15, 15, 15, 15, 15,
239 15, 15, 15, 15, 15, 15, 15, 15,
240 15, 15, 15, 15, 15, 15, 15, 15,
241 15, 15, 15, 15, 15, 15, 15, 15
244 // SafetyTable[] contains the actual king safety scores. It is initialized
246 Value SafetyTable[100];
248 // Pawn and material hash tables, indexed by the current thread id:
249 PawnInfoTable *PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
250 MaterialInfoTable *MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
252 // Sizes of pawn and material hash tables:
253 const int PawnTableSize = 16384;
254 const int MaterialTableSize = 1024;
256 // Array which gives the number of nonzero bits in an 8-bit integer:
257 uint8_t BitCount8Bit[256];
259 // Function prototypes:
260 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei);
261 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei);
262 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei);
263 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei);
264 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei);
266 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei);
267 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
269 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
272 inline Value apply_weight(Value v, int w);
273 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
275 int count_1s_8bit(Bitboard b);
277 int compute_weight(int uciWeight, int internalWeight);
278 int weight_option(const std::string& opt, int weight);
288 /// evaluate() is the main evaluation function. It always computes two
289 /// values, an endgame score and a middle game score, and interpolates
290 /// between them based on the remaining material.
292 Value evaluate(const Position &pos, EvalInfo &ei, int threadID) {
295 assert(threadID >= 0 && threadID < THREAD_MAX);
297 memset(&ei, 0, sizeof(EvalInfo));
299 // Initialize by reading the incrementally updated scores included in the
300 // position object (material + piece square tables)
301 ei.mgValue = pos.mg_value();
302 ei.egValue = pos.eg_value();
304 // Probe the material hash table
305 ei.mi = MaterialTable[threadID]->get_material_info(pos);
306 ei.mgValue += ei.mi->mg_value();
307 ei.egValue += ei.mi->eg_value();
309 // If we have a specialized evaluation function for the current material
310 // configuration, call it and return
311 if (ei.mi->specialized_eval_exists())
312 return ei.mi->evaluate(pos);
314 // After get_material_info() call that modifies them
315 ScaleFactor factor[2];
316 factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
317 factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
319 // Probe the pawn hash table
320 ei.pi = PawnTable[threadID]->get_pawn_info(pos);
321 ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
322 ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
324 // Initialize king attack bitboards and king attack zones for both sides
325 ei.attackedBy[WHITE][KING] = pos.king_attacks(pos.king_square(WHITE));
326 ei.attackedBy[BLACK][KING] = pos.king_attacks(pos.king_square(BLACK));
327 ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
328 ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
330 // Initialize pawn attack bitboards for both sides
331 ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
332 ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
333 ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
334 ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
337 for (Color c = WHITE; c <= BLACK; c++)
340 for (int i = 0; i < pos.knight_count(c); i++)
341 evaluate_knight(pos, pos.knight_list(c, i), c, ei);
344 for (int i = 0; i < pos.bishop_count(c); i++)
345 evaluate_bishop(pos, pos.bishop_list(c, i), c, ei);
348 for (int i = 0; i < pos.rook_count(c); i++)
349 evaluate_rook(pos, pos.rook_list(c, i), c, ei);
352 for(int i = 0; i < pos.queen_count(c); i++)
353 evaluate_queen(pos, pos.queen_list(c, i), c, ei);
355 // Special pattern: trapped bishops on a7/h7/a2/h2
356 Bitboard b = pos.bishops(c) & MaskA7H7[c];
359 Square s = pop_1st_bit(&b);
360 evaluate_trapped_bishop_a7h7(pos, s, c, ei);
363 // Special pattern: trapped bishops on a1/h1/a8/h8 in Chess960:
366 b = pos.bishops(c) & MaskA1H1[c];
369 Square s = pop_1st_bit(&b);
370 evaluate_trapped_bishop_a1h1(pos, s, c, ei);
374 // Sum up all attacked squares
375 ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
376 | ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
377 | ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
380 // Kings. Kings are evaluated after all other pieces for both sides,
381 // because we need complete attack information for all pieces when computing
382 // the king safety evaluation.
383 for (Color c = WHITE; c <= BLACK; c++)
384 evaluate_king(pos, pos.king_square(c), c, ei);
386 // Evaluate passed pawns. We evaluate passed pawns for both sides at once,
387 // because we need to know which side promotes first in positions where
388 // both sides have an unstoppable passed pawn.
389 if (ei.pi->passed_pawns())
390 evaluate_passed_pawns(pos, ei);
392 Phase phase = pos.game_phase();
394 // Middle-game specific evaluation terms
395 if (phase > PHASE_ENDGAME)
397 // Pawn storms in positions with opposite castling.
398 if ( square_file(pos.king_square(WHITE)) >= FILE_E
399 && square_file(pos.king_square(BLACK)) <= FILE_D)
401 ei.mgValue += ei.pi->queenside_storm_value(WHITE)
402 - ei.pi->kingside_storm_value(BLACK);
404 else if ( square_file(pos.king_square(WHITE)) <= FILE_D
405 && square_file(pos.king_square(BLACK)) >= FILE_E)
407 ei.mgValue += ei.pi->kingside_storm_value(WHITE)
408 - ei.pi->queenside_storm_value(BLACK);
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.pawn_count(WHITE) + pos.pawn_count(BLACK) == 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);
454 /// quick_evaluate() does a very approximate evaluation of the current position.
455 /// It currently considers only material and piece square table scores. Perhaps
456 /// we should add scores from the pawn and material hash tables?
458 Value quick_evaluate(const Position &pos) {
463 ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
465 Value mgv = pos.mg_value();
466 Value egv = pos.eg_value();
467 Phase ph = pos.game_phase();
468 Color stm = pos.side_to_move();
470 return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
474 /// init_eval() initializes various tables used by the evaluation function.
476 void init_eval(int threads) {
478 assert(threads <= THREAD_MAX);
480 for (int i = 0; i < THREAD_MAX; i++)
485 delete MaterialTable[i];
487 MaterialTable[i] = NULL;
491 PawnTable[i] = new PawnInfoTable(PawnTableSize);
492 if (!MaterialTable[i])
493 MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
496 for (Bitboard b = 0ULL; b < 256ULL; b++)
497 BitCount8Bit[b] = count_1s(b);
501 /// quit_eval() releases heap-allocated memory at program termination.
504 for(int i = 0; i < THREAD_MAX; i++) {
506 delete MaterialTable[i];
511 /// read_weights() reads evaluation weights from the corresponding UCI
514 void read_weights(Color us) {
516 WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
517 WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
518 WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
519 WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
520 WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
521 WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
523 Color them = opposite_color(us);
525 WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
526 WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
534 // evaluate_common() computes terms common to all pieces attack
536 int evaluate_common(const Position&p, const Bitboard& b, Color us, EvalInfo& ei,
537 int AttackWeight, const Value* mgBonus, const Value* egBonus,
538 Square s = SQ_NONE, const Value* OutpostBonus = NULL) {
540 Color them = opposite_color(us);
543 if (b & ei.kingZone[us])
545 ei.kingAttackersCount[us]++;
546 ei.kingAttackersWeight[us] += AttackWeight;
547 Bitboard bb = (b & ei.attackedBy[them][KING]);
549 ei.kingZoneAttacksCount[us] += count_1s_max_15(bb);
553 int mob = count_1s_max_15(b & ~p.pieces_of_color(us));
554 ei.mgMobility += Sign[us] * mgBonus[mob];
555 ei.egMobility += Sign[us] * egBonus[mob];
557 // Bishop and Knight outposts
558 if (!OutpostBonus || !p.square_is_weak(s, them))
561 // Initial bonus based on square
563 v = bonus = OutpostBonus[relative_square(us, s)];
565 // Increase bonus if supported by pawn, especially if the opponent has
566 // no minor piece which can exchange the outpost piece
567 if (v && (p.pawn_attacks(them, s) & p.pawns(us)))
570 if ( p.knight_count(them) == 0
571 && (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
574 ei.mgValue += Sign[us] * bonus;
575 ei.egValue += Sign[us] * bonus;
580 // evaluate_knight() assigns bonuses and penalties to a knight of a given
581 // color on a given square.
583 void evaluate_knight(const Position &p, Square s, Color us, EvalInfo &ei) {
585 Bitboard b = p.knight_attacks(s);
586 ei.attackedBy[us][KNIGHT] |= b;
588 // King attack, mobility and outposts
589 evaluate_common(p, b, us, ei, KnightAttackWeight, MidgameKnightMobilityBonus,
590 EndgameKnightMobilityBonus, s, KnightOutpostBonus);
594 // evaluate_bishop() assigns bonuses and penalties to a bishop of a given
595 // color on a given square.
597 void evaluate_bishop(const Position &p, Square s, Color us, EvalInfo &ei) {
599 Bitboard b = bishop_attacks_bb(s, p.occupied_squares() & ~p.queens(us));
600 ei.attackedBy[us][BISHOP] |= b;
602 // King attack, mobility and outposts
603 evaluate_common(p, b, us, ei, BishopAttackWeight, MidgameBishopMobilityBonus,
604 EndgameBishopMobilityBonus, s, BishopOutpostBonus);
608 // evaluate_rook() assigns bonuses and penalties to a rook of a given
609 // color on a given square.
611 void evaluate_rook(const Position &p, Square s, Color us, EvalInfo &ei) {
613 //Bitboard b = p.rook_attacks(s);
614 Bitboard b = rook_attacks_bb(s, p.occupied_squares() & ~p.rooks_and_queens(us));
615 ei.attackedBy[us][ROOK] |= b;
617 // King attack and mobility
618 int mob = evaluate_common(p, b, us, ei, RookAttackWeight, MidgameRookMobilityBonus,
619 EndgameRookMobilityBonus);
622 Color them = opposite_color(us);
624 if ( relative_rank(us, s) == RANK_7
625 && relative_rank(us, p.king_square(them)) == RANK_8)
627 ei.mgValue += Sign[us] * MidgameRookOn7thBonus;
628 ei.egValue += Sign[us] * EndgameRookOn7thBonus;
631 // Open and half-open files
632 File f = square_file(s);
633 if (ei.pi->file_is_half_open(us, f))
635 if (ei.pi->file_is_half_open(them, f))
637 ei.mgValue += Sign[us] * RookOpenFileBonus;
638 ei.egValue += Sign[us] * RookOpenFileBonus;
642 ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
643 ei.egValue += Sign[us] * RookHalfOpenFileBonus;
647 // Penalize rooks which are trapped inside a king. Penalize more if
648 // king has lost right to castle
649 if (mob > 6 || ei.pi->file_is_half_open(us, f))
652 Square ksq = p.king_square(us);
654 if ( square_file(ksq) >= FILE_E
655 && square_file(s) > square_file(ksq)
656 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
658 // Is there a half-open file between the king and the edge of the board?
659 if (!ei.pi->has_open_file_to_right(us, square_file(ksq)))
660 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
661 : Sign[us] * (TrappedRookPenalty - mob * 16);
663 else if ( square_file(ksq) <= FILE_D
664 && square_file(s) < square_file(ksq)
665 && (relative_rank(us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
667 // Is there a half-open file between the king and the edge of the board?
668 if (!ei.pi->has_open_file_to_left(us, square_file(ksq)))
669 ei.mgValue -= p.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
670 : Sign[us] * (TrappedRookPenalty - mob * 16);
675 // evaluate_queen() assigns bonuses and penalties to a queen of a given
676 // color on a given square.
678 void evaluate_queen(const Position &p, Square s, Color us, EvalInfo &ei) {
680 Bitboard b = p.queen_attacks(s);
681 ei.attackedBy[us][QUEEN] |= b;
683 // King attack and mobility
684 evaluate_common(p, b, us, ei, QueenAttackWeight, MidgameQueenMobilityBonus,
685 EndgameQueenMobilityBonus);
688 Color them = opposite_color(us);
690 if ( relative_rank(us, s) == RANK_7
691 && relative_rank(us, p.king_square(them)) == RANK_8)
693 ei.mgValue += Sign[us] * MidgameQueenOn7thBonus;
694 ei.egValue += Sign[us] * EndgameQueenOn7thBonus;
699 // evaluate_king() assigns bonuses and penalties to a king of a given
700 // color on a given square.
702 void evaluate_king(const Position &p, Square s, Color us, EvalInfo &ei) {
704 int shelter = 0, sign = Sign[us];
707 if(relative_rank(us, s) <= RANK_4) {
708 Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
709 Rank r = square_rank(s);
710 for(int i = 0; i < 3; i++)
711 shelter += count_1s_8bit(pawns >> ((r+(i+1)*sign) * 8)) * (64>>i);
712 ei.mgValue += sign * Value(shelter);
715 // King safety. This is quite complicated, and is almost certainly far
716 // from optimally tuned.
717 Color them = opposite_color(us);
718 if(p.queen_count(them) >= 1 && ei.kingAttackersCount[them] >= 2
719 && p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
720 && ei.kingZoneAttacksCount[them]) {
722 // Is it the attackers turn to move?
723 bool sente = (them == p.side_to_move());
725 // Find the attacked squares around the king which has no defenders
726 // apart from the king itself:
727 Bitboard undefended =
728 ei.attacked_by(them) & ~ei.attacked_by(us, PAWN)
729 & ~ei.attacked_by(us, KNIGHT) & ~ei.attacked_by(us, BISHOP)
730 & ~ei.attacked_by(us, ROOK) & ~ei.attacked_by(us, QUEEN)
731 & ei.attacked_by(us, KING);
732 Bitboard occ = p.occupied_squares(), b, b2;
734 // Initialize the 'attackUnits' variable, which is used later on as an
735 // index to the SafetyTable[] array. The initial is based on the number
736 // and types of the attacking pieces, the number of attacked and
737 // undefended squares around the king, the square of the king, and the
738 // quality of the pawn shelter.
740 Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
741 + (ei.kingZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
742 + InitKingDanger[relative_square(us, s)] - shelter / 32;
744 // Analyse safe queen contact checks:
745 b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
747 Bitboard attackedByOthers =
748 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
749 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
750 b &= attackedByOthers;
752 // The bitboard b now contains the squares available for safe queen
754 int count = count_1s_max_15(b);
755 attackUnits += QueenContactCheckBonus * count * (sente? 2 : 1);
757 // Is there a mate threat?
758 if(QueenContactMates && !p.is_check()) {
759 Bitboard escapeSquares =
760 p.king_attacks(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
762 Square from, to = pop_1st_bit(&b);
764 & ~queen_attacks_bb(to, occ & clear_mask_bb(s)))) {
765 // We have a mate, unless the queen is pinned or there
766 // is an X-ray attack through the queen.
767 for(int i = 0; i < p.queen_count(them); i++) {
768 from = p.queen_list(them, i);
769 if(bit_is_set(p.queen_attacks(from), to)
770 && !bit_is_set(p.pinned_pieces(them), from)
771 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
772 & p.rooks_and_queens(us))
773 && !(rook_attacks_bb(to, occ & clear_mask_bb(from))
774 & p.rooks_and_queens(us)))
775 ei.mateThreat[them] = make_move(from, to);
783 // Analyse safe rook contact checks:
784 if(RookContactCheckBonus) {
785 b = undefended & ei.attacked_by(them, ROOK) & ~p.pieces_of_color(them);
787 Bitboard attackedByOthers =
788 ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
789 | ei.attacked_by(them, BISHOP) | ei.attacked_by(them, QUEEN);
790 b &= attackedByOthers;
792 int count = count_1s_max_15(b);
793 attackUnits += (RookContactCheckBonus * count * (sente? 2 : 1));
798 // Analyse safe distance checks:
799 if(QueenCheckBonus > 0 || RookCheckBonus > 0) {
800 b = p.rook_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
803 b2 = b & ei.attacked_by(them, QUEEN);
804 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
807 b2 = b & ei.attacked_by(them, ROOK);
808 if(b2) attackUnits += RookCheckBonus * count_1s_max_15(b2);
810 if(QueenCheckBonus > 0 || BishopCheckBonus > 0) {
811 b = p.bishop_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
813 b2 = b & ei.attacked_by(them, QUEEN);
814 if(b2) attackUnits += QueenCheckBonus * count_1s_max_15(b2);
817 b2 = b & ei.attacked_by(them, BISHOP);
818 if(b2) attackUnits += BishopCheckBonus * count_1s_max_15(b2);
820 if(KnightCheckBonus > 0) {
821 b = p.knight_attacks(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
823 b2 = b & ei.attacked_by(them, KNIGHT);
824 if(b2) attackUnits += KnightCheckBonus * count_1s_max_15(b2);
827 // Analyse discovered checks (only for non-pawns right now, consider
828 // adding pawns later).
829 if(DiscoveredCheckBonus) {
830 b = p.discovered_check_candidates(them) & ~p.pawns();
833 DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
836 // Has a mate threat been found? We don't do anything here if the
837 // side with the mating move is the side to move, because in that
838 // case the mating side will get a huge bonus at the end of the main
839 // evaluation function instead.
840 if(ei.mateThreat[them] != MOVE_NONE)
841 attackUnits += MateThreatBonus;
843 // Ensure that attackUnits is between 0 and 99, in order to avoid array
844 // out of bounds errors:
845 if(attackUnits < 0) attackUnits = 0;
846 if(attackUnits >= 100) attackUnits = 99;
848 // Finally, extract the king safety score from the SafetyTable[] array.
849 // Add the score to the evaluation, and also to ei.futilityMargin. The
850 // reason for adding the king safety score to the futility margin is
851 // that the king safety scores can sometimes be very big, and that
852 // capturing a single attacking piece can therefore result in a score
853 // change far bigger than the value of the captured piece.
854 Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
855 ei.mgValue -= sign * v;
856 if(us == p.side_to_move())
857 ei.futilityMargin += v;
862 // evaluate_passed_pawns() evaluates the passed pawns for both sides.
864 void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
865 bool hasUnstoppable[2] = {false, false};
866 int movesToGo[2] = {100, 100};
868 for(Color us = WHITE; us <= BLACK; us++) {
869 Color them = opposite_color(us);
870 Square ourKingSq = pos.king_square(us);
871 Square theirKingSq = pos.king_square(them);
872 Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
875 Square s = pop_1st_bit(&b);
876 assert(pos.piece_on(s) == pawn_of_color(us));
877 assert(pos.pawn_is_passed(us, s));
879 int r = int(relative_rank(us, s) - RANK_2);
880 int tr = Max(0, r * (r-1));
881 Square blockSq = s + pawn_push(us);
883 // Base bonus based on rank:
884 Value mbonus = Value(20 * tr);
885 Value ebonus = Value(10 + r * r * 10);
887 // Adjust bonus based on king proximity:
888 ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
890 Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
891 ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
893 // If the pawn is free to advance, increase bonus:
894 if(pos.square_is_empty(blockSq)) {
896 b2 = squares_in_front_of(us, s);
897 b3 = b2 & ei.attacked_by(them);
898 b4 = b2 & ei.attacked_by(us);
899 if((b2 & pos.pieces_of_color(them)) == EmptyBoardBB) {
900 // There are no enemy pieces in the pawn's path! Are any of the
901 // squares in the pawn's path attacked by the enemy?
902 if(b3 == EmptyBoardBB)
903 // No enemy attacks, huge bonus!
904 ebonus += Value(tr * ((b2 == b4)? 17 : 15));
906 // OK, there are enemy attacks. Are those squares which are
907 // attacked by the enemy also attacked by us? If yes, big bonus
908 // (but smaller than when there are no enemy attacks), if no,
909 // somewhat smaller bonus.
910 ebonus += Value(tr * (((b3 & b4) == b3)? 13 : 8));
913 // There are some enemy pieces in the pawn's path. While this is
914 // sad, we still assign a moderate bonus if all squares in the path
915 // which are either occupied by or attacked by enemy pieces are
916 // also attacked by us.
917 if(((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
918 ebonus += Value(tr * 6);
920 // At last, add a small bonus when there are no *friendly* pieces
921 // in the pawn's path:
922 if((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
926 // If the pawn is supported by a friendly pawn, increase bonus.
927 b2 = pos.pawns(us) & neighboring_files_bb(s);
929 ebonus += Value(r * 20);
930 else if(pos.pawn_attacks(them, s) & b2)
931 ebonus += Value(r * 12);
933 // If the other side has only a king, check whether the pawn is
935 if(pos.non_pawn_material(them) == Value(0)) {
939 qsq = relative_square(us, make_square(square_file(s), RANK_8));
940 d = square_distance(s, qsq) - square_distance(theirKingSq, qsq)
941 + ((us == pos.side_to_move())? 0 : 1);
944 int mtg = RANK_8 - relative_rank(us, s);
946 count_1s_max_15(squares_in_front_of(us,s)&pos.occupied_squares());
950 hasUnstoppable[us] = true;
951 movesToGo[us] = Min(movesToGo[us], mtg);
955 // Rook pawns are a special case: They are sometimes worse, and
956 // sometimes better than other passed pawns. It is difficult to find
957 // good rules for determining whether they are good or bad. For now,
958 // we try the following: Increase the value for rook pawns if the
959 // other side has no pieces apart from a knight, and decrease the
960 // value if the other side has a rook or queen.
961 if(square_file(s) == FILE_A || square_file(s) == FILE_H) {
962 if(pos.non_pawn_material(them) == KnightValueMidgame
963 && pos.knight_count(them) == 1)
964 ebonus += ebonus / 4;
965 else if(pos.rooks_and_queens(them))
966 ebonus -= ebonus / 4;
969 // Add the scores for this pawn to the middle game and endgame eval.
970 ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
971 ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
975 // Does either side have an unstoppable passed pawn?
976 if(hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
977 ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
978 else if(hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
979 ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
980 else if(hasUnstoppable[BLACK] && hasUnstoppable[WHITE]) {
981 // Both sides have unstoppable pawns! Try to find out who queens
982 // first. We begin by transforming 'movesToGo' to the number of
983 // plies until the pawn queens for both sides:
984 movesToGo[WHITE] *= 2;
985 movesToGo[BLACK] *= 2;
986 movesToGo[pos.side_to_move()]--;
988 // If one side queens at least three plies before the other, that
990 if(movesToGo[WHITE] <= movesToGo[BLACK] - 3)
991 ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
992 else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
993 ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
995 // We could also add some rules about the situation when one side
996 // queens exactly one ply before the other: Does the first queen
997 // check the opponent's king, or attack the opponent's queening square?
998 // This is slightly tricky to get right, because it is possible that
999 // the opponent's king has moved somewhere before the first pawn queens.
1004 // evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
1005 // (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
1008 void evaluate_trapped_bishop_a7h7(const Position &pos, Square s, Color us,
1011 assert(square_is_ok(s));
1012 assert(pos.piece_on(s) == bishop_of_color(us));
1014 Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
1015 Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
1017 if ( pos.piece_on(b6) == pawn_of_color(opposite_color(us))
1018 && pos.see(s, b6) < 0
1019 && pos.see(s, b8) < 0)
1021 ei.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
1022 ei.egValue -= Sign[us] * TrappedBishopA7H7Penalty;
1027 // evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
1028 // (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
1029 // black), and assigns a penalty if it is. This pattern can obviously
1030 // only occur in Chess960 games.
1032 void evaluate_trapped_bishop_a1h1(const Position &pos, Square s, Color us,
1034 Piece pawn = pawn_of_color(us);
1038 assert(square_is_ok(s));
1039 assert(pos.piece_on(s) == bishop_of_color(us));
1041 if(square_file(s) == FILE_A) {
1042 b2 = relative_square(us, SQ_B2);
1043 b3 = relative_square(us, SQ_B3);
1044 c3 = relative_square(us, SQ_C3);
1047 b2 = relative_square(us, SQ_G2);
1048 b3 = relative_square(us, SQ_G3);
1049 c3 = relative_square(us, SQ_F3);
1052 if(pos.piece_on(b2) == pawn) {
1055 if(!pos.square_is_empty(b3))
1056 penalty = 2*TrappedBishopA1H1Penalty;
1057 else if(pos.piece_on(c3) == pawn)
1058 penalty = TrappedBishopA1H1Penalty;
1060 penalty = TrappedBishopA1H1Penalty / 2;
1062 ei.mgValue -= Sign[us] * penalty;
1063 ei.egValue -= Sign[us] * penalty;
1069 // apply_weight applies an evaluation weight to a value.
1071 inline Value apply_weight(Value v, int w) {
1072 return (v*w) / 0x100;
1076 // scale_by_game_phase interpolates between a middle game and an endgame
1077 // score, based on game phase. It also scales the return value by a
1078 // ScaleFactor array.
1080 Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
1082 assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
1083 assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
1084 assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
1086 ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
1088 // Linearized sigmoid interpolator
1090 sph -= (64 - sph) / 4;
1091 sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
1093 Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
1095 return Value(int(result) & ~(GrainSize - 1));
1099 // count_1s_8bit() counts the number of nonzero bits in the 8 least
1100 // significant bits of a Bitboard. This function is used by the king
1101 // shield evaluation.
1103 int count_1s_8bit(Bitboard b) {
1104 return int(BitCount8Bit[b & 0xFF]);
1108 // compute_weight() computes the value of an evaluation weight, by combining
1109 // an UCI-configurable weight with an internal weight.
1111 int compute_weight(int uciWeight, int internalWeight) {
1112 uciWeight = (uciWeight * 0x100) / 100;
1113 return (uciWeight * internalWeight) / 0x100;
1117 // helper used in read_weights()
1118 int weight_option(const std::string& opt, int weight) {
1120 return compute_weight(get_option_value_int(opt), weight);
1124 // init_safety() initizes the king safety evaluation, based on UCI
1125 // parameters. It is called from read_weights().
1127 void init_safety() {
1129 QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
1130 RookContactCheckBonus = get_option_value_int("Rook Contact Check Bonus");
1131 QueenCheckBonus = get_option_value_int("Queen Check Bonus");
1132 RookCheckBonus = get_option_value_int("Rook Check Bonus");
1133 BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
1134 KnightCheckBonus = get_option_value_int("Knight Check Bonus");
1135 DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
1136 MateThreatBonus = get_option_value_int("Mate Threat Bonus");
1138 int maxSlope = get_option_value_int("King Safety Max Slope");
1139 int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
1140 double a = get_option_value_int("King Safety Coefficient") / 100.0;
1141 double b = get_option_value_int("King Safety X Intercept");
1142 bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
1143 bool linear = (get_option_value_string("King Safety Curve") == "Linear");
1145 for (int i = 0; i < 100; i++)
1148 SafetyTable[i] = Value(0);
1150 SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
1152 SafetyTable[i] = Value((int)(100 * a * (i - b)));
1155 for (int i = 0; i < 100; i++)
1157 if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
1158 for (int j = i + 1; j < 100; j++)
1159 SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
1161 if (SafetyTable[i] > Value(peak))
1162 SafetyTable[i] = Value(peak);