/* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see . */ #include #include #include "bitboard.h" #include "pawns.h" #include "position.h" #include "thread.h" namespace { #define V Value #define S(mg, eg) make_score(mg, eg) // Pawn penalties constexpr Score Backward = S( 9, 24); constexpr Score Doubled = S(11, 56); constexpr Score Isolated = S( 5, 15); constexpr Score WeakUnopposed = S( 13, 27); // Connected pawn bonus constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 }; // Strength of pawn shelter for our king by [distance from edge][rank]. // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king. constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = { { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) }, { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) }, { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) }, { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) } }; // Danger of enemy pawns moving toward our king by [distance from edge][rank]. // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn // is behind our king. constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) }, { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) }, { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) }, { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) } }; #undef S #undef V template Score evaluate(const Position& pos, Pawns::Entry* e) { constexpr Color Them = (Us == WHITE ? BLACK : WHITE); constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH); Bitboard b, neighbours, stoppers, doubled, support, phalanx; Bitboard lever, leverPush; Square s; bool opposed, backward; Score score = SCORE_ZERO; const Square* pl = pos.squares(Us); Bitboard ourPawns = pos.pieces( Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0; e->kingSquares[Us] = SQ_NONE; e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); // Loop through all pawns of the current color and score each pawn while ((s = *pl++) != SQ_NONE) { assert(pos.piece_on(s) == make_piece(Us, PAWN)); Rank r = relative_rank(Us, s); e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); // Flag the pawn opposed = theirPawns & forward_file_bb(Us, s); stoppers = theirPawns & passed_pawn_span(Us, s); lever = theirPawns & PawnAttacks[Us][s]; leverPush = theirPawns & PawnAttacks[Us][s + Up]; doubled = ourPawns & (s - Up); neighbours = ourPawns & adjacent_files_bb(s); phalanx = neighbours & rank_bb(s); support = neighbours & rank_bb(s - Up); // A pawn is backward when it is behind all pawns of the same color // on the adjacent files and cannot be safely advanced. backward = !(ourPawns & pawn_attack_span(Them, s + Up)) && (stoppers & (leverPush | (s + Up))); // Passed pawns will be properly scored in evaluation because we need // full attack info to evaluate them. Include also not passed pawns // which could become passed after one or two pawn pushes when are // not attacked more times than defended. if ( !(stoppers ^ lever) || (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush))) e->passedPawns[Us] |= s; else if (stoppers == square_bb(s + Up) && r >= RANK_5) { b = shift(support) & ~theirPawns; while (b) if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) e->passedPawns[Us] |= s; } // Score this pawn if (support | phalanx) { int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1) + 17 * popcount(support); score += make_score(v, v * (r - 2) / 4); } else if (!neighbours) score -= Isolated + WeakUnopposed * int(!opposed); else if (backward) score -= Backward + WeakUnopposed * int(!opposed); if (doubled && !support) score -= Doubled; } return score; } } // namespace namespace Pawns { /// Pawns::probe() looks up the current position's pawns configuration in /// the pawns hash table. It returns a pointer to the Entry if the position /// is found. Otherwise a new Entry is computed and stored there, so we don't /// have to recompute all when the same pawns configuration occurs again. Entry* probe(const Position& pos) { Key key = pos.pawn_key(); Entry* e = pos.this_thread()->pawnsTable[key]; if (e->key == key) return e; e->key = key; e->scores[WHITE] = evaluate(pos, e); e->scores[BLACK] = evaluate(pos, e); return e; } /// Entry::evaluate_shelter() calculates the shelter bonus and the storm /// penalty for a king, looking at the king file and the two closest files. template void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) { constexpr Color Them = (Us == WHITE ? BLACK : WHITE); constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH); constexpr Bitboard BlockSquares = (Rank1BB | Rank2BB | Rank7BB | Rank8BB) & (FileABB | FileHBB); Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); Bitboard ourPawns = b & pos.pieces(Us); Bitboard theirPawns = b & pos.pieces(Them); Value bonus[] = { (shift(theirPawns) & BlockSquares & ksq) ? Value(374) : Value(5), VALUE_ZERO }; File center = clamp(file_of(ksq), FILE_B, FILE_G); for (File f = File(center - 1); f <= File(center + 1); ++f) { b = ourPawns & file_bb(f); Rank ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; b = theirPawns & file_bb(f); Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; int d = std::min(f, ~f); bonus[MG] += ShelterStrength[d][ourRank]; if (ourRank && (ourRank == theirRank - 1)) bonus[MG] -= 82 * (theirRank == RANK_3), bonus[EG] -= 82 * (theirRank == RANK_3); else bonus[MG] -= UnblockedStorm[d][theirRank]; } if (bonus[MG] > mg_value(shelter)) shelter = make_score(bonus[MG], bonus[EG]); } /// Entry::do_king_safety() calculates a bonus for king safety. It is called only /// when king square changes, which is about 20% of total king_safety() calls. template Score Entry::do_king_safety(const Position& pos) { Square ksq = pos.square(Us); kingSquares[Us] = ksq; castlingRights[Us] = pos.castling_rights(Us); Bitboard pawns = pos.pieces(Us, PAWN); int minPawnDist = pawns ? 8 : 0; if (pawns & PseudoAttacks[KING][ksq]) minPawnDist = 1; else while (pawns) minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO); evaluate_shelter(pos, ksq, shelter); // If we can castle use the bonus after the castling if it is bigger if (pos.can_castle(Us | KING_SIDE)) evaluate_shelter(pos, relative_square(Us, SQ_G1), shelter); if (pos.can_castle(Us | QUEEN_SIDE)) evaluate_shelter(pos, relative_square(Us, SQ_C1), shelter); return shelter - make_score(VALUE_ZERO, 16 * minPawnDist); } // Explicit template instantiation template Score Entry::do_king_safety(const Position& pos); template Score Entry::do_king_safety(const Position& pos); } // namespace Pawns