2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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/>.
21 #if !defined(PAWNS_H_INCLUDED)
22 #define PAWNS_H_INCLUDED
36 const int PawnTableSize = 16384;
38 /// PawnInfo is a class which contains various information about a pawn
39 /// structure. Currently, it only includes a middle game and an end game
40 /// pawn structure evaluation, and a bitboard of passed pawns. We may want
41 /// to add further information in the future. A lookup to the pawn hash table
42 /// (performed by calling the get_pawn_info method in a PawnInfoTable object)
43 /// returns a pointer to a PawnInfo object.
46 friend class PawnInfoTable;
49 Score pawns_value() const;
50 Bitboard pawn_attacks(Color c) const;
51 Bitboard passed_pawns(Color c) const;
52 int file_is_half_open(Color c, File f) const;
53 int has_open_file_to_left(Color c, File f) const;
54 int has_open_file_to_right(Color c, File f) const;
57 Score king_shelter(const Position& pos, Square ksq);
61 Score updateShelter(const Position& pos, Square ksq);
64 Bitboard passedPawns[2];
65 Bitboard pawnAttacks[2];
66 Square kingSquares[2];
69 Score kingShelters[2];
72 /// The PawnInfoTable class represents a pawn hash table. It is basically
73 /// just an array of PawnInfo objects and a few methods for accessing these
74 /// objects. The most important method is get_pawn_info, which looks up a
75 /// position in the table and returns a pointer to a PawnInfo object.
79 enum SideType { KingSide, QueenSide };
84 PawnInfo* get_pawn_info(const Position& pos) const;
85 void prefetch(Key key) const;
89 Score evaluate_pawns(const Position& pos, Bitboard ourPawns, Bitboard theirPawns, PawnInfo* pi) const;
99 inline void PawnInfoTable::prefetch(Key key) const {
101 unsigned index = unsigned(key & (PawnTableSize - 1));
102 PawnInfo* pi = entries + index;
103 ::prefetch((char*) pi);
106 inline Score PawnInfo::pawns_value() const {
110 inline Bitboard PawnInfo::pawn_attacks(Color c) const {
111 return pawnAttacks[c];
114 inline Bitboard PawnInfo::passed_pawns(Color c) const {
115 return passedPawns[c];
118 inline int PawnInfo::file_is_half_open(Color c, File f) const {
119 return (halfOpenFiles[c] & (1 << int(f)));
122 inline int PawnInfo::has_open_file_to_left(Color c, File f) const {
123 return halfOpenFiles[c] & ((1 << int(f)) - 1);
126 inline int PawnInfo::has_open_file_to_right(Color c, File f) const {
127 return halfOpenFiles[c] & ~((1 << int(f+1)) - 1);
130 /// PawnInfo::updateShelter() calculates and caches king shelter. It is called
131 /// only when king square changes, about 20% of total king_shelter() calls.
133 Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
135 const int Shift = (Us == WHITE ? 8 : -8);
140 if (relative_rank(Us, ksq) <= RANK_4)
142 pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
143 r = square_rank(ksq) * 8;
144 for (int i = 1; i < 4; i++)
147 shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
150 kingSquares[Us] = ksq;
151 kingShelters[Us] = make_score(shelter, 0);
152 return kingShelters[Us];
156 inline Score PawnInfo::king_shelter(const Position& pos, Square ksq) {
157 return kingSquares[Us] == ksq ? kingShelters[Us] : updateShelter<Us>(pos, ksq);
160 #endif // !defined(PAWNS_H_INCLUDED)