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
38 const int PawnTableSize = 16384;
40 /// PawnInfo is a class which contains various information about a pawn
41 /// structure. Currently, it only includes a middle game and an end game
42 /// pawn structure evaluation, and a bitboard of passed pawns. We may want
43 /// to add further information in the future. A lookup to the pawn hash table
44 /// (performed by calling the get_pawn_info method in a PawnInfoTable object)
45 /// returns a pointer to a PawnInfo object.
48 friend class PawnInfoTable;
51 Score pawns_value() const;
52 Bitboard pawn_attacks(Color c) const;
53 Bitboard passed_pawns(Color c) const;
54 int file_is_half_open(Color c, File f) const;
55 int has_open_file_to_left(Color c, File f) const;
56 int has_open_file_to_right(Color c, File f) const;
59 Score king_shelter(const Position& pos, Square ksq);
63 Score updateShelter(const Position& pos, Square ksq);
66 Bitboard passedPawns[2];
67 Bitboard pawnAttacks[2];
68 Square kingSquares[2];
71 Score kingShelters[2];
75 /// The PawnInfoTable class represents a pawn hash table. The most important
76 /// method is get_pawn_info, which returns a pointer to a PawnInfo object.
78 class PawnInfoTable : public SimpleHash<PawnInfo, PawnTableSize> {
80 enum SideType { KingSide, QueenSide };
83 PawnInfo* get_pawn_info(const Position& pos) const;
84 void prefetch(Key key) const;
88 Score evaluate_pawns(const Position& pos, Bitboard ourPawns, Bitboard theirPawns, PawnInfo* pi) const;
96 inline void PawnInfoTable::prefetch(Key key) const {
98 unsigned index = unsigned(key & (PawnTableSize - 1));
99 PawnInfo* pi = entries + index;
100 ::prefetch((char*) pi);
103 inline Score PawnInfo::pawns_value() const {
107 inline Bitboard PawnInfo::pawn_attacks(Color c) const {
108 return pawnAttacks[c];
111 inline Bitboard PawnInfo::passed_pawns(Color c) const {
112 return passedPawns[c];
115 inline int PawnInfo::file_is_half_open(Color c, File f) const {
116 return (halfOpenFiles[c] & (1 << int(f)));
119 inline int PawnInfo::has_open_file_to_left(Color c, File f) const {
120 return halfOpenFiles[c] & ((1 << int(f)) - 1);
123 inline int PawnInfo::has_open_file_to_right(Color c, File f) const {
124 return halfOpenFiles[c] & ~((1 << int(f+1)) - 1);
127 /// PawnInfo::updateShelter() calculates and caches king shelter. It is called
128 /// only when king square changes, about 20% of total king_shelter() calls.
130 Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
132 const int Shift = (Us == WHITE ? 8 : -8);
137 if (relative_rank(Us, ksq) <= RANK_4)
139 pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
140 r = square_rank(ksq) * 8;
141 for (int i = 1; i < 4; i++)
144 shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
147 kingSquares[Us] = ksq;
148 kingShelters[Us] = make_score(shelter, 0);
149 return kingShelters[Us];
153 inline Score PawnInfo::king_shelter(const Position& pos, Square ksq) {
154 return kingSquares[Us] == ksq ? kingShelters[Us] : updateShelter<Us>(pos, ksq);
157 #endif // !defined(PAWNS_H_INCLUDED)