2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2013 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/>.
20 #if !defined MOVEPICK_H_INCLUDED
21 #define MOVEPICK_H_INCLUDED
23 #include <algorithm> // For std::max
24 #include <cstring> // For memset
32 /// The Stats struct stores moves statistics. According to the template parameter
33 /// the class can store History, Gains and Countermoves. History records how often
34 /// different moves have been successful or unsuccessful during the current search
35 /// and is used for reduction and move ordering decisions. Gains records the move's
36 /// best evaluation gain from one ply to the next and is used for pruning decisions.
37 /// Countermoves store the move that refute a previous one. Entries are stored
38 /// according only to moving piece and destination square, hence two moves with
39 /// different origin but same destination and piece will be considered identical.
40 template<bool Gain, typename T>
43 static const Value Max = Value(2000);
45 const T* operator[](Piece p) const { return &table[p][0]; }
46 void clear() { memset(table, 0, sizeof(table)); }
48 void update(Piece p, Square to, Move m) { table[p][to] = m; }
49 void update(Piece p, Square to, Value v) {
52 table[p][to] = std::max(v, table[p][to] - 1);
54 else if (abs(table[p][to] + v) < Max)
59 T table[PIECE_NB][SQUARE_NB];
62 typedef Stats< true, Value> GainsStats;
63 typedef Stats<false, Value> HistoryStats;
64 typedef Stats<false, Move> CountermovesStats;
67 /// MovePicker class is used to pick one pseudo legal move at a time from the
68 /// current position. The most important method is next_move(), which returns a
69 /// new pseudo legal move each time it is called, until there are no moves left,
70 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
71 /// beta algorithm, MovePicker attempts to return the moves which are most likely
72 /// to get a cut-off first.
76 MovePicker& operator=(const MovePicker&); // Silence a warning under MSVC
79 MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
80 MovePicker(const Position&, Move, const HistoryStats&, PieceType);
81 MovePicker(const Position&, Move, Depth, const HistoryStats&,
82 const CountermovesStats&, Search::Stack*, Value);
84 template<bool SpNode> Move next_move();
87 template<GenType> void score();
91 const HistoryStats& history;
96 Square recaptureSquare;
97 int captureThreshold, phase;
98 MoveStack *cur, *end, *endQuiets, *endBadCaptures;
99 MoveStack moves[MAX_MOVES];
102 #endif // !defined(MOVEPICK_H_INCLUDED)