2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 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 #ifndef MOVEPICK_H_INCLUDED
21 #define MOVEPICK_H_INCLUDED
23 #include <algorithm> // For std::max
24 #include <cstring> // For std::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 /// using only the 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(250);
45 const T* operator[](Piece pc) const { return table[pc]; }
46 T* operator[](Piece pc) { return table[pc]; }
47 void clear() { std::memset(table, 0, sizeof(table)); }
49 void update(Piece pc, Square to, Move m) {
51 if (m != table[pc][to])
55 void update(Piece pc, Square to, Value v) {
58 table[pc][to] = std::max(v, table[pc][to] - 1);
60 else if (abs(table[pc][to] + v) < Max)
65 T table[PIECE_NB][SQUARE_NB];
68 typedef Stats< true, Value> GainsStats;
69 typedef Stats<false, Value> HistoryStats;
70 typedef Stats<false, Move> MovesStats;
71 typedef Stats<false, HistoryStats> CounterMovesHistoryStats;
74 /// MovePicker class is used to pick one pseudo legal move at a time from the
75 /// current position. The most important method is next_move(), which returns a
76 /// new pseudo legal move each time it is called, until there are no moves left,
77 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
78 /// beta algorithm, MovePicker attempts to return the moves which are most likely
79 /// to get a cut-off first.
83 MovePicker(const MovePicker&) = delete;
84 MovePicker& operator=(const MovePicker&) = delete;
86 MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Square);
87 MovePicker(const Position&, Move, const HistoryStats&, const CounterMovesHistoryStats&, PieceType);
88 MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Move, Search::Stack*);
90 template<bool SpNode> Move next_move();
93 template<GenType> void score();
94 void generate_next_stage();
95 ExtMove* begin() { return moves; }
96 ExtMove* end() { return endMoves; }
99 const HistoryStats& history;
100 const CounterMovesHistoryStats& counterMovesHistory;
106 Square recaptureSquare;
107 Value captureThreshold;
109 ExtMove *endQuiets, *endBadCaptures;
110 ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = moves;
113 #endif // #ifndef MOVEPICK_H_INCLUDED