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
31 /// The Stats struct stores moves statistics. According to the template parameter
32 /// the class can store History, Gains and Countermoves. History records how often
33 /// different moves have been successful or unsuccessful during the current search
34 /// and is used for reduction and move ordering decisions. Gains records the move's
35 /// best evaluation gain from one ply to the next and is used for pruning decisions.
36 /// Countermoves store the move that refute a previous one. Entries are stored
37 /// using only the moving piece and destination square, hence two moves with
38 /// different origin but same destination and piece will be considered identical.
39 template<bool Gain, typename T>
42 static const Value Max = Value(250);
44 const T* operator[](Piece pc) const { return table[pc]; }
45 T* operator[](Piece pc) { return table[pc]; }
47 void update(Piece pc, Square to, Move m) {
49 if (m != table[pc][to])
53 void update(Piece pc, Square to, Value v) {
56 table[pc][to] = std::max(v, table[pc][to] - 1);
58 else if (abs(table[pc][to] + v) < Max)
63 T table[PIECE_NB][SQUARE_NB];
66 typedef Stats< true, Value> GainsStats;
67 typedef Stats<false, Value> HistoryStats;
68 typedef Stats<false, Move> MovesStats;
69 typedef Stats<false, HistoryStats> CounterMovesHistoryStats;
72 /// MovePicker class is used to pick one pseudo legal move at a time from the
73 /// current position. The most important method is next_move(), which returns a
74 /// new pseudo legal move each time it is called, until there are no moves left,
75 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
76 /// beta algorithm, MovePicker attempts to return the moves which are most likely
77 /// to get a cut-off first.
81 MovePicker(const MovePicker&) = delete;
82 MovePicker& operator=(const MovePicker&) = delete;
84 MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Square);
85 MovePicker(const Position&, Move, const HistoryStats&, const CounterMovesHistoryStats&, PieceType);
86 MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Move, Search::Stack*);
88 template<bool SpNode> Move next_move();
91 template<GenType> void score();
92 void generate_next_stage();
93 ExtMove* begin() { return moves; }
94 ExtMove* end() { return endMoves; }
97 const HistoryStats& history;
98 const CounterMovesHistoryStats& counterMovesHistory;
104 Square recaptureSquare;
105 Value captureThreshold;
107 ExtMove *endQuiets, *endBadCaptures;
108 ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = moves;
111 #endif // #ifndef MOVEPICK_H_INCLUDED