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
5 Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef MOVEPICK_H_INCLUDED
22 #define MOVEPICK_H_INCLUDED
24 #include <algorithm> // For std::max
25 #include <cstring> // For std::memset
32 /// HistoryStats records how often quiet moves have been successful or unsuccessful
33 /// during the current search, and is used for reduction and move ordering decisions.
36 static const Value Max = Value(1 << 28);
38 Value get(Color c, Move m) const { return table[c][from_sq(m)][to_sq(m)]; }
39 void clear() { std::memset(table, 0, sizeof(table)); }
40 void update(Color c, Move m, Value v) {
42 Square from = from_sq(m);
45 const int denom = 324;
47 assert(abs(int(v)) <= denom); // Needed for stability.
49 table[c][from][to] -= table[c][from][to] * abs(int(v)) / denom;
50 table[c][from][to] += int(v) * 32;
54 Value table[COLOR_NB][SQUARE_NB][SQUARE_NB];
58 /// A template struct, used to generate MoveStats and CounterMoveHistoryStats:
59 /// MoveStats store the move that refute a previous one.
60 /// CounterMoveHistoryStats is like HistoryStats, but with two consecutive moves.
61 /// Entries are stored using only the moving piece and destination square, hence
62 /// two moves with different origin but same destination and piece will be
63 /// considered identical.
66 const T* operator[](Piece pc) const { return table[pc]; }
67 T* operator[](Piece pc) { return table[pc]; }
68 void clear() { std::memset(table, 0, sizeof(table)); }
69 void fill(const Value& v) { std::fill(&table[0][0], &table[PIECE_NB-1][SQUARE_NB-1]+1, v); };
70 void update(Piece pc, Square to, Move m) { table[pc][to] = m; }
71 void update(Piece pc, Square to, Value v) {
73 const int denom = 936;
75 assert(abs(int(v)) <= denom); // Needed for stability.
77 table[pc][to] -= table[pc][to] * abs(int(v)) / denom;
78 table[pc][to] += int(v) * 32;
82 T table[PIECE_NB][SQUARE_NB];
85 typedef Stats<Move> MoveStats;
86 typedef Stats<Value> CounterMoveStats;
87 typedef Stats<CounterMoveStats> CounterMoveHistoryStats;
90 /// MovePicker class is used to pick one pseudo legal move at a time from the
91 /// current position. The most important method is next_move(), which returns a
92 /// new pseudo legal move each time it is called, until there are no moves left,
93 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
94 /// beta algorithm, MovePicker attempts to return the moves which are most likely
95 /// to get a cut-off first.
96 namespace Search { struct Stack; }
100 MovePicker(const MovePicker&) = delete;
101 MovePicker& operator=(const MovePicker&) = delete;
103 MovePicker(const Position&, Move, Value);
104 MovePicker(const Position&, Move, Depth, Square);
105 MovePicker(const Position&, Move, Depth, Search::Stack*);
107 Move next_move(bool skipQuiets = false);
110 template<GenType> void score();
111 ExtMove* begin() { return cur; }
112 ExtMove* end() { return endMoves; }
115 const Search::Stack* ss;
119 Square recaptureSquare;
122 ExtMove *cur, *endMoves, *endBadCaptures;
123 ExtMove moves[MAX_MOVES];
126 #endif // #ifndef MOVEPICK_H_INCLUDED