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
30 /// StatBoards is a generic 2-dimensional array used to store various statistics
31 template<int Size1, int Size2, typename T = int>
32 struct StatBoards : public std::array<std::array<T, Size2>, Size1> {
34 void fill(const T& v) {
35 T* p = &(*this)[0][0];
36 std::fill(p, p + sizeof(*this) / sizeof(*p), v);
40 /// ButterflyBoards are 2 tables (one for each color) indexed by the move's from
41 /// and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
42 typedef StatBoards<COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyBoards;
44 /// PieceToBoards are addressed by a move's [piece][to] information
45 typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
47 /// ButterflyHistory records how often quiet moves have been successful or
48 /// unsuccessful during the current search, and is used for reduction and move
49 /// ordering decisions. It uses ButterflyBoards as backing store.
50 struct ButterflyHistory : public ButterflyBoards {
52 void update(Color c, Move m, int bonus) {
55 auto& entry = (*this)[c][from_to(m)];
57 assert(abs(bonus) <= D); // Consistency check for below formula
59 entry += bonus * 32 - entry * abs(bonus) / D;
61 assert(abs(entry) <= 32 * D);
65 /// PieceToHistory is like ButterflyHistory, but is based on PieceToBoards
66 struct PieceToHistory : public PieceToBoards {
68 void update(Piece pc, Square to, int bonus) {
71 auto& entry = (*this)[pc][to];
73 assert(abs(bonus) <= D); // Consistency check for below formula
75 entry += bonus * 32 - entry * abs(bonus) / D;
77 assert(abs(entry) <= 32 * D);
81 /// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
82 /// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
83 typedef StatBoards<PIECE_NB, SQUARE_NB, Move> CounterMoveHistory;
85 /// ContinuationHistory is the history of a given pair of moves, usually the
86 /// current one given a previous one. History table is based on PieceToBoards
87 /// instead of ButterflyBoards.
88 typedef StatBoards<PIECE_NB, SQUARE_NB, PieceToHistory> ContinuationHistory;
91 /// MovePicker class is used to pick one pseudo legal move at a time from the
92 /// current position. The most important method is next_move(), which returns a
93 /// new pseudo legal move each time it is called, until there are no moves left,
94 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
95 /// beta algorithm, MovePicker attempts to return the moves which are most likely
96 /// to get a cut-off first.
100 MovePicker(const MovePicker&) = delete;
101 MovePicker& operator=(const MovePicker&) = delete;
102 MovePicker(const Position&, Move, Value);
103 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const PieceToHistory**, Square);
104 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const PieceToHistory**, Move, Move*);
105 Move next_move(bool skipQuiets = false);
108 template<GenType> void score();
109 ExtMove* begin() { return cur; }
110 ExtMove* end() { return endMoves; }
113 const ButterflyHistory* mainHistory;
114 const PieceToHistory** contHistory;
115 Move ttMove, countermove, killers[2];
116 ExtMove *cur, *endMoves, *endBadCaptures;
118 Square recaptureSquare;
121 ExtMove moves[MAX_MOVES];
124 #endif // #ifndef MOVEPICK_H_INCLUDED