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 = int16_t>
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);
39 void update(T& entry, int bonus, const int D) {
41 assert(abs(bonus) <= D); // Ensure range is [-32 * D, 32 * D]
42 assert(abs(32 * D) < INT16_MAX); // Ensure we don't overflow
44 entry += bonus * 32 - entry * abs(bonus) / D;
46 assert(abs(entry) <= 32 * D);
50 /// ButterflyBoards are 2 tables (one for each color) indexed by the move's from
51 /// and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
52 typedef StatBoards<COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyBoards;
54 /// PieceToBoards are addressed by a move's [piece][to] information
55 typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
57 /// ButterflyHistory records how often quiet moves have been successful or
58 /// unsuccessful during the current search, and is used for reduction and move
59 /// ordering decisions. It uses ButterflyBoards as backing store.
60 struct ButterflyHistory : public ButterflyBoards {
62 void update(Color c, Move m, int bonus) {
63 StatBoards::update((*this)[c][from_to(m)], bonus, 324);
67 /// PieceToHistory is like ButterflyHistory, but is based on PieceToBoards
68 struct PieceToHistory : public PieceToBoards {
70 void update(Piece pc, Square to, int bonus) {
71 StatBoards::update((*this)[pc][to], bonus, 936);
75 /// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
76 /// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
77 typedef StatBoards<PIECE_NB, SQUARE_NB, Move> CounterMoveHistory;
79 /// ContinuationHistory is the history of a given pair of moves, usually the
80 /// current one given a previous one. History table is based on PieceToBoards
81 /// instead of ButterflyBoards.
82 typedef StatBoards<PIECE_NB, SQUARE_NB, PieceToHistory> ContinuationHistory;
85 /// MovePicker class is used to pick one pseudo legal move at a time from the
86 /// current position. The most important method is next_move(), which returns a
87 /// new pseudo legal move each time it is called, until there are no moves left,
88 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
89 /// beta algorithm, MovePicker attempts to return the moves which are most likely
90 /// to get a cut-off first.
94 MovePicker(const MovePicker&) = delete;
95 MovePicker& operator=(const MovePicker&) = delete;
96 MovePicker(const Position&, Move, Value);
97 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, Square);
98 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const PieceToHistory**, Move, Move*);
99 Move next_move(bool skipQuiets = false);
102 template<GenType> void score();
103 ExtMove* begin() { return cur; }
104 ExtMove* end() { return endMoves; }
107 const ButterflyHistory* mainHistory;
108 const PieceToHistory** contHistory;
109 Move ttMove, countermove, killers[2];
110 ExtMove *cur, *endMoves, *endBadCaptures;
112 Square recaptureSquare;
115 ExtMove moves[MAX_MOVES];
118 #endif // #ifndef MOVEPICK_H_INCLUDED