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) 2015-2018 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
31 /// StatBoards is a generic 2-dimensional array used to store various statistics
32 template<int Size1, int Size2, typename T = int16_t>
33 struct StatBoards : public std::array<std::array<T, Size2>, Size1> {
35 void fill(const T& v) {
36 T* p = &(*this)[0][0];
37 std::fill(p, p + sizeof(*this) / sizeof(*p), v);
40 void update(T& entry, int bonus, const int D) {
42 assert(abs(bonus) <= D); // Ensure range is [-32 * D, 32 * D]
43 assert(abs(32 * D) < (std::numeric_limits<T>::max)()); // Ensure we don't overflow
45 entry += bonus * 32 - entry * abs(bonus) / D;
47 assert(abs(entry) <= 32 * D);
51 /// StatCubes is a generic 3-dimensional array used to store various statistics
52 template<int Size1, int Size2, int Size3, typename T = int16_t>
53 struct StatCubes : public std::array<std::array<std::array<T, Size3>, Size2>, Size1> {
55 void fill(const T& v) {
56 T* p = &(*this)[0][0][0];
57 std::fill(p, p + sizeof(*this) / sizeof(*p), v);
60 void update(T& entry, int bonus, const int D, const int W) {
62 assert(abs(bonus) <= D); // Ensure range is [-W * D, W * D]
63 assert(abs(W * D) < (std::numeric_limits<T>::max)()); // Ensure we don't overflow
65 entry += bonus * W - entry * abs(bonus) / D;
67 assert(abs(entry) <= W * D);
71 /// ButterflyBoards are 2 tables (one for each color) indexed by the move's from
72 /// and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
73 typedef StatBoards<COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyBoards;
75 /// PieceToBoards are addressed by a move's [piece][to] information
76 typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
78 /// CapturePieceToBoards are addressed by a move's [piece][to][captured piece type] information
79 typedef StatCubes<PIECE_NB, SQUARE_NB, PIECE_TYPE_NB> CapturePieceToBoards;
81 /// ButterflyHistory records how often quiet moves have been successful or
82 /// unsuccessful during the current search, and is used for reduction and move
83 /// ordering decisions. It uses ButterflyBoards as backing store.
84 struct ButterflyHistory : public ButterflyBoards {
86 void update(Color c, Move m, int bonus) {
87 StatBoards::update((*this)[c][from_to(m)], bonus, 324);
91 /// PieceToHistory is like ButterflyHistory, but is based on PieceToBoards
92 struct PieceToHistory : public PieceToBoards {
94 void update(Piece pc, Square to, int bonus) {
95 StatBoards::update((*this)[pc][to], bonus, 936);
99 /// CapturePieceToHistory is like PieceToHistory, but is based on CapturePieceToBoards
100 struct CapturePieceToHistory : public CapturePieceToBoards {
102 void update(Piece pc, Square to, PieceType captured, int bonus) {
103 StatCubes::update((*this)[pc][to][captured], bonus, 324, 2);
107 /// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
108 /// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
109 typedef StatBoards<PIECE_NB, SQUARE_NB, Move> CounterMoveHistory;
111 /// ContinuationHistory is the history of a given pair of moves, usually the
112 /// current one given a previous one. History table is based on PieceToBoards
113 /// instead of ButterflyBoards.
114 typedef StatBoards<PIECE_NB, SQUARE_NB, PieceToHistory> ContinuationHistory;
117 /// MovePicker class is used to pick one pseudo legal move at a time from the
118 /// current position. The most important method is next_move(), which returns a
119 /// new pseudo legal move each time it is called, until there are no moves left,
120 /// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
121 /// beta algorithm, MovePicker attempts to return the moves which are most likely
122 /// to get a cut-off first.
126 MovePicker(const MovePicker&) = delete;
127 MovePicker& operator=(const MovePicker&) = delete;
128 MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
129 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, Square);
130 MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, const PieceToHistory**, Move, Move*);
131 Move next_move(bool skipQuiets = false);
134 template<GenType> void score();
135 ExtMove* begin() { return cur; }
136 ExtMove* end() { return endMoves; }
139 const ButterflyHistory* mainHistory;
140 const CapturePieceToHistory* captureHistory;
141 const PieceToHistory** contHistory;
142 Move ttMove, countermove, killers[2];
143 ExtMove *cur, *endMoves, *endBadCaptures;
145 Square recaptureSquare;
148 ExtMove moves[MAX_MOVES];
151 #endif // #ifndef MOVEPICK_H_INCLUDED