113 lines
3.7 KiB
C++
113 lines
3.7 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef MOVEPICK_H_INCLUDED
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#define MOVEPICK_H_INCLUDED
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#include <algorithm> // For std::max
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#include <cstring> // For std::memset
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#include "movegen.h"
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#include "position.h"
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#include "search.h"
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#include "types.h"
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/// The Stats struct stores moves statistics. According to the template parameter
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/// the class can store History and Countermoves. History records how often
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/// different moves have been successful or unsuccessful during the current search
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/// and is used for reduction and move ordering decisions.
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/// Countermoves store the move that refute a previous one. Entries are stored
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/// using only the moving piece and destination square, hence two moves with
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/// different origin but same destination and piece will be considered identical.
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template<typename T, bool CM = false>
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struct Stats {
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static const Value Max = Value(1 << 28);
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const T* operator[](Piece pc) const { return table[pc]; }
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T* operator[](Piece pc) { return table[pc]; }
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void clear() { std::memset(table, 0, sizeof(table)); }
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void update(Piece pc, Square to, Move m) {
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if (m != table[pc][to])
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table[pc][to] = m;
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}
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void update(Piece pc, Square to, Value v) {
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if (abs(int(v)) >= 324)
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return;
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table[pc][to] -= table[pc][to] * abs(int(v)) / (CM ? 512 : 324);
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table[pc][to] += int(v) * (CM ? 64 : 32);
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}
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private:
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T table[PIECE_NB][SQUARE_NB];
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};
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typedef Stats<Move> MovesStats;
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typedef Stats<Value, false> HistoryStats;
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typedef Stats<Value, true> CounterMovesStats;
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typedef Stats<CounterMovesStats> CounterMovesHistoryStats;
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/// MovePicker class is used to pick one pseudo legal move at a time from the
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/// current position. The most important method is next_move(), which returns a
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/// new pseudo legal move each time it is called, until there are no moves left,
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/// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
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/// beta algorithm, MovePicker attempts to return the moves which are most likely
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/// to get a cut-off first.
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class MovePicker {
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public:
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MovePicker(const MovePicker&) = delete;
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MovePicker& operator=(const MovePicker&) = delete;
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MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
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MovePicker(const Position&, Move, const HistoryStats&, Value);
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MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesStats&, Move, Search::Stack*);
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Move next_move();
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private:
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template<GenType> void score();
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void generate_next_stage();
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ExtMove* begin() { return moves; }
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ExtMove* end() { return endMoves; }
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const Position& pos;
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const HistoryStats& history;
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const CounterMovesStats* counterMovesHistory;
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Search::Stack* ss;
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Move countermove;
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Depth depth;
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Move ttMove;
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ExtMove killers[3];
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Square recaptureSquare;
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Value threshold;
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int stage;
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ExtMove *endQuiets, *endBadCaptures = moves + MAX_MOVES - 1;
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ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = moves;
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};
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#endif // #ifndef MOVEPICK_H_INCLUDED
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