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113 lines
3.6 KiB
C++
113 lines
3.6 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) 2008-2014 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, Gains 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. Gains records the move's
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/// best evaluation gain from one ply to the next and is used for pruning 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<bool Gain, typename T>
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struct Stats {
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static const Value Max = Value(2000);
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const T* operator[](Piece pc) const { 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].first)
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return;
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table[pc][to].second = table[pc][to].first;
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table[pc][to].first = m;
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}
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void update(Piece pc, Square to, Value v) {
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if (Gain)
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table[pc][to] = std::max(v, table[pc][to] - 1);
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else if (abs(table[pc][to] + v) < Max)
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table[pc][to] += v;
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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< true, Value> GainsStats;
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typedef Stats<false, Value> HistoryStats;
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typedef Stats<false, std::pair<Move, Move> > MovesStats;
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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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MovePicker& operator=(const MovePicker&); // Silence a warning under MSVC
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public:
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MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
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MovePicker(const Position&, Move, const HistoryStats&, PieceType);
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MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Move*, Search::Stack*);
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template<bool SpNode> 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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const Position& pos;
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const HistoryStats& history;
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Search::Stack* ss;
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Move* countermoves;
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Move* followupmoves;
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Depth depth;
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Move ttMove;
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ExtMove killers[6];
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Square recaptureSquare;
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Value captureThreshold;
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int stage;
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ExtMove *cur, *end, *endQuiets, *endBadCaptures;
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ExtMove moves[MAX_MOVES];
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};
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#endif // #ifndef MOVEPICK_H_INCLUDED
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