Subversion Repositories Games.Chess Giants

/*

  Stockfish, a UCI chess playing engine derived from Glaurung 2.1

  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)

  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad

  Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad

  Stockfish is free software: you can redistribute it and/or modify

  it under the terms of the GNU General Public License as published by

  the Free Software Foundation, either version 3 of the License, or

  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,

  but WITHOUT ANY WARRANTY; without even the implied warranty of

  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License

  along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#ifndef MOVEPICK_H_INCLUDED

#define MOVEPICK_H_INCLUDED

#include <algorithm> // For std::max

#include <cstring>   // For std::memset

#include "movegen.h"

#include "position.h"

#include "search.h"

#include "types.h"

/// The Stats struct stores moves statistics. According to the template parameter

/// the class can store History and Countermoves. History records how often

/// different moves have been successful or unsuccessful during the current search

/// and is used for reduction and move ordering decisions.

/// Countermoves store the move that refute a previous one. Entries are stored

/// using only the moving piece and destination square, hence two moves with

/// different origin but same destination and piece will be considered identical.

template<typename T, bool CM = false>

struct Stats {

  static const Value Max = Value(1 << 28);

  const T* operator[](Piece pc) const { return table[pc]; }

  T* operator[](Piece pc) { return table[pc]; }

  void clear() { std::memset(table, 0, sizeof(table)); }

  void update(Piece pc, Square to, Move m) {

    if (m != table[pc][to])

        table[pc][to] = m;

  }

  void update(Piece pc, Square to, Value v) {

    if (abs(int(v)) >= 324)

        return;

    table[pc][to] -= table[pc][to] * abs(int(v)) / (CM ? 512 : 324);

    table[pc][to] += int(v) * (CM ? 64 : 32);

  }

private:

  T table[PIECE_NB][SQUARE_NB];

};

typedef Stats<Move> MoveStats;

typedef Stats<Value, false> HistoryStats;

typedef Stats<Value,  true> CounterMoveStats;

typedef Stats<CounterMoveStats> CounterMoveHistoryStats;

/// MovePicker class is used to pick one pseudo legal move at a time from the

/// current position. The most important method is next_move(), which returns a

/// new pseudo legal move each time it is called, until there are no moves left,

/// when MOVE_NONE is returned. In order to improve the efficiency of the alpha

/// beta algorithm, MovePicker attempts to return the moves which are most likely

/// to get a cut-off first.

class MovePicker {

public:

  MovePicker(const MovePicker&) = delete;

  MovePicker& operator=(const MovePicker&) = delete;

  MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);

  MovePicker(const Position&, Move, const HistoryStats&, Value);

  MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMoveStats&, Move, Search::Stack*);

  Move next_move();

private:

  template<GenType> void score();

  void generate_next_stage();

  ExtMove* begin() { return moves; }

  ExtMove* end() { return endMoves; }

  const Position& pos;

  const HistoryStats& history;

  const CounterMoveStats* counterMoveHistory;

  Search::Stack* ss;

  Move countermove;

  Depth depth;

  Move ttMove;

  ExtMove killers[3];

  Square recaptureSquare;

  Value threshold;

  int stage;

  ExtMove *endQuiets, *endBadCaptures = moves + MAX_MOVES - 1;

  ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = moves;

};

#endif // #ifndef MOVEPICK_H_INCLUDED