movepick.h

/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, 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/>.
*/


#if !defined MOVEPICK_H_INCLUDED
#define MOVEPICK_H_INCLUDED

////
//// Includes
////

#include "depth.h"
#include "history.h"
#include "position.h"


////
//// Types
////

struct SearchStack;

/// MovePicker is a class which is used to pick one legal move at a time from
/// the current position. It is initialized with a Position object and a few
/// moves we have reason to believe are good. The most important method is
/// MovePicker::pick_next_move(), which returns a new legal move each time it
/// is called, until there are no legal 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 be strongest first.

class MovePicker {

  MovePicker& operator=(const MovePicker&); // silence a warning under MSVC

public:
  MovePicker(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss = NULL, Value beta = -VALUE_INFINITE);
  Move get_next_move();
  int number_of_evasions() const;

private:
  void score_captures();
  void score_noncaptures();
  void score_evasions();
  void go_next_phase();

  const Position& pos;
  const History& H;
  Bitboard pinned;
  MoveStack ttMoves[2], killers[2];
  int badCaptureThreshold, phase;
  const uint8_t* phasePtr;
  MoveStack *curMove, *lastMove, *lastGoodNonCapture, *badCaptures;
  MoveStack moves[MOVES_MAX];
};


////
//// Inline functions
////

/// MovePicker::number_of_evasions() simply returns the number of moves in
/// evasions phase. It is intended to be used in positions where the side to
/// move is in check, for detecting checkmates or situations where there is
/// only a single reply to check.
/// WARNING: It works as long as PH_EVASIONS is the _only_ phase for evasions.

inline int MovePicker::number_of_evasions() const {
  return int(lastMove - moves);
}

#endif // !defined(MOVEPICK_H_INCLUDED)