/*
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) 2015-2018 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 .
*/
#ifndef MOVEPICK_H_INCLUDED
#define MOVEPICK_H_INCLUDED
#include
#include
#include
#include "movegen.h"
#include "position.h"
#include "types.h"
/// StatsEntry stores the stat table value. It is usually a number but could
/// be a move or even a nested history. We use a class instead of naked value
/// to directly call history update operator<<() on the entry so to use stats
/// tables at caller sites as simple multi-dim arrays.
template
class StatsEntry {
static const bool IsInt = std::is_integral::value;
typedef typename std::conditional::type TT;
T entry;
public:
T* get() { return &entry; }
void operator=(const T& v) { entry = v; }
operator TT() const { return entry; }
void operator<<(int bonus) {
assert(abs(bonus) <= D); // Ensure range is [-W * D, W * D]
assert(abs(W * D) < std::numeric_limits::max()); // Ensure we don't overflow
entry += bonus * W - entry * abs(bonus) / D;
assert(abs(entry) <= W * D);
}
};
/// Stats is a generic N-dimensional array used to store various statistics.
/// The first template T parameter is the base type of the array, the W parameter
/// is the weight applied to the bonuses when we update values with the << operator,
/// the D parameter limits the range of updates (range is [-W * D, W * D]), and
/// the last parameters (Size and Sizes) encode the dimensions of the array.
template
struct Stats : public std::array, Size>
{
T* get() { return this->at(0).get(); }
void fill(const T& v) {
T* p = get();
std::fill(p, p + sizeof(*this) / sizeof(*p), v);
}
};
template
struct Stats : public std::array, Size> {
T* get() { return this->at(0).get(); }
};
/// Different tables use different W/D parameter, name them to ease readibility
enum StatsParams { W2 = 2, W32 = 32, D324 = 324, D936 = 936, NOT_USED = 0 };
/// ButterflyHistory records how often quiet moves have been successful or
/// unsuccessful during the current search, and is used for reduction and move
/// ordering decisions. It uses 2 tables (one for each color) indexed by
/// the move's from and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
typedef Stats ButterflyHistory;
/// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
/// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
typedef Stats CounterMoveHistory;
/// CapturePieceToHistory is addressed by a move's [piece][to][captured piece type]
typedef Stats CapturePieceToHistory;
/// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
typedef Stats PieceToHistory;
/// ContinuationHistory is the combined history of a given pair of moves, usually
/// the current one given a previous one. The nested history table is based on
/// PieceToHistory instead of ButterflyBoards.
typedef Stats ContinuationHistory;
/// 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, Value, const CapturePieceToHistory*);
MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, Square);
MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const CapturePieceToHistory*, const PieceToHistory**, Move, Move*);
Move next_move(bool skipQuiets = false);
private:
template void score();
ExtMove* begin() { return cur; }
ExtMove* end() { return endMoves; }
const Position& pos;
const ButterflyHistory* mainHistory;
const CapturePieceToHistory* captureHistory;
const PieceToHistory** contHistory;
Move ttMove, countermove, killers[2];
ExtMove *cur, *endMoves, *endBadCaptures;
int stage;
Square recaptureSquare;
Value threshold;
Depth depth;
ExtMove moves[MAX_MOVES];
};
#endif // #ifndef MOVEPICK_H_INCLUDED