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
+ Copyright (C) 2015-2019 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
/// 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<typename T, int W, int D>
+template<typename T, int D>
class StatsEntry {
- static const bool IsInt = std::is_integral<T>::value;
- typedef typename std::conditional<IsInt, int, T>::type TT;
-
T entry;
public:
- T* get() { return &entry; }
void operator=(const T& v) { entry = v; }
- operator TT() const { return entry; }
+ T* operator&() { return &entry; }
+ T* operator->() { return &entry; }
+ operator const T&() const { return entry; }
void operator<<(int bonus) {
+ assert(abs(bonus) <= D); // Ensure range is [-D, D]
+ static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
- assert(abs(bonus) <= D); // Ensure range is [-W * D, W * D]
- assert(abs(W * D) < std::numeric_limits<T>::max()); // Ensure we don't overflow
-
- entry += bonus * W - entry * abs(bonus) / D;
+ entry += bonus - entry * abs(bonus) / D;
- assert(abs(entry) <= W * D);
+ assert(abs(entry) <= 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 <typename T, int W, int D, int Size, int... Sizes>
-struct Stats : public std::array<Stats<T, W, D, Sizes...>, Size>
+/// The first template parameter T is the base type of the array, the second
+/// template parameter D limits the range of updates in [-D, D] when we update
+/// values with the << operator, while the last parameters (Size and Sizes)
+/// encode the dimensions of the array.
+template <typename T, int D, int Size, int... Sizes>
+struct Stats : public std::array<Stats<T, D, Sizes...>, Size>
{
- T* get() { return this->at(0).get(); }
+ typedef Stats<T, D, Size, Sizes...> stats;
void fill(const T& v) {
- T* p = get();
- std::fill(p, p + sizeof(*this) / sizeof(*p), v);
+
+ // For standard-layout 'this' points to first struct member
+ assert(std::is_standard_layout<stats>::value);
+
+ typedef StatsEntry<T, D> entry;
+ entry* p = reinterpret_cast<entry*>(this);
+ std::fill(p, p + sizeof(*this) / sizeof(entry), v);
}
};
-template <typename T, int W, int D, int Size>
-struct Stats<T, W, D, Size> : public std::array<StatsEntry<T, W, D>, Size> {
- T* get() { return this->at(0).get(); }
-};
+template <typename T, int D, int Size>
+struct Stats<T, D, Size> : public std::array<StatsEntry<T, D>, Size> {};
+
+/// In stats table, D=0 means that the template parameter is not used
+enum StatsParams { NOT_USED = 0 };
-/// 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<int16_t, W32, D324, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyHistory;
+/// the move's from and to squares, see www.chessprogramming.org/Butterfly_Boards
+typedef Stats<int16_t, 10692, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyHistory;
/// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
-/// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
-typedef Stats<Move, NOT_USED, NOT_USED, PIECE_NB, SQUARE_NB> CounterMoveHistory;
+/// move, see www.chessprogramming.org/Countermove_Heuristic
+typedef Stats<Move, NOT_USED, PIECE_NB, SQUARE_NB> CounterMoveHistory;
/// CapturePieceToHistory is addressed by a move's [piece][to][captured piece type]
-typedef Stats<int16_t, W2, D324, PIECE_NB, SQUARE_NB, PIECE_TYPE_NB> CapturePieceToHistory;
+typedef Stats<int16_t, 10692, PIECE_NB, SQUARE_NB, PIECE_TYPE_NB> CapturePieceToHistory;
/// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
-typedef Stats<int16_t, W32, D936, PIECE_NB, SQUARE_NB> PieceToHistory;
+typedef Stats<int16_t, 29952, PIECE_NB, SQUARE_NB> 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<PieceToHistory, W32, NOT_USED, PIECE_NB, SQUARE_NB> ContinuationHistory;
+typedef Stats<PieceToHistory, NOT_USED, PIECE_NB, SQUARE_NB> ContinuationHistory;
/// MovePicker class is used to pick one pseudo legal move at a time from the
/// 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 {
+
+ enum PickType { Next, Best };
+
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*);
+ MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+ const CapturePieceToHistory*,
+ const PieceToHistory**,
+ Square);
+ MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+ const CapturePieceToHistory*,
+ const PieceToHistory**,
+ Move,
+ Move*);
Move next_move(bool skipQuiets = false);
private:
+ template<PickType T, typename Pred> Move select(Pred);
template<GenType> void score();
ExtMove* begin() { return cur; }
ExtMove* end() { return endMoves; }
const Position& pos;
const ButterflyHistory* mainHistory;
const CapturePieceToHistory* captureHistory;
- const PieceToHistory** contHistory;
- Move ttMove, refutations[3];
- ExtMove *cur, *endMoves, *endBadCaptures;
+ const PieceToHistory** continuationHistory;
+ Move ttMove;
+ ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
int stage;
Square recaptureSquare;
Value threshold;
projects / stockfish / blobdiff