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) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2020 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
#define MOVEPICK_H_INCLUDED
#include <array>
+#include <limits>
+#include <type_traits>
#include "movegen.h"
#include "position.h"
#include "types.h"
-/// StatBoards is a generic 2-dimensional array used to store various statistics
-template<int Size1, int Size2, typename T = int16_t>
-struct StatBoards : public std::array<std::array<T, Size2>, Size1> {
+/// 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<typename T, int D>
+class StatsEntry {
- void fill(const T& v) {
- T* p = &(*this)[0][0];
- std::fill(p, p + sizeof(*this) / sizeof(*p), v);
- }
-
- void update(T& entry, int bonus, const int D) {
+ T entry;
- assert([&]{
- int v = entry + bonus * 32 - entry * abs(bonus) / D;
- return INT16_MIN < v && v < INT16_MAX;
- }());
+public:
+ void operator=(const T& v) { entry = v; }
+ T* operator&() { return &entry; }
+ T* operator->() { return &entry; }
+ operator const T&() const { return entry; }
- assert(abs(bonus) <= D); // Consistency check for below formula
+ void operator<<(int bonus) {
+ assert(abs(bonus) <= D); // Ensure range is [-D, D]
+ static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
- entry += bonus * 32 - entry * abs(bonus) / D;
+ entry += bonus - entry * abs(bonus) / D;
- assert(abs(entry) <= 32 * D);
+ assert(abs(entry) <= D);
}
};
-/// ButterflyBoards are 2 tables (one for each color) indexed by the move's from
-/// and to squares, see chessprogramming.wikispaces.com/Butterfly+Boards
-typedef StatBoards<COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyBoards;
+/// Stats is a generic N-dimensional array used to store various statistics.
+/// 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>
+{
+ typedef Stats<T, D, Size, Sizes...> stats;
-/// PieceToBoards are addressed by a move's [piece][to] information
-typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
+ void fill(const T& v) {
-/// 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 ButterflyBoards as backing store.
-struct ButterflyHistory : public ButterflyBoards {
+ // For standard-layout 'this' points to first struct member
+ assert(std::is_standard_layout<stats>::value);
- void update(Color c, Move m, int bonus) {
- StatBoards::update((*this)[c][from_to(m)], bonus, 324);
+ typedef StatsEntry<T, D> entry;
+ entry* p = reinterpret_cast<entry*>(this);
+ std::fill(p, p + sizeof(*this) / sizeof(entry), v);
}
};
-/// PieceToHistory is like ButterflyHistory, but is based on PieceToBoards
-struct PieceToHistory : public PieceToBoards {
+template <typename T, int D, int Size>
+struct Stats<T, D, Size> : public std::array<StatsEntry<T, D>, Size> {};
- void update(Piece pc, Square to, int bonus) {
- StatBoards::update((*this)[pc][to], bonus, 936);
- }
-};
+/// In stats table, D=0 means that the template parameter is not used
+enum StatsParams { NOT_USED = 0 };
+enum StatsType { NoCaptures, Captures };
+
+/// 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 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 StatBoards<PIECE_NB, SQUARE_NB, Move> 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, 10692, PIECE_NB, SQUARE_NB, PIECE_TYPE_NB> CapturePieceToHistory;
-/// ContinuationHistory is the history of a given pair of moves, usually the
-/// current one given a previous one. History table is based on PieceToBoards
-/// instead of ButterflyBoards.
-typedef StatBoards<PIECE_NB, SQUARE_NB, PieceToHistory> ContinuationHistory;
+/// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
+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, 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);
- MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const PieceToHistory**, Square);
- MovePicker(const Position&, Move, Depth, const ButterflyHistory*, const PieceToHistory**, Move, Move*);
+ MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
+ 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 PieceToHistory** contHistory;
- Move ttMove, countermove, killers[2];
- ExtMove *cur, *endMoves, *endBadCaptures;
+ const CapturePieceToHistory* captureHistory;
+ const PieceToHistory** continuationHistory;
+ Move ttMove;
+ ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
int stage;
Square recaptureSquare;
Value threshold;
projects / stockfish / blobdiff