/*
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) 2004-2023 The Stockfish developers (see AUTHORS file)
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 <cassert>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <limits>
+#include <type_traits> // IWYU pragma: keep
#include "movegen.h"
-#include "position.h"
#include "types.h"
+#include "position.h"
-/// StatBoards is a generic 2-dimensional array used to store various statistics
-template<int Size1, int Size2, typename T = int>
-struct StatBoards : public std::array<std::array<T, Size2>, Size1> {
+namespace Stockfish {
- void fill(const T& v) {
- T* p = &(*this)[0][0];
- std::fill(p, p + sizeof(*this) / sizeof(*p), v);
- }
-};
+constexpr int PAWN_HISTORY_SIZE = 512; // has to be a power of 2
-/// 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;
+static_assert((PAWN_HISTORY_SIZE & (PAWN_HISTORY_SIZE - 1)) == 0,
+ "PAWN_HISTORY_SIZE has to be a power of 2");
-/// PieceToBoards are addressed by a move's [piece][to] information
-typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
+inline int pawn_structure(const Position& pos) { return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1); }
-/// 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 {
+// 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 a 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 update(Color c, Move m, int v) {
+ T entry;
- const int D = 324;
- auto& entry = (*this)[c][from_to(m)];
+ public:
+ void operator=(const T& v) { entry = v; }
+ T* operator&() { return &entry; }
+ T* operator->() { return &entry; }
+ operator const T&() const { return entry; }
- assert(abs(v) <= D); // Consistency check for below formula
+ void operator<<(int bonus) {
+ assert(std::abs(bonus) <= D); // Ensure range is [-D, D]
+ static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
- entry += v * 32 - entry * abs(v) / D;
+ entry += bonus - entry * std::abs(bonus) / D;
- assert(abs(entry) <= 32 * D);
- }
+ assert(std::abs(entry) <= D);
+ }
};
-/// PieceToHistory is like ButterflyHistory, but is based on PieceToBoards
-struct PieceToHistory : public PieceToBoards {
+// Stats is a generic N-dimensional array used to store various statistics.
+// The first template parameter T is the base type of the array, and 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> {
+ using stats = Stats<T, D, Size, Sizes...>;
- void update(Piece pc, Square to, int v) {
+ void fill(const T& v) {
- const int D = 936;
- auto& entry = (*this)[pc][to];
+ // For standard-layout 'this' points to the first struct member
+ assert(std::is_standard_layout_v<stats>);
- assert(abs(v) <= D); // Consistency check for below formula
-
- entry += v * 32 - entry * abs(v) / D;
-
- assert(abs(entry) <= 32 * D);
- }
+ using entry = StatsEntry<T, D>;
+ entry* p = reinterpret_cast<entry*>(this);
+ std::fill(p, p + sizeof(*this) / sizeof(entry), v);
+ }
};
-/// CounterMoveStat stores counter moves indexed by [piece][to] of the previous
-/// move, see chessprogramming.wikispaces.com/Countermove+Heuristic
-typedef StatBoards<PIECE_NB, SQUARE_NB, Move> CounterMoveStat;
-
-/// CounterMoveHistoryStat is like CounterMoveStat but instead of a move it
-/// stores a full history (based on PieceTo boards instead of ButterflyBoards).
-typedef StatBoards<PIECE_NB, SQUARE_NB, PieceToHistory> CounterMoveHistoryStat;
+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
+};
+enum StatsType {
+ NoCaptures,
+ Captures
+};
-/// 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.
-namespace Search { struct Stack; }
-
+// 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 (~11 elo)
+using ButterflyHistory = Stats<int16_t, 7183, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)>;
+
+// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
+// move, see www.chessprogramming.org/Countermove_Heuristic
+using CounterMoveHistory = Stats<Move, NOT_USED, PIECE_NB, SQUARE_NB>;
+
+// CapturePieceToHistory is addressed by a move's [piece][to][captured piece type]
+using CapturePieceToHistory = Stats<int16_t, 10692, PIECE_NB, SQUARE_NB, PIECE_TYPE_NB>;
+
+// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
+using PieceToHistory = Stats<int16_t, 29952, PIECE_NB, SQUARE_NB>;
+
+// 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.
+// (~63 elo)
+using ContinuationHistory = Stats<PieceToHistory, NOT_USED, PIECE_NB, SQUARE_NB>;
+
+// PawnHistory is addressed by the pawn structure and a move's [piece][to]
+using PawnHistory = Stats<int16_t, 8192, PAWN_HISTORY_SIZE, PIECE_NB, SQUARE_NB>;
+
+// 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);
- MovePicker(const Position&, Move, Depth, Square);
- MovePicker(const Position&, Move, Depth, Search::Stack*);
-
- Move next_move(bool skipQuiets = false);
-
-private:
- template<GenType> void score();
- ExtMove* begin() { return cur; }
- ExtMove* end() { return endMoves; }
-
- const Position& pos;
- const Search::Stack* ss;
- Move killers[2];
- Move countermove;
- Depth depth;
- Move ttMove;
- Square recaptureSquare;
- Value threshold;
- int stage;
- ExtMove *cur, *endMoves, *endBadCaptures;
- ExtMove moves[MAX_MOVES];
+
+ enum PickType {
+ Next,
+ Best
+ };
+
+ public:
+ MovePicker(const MovePicker&) = delete;
+ MovePicker& operator=(const MovePicker&) = delete;
+ MovePicker(const Position&,
+ Move,
+ Depth,
+ const ButterflyHistory*,
+ const CapturePieceToHistory*,
+ const PieceToHistory**,
+ const PawnHistory*,
+ Move,
+ const Move*);
+ MovePicker(const Position&,
+ Move,
+ Depth,
+ const ButterflyHistory*,
+ const CapturePieceToHistory*,
+ const PieceToHistory**,
+ const PawnHistory*);
+ MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
+ 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** continuationHistory;
+ const PawnHistory* pawnHistory;
+ Move ttMove;
+ ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
+ int stage;
+ Value threshold;
+ Depth depth;
+ ExtMove moves[MAX_MOVES];
};
-#endif // #ifndef MOVEPICK_H_INCLUDED
+} // namespace Stockfish
+
+#endif // #ifndef MOVEPICK_H_INCLUDED
projects / stockfish / blobdiff