/*
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) 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
#ifndef MOVEPICK_H_INCLUDED
#define MOVEPICK_H_INCLUDED
-#include <algorithm> // For std::max
-#include <cstring> // For std::memset
+#include <array>
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <limits>
+#include <type_traits> // IWYU pragma: keep
#include "movegen.h"
-#include "position.h"
-#include "search.h"
#include "types.h"
+#include "position.h"
+namespace Stockfish {
-/// The Stats struct stores moves statistics. According to the template parameter
-/// the class can store History and Countermoves. History records how often
-/// different moves have been successful or unsuccessful during the current search
-/// and is used for reduction and move ordering decisions.
-/// Countermoves store the move that refute a previous one. Entries are stored
-/// using only the moving piece and destination square, hence two moves with
-/// different origin but same destination and piece will be considered identical.
-template<typename T>
-struct Stats {
+constexpr int PAWN_HISTORY_SIZE = 512;
- static const Value Max = Value(1<<28);
+inline int pawn_structure(const Position& pos) { return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1); }
- const T* operator[](Piece pc) const { return table[pc]; }
- T* operator[](Piece pc) { return table[pc]; }
- void clear() { std::memset(table, 0, sizeof(table)); }
+// 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(Piece pc, Square to, Move m) {
+ T entry;
- if (m != table[pc][to])
- table[pc][to] = m;
- }
+ public:
+ void operator=(const T& v) { entry = v; }
+ T* operator&() { return &entry; }
+ T* operator->() { return &entry; }
+ operator const T&() const { return entry; }
- void updateH(Piece pc, Square to, Value v) {
+ void operator<<(int bonus) {
+ assert(abs(bonus) <= D); // Ensure range is [-D, D]
+ static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
- if (abs(int(v)) >= 324)
- return;
- table[pc][to] -= table[pc][to] * abs(int(v)) / 324;
- table[pc][to] += int(v) * 32;
- }
+ entry += (bonus * D - entry * abs(bonus)) / (D * 5 / 4);
- void updateCMH(Piece pc, Square to, Value v) {
+ assert(abs(entry) <= D);
+ }
+};
- if (abs(int(v)) >= 324)
- return;
- table[pc][to] -= table[pc][to] * abs(int(v)) / 512;
- table[pc][to] += int(v) * 64;
- }
+// 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...>;
-private:
- T table[PIECE_NB][SQUARE_NB];
-};
+ void fill(const T& v) {
+
+ // For standard-layout 'this' points to the first struct member
+ assert(std::is_standard_layout_v<stats>);
-typedef Stats<Value> HistoryStats;
-typedef Stats<Move> MovesStats;
-typedef Stats<HistoryStats> CounterMovesHistoryStats;
+ using entry = StatsEntry<T, D>;
+ entry* p = reinterpret_cast<entry*>(this);
+ std::fill(p, p + sizeof(*this) / sizeof(entry), v);
+ }
+};
+template<typename T, int D, int Size>
+struct Stats<T, D, Size>: public std::array<StatsEntry<T, D>, Size> {};
-/// 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.
+// 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
+// (~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>;
+
+// PawnStructureHistory 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, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Square);
- MovePicker(const Position&, Move, const HistoryStats&, const CounterMovesHistoryStats&, Value);
- MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMovesHistoryStats&, Move, Search::Stack*);
-
- template<bool SpNode> Move next_move();
-
-private:
- template<GenType> void score();
- void generate_next_stage();
- ExtMove* begin() { return moves; }
- ExtMove* end() { return endMoves; }
-
- const Position& pos;
- const HistoryStats& history;
- const CounterMovesHistoryStats& counterMovesHistory;
- Search::Stack* ss;
- Move countermove;
- Depth depth;
- Move ttMove;
- ExtMove killers[3];
- Square recaptureSquare;
- Value threshold;
- int stage;
- ExtMove *endQuiets, *endBadCaptures = moves + MAX_MOVES - 1;
- ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = 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&,
+ Square);
+ MovePicker(const Position&, Move, Value, const CapturePieceToHistory*, const PawnHistory&);
+ 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;
+ Square recaptureSquare;
+ Value threshold;
+ Depth depth;
+ ExtMove moves[MAX_MOVES];
};
-#endif // #ifndef MOVEPICK_H_INCLUDED
+} // namespace Stockfish
+
+#endif // #ifndef MOVEPICK_H_INCLUDED
projects / stockfish / blobdiff