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) 2015-2016 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
#ifndef MOVEPICK_H_INCLUDED
#define MOVEPICK_H_INCLUDED
-#include <algorithm> // For std::max
-#include <cstring> // For std::memset
+#include <array>
+#include <limits>
+#include <type_traits>
#include "movegen.h"
#include "position.h"
-#include "search.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<typename T, int D>
+class StatsEntry {
-/// 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, bool CM = false>
-struct Stats {
+ T entry;
- static const Value Max = Value(1 << 28);
+public:
+ void operator=(const T& v) { entry = v; }
+ T* operator&() { return &entry; }
+ T* operator->() { return &entry; }
+ operator const T&() const { return entry; }
- const T* operator[](Piece pc) const { return table[pc]; }
- T* operator[](Piece pc) { return table[pc]; }
- void clear() { std::memset(table, 0, sizeof(table)); }
+ void operator<<(int bonus) {
+ assert(abs(bonus) <= D); // Ensure range is [-D, D]
+ static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
- void update(Piece pc, Square to, Move m) { table[pc][to] = m; }
+ entry += bonus - entry * abs(bonus) / D;
- void update(Piece pc, Square to, Value v) {
+ assert(abs(entry) <= D);
+ }
+};
- if (abs(int(v)) >= 324)
- return;
+/// 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;
- table[pc][to] -= table[pc][to] * abs(int(v)) / (CM ? 936 : 324);
- table[pc][to] += int(v) * 32;
- }
+ void fill(const T& v) {
-private:
- T table[PIECE_NB][SQUARE_NB];
+ // 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);
+ }
};
-typedef Stats<Move> MoveStats;
-typedef Stats<Value, false> HistoryStats;
-typedef Stats<Value, true> CounterMoveStats;
-typedef Stats<CounterMoveStats> CounterMoveHistoryStats;
+template <typename T, int D, int Size>
+struct Stats<T, D, Size> : public std::array<StatsEntry<T, D>, Size> {};
-struct FromToStats {
+/// In stats table, D=0 means that the template parameter is not used
+enum StatsParams { NOT_USED = 0 };
- Value get(Color c, Move m) const { return table[c][from_sq(m)][to_sq(m)]; }
- void clear() { std::memset(table, 0, sizeof(table)); }
- void update(Color c, Move m, Value v)
- {
- if (abs(int(v)) >= 324)
- return;
+/// 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;
- Square f = from_sq(m);
- Square t = to_sq(m);
+/// CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
+/// move, see www.chessprogramming.org/Countermove_Heuristic
+typedef Stats<Move, NOT_USED, PIECE_NB, SQUARE_NB> CounterMoveHistory;
- table[c][f][t] -= table[c][f][t] * abs(int(v)) / 324;
- table[c][f][t] += int(v) * 32;
- }
+/// 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;
+
+/// 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;
-private:
- Value table[COLOR_NB][SQUARE_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
/// 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, Square);
- MovePicker(const Position&, Move, Depth, Search::Stack*);
-
- Move next_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 Search::Stack* ss;
- Move countermove;
- Depth depth;
+ const ButterflyHistory* mainHistory;
+ const CapturePieceToHistory* captureHistory;
+ const PieceToHistory** continuationHistory;
Move ttMove;
+ ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
+ int stage;
Square recaptureSquare;
Value threshold;
- int stage;
- ExtMove* cur, *endMoves, *endBadCaptures;
+ Depth depth;
ExtMove moves[MAX_MOVES];
};
projects / stockfish / blobdiff