X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fmovepick.h;h=652ef16166d8295b8d2561e03b00e3a866ae6071;hb=edb4ab924f09abd7c6836c7017365dceccd76b80;hp=db9439f715ed1860718f712d9afb855987117fd9;hpb=4bc11984fc5a148ee8f1b55d6ac47c4a397cc8b8;p=stockfish

diff --git a/src/movepick.h b/src/movepick.h
index db9439f7..652ef161 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -1,8 +1,6 @@
 /*
   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
@@ -22,115 +20,122 @@
 #define MOVEPICK_H_INCLUDED
 
 #include <array>
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
 #include <limits>
+#include <type_traits> // IWYU pragma: keep
 
 #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> {
+namespace Stockfish {
+class Position;
 
-  void fill(const T& v) {
-    T* p = &(*this)[0][0];
-    std::fill(p, p + sizeof(*this) / sizeof(*p), v);
-  }
+// 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(T& entry, int bonus, const int D) {
+  T entry;
 
-    assert(abs(bonus) <= D); // Ensure range is [-32 * D, 32 * D]
-    assert(abs(32 * D) < (std::numeric_limits<T>::max)()); // Ensure we don't overflow
+public:
+  void operator=(const T& v) { entry = v; }
+  T* operator&() { return &entry; }
+  T* operator->() { return &entry; }
+  operator const T&() const { return entry; }
 
-    entry += bonus * 32 - entry * abs(bonus) / D;
+  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(entry) <= 32 * D);
+    entry += bonus - entry * abs(bonus) / D;
+
+    assert(abs(entry) <= D);
   }
 };
 
-/// StatCubes is a generic 3-dimensional array used to store various statistics
-template<int Size1, int Size2, int Size3, typename T = int16_t>
-struct StatCubes : public std::array<std::array<std::array<T, Size3>, Size2>, Size1> {
+// 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 fill(const T& v) {
-    T* p = &(*this)[0][0][0];
-    std::fill(p, p + sizeof(*this) / sizeof(*p), v);
-  }
 
-  void update(T& entry, int bonus, const int D, const int W) {
+    // For standard-layout 'this' points to the first struct member
+    assert(std::is_standard_layout_v<stats>);
 
-    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;
-
-    assert(abs(entry) <= W * D);
+    using entry = StatsEntry<T, D>;
+    entry* p = reinterpret_cast<entry*>(this);
+    std::fill(p, p + sizeof(*this) / sizeof(entry), v);
   }
 };
 
-/// 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;
+template <typename T, int D, int Size>
+struct Stats<T, D, Size> : public std::array<StatsEntry<T, D>, Size> {};
 
-/// PieceToBoards are addressed by a move's [piece][to] information
-typedef StatBoards<PIECE_NB, SQUARE_NB> PieceToBoards;
+// In stats table, D=0 means that the template parameter is not used
+enum StatsParams { NOT_USED = 0 };
+enum StatsType { NoCaptures, Captures };
 
-/// CapturePieceToBoards are addressed by a move's [piece][to][captured piece type] information
-typedef StatCubes<PIECE_NB, SQUARE_NB, PIECE_TYPE_NB> CapturePieceToBoards;
+// 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)>;
 
-/// 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 {
+// 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>;
 
-  void update(Color c, Move m, int bonus) {
-    StatBoards::update((*this)[c][from_to(m)], bonus, 324);
-  }
-};
+// 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 based on PieceToBoards
-struct PieceToHistory : public PieceToBoards {
+// PieceToHistory is like ButterflyHistory but is addressed by a move's [piece][to]
+using PieceToHistory = Stats<int16_t, 29952, PIECE_NB, SQUARE_NB>;
 
-  void update(Piece pc, Square to, int bonus) {
-    StatBoards::update((*this)[pc][to], bonus, 936);
-  }
-};
-
-/// CapturePieceToHistory is like PieceToHistory, but is based on CapturePieceToBoards
-struct CapturePieceToHistory : public CapturePieceToBoards {
-
-  void update(Piece pc, Square to, PieceType captured, int bonus) {
-    StatCubes::update((*this)[pc][to][captured], bonus, 324, 2);
-  }
-};
+// 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>;
 
-/// 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;
-
-/// 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;
 
+// 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 {
 
-/// 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.
+  enum PickType { Next, Best };
 
-class MovePicker {
 public:
   MovePicker(const MovePicker&) = delete;
   MovePicker& operator=(const MovePicker&) = delete;
+  MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+                                           const CapturePieceToHistory*,
+                                           const PieceToHistory**,
+                                           Move,
+                                           const Move*);
+  MovePicker(const Position&, Move, Depth, const ButterflyHistory*,
+                                           const CapturePieceToHistory*,
+                                           const PieceToHistory**,
+                                           Square);
   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*);
   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; }
@@ -138,9 +143,9 @@ private:
   const Position& pos;
   const ButterflyHistory* mainHistory;
   const CapturePieceToHistory* captureHistory;
-  const PieceToHistory** contHistory;
-  Move ttMove, countermove, killers[2];
-  ExtMove *cur, *endMoves, *endBadCaptures;
+  const PieceToHistory** continuationHistory;
+  Move ttMove;
+  ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
   int stage;
   Square recaptureSquare;
   Value threshold;
@@ -148,4 +153,6 @@ private:
   ExtMove moves[MAX_MOVES];
 };
 
+} // namespace Stockfish
+
 #endif // #ifndef MOVEPICK_H_INCLUDED