X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fmovepick.h;h=5010ee627f41ef8b94464dd07c15a24c2ee79325;hb=d0e87104aa782176735442e1f6668f91014f07eb;hp=acb57b2e7a4d9fa2260cda3bde57ac8959a7747c;hpb=19dd0de4ff83e682bafa56d27f302d8f00d3040d;p=stockfish

diff --git a/src/movepick.h b/src/movepick.h
index acb57b2e..9f189974 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -1,7 +1,6 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2013 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
@@ -17,85 +16,170 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#if !defined MOVEPICK_H_INCLUDED
+#ifndef MOVEPICK_H_INCLUDED
 #define MOVEPICK_H_INCLUDED
 
-#include <algorithm> // For std::max
-#include <cstring>   // For 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 {
 
+constexpr int PAWN_HISTORY_SIZE = 512;  // has to be a power of 2
 
-/// The Stats struct stores moves statistics. According to the template parameter
-/// the class can store History, Gains and Refutations statistics. History records
-/// how often different moves have been successful or unsuccessful during the
-/// current search and is used for reduction and move ordering decisions. Gains
-/// records the move's best evaluation gain from one ply to the next and is used
-/// for pruning decisions. Refutations store the move that refute a previous one.
-/// Entries are stored according only to moving piece and destination square, in
-/// particular two moves with different origin but same destination and same piece
-/// will be considered identical.
-template<bool Gain, typename T>
-struct Stats {
+static_assert((PAWN_HISTORY_SIZE & (PAWN_HISTORY_SIZE - 1)) == 0,
+              "PAWN_HISTORY_SIZE has to be a power of 2");
 
-  static const Value Max = Value(2000);
+inline int pawn_structure(const Position& pos) { return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1); }
 
-  const T* operator[](Piece p) const { return &table[p][0]; }
-  void clear() { 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 p, Square to, Move m) { table[p][to] = m; }
-  void update(Piece p, Square to, Value v) {
+    T entry;
 
-    if (Gain)
-        table[p][to] = std::max(v, table[p][to] - 1);
+   public:
+    void operator=(const T& v) { entry = v; }
+    T*   operator&() { return &entry; }
+    T*   operator->() { return &entry; }
+    operator const T&() const { return entry; }
 
-    else if (abs(table[p][to] + v) < Max)
-        table[p][to] +=  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");
 
-private:
-  T table[PIECE_NB][SQUARE_NB];
+        entry += (bonus * D - entry * abs(bonus)) / (D * 5 / 4);
+
+        assert(abs(entry) <= D);
+    }
 };
 
-typedef Stats<true, Value> Gains;
-typedef Stats<false, Value> History;
-typedef Stats<false, Move> Refutations;
+// 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) {
 
+        // For standard-layout 'this' points to the first struct member
+        assert(std::is_standard_layout_v<stats>);
 
-/// 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.
+        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> {};
+
+// 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>;
+
+// 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 {
 
-  MovePicker& operator=(const MovePicker&); // Silence a warning under MSVC
-
-public:
-  MovePicker(const Position&, Move, Depth, const History&, const Refutations&, Search::Stack*, Value);
-  MovePicker(const Position&, Move, Depth, const History&, Square);
-  MovePicker(const Position&, Move, const History&, PieceType);
-  template<bool SpNode> Move next_move();
-
-private:
-  template<GenType> void score();
-  void generate_next();
-
-  const Position& pos;
-  const History& Hist;
-  Search::Stack* ss;
-  Depth depth;
-  Move ttMove;
-  MoveStack killers[3];
-  Square recaptureSquare;
-  int captureThreshold, phase;
-  MoveStack *cur, *end, *endQuiets, *endBadCaptures;
-  MoveStack 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*,
+               Square);
+    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;
+    Square                       recaptureSquare;
+    Value                        threshold;
+    Depth                        depth;
+    ExtMove                      moves[MAX_MOVES];
 };
 
-#endif // !defined(MOVEPICK_H_INCLUDED)
+}  // namespace Stockfish
+
+#endif  // #ifndef MOVEPICK_H_INCLUDED