X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmovepick.h;h=cdedc9b616f9f78c6a652626c0c0a5ba096ed71b;hp=44be9636e45974a67b3d6cf47817b87295d6dad0;hb=114ddb789bed2d74d6a786f5da6c9ce63d44de27;hpb=e53774bc49dd0aaa1c129ee98c09e1a56ef974fb

diff --git a/src/movepick.h b/src/movepick.h
index 44be9636..cdedc9b6 100644
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -2,6 +2,7 @@
   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) 2015-2020 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
@@ -20,56 +21,87 @@
 #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, Gains 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. Gains records the move's
-/// best evaluation gain from one ply to the next and is used for pruning 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<bool Gain, typename T>
-struct Stats {
+  T entry;
 
-  static const Value Max = Value(250);
-
-  const T* operator[](Piece pc) const { return table[pc]; }
-  void clear() { std::memset(table, 0, sizeof(table)); }
+public:
+  void operator=(const T& v) { entry = v; }
+  T* operator&() { return &entry; }
+  T* operator->() { return &entry; }
+  operator const T&() const { return entry; }
 
-  void update(Piece pc, Square to, Move m) {
+  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 (m == table[pc][to].first)
-        return;
+    entry += bonus - entry * abs(bonus) / D;
 
-    table[pc][to].second = table[pc][to].first;
-    table[pc][to].first = m;
+    assert(abs(entry) <= D);
   }
+};
 
-  void update(Piece pc, Square to, Value v) {
+/// 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;
 
-    if (Gain)
-        table[pc][to] = std::max(v, table[pc][to] - 1);
+  void fill(const T& v) {
 
-    else if (abs(table[pc][to] + v) < Max)
-        table[pc][to] +=  v;
-  }
+    // For standard-layout 'this' points to first struct member
+    assert(std::is_standard_layout<stats>::value);
 
-private:
-  T table[PIECE_NB][SQUARE_NB];
+    typedef StatsEntry<T, D> entry;
+    entry* p = reinterpret_cast<entry*>(this);
+    std::fill(p, p + sizeof(*this) / sizeof(entry), v);
+  }
 };
 
-typedef Stats< true, Value> GainsStats;
-typedef Stats<false, Value> HistoryStats;
-typedef Stats<false, std::pair<Move, Move> > MovesStats;
+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
+typedef Stats<int16_t, 10692, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)> ButterflyHistory;
+
+/// 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;
+
+/// 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;
 
 
 /// MovePicker class is used to pick one pseudo legal move at a time from the
@@ -78,37 +110,42 @@ typedef Stats<false, std::pair<Move, Move> > MovesStats;
 /// 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, Depth, const HistoryStats&, Square);
-  MovePicker(const Position&, Move, const HistoryStats&, PieceType);
-  MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Move*, Search::Stack*);
-
-  template<bool SpNode> 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();
-  void generate_next_stage();
-  ExtMove* begin() { return moves; }
+  ExtMove* begin() { return cur; }
   ExtMove* end() { return endMoves; }
 
   const Position& pos;
-  const HistoryStats& history;
-  Search::Stack* ss;
-  Move* countermoves;
-  Move* followupmoves;
-  Depth depth;
+  const ButterflyHistory* mainHistory;
+  const CapturePieceToHistory* captureHistory;
+  const PieceToHistory** continuationHistory;
   Move ttMove;
-  ExtMove killers[6];
-  Square recaptureSquare;
-  Value captureThreshold;
+  ExtMove refutations[3], *cur, *endMoves, *endBadCaptures;
   int stage;
-  ExtMove *endQuiets, *endBadCaptures;
-  ExtMove moves[MAX_MOVES], *cur = moves, *endMoves = moves;
+  Square recaptureSquare;
+  Value threshold;
+  Depth depth;
+  ExtMove moves[MAX_MOVES];
 };
 
 #endif // #ifndef MOVEPICK_H_INCLUDED