simplify logic for history based pruning

[stockfish] / src / movepick.h

diff --git a/src/movepick.h b/src/movepick.h
index f4a104d63f676249ee4b67691caa011d9df28ddc..ef3be6c240f8d553b42c68756e48fa512b5bdf3d 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -2,7 +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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2017 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
@@ -26,39 +26,56 @@
 
 #include "movegen.h"
 #include "position.h"
-#include "search.h"
 #include "types.h"
 
 
-/// 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 {
+/// HistoryStats records how often quiet moves have been successful or unsuccessful
+/// during the current search, and is used for reduction and move ordering decisions.
+struct HistoryStats {
 
   static const Value Max = Value(1 << 28);
 
-  const T* operator[](Piece pc) const { return table[pc]; }
-  T* operator[](Piece pc) { return table[pc]; }
+  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) {
+
+    Square from = from_sq(m);
+    Square to = to_sq(m);
 
-  void update(Piece pc, Square to, Move m) {
+    const int denom = 324;
 
-    if (m != table[pc][to])
-        table[pc][to] = m;
+    assert(abs(int(v)) <= denom); // Needed for stability.
+
+    table[c][from][to] -= table[c][from][to] * abs(int(v)) / denom;
+    table[c][from][to] += int(v) * 32;
   }
 
+private:
+  Value table[COLOR_NB][SQUARE_NB][SQUARE_NB];
+};
+
+
+/// A template struct, used to generate MoveStats and CounterMoveHistoryStats:
+/// MoveStats store the move that refute a previous one.
+/// CounterMoveHistoryStats is like HistoryStats, but with two consecutive moves.
+/// 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 {
+  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 fill(const Value& v) { std::fill(&table[0][0], &table[PIECE_NB-1][SQUARE_NB-1]+1, v); };
+  void update(Piece pc, Square to, Move m) { table[pc][to] = m; }
   void update(Piece pc, Square to, Value v) {
 
-    if (abs(int(v)) >= 324)
-        return;
+    const int denom = 936;
+
+    assert(abs(int(v)) <= denom); // Needed for stability.
 
-    table[pc][to] -= table[pc][to] * abs(int(v)) / (CM ? 512 : 324);
-    table[pc][to] += int(v) * (CM ? 64 : 32);
+    table[pc][to] -= table[pc][to] * abs(int(v)) / denom;
+    table[pc][to] += int(v) * 32;
   }
 
 private:
@@ -66,8 +83,7 @@ private:
 };
 
 typedef Stats<Move> MoveStats;
-typedef Stats<Value, false> HistoryStats;
-typedef Stats<Value,  true> CounterMoveStats;
+typedef Stats<Value> CounterMoveStats;
 typedef Stats<CounterMoveStats> CounterMoveHistoryStats;
 
 
@@ -77,37 +93,34 @@ typedef Stats<CounterMoveStats> CounterMoveHistoryStats;
 /// 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.
+namespace Search { struct Stack; }
 
 class MovePicker {
 public:
   MovePicker(const MovePicker&) = delete;
   MovePicker& operator=(const MovePicker&) = delete;
 
-  MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
-  MovePicker(const Position&, Move, const HistoryStats&, Value);
-  MovePicker(const Position&, Move, Depth, const HistoryStats&, const CounterMoveStats&, Move, Search::Stack*);
+  MovePicker(const Position&, Move, Value);
+  MovePicker(const Position&, Move, Depth, Square);
+  MovePicker(const Position&, Move, Depth, Search::Stack*);
 
-  Move next_move();
+  Move next_move(bool skipQuiets = false);
 
 private:
   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;
-  const CounterMoveStats* counterMoveHistory;
-  Search::Stack* ss;
+  const 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;
+  ExtMove *cur, *endMoves, *endBadCaptures;
+  ExtMove moves[MAX_MOVES];
 };
 
 #endif // #ifndef MOVEPICK_H_INCLUDED