X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.h;h=d915d92e43f545da1826e8408e148e952c90316a;hp=6aa066c56503612da6afe8dad2b47e2e8863ed29;hb=36f8d3806bb1c6e498ac8fd1a746c1714d1485a3;hpb=485d517c687a2d3cb0b88cc8c198483759eaf2c7

diff --git a/src/tt.h b/src/tt.h
index 6aa066c5..d915d92e 100644
--- a/src/tt.h
+++ b/src/tt.h
@@ -1,6 +1,6 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
-  Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
+  Copyright (C) 2004-2021 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
@@ -22,6 +22,8 @@
 #include "misc.h"
 #include "types.h"
 
+namespace Stockfish {
+
 /// TTEntry struct is the 10 bytes transposition table entry, defined as below:
 ///
 /// key        16 bit
@@ -72,9 +74,15 @@ class TranspositionTable {
 
   static_assert(sizeof(Cluster) == 32, "Unexpected Cluster size");
 
+  // Constants used to refresh the hash table periodically
+  static constexpr unsigned GENERATION_BITS  = 3;                                // nb of bits reserved for other things
+  static constexpr int      GENERATION_DELTA = (1 << GENERATION_BITS);           // increment for generation field
+  static constexpr int      GENERATION_CYCLE = 255 + (1 << GENERATION_BITS);     // cycle length
+  static constexpr int      GENERATION_MASK  = (0xFF << GENERATION_BITS) & 0xFF; // mask to pull out generation number
+
 public:
  ~TranspositionTable() { aligned_large_pages_free(table); }
-  void new_search() { generation8 += 8; } // Lower 3 bits are used by PV flag and Bound
+  void new_search() { generation8 += GENERATION_DELTA; } // Lower bits are used for other things
   TTEntry* probe(const Key key, bool& found) const;
   int hashfull() const;
   void resize(size_t mbSize);
@@ -94,4 +102,6 @@ private:
 
 extern TranspositionTable TT;
 
+} // namespace Stockfish
+
 #endif // #ifndef TT_H_INCLUDED