Merge branch 'master' into clusterMergeMaster12

fixes minor merge conflicts

looks good:

Score of cluster vs master: 15 - 1 - 134  [0.547] 150
Elo difference: 32.5 +/- 17.5, LOS: 100.0 %, DrawRatio: 89.3 %

for 4 threads against 4x4 threads at 10+0.1s

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
@@ -22,10 +22,12 @@
 #include "misc.h"
 #include "types.h"
 
+namespace Stockfish {
+
+//void Cluster::init();
 namespace Cluster {
   void init();
 }
-//void Cluster::init();
 
 /// TTEntry struct is the 10 bytes transposition table entry, defined as below:
 ///
@@ -80,9 +82,15 @@ 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_ttmem_free(mem); }
-  void new_search() { generation8 += 8; } // Lower 3 bits are used by PV flag and Bound
+ ~TranspositionTable() { aligned_large_pages_free(table); }
+  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);
@@ -97,10 +105,11 @@ private:
 
   size_t clusterCount;
   Cluster* table;
-  void* mem;
   uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
 };
 
 extern TranspositionTable TT;
 
+} // namespace Stockfish
+
 #endif // #ifndef TT_H_INCLUDED