X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Ftt.h;h=d915d92e43f545da1826e8408e148e952c90316a;hp=eeb18e32acff0510656537dad8cdac29b4a8f1f6;hb=af0d82792e21f0362b781fc671ae8b7a0642e61a;hpb=585655b16eb88579ac9af001fb5494b51134b1f7

diff --git a/src/tt.h b/src/tt.h
index eeb18e32..d915d92e 100644
--- a/src/tt.h
+++ b/src/tt.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) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+  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
@@ -23,82 +22,86 @@
 #include "misc.h"
 #include "types.h"
 
-/// The TTEntry is the 14 bytes transposition table entry, defined as below:
+namespace Stockfish {
+
+/// TTEntry struct is the 10 bytes transposition table entry, defined as below:
 ///
-/// key        32 bit
+/// key        16 bit
+/// depth       8 bit
+/// generation  5 bit
+/// pv node     1 bit
+/// bound type  2 bit
 /// move       16 bit
-/// bound type  8 bit
-/// generation  8 bit
 /// value      16 bit
-/// depth      16 bit
 /// eval value 16 bit
 
 struct TTEntry {
 
-  Move  move()  const      { return (Move )move16; }
-  Bound bound() const      { return (Bound)bound8; }
-  Value value() const      { return (Value)value16; }
-  Depth depth() const      { return (Depth)depth16; }
-  Value eval_value() const { return (Value)evalValue; }
+  Move  move()  const { return (Move )move16; }
+  Value value() const { return (Value)value16; }
+  Value eval()  const { return (Value)eval16; }
+  Depth depth() const { return (Depth)depth8 + DEPTH_OFFSET; }
+  bool is_pv()  const { return (bool)(genBound8 & 0x4); }
+  Bound bound() const { return (Bound)(genBound8 & 0x3); }
+  void save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev);
 
 private:
   friend class TranspositionTable;
 
-  void save(uint32_t k, Value v, Bound b, Depth d, Move m, uint8_t g, Value ev) {
-
-    key32       = (uint32_t)k;
-    move16      = (uint16_t)m;
-    bound8      = (uint8_t)b;
-    generation8 = (uint8_t)g;
-    value16     = (int16_t)v;
-    depth16     = (int16_t)d;
-    evalValue   = (int16_t)ev;
-  }
-
-  uint32_t key32;
+  uint16_t key16;
+  uint8_t  depth8;
+  uint8_t  genBound8;
   uint16_t move16;
-  uint8_t bound8, generation8;
-  int16_t value16, depth16, evalValue;
+  int16_t  value16;
+  int16_t  eval16;
 };
 
 
-/// A TranspositionTable consists of a power of 2 number of clusters and each
-/// cluster consists of ClusterSize number of TTEntry. Each non-empty entry
-/// contains information of exactly one position. The size of a cluster should
-/// not be bigger than a cache line size. In case it is less, it should be padded
-/// to guarantee always aligned accesses.
+/// A TranspositionTable is an array of Cluster, of size clusterCount. Each
+/// cluster consists of ClusterSize number of TTEntry. Each non-empty TTEntry
+/// contains information on exactly one position. The size of a Cluster should
+/// divide the size of a cache line for best performance, as the cacheline is
+/// prefetched when possible.
 
 class TranspositionTable {
 
-  static const unsigned ClusterSize = 4;
+  static constexpr int ClusterSize = 3;
 
-public:
- ~TranspositionTable() { free(mem); }
-  void new_search() { ++generation; }
+  struct Cluster {
+    TTEntry entry[ClusterSize];
+    char padding[2]; // Pad to 32 bytes
+  };
+
+  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
 
-  const TTEntry* probe(const Key key) const;
-  TTEntry* first_entry(const Key key) const;
-  void resize(uint64_t mbSize);
+public:
+ ~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);
   void clear();
-  void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);
+
+  TTEntry* first_entry(const Key key) const {
+    return &table[mul_hi64(key, clusterCount)].entry[0];
+  }
 
 private:
-  uint32_t hashMask;
-  TTEntry* table;
-  void* mem;
-  uint8_t generation; // Size must be not bigger than TTEntry::generation8
+  friend struct TTEntry;
+
+  size_t clusterCount;
+  Cluster* table;
+  uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
 };
 
 extern TranspositionTable TT;
 
-
-/// TranspositionTable::first_entry() returns a pointer to the first entry of
-/// a cluster given a position. The lowest order bits of the key are used to
-/// get the index of the cluster.
-
-inline TTEntry* TranspositionTable::first_entry(const Key key) const {
-
-  return table + ((uint32_t)key & hashMask);
-}
+} // namespace Stockfish
 
 #endif // #ifndef TT_H_INCLUDED