Use a flag in TT to track null search values

[stockfish] / src / tt.h

diff --git a/src/tt.h b/src/tt.h
index 03ce1f553df77f9d5e46cf5232602bd7b956b13d..021019be4c18ef71f2a04fe18c71ebfd51fa8bc9 100644 (file)
--- a/src/tt.h
+++ b/src/tt.h
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008 Marco Costalba
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, 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
@@ -34,60 +34,91 @@
 //// Types
 ////
 
-/// The TTEntry class is the class of transposition table entries.
+/// The TTEntry class is the class of transposition table entries
+///
+/// A TTEntry needs 96 bits to be stored
+///
+/// bit  0-31: key
+/// bit 32-63: data
+/// bit 64-79: value
+/// bit 80-95: depth
+///
+/// the 32 bits of the data field are so defined
+///
+/// bit  0-16: move
+/// bit 17-18: not used
+/// bit 19-22: value type
+/// bit 23-31: generation
 
 class TTEntry {
 
 public:
-  TTEntry();
-  TTEntry(Key k, Value v, ValueType t, Depth d, Move m, int generation);
-  Key key() const { return key_; }
+  TTEntry() {}
+  TTEntry(uint32_t k, Value v, ValueType t, Depth d, Move m, int generation)
+        : key_ (k), data((m & 0x1FFFF) | (t << 19) | (generation << 23)),
+          value_(int16_t(v)), depth_(int16_t(d)) {}
+
+  uint32_t key() const { return key_; }
   Depth depth() const { return Depth(depth_); }
-  Move move() const { return Move(data & 0x7FFFF); }
+  Move move() const { return Move(data & 0x1FFFF); }
   Value value() const { return Value(value_); }
-  ValueType type() const { return ValueType((data >> 20) & 3); }
+  ValueType type() const { return ValueType((data >> 19) & 0xF); }
   int generation() const { return (data >> 23); }
 
 private:
-  Key key_;
+  uint32_t key_;
   uint32_t data;
   int16_t value_;
   int16_t depth_;
 };
 
-/// The transposition table class.  This is basically just a huge array
+
+/// This is the number of TTEntry slots for each position
+const int ClusterSize = 5;
+
+/// Each group of ClusterSize number of TTEntry form a TTCluster
+/// that is indexed by a single position key. Cluster is padded
+/// to a cache line size so to guarantee always aligned accesses.
+
+struct TTCluster {
+  TTEntry data[ClusterSize];
+  char cache_line_padding[64 - sizeof(TTEntry[ClusterSize])];
+};
+
+
+/// The transposition table class. This is basically just a huge array
 /// containing TTEntry objects, and a few methods for writing new entries
 /// and reading new ones.
 
 class TranspositionTable {
 
 public:
-  TranspositionTable(unsigned mbSize);
+  TranspositionTable();
   ~TranspositionTable();
-  void set_size(unsigned mbSize);
+  void set_size(size_t mbSize);
   void clear();
-  void store(const Position &pos, Value v, Depth d, Move m, ValueType type);
-  const TTEntry* retrieve(const Position &pos) const;
+  void store(const Key posKey, Value v, ValueType type, Depth d, Move m);
+  TTEntry* retrieve(const Key posKey) const;
+  void prefetch(const Key posKey) const;
   void new_search();
-  void insert_pv(const Position &pos, Move pv[]);
-  int full();
+  void insert_pv(const Position& pos, Move pv[]);
+  void extract_pv(const Position& pos, Move pv[], const int PLY_MAX);
+  int full() const;
 
 private:
-  inline TTEntry* first_entry(const Position &pos) const;
+  inline TTEntry* first_entry(const Key posKey) const;
 
-  unsigned size;
-  int writes;
-  TTEntry* entries;
+  // Be sure 'writes' is at least one cache line away
+  // from read only variables.
+  unsigned char pad_before[64 - sizeof(unsigned)];
+  unsigned writes; // heavy SMP read/write access here
+  unsigned char pad_after[64];
+
+  size_t size;
+  TTCluster* entries;
   uint8_t generation;
 };
 
-
-////
-//// Constants and variables
-////
-
-// Default transposition table size, in megabytes:
-const int TTDefaultSize = 32;
-
+extern TranspositionTable TT;
 
 #endif // !defined(TT_H_INCLUDED)