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Member "stockfish-11-linux/src/tt.h" (18 Jan 2020, 3274 Bytes) of package /linux/privat/stockfish-11-linux.zip:


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    1 /*
    2   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
    3   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
    4   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
    5   Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
    6 
    7   Stockfish is free software: you can redistribute it and/or modify
    8   it under the terms of the GNU General Public License as published by
    9   the Free Software Foundation, either version 3 of the License, or
   10   (at your option) any later version.
   11 
   12   Stockfish is distributed in the hope that it will be useful,
   13   but WITHOUT ANY WARRANTY; without even the implied warranty of
   14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   15   GNU General Public License for more details.
   16 
   17   You should have received a copy of the GNU General Public License
   18   along with this program.  If not, see <http://www.gnu.org/licenses/>.
   19 */
   20 
   21 #ifndef TT_H_INCLUDED
   22 #define TT_H_INCLUDED
   23 
   24 #include "misc.h"
   25 #include "types.h"
   26 
   27 /// TTEntry struct is the 10 bytes transposition table entry, defined as below:
   28 ///
   29 /// key        16 bit
   30 /// move       16 bit
   31 /// value      16 bit
   32 /// eval value 16 bit
   33 /// generation  5 bit
   34 /// pv node     1 bit
   35 /// bound type  2 bit
   36 /// depth       8 bit
   37 
   38 struct TTEntry {
   39 
   40   Move  move()  const { return (Move )move16; }
   41   Value value() const { return (Value)value16; }
   42   Value eval()  const { return (Value)eval16; }
   43   Depth depth() const { return (Depth)depth8 + DEPTH_OFFSET; }
   44   bool is_pv() const { return (bool)(genBound8 & 0x4); }
   45   Bound bound() const { return (Bound)(genBound8 & 0x3); }
   46   void save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev);
   47 
   48 private:
   49   friend class TranspositionTable;
   50 
   51   uint16_t key16;
   52   uint16_t move16;
   53   int16_t  value16;
   54   int16_t  eval16;
   55   uint8_t  genBound8;
   56   uint8_t  depth8;
   57 };
   58 
   59 
   60 /// A TranspositionTable consists of a power of 2 number of clusters and each
   61 /// cluster consists of ClusterSize number of TTEntry. Each non-empty entry
   62 /// contains information of exactly one position. The size of a cluster should
   63 /// divide the size of a cache line size, to ensure that clusters never cross
   64 /// cache lines. This ensures best cache performance, as the cacheline is
   65 /// prefetched, as soon as possible.
   66 
   67 class TranspositionTable {
   68 
   69   static constexpr int CacheLineSize = 64;
   70   static constexpr int ClusterSize = 3;
   71 
   72   struct Cluster {
   73     TTEntry entry[ClusterSize];
   74     char padding[2]; // Align to a divisor of the cache line size
   75   };
   76 
   77   static_assert(CacheLineSize % sizeof(Cluster) == 0, "Cluster size incorrect");
   78 
   79 public:
   80  ~TranspositionTable() { free(mem); }
   81   void new_search() { generation8 += 8; } // Lower 3 bits are used by PV flag and Bound
   82   TTEntry* probe(const Key key, bool& found) const;
   83   int hashfull() const;
   84   void resize(size_t mbSize);
   85   void clear();
   86 
   87   // The 32 lowest order bits of the key are used to get the index of the cluster
   88   TTEntry* first_entry(const Key key) const {
   89     return &table[(uint32_t(key) * uint64_t(clusterCount)) >> 32].entry[0];
   90   }
   91 
   92 private:
   93   friend struct TTEntry;
   94 
   95   size_t clusterCount;
   96   Cluster* table;
   97   void* mem;
   98   uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
   99 };
  100 
  101 extern TranspositionTable TT;
  102 
  103 #endif // #ifndef TT_H_INCLUDED