BadFish/src/tt.h

/*
  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  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
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  Stockfish is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#if !defined(TT_H_INCLUDED)
#define TT_H_INCLUDED

#include <iostream>

#include "move.h"
#include "types.h"

/// A simple fixed size hash table used to store pawns and material
/// configurations. It is basically just an array of Entry objects.
/// Without cluster concept or overwrite policy.

template<class Entry, int HashSize>
class SimpleHash {

  SimpleHash(const SimpleHash&);
  SimpleHash& operator=(const SimpleHash&);

public:
  SimpleHash() {

    entries = new (std::nothrow) Entry[HashSize];
    if (!entries)
    {
        std::cerr << "Failed to allocate " << HashSize * sizeof(Entry)
                  << " bytes for material hash table." << std::endl;
        exit(EXIT_FAILURE);
    }
    memset(entries, 0, HashSize * sizeof(Entry));
  }

  virtual ~SimpleHash() { delete [] entries; }

  Entry* find(Key key) const { return entries + ((uint32_t)key & (HashSize - 1)); }

protected:
  Entry* entries;
};


/// The TTEntry class is the class of transposition table entries
///
/// A TTEntry needs 128 bits to be stored
///
/// bit  0-31: key
/// bit 32-63: data
/// bit 64-79: value
/// bit 80-95: depth
/// bit 96-111: static value
/// bit 112-127: margin of static value
///
/// the 32 bits of the data field are so defined
///
/// bit  0-15: move
/// bit 16-20: not used
/// bit 21-22: value type
/// bit 23-31: generation

class TTEntry {

public:
  void save(uint32_t k, Value v, ValueType t, Depth d, Move m, int g, Value statV, Value statM) {

    key32        = (uint32_t)k;
    move16       = (uint16_t)m;
    valueType    = (uint8_t)t;
    generation8  = (uint8_t)g;
    value16      = (int16_t)v;
    depth16      = (int16_t)d;
    staticValue  = (int16_t)statV;
    staticMargin = (int16_t)statM;
  }
  void set_generation(int g) { generation8 = (uint8_t)g; }

  uint32_t key() const { return key32; }
  Depth depth() const { return Depth(depth16); }
  Move move() const { return Move(move16); }
  Value value() const { return Value(value16); }
  ValueType type() const { return ValueType(valueType); }
  int generation() const { return generation8; }
  Value static_value() const { return Value(staticValue); }
  Value static_value_margin() const { return Value(staticMargin); }

private:
  uint32_t key32;
  uint16_t move16;
  uint8_t valueType;
  uint8_t generation8;
  int16_t value16;
  int16_t depth16;
  int16_t staticValue;
  int16_t staticMargin;
};


/// This is the number of TTEntry slots for each cluster
const int ClusterSize = 4;

/// TTCluster consists of ClusterSize number of TTEntries.
/// Size of TTCluster must not be bigger than a cache line size.
/// In case it is less, it should be padded to guarantee always aligned accesses.

struct TTCluster {
  TTEntry data[ClusterSize];
};


/// The transposition table class. This is basically just a huge array
/// containing TTCluster objects, and a few methods for writing new entries
/// and reading new ones.

class TranspositionTable {

  TranspositionTable(const TranspositionTable&);
  TranspositionTable& operator=(const TranspositionTable&);

public:
  TranspositionTable();
  ~TranspositionTable();
  void set_size(size_t mbSize);
  void clear();
  void store(const Key posKey, Value v, ValueType type, Depth d, Move m, Value statV, Value kingD);
  TTEntry* retrieve(const Key posKey) const;
  void new_search();
  TTEntry* first_entry(const Key posKey) const;
  void refresh(const TTEntry* tte) const;

private:
  size_t size;
  TTCluster* entries;
  uint8_t generation; // To properly compare, size must be smaller then TT stored value
};

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 posKey) const {

  return entries[((uint32_t)posKey) & (size - 1)].data;
}


/// TranspositionTable::refresh updates the 'generation' value of the TTEntry
/// to avoid aging. Normally called after a TT hit, before to return.

inline void TranspositionTable::refresh(const TTEntry* tte) const {

  const_cast<TTEntry*>(tte)->set_generation(generation);
}

#endif // !defined(TT_H_INCLUDED)