/*
  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

  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/>.
*/

#ifndef TT_H_INCLUDED
#define TT_H_INCLUDED

#include "misc.h"
#include "types.h"

/// The TTEntry is the 10 bytes transposition table entry, defined as below:
///
/// key        16 bit
/// move       16 bit
/// value      16 bit
/// eval value 16 bit
/// generation  6 bit
/// bound type  2 bit
/// depth       8 bit

struct TTEntry {

  Move  move()  const      { return (Move )move16; }
  Value value() const      { return (Value)value16; }
  Value eval_value() const { return (Value)evalValue; }
  Depth depth() const      { return (Depth)depth8; }
  Bound bound() const      { return (Bound)(genBound8 & 0x3); }

private:
  friend class TranspositionTable;

  void save(uint16_t k, Value v, Bound b, Depth d, Move m, uint8_t g, Value ev) {

    key16     = (uint16_t)k;
    move16    = (uint16_t)m;
    value16   = (int16_t)v;
    evalValue = (int16_t)ev;
    genBound8 = (uint8_t)(g | b);
    depth8    = (int8_t)d;
  }

  uint16_t key16;
  uint16_t move16;
  int16_t  value16;
  int16_t  evalValue;
  uint8_t  genBound8;
  int8_t   depth8;
};

/// TTCluster is a 32 bytes cluster of TT entries consisting of:
///
/// 3 x TTEntry (3 x 10 bytes)
/// padding     (2 bytes)

const unsigned TTClusterSize = 3;

struct TTCluster {
  TTEntry entry[TTClusterSize];
  char padding[2];
};

/// A TranspositionTable consists of a power of 2 number of clusters and each
/// cluster consists of TTClusterSize 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.

class TranspositionTable {

public:
 ~TranspositionTable() { free(mem); }
  void new_search() { generation += 4; } // Lower 2 bits are used by Bound

  const TTEntry* probe(const Key key) const;
  TTEntry* first_entry(const Key key) const;
  void resize(size_t mbSize);
  void clear();
  void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);

private:
  size_t clusterCount;
  TTCluster* table;
  void* mem;
  uint8_t generation; // 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 inside the table.

inline TTEntry* TranspositionTable::first_entry(const Key key) const {

  return &table[(size_t)key & (clusterCount - 1)].entry[0];
}

#endif // #ifndef TT_H_INCLUDED