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tt.h
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tt.h
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/*
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 128 bit transposition table entry, defined as below:
///
/// key: 32 bit
/// move: 16 bit
/// bound type: 8 bit
/// generation: 8 bit
/// value: 16 bit
/// depth: 16 bit
/// static value: 16 bit
struct TTEntry {
void save(uint32_t k, Value v, Bound b, Depth d, Move m, int 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 key() const { return key32; }
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; }
private:
friend class TranspositionTable;
uint32_t key32;
uint16_t move16;
uint8_t bound8, generation8;
int16_t value16, depth16, evalValue;
};
/// 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.
class TranspositionTable {
static const unsigned ClusterSize = 4; // A cluster is 64 Bytes
public:
~TranspositionTable() { free(mem); }
void new_search() { ++generation; }
const TTEntry* probe(const Key key) const;
TTEntry* first_entry(const Key key) const;
void resize(uint64_t mbSize);
void clear();
void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);
private:
uint32_t hashMask;
TTEntry* table;
void* mem;
uint8_t generation; // Size must be not bigger than TTEntry::generation8
};
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);
}
#endif // #ifndef TT_H_INCLUDED