/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+ Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
- Glaurung is distributed in the hope that it will be useful,
+ 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.
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-#if !defined(TT_H_INCLUDED)
+#ifndef TT_H_INCLUDED
#define TT_H_INCLUDED
-////
-//// Includes
-////
-
-#include "depth.h"
-#include "position.h"
-#include "value.h"
-
+#include "misc.h"
+#include "types.h"
-////
-//// Types
-////
+/// TTEntry struct 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
-/// The TTEntry class is the class of transposition table entries.
+struct TTEntry {
-class TTEntry {
-
-public:
- TTEntry();
- TTEntry(Key k, Value v, ValueType t, Depth d, Move m, int generation);
- Key key() const;
- Depth depth() const;
- Move move() const;
- Value value() const;
- ValueType type() const;
- int generation() const;
+ Move move() const { return (Move )move16; }
+ Value value() const { return (Value)value16; }
+ Value eval() const { return (Value)eval16; }
+ Depth depth() const { return (Depth)(depth8 * int(ONE_PLY)); }
+ Bound bound() const { return (Bound)(genBound8 & 0x3); }
+ void save(Key k, Value v, Bound b, Depth d, Move m, Value ev);
private:
- Key key_;
- uint32_t data;
- int16_t value_;
- int16_t depth_;
+ friend class TranspositionTable;
+
+ uint16_t key16;
+ uint16_t move16;
+ int16_t value16;
+ int16_t eval16;
+ uint8_t genBound8;
+ int8_t depth8;
};
-/// 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.
+/// 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
+/// divide the size of a cache line size, to ensure that clusters never cross
+/// cache lines. This ensures best cache performance, as the cacheline is
+/// prefetched, as soon as possible.
class TranspositionTable {
+ static constexpr int CacheLineSize = 64;
+ static constexpr int ClusterSize = 3;
+
+ struct Cluster {
+ TTEntry entry[ClusterSize];
+ char padding[2]; // Align to a divisor of the cache line size
+ };
+
+ static_assert(CacheLineSize % sizeof(Cluster) == 0, "Cluster size incorrect");
+
public:
- TranspositionTable(unsigned mbSize);
- ~TranspositionTable();
- void set_size(unsigned mbSize);
+ ~TranspositionTable() { free(mem); }
+ void new_search() { generation8 += 4; } // Lower 2 bits are used by Bound
+ TTEntry* probe(const Key key, bool& found) const;
+ int hashfull() const;
+ void resize(size_t mbSize);
void clear();
- void store(const Position &pos, Value v, Depth d, Move m, ValueType type);
- bool retrieve(const Position &pos, Value *value, Depth *d, Move *move,
- ValueType *type) const;
- void new_search();
- void insert_pv(const Position &pos, Move pv[]);
- int full();
+
+ // The 32 lowest order bits of the key are used to get the index of the cluster
+ TTEntry* first_entry(const Key key) const {
+ return &table[(uint32_t(key) * uint64_t(clusterCount)) >> 32].entry[0];
+ }
private:
- TTEntry* first_entry(const Position &pos) const;
+ friend struct TTEntry;
- unsigned size;
- int writes;
- TTEntry* entries;
- uint8_t generation;
+ size_t clusterCount;
+ Cluster* table;
+ void* mem;
+ uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
};
+extern TranspositionTable TT;
-////
-//// Constants and variables
-////
-
-// Default transposition table size, in megabytes:
-const int TTDefaultSize = 32;
-
-
-#endif // !defined(TT_H_INCLUDED)
+#endif // #ifndef TT_H_INCLUDED