/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2009 Marco Costalba
+ Copyright (C) 2004-2023 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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"
-
-
-////
-//// Types
-////
-
-/// The TTEntry class is the class of transposition table entries
-///
-/// A TTEntry needs 96 bits to be stored
-///
-/// bit 0-31: key
-/// bit 32-63: data
-/// bit 64-79: value
-/// bit 80-95: depth
-///
-/// the 32 bits of the data field are so defined
-///
-/// bit 0-16: move
-/// bit 17-19: not used
-/// bit 20-22: value type
-/// bit 23-31: generation
-
-class TTEntry {
-
-public:
- TTEntry() {}
- TTEntry(uint32_t k, Value v, ValueType t, Depth d, Move m, int generation)
- : key_ (k), data((m & 0x1FFFF) | (t << 20) | (generation << 23)),
- value_(int16_t(v)), depth_(int16_t(d)) {}
-
- uint32_t key() const { return key_; }
- Depth depth() const { return Depth(depth_); }
- Move move() const { return Move(data & 0x1FFFF); }
- Value value() const { return Value(value_); }
- ValueType type() const { return ValueType((data >> 20) & 7); }
- int generation() const { return (data >> 23); }
-
-private:
- uint32_t key_;
- uint32_t data;
- int16_t value_;
- int16_t depth_;
+#include <cstddef>
+#include <cstdint>
+
+#include "misc.h"
+#include "types.h"
+
+namespace Stockfish {
+
+// TTEntry struct is the 10 bytes transposition table entry, defined as below:
+//
+// key 16 bit
+// depth 8 bit
+// generation 5 bit
+// pv node 1 bit
+// bound type 2 bit
+// move 16 bit
+// value 16 bit
+// eval value 16 bit
+struct TTEntry {
+
+ Move move() const { return Move(move16); }
+ Value value() const { return Value(value16); }
+ Value eval() const { return Value(eval16); }
+ Depth depth() const { return Depth(depth8 + DEPTH_OFFSET); }
+ bool is_pv() const { return bool(genBound8 & 0x4); }
+ Bound bound() const { return Bound(genBound8 & 0x3); }
+ void save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev);
+
+ private:
+ friend class TranspositionTable;
+
+ uint16_t key16;
+ uint8_t depth8;
+ uint8_t genBound8;
+ uint16_t move16;
+ int16_t value16;
+ int16_t eval16;
};
-/// 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 is an array of Cluster, of size clusterCount. Each
+// cluster consists of ClusterSize number of TTEntry. Each non-empty TTEntry
+// contains information on exactly one position. The size of a Cluster should
+// divide the size of a cache line for best performance, as the cacheline is
+// prefetched when possible.
class TranspositionTable {
-public:
- TranspositionTable();
- ~TranspositionTable();
- void set_size(unsigned mbSize);
- void clear();
- void store(const Key posKey, Value v, ValueType type, Depth d, Move m);
- TTEntry* retrieve(const Key posKey) const;
- void prefetch(const Key posKey) const;
- void new_search();
- void insert_pv(const Position& pos, Move pv[]);
- void extract_pv(const Position& pos, Move pv[]);
- int full() const;
-
-private:
- inline TTEntry* first_entry(const Key posKey) const;
-
- // Be sure 'writes' is at least one cacheline away
- // from read only variables.
- unsigned char pad_before[64 - sizeof(unsigned)];
- unsigned writes; // heavy SMP read/write access here
- unsigned char pad_after[64];
-
- unsigned size;
- TTEntry* entries;
- uint8_t generation;
+ static constexpr int ClusterSize = 3;
+
+ struct Cluster {
+ TTEntry entry[ClusterSize];
+ char padding[2]; // Pad to 32 bytes
+ };
+
+ static_assert(sizeof(Cluster) == 32, "Unexpected Cluster size");
+
+ // Constants used to refresh the hash table periodically
+ static constexpr unsigned GENERATION_BITS = 3; // nb of bits reserved for other things
+ static constexpr int GENERATION_DELTA =
+ (1 << GENERATION_BITS); // increment for generation field
+ static constexpr int GENERATION_CYCLE = 255 + (1 << GENERATION_BITS); // cycle length
+ static constexpr int GENERATION_MASK =
+ (0xFF << GENERATION_BITS) & 0xFF; // mask to pull out generation number
+
+ public:
+ ~TranspositionTable() { aligned_large_pages_free(table); }
+ void new_search() { generation8 += GENERATION_DELTA; } // Lower bits are used for other things
+ TTEntry* probe(const Key key, bool& found) const;
+ int hashfull() const;
+ void resize(size_t mbSize);
+ void clear();
+
+ TTEntry* first_entry(const Key key) const {
+ return &table[mul_hi64(key, clusterCount)].entry[0];
+ }
+
+ private:
+ friend struct TTEntry;
+
+ size_t clusterCount;
+ Cluster* table;
+ uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
};
extern TranspositionTable TT;
-#endif // !defined(TT_H_INCLUDED)
+} // namespace Stockfish
+
+#endif // #ifndef TT_H_INCLUDED
projects / stockfish / blobdiff