/*
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) 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
#ifndef TT_H_INCLUDED
#define TT_H_INCLUDED
+#include <cstddef>
+#include <cstdint>
+
#include "misc.h"
#include "types.h"
-/// 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
-
+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; }
- Bound bound() const { return (Bound)(genBound8 & 0x3); }
-
- void save(Key k, Value v, Bound b, Depth d, Move m, Value ev, uint8_t g) {
-
- // Preserve any existing move for the same position
- if (m || (k >> 48) != key16)
- move16 = (uint16_t)m;
-
- // Don't overwrite more valuable entries
- if ( (k >> 48) != key16
- || d > depth8 - 2
- /* || g != (genBound8 & 0xFC) // Matching non-zero keys are already refreshed by probe() */
- || b == BOUND_EXACT)
- {
- key16 = (uint16_t)(k >> 48);
- value16 = (int16_t)v;
- eval16 = (int16_t)ev;
- genBound8 = (uint8_t)(g | b);
- depth8 = (int8_t)d;
- }
- }
-
-private:
- friend class TranspositionTable;
-
- uint16_t key16;
- uint16_t move16;
- int16_t value16;
- int16_t eval16;
- uint8_t genBound8;
- int8_t depth8;
+ 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;
};
-/// 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.
-
+// 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 {
- static const int CacheLineSize = 64;
- static const int ClusterSize = 3;
-
- struct Cluster {
- TTEntry entry[ClusterSize];
- char padding[2]; // Align to the cache line size
- };
-
- static_assert(sizeof(Cluster) == CacheLineSize / 2, "Cluster size incorrect");
-
-public:
- ~TranspositionTable() { free(mem); }
- void new_search() { generation8 += 4; } // Lower 2 bits are used by Bound
- uint8_t generation() const { return generation8; }
- TTEntry* probe(const Key key, bool& found) const;
- int hashfull() const;
- void resize(size_t mbSize);
- void clear();
-
- // The lowest order bits of the key are used to get the index of the cluster
- TTEntry* first_entry(const Key key) const {
- return &table[(size_t)key & (clusterCount - 1)].entry[0];
- }
-
-private:
- size_t clusterCount;
- Cluster* table;
- void* mem;
- uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
+ 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 // #ifndef TT_H_INCLUDED
+} // namespace Stockfish
+
+#endif // #ifndef TT_H_INCLUDED
projects / stockfish / blobdiff