/*
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) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, 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 5 bit
-/// pv node 1 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 + 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;
- uint16_t move16;
- int16_t value16;
- int16_t eval16;
- uint8_t genBound8;
- uint8_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 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.
-
+// 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 constexpr int ClusterSize = 3;
- static constexpr int ClustersPerSuperCluster = 256;
-
- struct Cluster {
- TTEntry entry[ClusterSize];
- char padding[2]; // Pad to 32 bytes
- };
-
- static_assert(sizeof(Cluster) == 32, "Unexpected Cluster size");
-
-public:
- ~TranspositionTable() { aligned_ttmem_free(mem); }
- void new_search() { generation8 += 8; } // Lower 3 bits are used by PV flag and Bound
- 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 {
-
- // The index is computed from
- // Idx = (K48 * SCC) / 2^40, with K48 the 48 lowest bits swizzled.
-
- const uint64_t firstTerm = uint32_t(key) * uint64_t(superClusterCount);
- const uint64_t secondTerm = (uint16_t(key >> 32) * uint64_t(superClusterCount)) >> 16;
-
- return &table[(firstTerm + secondTerm) >> 24].entry[0];
- }
-
-private:
- friend struct TTEntry;
-
- size_t superClusterCount;
- 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
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