/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, 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
#include "misc.h"
#include "types.h"
-/// The TTEntry is the 128 bit transposition table entry, defined as below:
+/// TTEntry struct is the 10 bytes 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
-/// static margin: 16 bit
+/// 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
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;
- }
- void set_generation(uint8_t g) { generation8 = g; }
-
- uint32_t key() const { return key32; }
- Depth depth() const { return (Depth)depth16; }
- Move move() const { return (Move)move16; }
- Value value() const { return (Value)value16; }
- Bound bound() const { return (Bound)bound8; }
- int generation() const { return (int)generation8; }
- Value eval_value() const { return (Value)evalValue; }
+ 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)) + 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:
- uint32_t key32;
+ friend class TranspositionTable;
+
+ uint16_t key16;
uint16_t move16;
- uint8_t bound8, generation8;
- int16_t value16, depth16, evalValue;
+ int16_t value16;
+ int16_t eval16;
+ uint8_t genBound8;
+ uint8_t depth8;
};
/// 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.
+/// 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 const unsigned ClusterSize = 4; // A cluster is 64 Bytes
+ 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() { free(mem); }
- void new_search() { ++generation; }
-
- const TTEntry* probe(const Key key) const;
- TTEntry* first_entry(const Key key) const;
- void refresh(const TTEntry* tte) const;
- void set_size(size_t mbSize);
+ 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();
- void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);
+
+ // 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:
- uint32_t hashMask;
- TTEntry* table;
+ friend struct TTEntry;
+
+ size_t clusterCount;
+ Cluster* table;
void* mem;
- uint8_t generation; // Size must be not bigger than TTEntry::generation8
+ uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
};
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);
-}
-
-
-/// TranspositionTable::refresh() updates the 'generation' value of the TTEntry
-/// to avoid aging. It is normally called after a TT hit.
-
-inline void TranspositionTable::refresh(const TTEntry* tte) const {
-
- const_cast<TTEntry*>(tte)->set_generation(generation);
-}
-
#endif // #ifndef TT_H_INCLUDED
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