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) 2015-2018 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
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 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, uint8_t g) {
-
- if (m || (k >> 48) != key16) // Preserve any existing move for the same position
- move16 = (uint16_t)m;
-
- key16 = (uint16_t)(k >> 48);
- value16 = (int16_t)v;
- eval16 = (int16_t)ev;
- genBound8 = (uint8_t)(g | b);
- depth8 = (int8_t)d;
- }
+ void save(Key k, Value v, Bound b, Depth d, Move m, Value ev);
private:
friend class TranspositionTable;
/// 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 int CacheLineSize = 64;
- static const int ClusterSize = 3;
+ static constexpr int CacheLineSize = 64;
+ static constexpr int ClusterSize = 3;
struct Cluster {
TTEntry entry[ClusterSize];
- char padding[2]; // Align to the cache line size
+ char padding[2]; // Align to a divisor of the cache line size
};
- static_assert(sizeof(Cluster) == CacheLineSize / 2, "Cluster size incorrect");
+ static_assert(CacheLineSize % sizeof(Cluster) == 0, "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
+ // 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[(size_t)key & (clusterCount - 1)].entry[0];
+ return &table[(uint32_t(key) * uint64_t(clusterCount)) >> 32].entry[0];
}
private:
+ friend struct TTEntry;
+
size_t clusterCount;
Cluster* table;
void* mem;