/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2016 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 10 bytes transposition table entry, defined as below:
+/// TTEntry struct is the 10 bytes transposition table entry, defined as below:
///
/// key 16 bit
/// move 16 bit
struct TTEntry {
- Move move() const { return (Move )move16; }
- Value value() const { return (Value)value16; }
- Value eval_value() const { return (Value)evalValue; }
- Depth depth() const { return (Depth)(depth8) + DEPTH_NONE; }
- Bound bound() const { return (Bound)(genBound8 & 0x3); }
+ 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)); }
+ Bound bound() const { return (Bound)(genBound8 & 0x3); }
+
+ void save(Key k, Value v, Bound b, Depth d, Move m, Value ev, uint8_t g) {
+
+ assert(d / ONE_PLY * ONE_PLY == d);
+
+ // 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 / ONE_PLY > depth8 - 4
+ /* || 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 / ONE_PLY);
+ }
+ }
private:
friend class TranspositionTable;
- void save(uint16_t k, Value v, Bound b, Depth d, Move m, uint8_t g, Value ev) {
-
- key16 = (uint16_t)k;
- move16 = (uint16_t)m;
- value16 = (int16_t)v;
- evalValue = (int16_t)ev;
- depth8 = (uint8_t)(d - DEPTH_NONE);
- genBound8 = g | (uint8_t)b;
- }
-
uint16_t key16;
uint16_t move16;
int16_t value16;
- int16_t evalValue;
+ int16_t eval16;
uint8_t genBound8;
- uint8_t depth8;
+ int8_t depth8;
};
-/// TTCluster is a 32 bytes cluster of TT entries consisting of:
-///
-/// 3 x TTEntry (3 x 10 bytes)
-/// padding (2 bytes)
-
-const unsigned TTClusterSize = 3;
-
-struct TTCluster {
-
- TTEntry entry[TTClusterSize];
- char padding[2];
-};
/// A TranspositionTable consists of a power of 2 number of clusters and each
-/// cluster consists of TTClusterSize number of TTEntry. Each non-empty entry
+/// 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;
+
+ 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 += 4; } // Lower 2 bits are used by Bound
-
- const TTEntry* probe(const Key key) const;
- TTEntry* first_entry(const Key key) const;
+ 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();
- void store(const Key key, Value v, Bound type, Depth d, Move m, Value statV);
+
+ // 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;
- TTCluster* table;
+ Cluster* table;
void* mem;
- uint8_t generation; // Size must be not bigger than TTEntry::genBound8
+ 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 inside the table.
-
-inline TTEntry* TranspositionTable::first_entry(const Key key) const {
-
- return &table[(uint32_t)key & (clusterCount - 1)].entry[0];
-}
-
#endif // #ifndef TT_H_INCLUDED
projects / stockfish / blobdiff