2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
5 Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
7 Stockfish is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
27 /// TTEntry struct is the 10 bytes transposition table entry, defined as below:
39 Move move() const { return (Move )move16; }
40 Value value() const { return (Value)value16; }
41 Value eval() const { return (Value)eval16; }
42 Depth depth() const { return (Depth)depth8; }
43 Bound bound() const { return (Bound)(genBound8 & 0x3); }
45 void save(Key k, Value v, Bound b, Depth d, Move m, Value ev, uint8_t g) {
47 // Preserve any existing move for the same position
48 if (m || (k >> 48) != key16)
51 // Don't overwrite more valuable entries
52 if ( (k >> 48) != key16
54 /* || g != (genBound8 & 0xFC) // Matching non-zero keys are already refreshed by probe() */
57 key16 = (uint16_t)(k >> 48);
60 genBound8 = (uint8_t)(g | b);
66 friend class TranspositionTable;
77 /// A TranspositionTable consists of a power of 2 number of clusters and each
78 /// cluster consists of ClusterSize number of TTEntry. Each non-empty entry
79 /// contains information of exactly one position. The size of a cluster should
80 /// divide the size of a cache line size, to ensure that clusters never cross
81 /// cache lines. This ensures best cache performance, as the cacheline is
82 /// prefetched, as soon as possible.
84 class TranspositionTable {
86 static const int CacheLineSize = 64;
87 static const int ClusterSize = 3;
90 TTEntry entry[ClusterSize];
91 char padding[2]; // Align to a divisor of the cache line size
94 static_assert(CacheLineSize % sizeof(Cluster) == 0, "Cluster size incorrect");
97 ~TranspositionTable() { free(mem); }
98 void new_search() { generation8 += 4; } // Lower 2 bits are used by Bound
99 uint8_t generation() const { return generation8; }
100 TTEntry* probe(const Key key, bool& found) const;
101 int hashfull() const;
102 void resize(size_t mbSize);
105 // The lowest order bits of the key are used to get the index of the cluster
106 TTEntry* first_entry(const Key key) const {
107 return &table[(size_t)key & (clusterCount - 1)].entry[0];
114 uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
117 extern TranspositionTable TT;
119 #endif // #ifndef TT_H_INCLUDED