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