mirror of
https://github.com/sockspls/badfish
synced 2025-07-12 03:59:15 +00:00
0a3eb1d8fa
Slight refactor of the TT code with the goal to make it easier to understand / tweak. Passed Non-Regression STC: https://tests.stockfishchess.org/tests/view/65d51e401d8e83c78bfdc427 LLR: 2.95 (-2.94,2.94) <-1.75,0.25> Total: 56416 W: 14750 L: 14550 D: 27116 Ptnml(0-2): 227, 6386, 14796, 6558, 241 closes https://github.com/official-stockfish/Stockfish/pull/5061 No functional change
121 lines
3.8 KiB
C++
121 lines
3.8 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef TT_H_INCLUDED
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#define TT_H_INCLUDED
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#include <cstddef>
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#include <cstdint>
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#include "misc.h"
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#include "types.h"
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namespace Stockfish {
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// TTEntry struct is the 10 bytes transposition table entry, defined as below:
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//
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// key 16 bit
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// depth 8 bit
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// generation 5 bit
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// pv node 1 bit
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// bound type 2 bit
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// move 16 bit
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// value 16 bit
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// eval value 16 bit
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struct TTEntry {
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Move move() const { return Move(move16); }
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Value value() const { return Value(value16); }
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Value eval() const { return Value(eval16); }
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Depth depth() const { return Depth(depth8 + DEPTH_OFFSET); }
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bool is_pv() const { return bool(genBound8 & 0x4); }
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Bound bound() const { return Bound(genBound8 & 0x3); }
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void save(Key k, Value v, bool pv, Bound b, Depth d, Move m, Value ev, uint8_t generation8);
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// The returned age is a multiple of TranspositionTable::GENERATION_DELTA
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uint8_t relative_age(const uint8_t generation8) const;
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private:
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friend class TranspositionTable;
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uint16_t key16;
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uint8_t depth8;
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uint8_t genBound8;
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Move move16;
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int16_t value16;
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int16_t eval16;
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};
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// A TranspositionTable is an array of Cluster, of size clusterCount. Each
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// cluster consists of ClusterSize number of TTEntry. Each non-empty TTEntry
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// contains information on exactly one position. The size of a Cluster should
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// divide the size of a cache line for best performance, as the cacheline is
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// prefetched when possible.
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class TranspositionTable {
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static constexpr int ClusterSize = 3;
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struct Cluster {
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TTEntry entry[ClusterSize];
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char padding[2]; // Pad to 32 bytes
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};
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static_assert(sizeof(Cluster) == 32, "Unexpected Cluster size");
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// Constants used to refresh the hash table periodically
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// We have 8 bits available where the lowest 3 bits are
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// reserved for other things.
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static constexpr unsigned GENERATION_BITS = 3;
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// increment for generation field
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static constexpr int GENERATION_DELTA = (1 << GENERATION_BITS);
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// cycle length
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static constexpr int GENERATION_CYCLE = 255 + GENERATION_DELTA;
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// mask to pull out generation number
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static constexpr int GENERATION_MASK = (0xFF << GENERATION_BITS) & 0xFF;
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public:
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~TranspositionTable() { aligned_large_pages_free(table); }
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void new_search() {
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// increment by delta to keep lower bits as is
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generation8 += GENERATION_DELTA;
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}
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TTEntry* probe(const Key key, bool& found) const;
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int hashfull() const;
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void resize(size_t mbSize, int threadCount);
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void clear(size_t threadCount);
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TTEntry* first_entry(const Key key) const {
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return &table[mul_hi64(key, clusterCount)].entry[0];
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}
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uint8_t generation() const { return generation8; }
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private:
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friend struct TTEntry;
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size_t clusterCount;
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Cluster* table = nullptr;
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uint8_t generation8 = 0; // Size must be not bigger than TTEntry::genBound8
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};
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} // namespace Stockfish
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#endif // #ifndef TT_H_INCLUDED
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