mirror of
https://github.com/opelly27/Stockfish.git
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Sami Kiminki
39437f4e55
Align the TT allocation by 2M to make it huge page friendly and advise the
kernel to use huge pages.
Benchmarks on my i7-8700K (6C/12T) box: (3 runs per bench per config)
vanilla (nps) hugepages (nps) avg
==================================================================================
bench | 3012490 3024364 3036331 3071052 3067544 3071052 +1.5%
bench 16 12 20 | 19237932 19050166 19085315 19266346 19207025 19548758 +1.1%
bench 16384 12 20 | 18182313 18371581 18336838 19381275 19738012 19620225 +7.0%
On my box, huge pages have a significant perf impact when using a big
hash size. They also speed up TT initialization big time:
vanilla (s) huge pages (s) speed-up
=======================================================================
time stockfish bench 16384 1 1 | 5.37 1.48 3.6x
In practice, huge pages with auto-defrag may always be enabled in the
system, in which case this patch has no effect. This
depends on the values in /sys/kernel/mm/transparent_hugepage/enabled
and /sys/kernel/mm/transparent_hugepage/defrag.
closes https://github.com/official-stockfish/Stockfish/pull/2463
No functional change
102 lines
3.0 KiB
C++
102 lines
3.0 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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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 "misc.h"
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#include "types.h"
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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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/// move 16 bit
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/// value 16 bit
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/// eval value 16 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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/// depth 8 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);
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private:
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friend class TranspositionTable;
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uint16_t key16;
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uint16_t move16;
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int16_t value16;
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int16_t eval16;
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uint8_t genBound8;
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uint8_t depth8;
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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,
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/// as the cacheline is 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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public:
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~TranspositionTable() { free(mem); }
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void new_search() { generation8 += 8; } // Lower 3 bits are used by PV flag and Bound
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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);
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void clear();
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// The 32 lowest order bits of the key are used to get the index of the cluster
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TTEntry* first_entry(const Key key) const {
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return &table[(uint32_t(key) * uint64_t(clusterCount)) >> 32].entry[0];
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}
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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;
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void* mem;
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uint8_t generation8; // Size must be not bigger than TTEntry::genBound8
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};
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extern TranspositionTable TT;
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#endif // #ifndef TT_H_INCLUDED
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