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Optimize B-tree node shifts for trivially copyable values #25

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Optimize B-tree node shifts for trivially copyable values #25

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9 changes: 9 additions & 0 deletions benchmark/btree_bench.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -296,9 +296,18 @@ using STLMultiMap = std::multimap<T, T>;
REGISTER_BENCHMARK_FUNCTIONS(container, std::int64_t); \
REGISTER_BENCHMARK_FUNCTIONS(container, std::string);

#define REGISTER_TRIVIAL_SHIFT_BENCHMARKS(container, type) \
STL_AND_BTREE_BENCHMARK(container, type, Insert); \
STL_AND_BTREE_BENCHMARK(container, type, Delete);

REGISTER_BENCHMARK_TYPES(Set);
REGISTER_BENCHMARK_TYPES(MultiSet);
REGISTER_BENCHMARK_TYPES(Map);
REGISTER_BENCHMARK_TYPES(MultiMap);

REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Set, int);
REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Set, std::pair<int, int>);
REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Map, int);
REGISTER_TRIVIAL_SHIFT_BENCHMARKS(Map, std::pair<int, int>);

BENCHMARK_MAIN();
21 changes: 19 additions & 2 deletions include/platanus/internal/btree_base_node.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,10 @@
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstring>
#include <iterator>
#include <memory>
#include <type_traits>

#include "btree_node_fwd.hpp"
#include "btree_util.hpp"
Expand Down Expand Up @@ -287,7 +290,14 @@ class btree_base_node {
assert(last + shift <= max_values_count());
auto begin = std::next(begin_values(), first);
auto end = std::next(begin_values(), last);
std::move_backward(begin, end, std::next(end, shift));
if constexpr (std::is_trivially_copyable_v<mutable_value_type>) {
auto* src = std::to_address(begin);
// std::memmove handles overlapping ranges, so right shifts (destination starts inside source)
// remain well-defined for trivially copyable values.
std::memmove(src + shift, src, static_cast<std::size_t>(last - first) * sizeof(*src));
} else {
std::move_backward(begin, end, std::next(end, shift));
}
}

// Shift values from first to last by shift toward left.
Expand All @@ -299,7 +309,14 @@ class btree_base_node {
assert(0 <= first - shift);
auto begin = std::next(begin_values(), first);
auto end = std::next(begin_values(), last);
std::move(begin, end, std::prev(begin, shift));
if constexpr (std::is_trivially_copyable_v<mutable_value_type>) {
auto* src = std::to_address(begin);
// std::memmove handles overlapping ranges, so left shifts (destination ends inside source)
// remain well-defined for trivially copyable values.
std::memmove(src - shift, src, static_cast<std::size_t>(last - first) * sizeof(*src));
} else {
std::move(begin, end, std::prev(begin, shift));
}
}

private:
Expand Down
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