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Fix <bitset> benchmark correctness #4817

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Merged
merged 5 commits into from
Jul 11, 2024
Merged

Fix <bitset> benchmark correctness #4817

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72f834d
Missing optimization barriers
AlexGuteniev Jul 7, 2024
4ff5a4a
Fix bitset<512> benchmark correctness
AlexGuteniev Jul 7, 2024
ef74777
Don't return const prvalues.
StephanTLavavej Jul 8, 2024
7789d63
N is an exact multiple of 64, so (N / 64) * 64 is N.
StephanTLavavej Jul 8, 2024
17b1930
Distinguish Elems from N.
StephanTLavavej Jul 8, 2024
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31 changes: 21 additions & 10 deletions benchmarks/src/bitset_to_string.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,41 +13,52 @@
using namespace std;

namespace {
const auto random_bits = [] {
template <size_t Elems>
auto random_bits_init() {
mt19937_64 rnd{};
array<uint64_t, 32> arr;
array<uint64_t, Elems> arr;
for (auto& d : arr) {
d = rnd();
}
return arr;
}();
}

template <size_t Elems = 32>
const auto random_bits = random_bits_init<Elems>();

template <size_t N, class charT>
void BM_bitset_to_string(benchmark::State& state) {
static_assert(N <= 64);

for (auto _ : state) {
for (const auto& bits : random_bits) {
for (const auto& bits : random_bits<>) {
benchmark::DoNotOptimize(bits);
bitset<N> bs{bits};
benchmark::DoNotOptimize(bs.to_string<charT>());
}
}
}

template <class charT>
template <size_t N, class charT>
void BM_bitset_to_string_large_single(benchmark::State& state) {
const auto large_bitset = bit_cast<bitset<CHAR_BIT * sizeof(random_bits)>>(random_bits);
static_assert(N % 64 == 0 && N >= 64);
const auto& bitset_data = random_bits<N / 64>;

const auto large_bitset = bit_cast<bitset<N>>(bitset_data);
for (auto _ : state) {
benchmark::DoNotOptimize(large_bitset);
benchmark::DoNotOptimize(large_bitset.to_string<charT>());
}
}
} // namespace

BENCHMARK(BM_bitset_to_string<15, char>);
BENCHMARK(BM_bitset_to_string<64, char>);
BENCHMARK(BM_bitset_to_string<512, char>);
BENCHMARK(BM_bitset_to_string_large_single<char>);
BENCHMARK(BM_bitset_to_string_large_single<512, char>);
BENCHMARK(BM_bitset_to_string_large_single<2048, char>);
BENCHMARK(BM_bitset_to_string<7, wchar_t>);
BENCHMARK(BM_bitset_to_string<64, wchar_t>);
BENCHMARK(BM_bitset_to_string<512, wchar_t>);
BENCHMARK(BM_bitset_to_string_large_single<wchar_t>);
BENCHMARK(BM_bitset_to_string_large_single<512, wchar_t>);
BENCHMARK(BM_bitset_to_string_large_single<2048, wchar_t>);

BENCHMARK_MAIN();