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Revert "Bug 39129: Speeding up partition_point/lower_bound/upper_bound/ by using unsigned division by 2 when possible."

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This reverts r345525. I'm reverting because that patch apparently caused
a regression on certain platforms (see https://reviews.llvm.org/D53994).
Since we don't fully understand the reasons for the regression, I'm
reverting until we can provide a fix we understand.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@345893 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Louis Dionne
2018-11-01 21:24:32 +00:00
parent 6115b72f60
commit 5dc37768e2
3 changed files with 4 additions and 153 deletions
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64
benchmarks/algorithms.bench.cpp
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@@ -58,69 +58,5 @@ BENCHMARK_CAPTURE(BM_Sort, sorted_descending_strings,
BENCHMARK_CAPTURE(BM_Sort, single_element_strings,
getDuplicateStringInputs)->Arg(TestNumInputs);
template <typename GenInputs, typename Alg>
void do_binary_search_benchmark(benchmark::State& st, GenInputs gen, Alg alg)
{
using ValueType = typename decltype(gen(0))::value_type;
auto in = gen(st.range(0));
std::sort(in.begin(), in.end());
const auto every_10_percentile = [&]() -> std::vector<ValueType*> {
size_t step = in.size() / 10;
if (step == 0) {
st.SkipWithError("Input doesn't contain enough elements");
return {};
}
std::vector<ValueType*> res;
for (size_t i = 0; i < in.size(); i += step)
res.push_back(&in[i]);
return res;
}();
for (auto _ : st)
{
for (auto* test : every_10_percentile)
benchmark::DoNotOptimize(alg(in.begin(), in.end(), *test));
}
}
template <typename GenInputs>
void BM_LowerBound(benchmark::State& st, GenInputs gen)
{
do_binary_search_benchmark(st, gen, [](auto f, auto l, const auto& v) {
return std::lower_bound(f, l, v);
});
}
BENCHMARK_CAPTURE(BM_LowerBound, random_int32, getRandomIntegerInputs<int32_t>)
->Arg(TestNumInputs) // Small int32_t vector
->Arg(TestNumInputs * TestNumInputs); // Big int32_t vector
BENCHMARK_CAPTURE(BM_LowerBound, random_int64, getRandomIntegerInputs<int64_t>)
->Arg(TestNumInputs); // Small int64_t vector. Should also represent pointers.
BENCHMARK_CAPTURE(BM_LowerBound, random_strings, getRandomStringInputs)
->Arg(TestNumInputs); // Small string vector. What happens if the comparison is not very cheap.
template <typename GenInputs>
void BM_EqualRange(benchmark::State& st, GenInputs gen)
{
do_binary_search_benchmark(st, gen, [](auto f, auto l, const auto& v) {
return std::equal_range(f, l, v);
});
}
BENCHMARK_CAPTURE(BM_EqualRange, random_int32, getRandomIntegerInputs<int32_t>)
->Arg(TestNumInputs) // Small int32_t vector
->Arg(TestNumInputs * TestNumInputs); // Big int32_t vector
BENCHMARK_CAPTURE(BM_EqualRange, random_int64, getRandomIntegerInputs<int64_t>)
->Arg(TestNumInputs); // Small int64_t vector. Should also represent pointers.
BENCHMARK_CAPTURE(BM_EqualRange, random_strings, getRandomStringInputs)
->Arg(TestNumInputs); // Small string vector. What happens if the comparison is not very cheap.
BENCHMARK_MAIN();