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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14, c++17
#include <algorithm>
#include <cstddef>
#include <deque>
#include <iterator>
#include <list>
#include <string>
#include <vector>
#include "benchmark/benchmark.h"
#include "../../GenerateInput.h"
auto compute_median(auto first, auto last) {
std::vector v(first, last);
auto middle = v.begin() + v.size() / 2;
std::nth_element(v.begin(), middle, v.end());
return *middle;
}
int main(int argc, char** argv) {
auto std_partition_point = [](auto first, auto last, auto pred) { return std::partition_point(first, last, pred); };
auto bm = []<class Container>(std::string name, auto partition_point) {
benchmark::RegisterBenchmark(
name,
[partition_point](auto& st) {
std::size_t const size = st.range(0);
using ValueType = typename Container::value_type;
Container c;
std::generate_n(std::back_inserter(c), size, [] { return Generate<ValueType>::random(); });
// Partition the container in two equally-sized halves. Based on experimentation, the running
// time of the algorithm doesn't change much depending on the size of the halves.
ValueType median = compute_median(c.begin(), c.end());
auto pred = [median](auto const& element) { return element < median; };
std::partition(c.begin(), c.end(), pred);
assert(std::is_partitioned(c.begin(), c.end(), pred));
for ([[maybe_unused]] auto _ : st) {
benchmark::DoNotOptimize(c);
auto result = partition_point(c.begin(), c.end(), pred);
benchmark::DoNotOptimize(result);
}
})
->Arg(32)
->Arg(50) // non power-of-two
->Arg(1024)
->Arg(8192);
};
// std::partition_point
bm.operator()<std::vector<int>>("std::partition_point(vector<int>)", std_partition_point);
bm.operator()<std::deque<int>>("std::partition_point(deque<int>)", std_partition_point);
bm.operator()<std::list<int>>("std::partition_point(list<int>)", std_partition_point);
// ranges::partition_point
bm.operator()<std::vector<int>>("rng::partition_point(vector<int>)", std::ranges::partition_point);
bm.operator()<std::deque<int>>("rng::partition_point(deque<int>)", std::ranges::partition_point);
bm.operator()<std::list<int>>("rng::partition_point(list<int>)", std::ranges::partition_point);
benchmark::Initialize(&argc, argv);
benchmark::RunSpecifiedBenchmarks();
benchmark::Shutdown();
return 0;
}
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