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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 <cassert>
#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_is_partitioned = [](auto first, auto last, auto pred) { return std::is_partitioned(first, last, pred); };
auto bm = []<class Container, bool Partitioned>(std::string name, auto is_partitioned) {
benchmark::RegisterBenchmark(
name,
[is_partitioned](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, ensuring the median
// value appears in the left half. Note that the median value isn't located
// in the middle -- this isn't std::nth_element.
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));
if constexpr (!Partitioned) {
// De-partition the container by swapping the element containing the median
// value with the last one.
auto median_it = std::find(c.begin(), c.end(), median);
auto last_it = std::next(c.begin(), c.size() - 1);
std::iter_swap(median_it, last_it);
assert(!std::is_partitioned(c.begin(), c.end(), pred));
}
for ([[maybe_unused]] auto _ : st) {
benchmark::DoNotOptimize(c);
auto result = is_partitioned(c.begin(), c.end(), pred);
benchmark::DoNotOptimize(result);
}
})
->Arg(32)
->Arg(50) // non power-of-two
->Arg(1024)
->Arg(8192);
};
// std::is_partitioned
bm.operator()<std::vector<int>, true>("std::is_partitioned(vector<int>) (partitioned)", std_is_partitioned);
bm.operator()<std::vector<int>, false>("std::is_partitioned(vector<int>) (unpartitioned)", std_is_partitioned);
bm.operator()<std::deque<int>, true>("std::is_partitioned(deque<int>) (partitioned)", std_is_partitioned);
bm.operator()<std::deque<int>, false>("std::is_partitioned(deque<int>) (unpartitioned)", std_is_partitioned);
bm.operator()<std::list<int>, true>("std::is_partitioned(list<int>) (partitioned)", std_is_partitioned);
bm.operator()<std::list<int>, false>("std::is_partitioned(list<int>) (unpartitioned)", std_is_partitioned);
// ranges::is_partitioned
bm.operator()<std::vector<int>, true>("rng::is_partitioned(vector<int>) (partitioned)", std::ranges::is_partitioned);
bm.operator()<std::vector<int>, false>(
"rng::is_partitioned(vector<int>) (unpartitioned)", std::ranges::is_partitioned);
bm.operator()<std::deque<int>, true>("rng::is_partitioned(deque<int>) (partitioned)", std::ranges::is_partitioned);
bm.operator()<std::deque<int>, false>("rng::is_partitioned(deque<int>) (unpartitioned)", std::ranges::is_partitioned);
bm.operator()<std::list<int>, true>("rng::is_partitioned(list<int>) (partitioned)", std::ranges::is_partitioned);
bm.operator()<std::list<int>, false>("rng::is_partitioned(list<int>) (unpartitioned)", std::ranges::is_partitioned);
benchmark::Initialize(&argc, argv);
benchmark::RunSpecifiedBenchmarks();
benchmark::Shutdown();
return 0;
}
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