1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03, c++11, c++14, c++17
10
11#include <algorithm>
12#include <cassert>
13#include <cstddef>
14#include <deque>
15#include <iterator>
16#include <list>
17#include <string>
18#include <vector>
19
20#include "benchmark/benchmark.h"
21#include "../../GenerateInput.h"
22
23auto compute_median(auto first, auto last) {
24 std::vector v(first, last);
25 auto middle = v.begin() + v.size() / 2;
26 std::nth_element(v.begin(), middle, v.end());
27 return *middle;
28}
29
30int main(int argc, char** argv) {
31 auto std_is_partitioned = [](auto first, auto last, auto pred) { return std::is_partitioned(first, last, pred); };
32
33 auto bm = []<class Container, bool Partitioned>(std::string name, auto is_partitioned) {
34 benchmark::RegisterBenchmark(
35 name,
36 [is_partitioned](auto& st) {
37 std::size_t const size = st.range(0);
38 using ValueType = typename Container::value_type;
39 Container c;
40 std::generate_n(std::back_inserter(c), size, [] { return Generate<ValueType>::random(); });
41
42 // Partition the container in two equally-sized halves, ensuring the median
43 // value appears in the left half. Note that the median value isn't located
44 // in the middle -- this isn't std::nth_element.
45 ValueType median = compute_median(c.begin(), c.end());
46 auto pred = [median](auto const& element) { return element <= median; };
47 std::partition(c.begin(), c.end(), pred);
48 assert(std::is_partitioned(c.begin(), c.end(), pred));
49
50 if constexpr (!Partitioned) {
51 // De-partition the container by swapping the element containing the median
52 // value with the last one.
53 auto median_it = std::find(c.begin(), c.end(), median);
54 auto last_it = std::next(c.begin(), c.size() - 1);
55 std::iter_swap(median_it, last_it);
56 assert(!std::is_partitioned(c.begin(), c.end(), pred));
57 }
58
59 for ([[maybe_unused]] auto _ : st) {
60 benchmark::DoNotOptimize(c);
61 auto result = is_partitioned(c.begin(), c.end(), pred);
62 benchmark::DoNotOptimize(result);
63 }
64 })
65 ->Arg(32)
66 ->Arg(50) // non power-of-two
67 ->Arg(1024)
68 ->Arg(8192);
69 };
70
71 // std::is_partitioned
72 bm.operator()<std::vector<int>, true>(name: "std::is_partitioned(vector<int>) (partitioned)", is_partitioned: std_is_partitioned);
73 bm.operator()<std::vector<int>, false>(name: "std::is_partitioned(vector<int>) (unpartitioned)", is_partitioned: std_is_partitioned);
74
75 bm.operator()<std::deque<int>, true>(name: "std::is_partitioned(deque<int>) (partitioned)", is_partitioned: std_is_partitioned);
76 bm.operator()<std::deque<int>, false>(name: "std::is_partitioned(deque<int>) (unpartitioned)", is_partitioned: std_is_partitioned);
77
78 bm.operator()<std::list<int>, true>(name: "std::is_partitioned(list<int>) (partitioned)", is_partitioned: std_is_partitioned);
79 bm.operator()<std::list<int>, false>(name: "std::is_partitioned(list<int>) (unpartitioned)", is_partitioned: std_is_partitioned);
80
81 // ranges::is_partitioned
82 bm.operator()<std::vector<int>, true>("rng::is_partitioned(vector<int>) (partitioned)", std::ranges::is_partitioned);
83 bm.operator()<std::vector<int>, false>(
84 "rng::is_partitioned(vector<int>) (unpartitioned)", std::ranges::is_partitioned);
85
86 bm.operator()<std::deque<int>, true>("rng::is_partitioned(deque<int>) (partitioned)", std::ranges::is_partitioned);
87 bm.operator()<std::deque<int>, false>("rng::is_partitioned(deque<int>) (unpartitioned)", std::ranges::is_partitioned);
88
89 bm.operator()<std::list<int>, true>("rng::is_partitioned(list<int>) (partitioned)", std::ranges::is_partitioned);
90 bm.operator()<std::list<int>, false>("rng::is_partitioned(list<int>) (unpartitioned)", std::ranges::is_partitioned);
91
92 benchmark::Initialize(&argc, argv);
93 benchmark::RunSpecifiedBenchmarks();
94 benchmark::Shutdown();
95 return 0;
96}
97

source code of libcxx/test/benchmarks/algorithms/partitions/is_partitioned.bench.cpp