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, c++20
10
11#include <algorithm>
12#include <cstddef>
13#include <deque>
14#include <list>
15#include <string>
16#include <vector>
17
18#include <benchmark/benchmark.h>
19#include "../../GenerateInput.h"
20
21int main(int argc, char** argv) {
22 auto ranges_starts_with_pred = [](auto first1, auto last1, auto first2, auto last2) {
23 return std::ranges::starts_with(first1, last1, first2, last2, [](auto x, auto y) {
24 benchmark::DoNotOptimize(x);
25 benchmark::DoNotOptimize(y);
26 return x == y;
27 });
28 };
29
30 // Benchmark ranges::starts_with where we find the mismatching element at the very end (worst case).
31 {
32 auto bm = []<class Container>(std::string name, auto starts_with) {
33 benchmark::RegisterBenchmark(
34 name,
35 [starts_with](auto& st) {
36 std::size_t const size = st.range(0);
37 using ValueType = typename Container::value_type;
38 ValueType x = Generate<ValueType>::random();
39 ValueType y = random_different_from({x});
40 Container c1(size, x);
41 Container c2(size, x);
42 c2.back() = y;
43
44 for ([[maybe_unused]] auto _ : st) {
45 benchmark::DoNotOptimize(c1);
46 benchmark::DoNotOptimize(c2);
47 auto result = starts_with(c1.begin(), c1.end(), c2.begin(), c2.end());
48 benchmark::DoNotOptimize(result);
49 }
50 })
51 ->Arg(8)
52 ->Arg(1000) // non power-of-two
53 ->Arg(1024)
54 ->Arg(8192)
55 ->Arg(1 << 20);
56 };
57 bm.operator()<std::vector<int>>("rng::starts_with(vector<int>)", std::ranges::starts_with);
58 bm.operator()<std::deque<int>>("rng::starts_with(deque<int>)", std::ranges::starts_with);
59 bm.operator()<std::list<int>>("rng::starts_with(list<int>)", std::ranges::starts_with);
60
61 bm.operator()<std::vector<int>>(name: "rng::starts_with(vector<int>, pred)", starts_with: ranges_starts_with_pred);
62 bm.operator()<std::deque<int>>(name: "rng::starts_with(deque<int>, pred)", starts_with: ranges_starts_with_pred);
63 bm.operator()<std::list<int>>(name: "rng::starts_with(list<int>, pred)", starts_with: ranges_starts_with_pred);
64 }
65
66 benchmark::Initialize(&argc, argv);
67 benchmark::RunSpecifiedBenchmarks();
68 benchmark::Shutdown();
69 return 0;
70}
71

source code of libcxx/test/benchmarks/algorithms/nonmodifying/starts_with.bench.cpp