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1 | // Copyright (C) 2020 Free Software Foundation, Inc. |
2 | // | |
3 | // This file is part of the GNU ISO C++ Library. This library is free | |
4 | // software; you can redistribute it and/or modify it under the | |
5 | // terms of the GNU General Public License as published by the | |
6 | // Free Software Foundation; either version 3, or (at your option) | |
7 | // any later version. | |
8 | ||
9 | // This library is distributed in the hope that it will be useful, | |
10 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | // GNU General Public License for more details. | |
13 | ||
14 | // You should have received a copy of the GNU General Public License along | |
15 | // with this library; see the file COPYING3. If not see | |
16 | // <http://www.gnu.org/licenses/>. | |
17 | ||
18 | // { dg-options "-O3" } | |
19 | // { dg-do run { target c++11 } } | |
20 | ||
21 | #include <future> | |
22 | #include <chrono> | |
23 | #include <iostream> | |
24 | #include <testsuite_hooks.h> | |
25 | ||
26 | const int iterations = 200; | |
27 | ||
28 | using namespace std; | |
29 | ||
30 | template<typename Duration> | |
31 | double | |
32 | print(const char* desc, Duration dur) | |
33 | { | |
34 | auto ns = chrono::duration_cast<chrono::nanoseconds>(dur).count(); | |
35 | double d = double(ns) / iterations; | |
36 | cout << desc << ": " << ns << "ns for " << iterations | |
37 | << " calls, avg " << d << "ns per call\n"; | |
38 | return d; | |
39 | } | |
40 | ||
41 | int main() | |
42 | { | |
43 | promise<int> p; | |
44 | future<int> f = p.get_future(); | |
45 | ||
46 | auto start = chrono::high_resolution_clock::now(); | |
47 | for(int i = 0; i < iterations; i++) | |
48 | f.wait_for(chrono::seconds(0)); | |
49 | auto stop = chrono::high_resolution_clock::now(); | |
50 | double wait_for_0 = print("wait_for(0s)", stop - start); | |
51 | ||
52 | start = chrono::high_resolution_clock::now(); | |
53 | for(int i = 0; i < iterations; i++) | |
54 | f.wait_until(chrono::system_clock::time_point()); | |
55 | stop = chrono::high_resolution_clock::now(); | |
56 | double wait_until_sys_epoch __attribute__((unused)) | |
57 | = print("wait_until(system_clock epoch)", stop - start); | |
58 | ||
59 | start = chrono::high_resolution_clock::now(); | |
60 | for(int i = 0; i < iterations; i++) | |
61 | f.wait_until(chrono::steady_clock::time_point()); | |
62 | stop = chrono::high_resolution_clock::now(); | |
63 | double wait_until_steady_epoch __attribute__((unused)) | |
64 | = print("wait_until(steady_clock epoch", stop - start); | |
65 | ||
66 | start = chrono::high_resolution_clock::now(); | |
67 | for(int i = 0; i < iterations; i++) | |
68 | f.wait_until(chrono::system_clock::time_point::min()); | |
69 | stop = chrono::high_resolution_clock::now(); | |
70 | double wait_until_sys_min __attribute__((unused)) | |
71 | = print("wait_until(system_clock minimum)", stop - start); | |
72 | ||
73 | start = chrono::high_resolution_clock::now(); | |
74 | for(int i = 0; i < iterations; i++) | |
75 | f.wait_until(chrono::steady_clock::time_point::min()); | |
76 | stop = chrono::high_resolution_clock::now(); | |
77 | double wait_until_steady_min __attribute__((unused)) | |
78 | = print("wait_until(steady_clock minimum)", stop - start); | |
79 | ||
80 | p.set_value(1); | |
81 | ||
82 | start = chrono::high_resolution_clock::now(); | |
83 | for(int i = 0; i < iterations; i++) | |
84 | f.wait_for(chrono::seconds(0)); | |
85 | stop = chrono::high_resolution_clock::now(); | |
86 | double ready = print("wait_for when ready", stop - start); | |
87 | ||
88 | // polling before ready with wait_for(0s) should be almost as fast as | |
89 | // after the result is ready. | |
90 | VERIFY( wait_for_0 < (ready * 10) ); | |
91 | ||
92 | // The following two tests fail with GCC 11, see | |
93 | // https://gcc.gnu.org/pipermail/libstdc++/2020-November/051422.html | |
94 | #if 0 | |
95 | // polling before ready using wait_until(epoch) should not be terribly slow. | |
96 | VERIFY( wait_until_sys_epoch < (ready * 100) ); | |
97 | VERIFY( wait_until_steady_epoch < (ready * 100) ); | |
98 | #endif | |
99 | ||
100 | // polling before ready using wait_until(min) should not be terribly slow. | |
101 | VERIFY( wait_until_sys_min < (ready * 100) ); | |
102 | VERIFY( wait_until_steady_min < (ready * 100) ); | |
103 | } |