libstdc++-v3/testsuite/performance/30_threads/future/polling.cc

   1 // Copyright (C) 2009-2020 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
  19 #include <future>
  20 #include <thread>
  21 #include <testsuite_performance.h>
  22
  23 inline bool is_ready(std::shared_future<void>& f)
  24 {
  25   return f.wait_for(std::chrono::microseconds(1)) == std::future_status::ready;
  26 }
  27
  28 void poll(std::shared_future<void> f)
  29 {
  30   while (!is_ready(f))
  31   { }
  32 }
  33
  34 int main()
  35 {
  36 #ifdef TEST_T1
  37 #define thread_type true
  38 #endif
  39
  40   using namespace __gnu_test;
  41   time_counter time;
  42   resource_counter resource;
  43
  44   const int n = 20;
  45   std::promise<void> p;
  46   std::shared_future<void> f = p.get_future();
  47   std::thread pollers[n];
  48   for (int i=0; i < n; ++i)
  49     pollers[i] = std::thread(poll, f);
  50
  51   start_counters(time, resource);
  52
  53   for (int i = 0; i < 1000000; ++i)
  54     (void)is_ready(f);
  55   p.set_value();
  56
  57   for (int i=0; i < n; ++i)
  58     pollers[i].join();
  59
  60   stop_counters(time, resource);
  61   report_performance(__FILE__, "", time, resource);
  62
  63   return 0;
  64 }