ceph/src/boost/libs/timer/test/cpu_timer_info.cpp

   1 //  boost cpu_timer_info.cpp  ----------------------------------------------------------//
   2
   3 //  Copyright Beman Dawes 2011
   4
   5 //  Distributed under the Boost Software License, Version 1.0.
   6 //  See http://www.boost.org/LICENSE_1_0.txt
   7
   8 //  See http://www.boost.org/libs/timer for documentation.
   9
  10 #include <boost/timer/timer.hpp>
  11 #include <boost/chrono/chrono.hpp>
  12 #include <boost/detail/lightweight_main.hpp>
  13 #include <cstdlib> // for atol()
  14 #include <iostream>
  15 #include <locale>
  16
  17 using boost::timer::nanosecond_type;
  18 using boost::timer::cpu_times;
  19 using boost::timer::cpu_timer;
  20 using boost::timer::auto_cpu_timer;
  21 using std::cout; using std::endl;
  22
  23 int cpp_main( int argc, char * argv[] )
  24 {
  25   cout << '\n';
  26   cout << "For cpu_times.wall, the underlying clock "
  27        << (boost::chrono::high_resolution_clock::is_steady
  28            ? "is steady. "
  29            : "is not steady. "
  30           )
  31        << "Steady clocks are defined by C++11 as clocks for which values "
  32           "of time_point never decrease as physical time advances and for "
  33           "which values of time_point advance at a steady rate relative to "
  34           "real time. That is, the clock may not be adjusted.\n\n";
  35
  36   cpu_times start_time;
  37   start_time.clear();
  38   cpu_times current_time;
  39
  40   {
  41     cpu_timer cpu;
  42     cout << "measure boost::timer::cpu_timer resolution for user time..."
  43               << endl;
  44     for (int i = 0; i < 3; ++i)
  45     {
  46       cpu.start();
  47       start_time = cpu.elapsed();
  48       current_time.user = start_time.user;
  49       while (current_time.user == start_time.user)
  50       {
  51         current_time = cpu.elapsed();
  52       }
  53       cout << current_time.user - start_time.user << "ns\n";
  54     }
  55   }
  56
  57   {
  58     cpu_timer cpu;
  59     cout << "measure boost::timer::cpu_timer resolution for wall-clock time..."
  60               << endl;
  61     for (int i = 0; i < 100; ++i)
  62     {
  63       cpu.start();
  64       start_time.wall = cpu.elapsed().wall;
  65       current_time.wall = start_time.wall;
  66       while (current_time.wall == start_time.wall)
  67       {
  68         current_time.wall = cpu.elapsed().wall;
  69       }
  70       cout << current_time.wall - start_time.wall << "ns ";
  71     }
  72   }
  73  return 0;
  74 }
  75