boost/timer.hpp

   1 //  boost timer.hpp header file  ---------------------------------------------//
   2
   3 //  Copyright Beman Dawes 1994-99.  Distributed under the Boost
   4 //  Software License, Version 1.0. (See accompanying file
   5 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 //  See http://www.boost.org/libs/timer for documentation.
   8
   9 //  Revision History
  10 //  01 Apr 01  Modified to use new <boost/limits.hpp> header. (JMaddock)
  11 //  12 Jan 01  Change to inline implementation to allow use without library
  12 //             builds. See docs for more rationale. (Beman Dawes)
  13 //  25 Sep 99  elapsed_max() and elapsed_min() added (John Maddock)
  14 //  16 Jul 99  Second beta
  15 //   6 Jul 99  Initial boost version
  16
  17 #ifndef BOOST_TIMER_HPP
  18 #define BOOST_TIMER_HPP
  19
  20 #include <boost/config.hpp>
  21 #include <ctime>
  22 #include <boost/limits.hpp>
  23
  24 # ifdef BOOST_NO_STDC_NAMESPACE
  25     namespace std { using ::clock_t; using ::clock; }
  26 # endif
  27
  28
  29 namespace boost {
  30
  31 //  timer  -------------------------------------------------------------------//
  32
  33 //  A timer object measures elapsed time.
  34
  35 //  It is recommended that implementations measure wall clock rather than CPU
  36 //  time since the intended use is performance measurement on systems where
  37 //  total elapsed time is more important than just process or CPU time.
  38
  39 //  Warnings: The maximum measurable elapsed time may well be only 596.5+ hours
  40 //  due to implementation limitations.  The accuracy of timings depends on the
  41 //  accuracy of timing information provided by the underlying platform, and
  42 //  this varies a great deal from platform to platform.
  43
  44 class timer
  45 {
  46  public:
  47          timer() { _start_time = std::clock(); } // postcondition: elapsed()==0
  48 //         timer( const timer& src );      // post: elapsed()==src.elapsed()
  49 //        ~timer(){}
  50 //  timer& operator=( const timer& src );  // post: elapsed()==src.elapsed()
  51   void   restart() { _start_time = std::clock(); } // post: elapsed()==0
  52   double elapsed() const                  // return elapsed time in seconds
  53     { return  double(std::clock() - _start_time) / CLOCKS_PER_SEC; }
  54
  55   double elapsed_max() const   // return estimated maximum value for elapsed()
  56   // Portability warning: elapsed_max() may return too high a value on systems
  57   // where std::clock_t overflows or resets at surprising values.
  58   {
  59     return (double((std::numeric_limits<std::clock_t>::max)())
  60        - double(_start_time)) / double(CLOCKS_PER_SEC);
  61   }
  62
  63   double elapsed_min() const            // return minimum value for elapsed()
  64    { return double(1)/double(CLOCKS_PER_SEC); }
  65
  66  private:
  67   std::clock_t _start_time;
  68 }; // timer
  69
  70 } // namespace boost
  71
  72 #endif  // BOOST_TIMER_HPP