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:
timer()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()
restart()51   void   restart() { _start_time = std::clock(); } // post: elapsed()==0
elapsed() const52   double elapsed() const                  // return elapsed time in seconds
53     { return  double(std::clock() - _start_time) / CLOCKS_PER_SEC; }
54 
elapsed_max() const55   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 
elapsed_min() const63   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
73