1 // boost timer.hpp header file ---------------------------------------------//
3 // Copyright Beman Dawes 1994-99.
4 // See accompanying license for terms and conditions of use.
6 // See http://www.boost.org/libs/timer for documentation.
9 // 01 Apr 01 Modified to use new <boost/limits.hpp> header. (JMaddock)
10 // 12 Jan 01 Change to inline implementation to allow use without library
11 // builds. See docs for more rationale. (Beman Dawes)
12 // 25 Sep 99 elapsed_max() and elapsed_min() added (John Maddock)
13 // 16 Jul 99 Second beta
14 // 6 Jul 99 Initial boost version
16 #ifndef BOOST_TIMER_HPP
17 #define BOOST_TIMER_HPP
19 #include <boost/config.hpp>
21 #include <boost/limits.hpp>
23 # ifdef BOOST_NO_STDC_NAMESPACE
24 namespace std { using ::clock_t; using ::clock; }
30 // timer -------------------------------------------------------------------//
32 // A timer object measures elapsed time.
34 // It is recommended that implementations measure wall clock rather than CPU
35 // time since the intended use is performance measurement on systems where
36 // total elapsed time is more important than just process or CPU time.
38 // Warnings: The maximum measurable elapsed time may well be only 596.5+ hours
39 // due to implementation limitations. The accuracy of timings depends on the
40 // accuracy of timing information provided by the underlying platform, and
41 // this varies a great deal from platform to platform.
46 timer() { _start_time = std::clock(); } // postcondition: elapsed()==0
47 // timer( const timer& src ); // post: elapsed()==src.elapsed()
49 // timer& operator=( const timer& src ); // post: elapsed()==src.elapsed()
50 void restart() { _start_time = std::clock(); } // post: elapsed()==0
51 double elapsed() const // return elapsed time in seconds
52 { return double(std::clock() - _start_time) / CLOCKS_PER_SEC; }
54 double elapsed_max() const // return estimated maximum value for elapsed()
55 // Portability warning: elapsed_max() may return too high a value on systems
56 // where std::clock_t overflows or resets at surprising values.
58 return (double(std::numeric_limits<std::clock_t>::max())
59 - double(_start_time)) / double(CLOCKS_PER_SEC);
62 double elapsed_min() const // return minimum value for elapsed()
63 { return double(1)/double(CLOCKS_PER_SEC); }
66 std::clock_t _start_time;
71 #endif // BOOST_TIMER_HPP