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