Line data    Source code

       1             : /**
       2             :  * @file gensvm_timer.c
       3             :  * @author G.J.J. van den Burg
       4             :  * @date 2014-01-07
       5             :  * @brief Utility functions relating to time
       6             :  *
       7             :  * @details
       8             :  * This file contains a simple function for calculating the time in seconds
       9             :  * elapsed between two Timer() calls.
      10             :  *
      11             :  * @copyright
      12             :  Copyright 2016, G.J.J. van den Burg.
      13             : 
      14             :  This file is part of GenSVM.
      15             : 
      16             :  GenSVM is free software: you can redistribute it and/or modify
      17             :  it under the terms of the GNU General Public License as published by
      18             :  the Free Software Foundation, either version 3 of the License, or
      19             :  (at your option) any later version.
      20             : 
      21             :  GenSVM is distributed in the hope that it will be useful,
      22             :  but WITHOUT ANY WARRANTY; without even the implied warranty of
      23             :  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
      24             :  GNU General Public License for more details.
      25             : 
      26             :  You should have received a copy of the GNU General Public License
      27             :  along with GenSVM. If not, see <http://www.gnu.org/licenses/>.
      28             : 
      29             :  */
      30             : 
      31             : #include "gensvm_timer.h"
      32             : 
      33             : /**
      34             :  * @brief Calculate the time between two time recordings
      35             :  *
      36             :  * @details
      37             :  * This function should be used with time recordings done by clock_gettime() 
      38             :  * using CLOCK_MONOTONIC_RAW. For this, the Timer() macro has been defined in 
      39             :  * the header file. Example usage:
      40             :  *
      41             :  * @code
      42             :  * struct timespec start, stop;
      43             :  * Timer(start);
      44             :  * // do some work //
      45             :  * Timer(stop);
      46             :  * double duration = gensvm_elapsed_time(&start, &stop);
      47             :  * @endcode
      48             :  *
      49             :  * This approach to measuring time has been chosen since CLOCK_MONOTONIC_RAW 
      50             :  * is guaranteed to be monotonically increasing, and is not affected by leap 
      51             :  * seconds or other changes to the system clock. It is therefore thread-safe 
      52             :  * and can be used to accurately measure time intervals.
      53             :  *
      54             :  * @param[in]   start   starting time
      55             :  * @param[in]   stop    end time
      56             :  * @returns             time elapsed in seconds
      57             :  */
      58           1 : double gensvm_elapsed_time(struct timespec *start, struct timespec *stop)
      59             : {
      60           1 :         double delta_s = stop->tv_sec - start->tv_sec;
      61           1 :         double delta_ns = stop->tv_nsec - start->tv_nsec;
      62           1 :         return delta_s + delta_ns * 1e-9;
      63             : }