Returns Elapsed Number of Seconds

elapsed_seconds_c

@(@\newcommand{\W}[1]{ \; #1 \; } \newcommand{\R}[1]{ {\rm #1} } \newcommand{\B}[1]{ {\bf #1} } \newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} } \newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} } \newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} } \newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }@)@Returns Elapsed Number of Seconds
Syntax
s = elapsed_seconds()

Purpose
This routine is accurate to within .02 seconds It does not necessary work for time intervals that are greater than a day.

s
is a double equal to the number of seconds since the first call to elapsed_seconds.

Source Code

# if _MSC_VER
// ---------------------------------------------------------------------------
// Microsoft version of timer
# include <windows.h>
# include <cassert>
double elapsed_seconds(void)
{     static bool       first_  = true;
     static SYSTEMTIME st_;
     double hour, minute, second, milli, diff;
     SYSTEMTIME st;

     if( first_ )
     {     GetSystemTime(&st_);
          first_ = false;
          return 0.;
     }
     GetSystemTime(&st);

     hour   = (double) st.wHour         - (double) st_.wHour;
     minute = (double) st.wMinute       - (double) st_.wMinute;
     second = (double) st.wSecond       - (double) st_.wSecond;
     milli  = (double) st.wMilliseconds - (double) st_.wMilliseconds;

     diff   = 1e-3*milli + second + 60.*minute + 3600.*hour;
     if( diff < 0. )
          diff += 3600.*24.;
     assert( 0 <= diff && diff < 3600.*24. );

     return diff;
}
# else
// ---------------------------------------------------------------------------
// Unix version of timer
# include <sys/time.h>
double elapsed_seconds(void)
{     double sec, usec, diff;

     static bool first_ = true;
     static struct timeval tv_first;
     struct timeval        tv;
     if( first_ )
     {     gettimeofday(&tv_first, NULL);
          first_ = false;
          return 0.;
     }
     gettimeofday(&tv, NULL);
     assert( tv.tv_sec >= tv_first.tv_sec );

     sec  = (double)(tv.tv_sec -  tv_first.tv_sec);
     usec = (double)tv.tv_usec - (double)tv_first.tv_usec;
     diff = sec + 1e-6*usec;

     return diff;
}
# endif

Input File: test_more/compare_c/det_by_minor.c