Re: [Boost-users] Boost.Date_Time - How to measure time elapsed?

I don't know it this helps, but I think it is getting system time to a reasonable precision on Windows and Linux platforms, I use two doubles representing the proleptic Julian day Number and the fraction of the day: #ifdef _MSC_VER struct __timeb64 timebuffer; struct tm *sysUTC = new tm; #if _MSC_VER < 1400 // Visual Studio 7.1 and earlier. _ftime64( &timebuffer ); sysUTC = _gmtime64( &timebuffer.time ); #else _ftime64_s( &timebuffer ); _gmtime64_s( sysUTC, &timebuffer.time ); #endif sec = sysUTC->tm_sec + double(timebuffer.millitm) / 1000.0; double sysDate = JulianDayNumber(sysUTC->tm_year+1900,(char)sysUTC->tm_mon+1,(char)sysUTC->tm_mday); double sysFoD = ToFoD(sysUTC->tm_hour,(char)sysUTC->tm_min,sec); delete sysUTC; #else struct timeval ltime; gettimeofday(<ime,NULL); // Obtain UTC from the computer. struct tm sysUTC; gmtime_r( <ime.tv_sec, &sysUTC ); sec = sysUTC.tm_sec+ltime.tv_usec/1000000.0; double sysDate = JulianDayNumber(sysUTC.tm_year+1900,(char)sysUTC.tm_mon+1,(char)sysUTC.tm_mday); double sysFoD = ToFoD(sysUTC.tm_hour,(char)sysUTC.tm_min,sec); #endif Andrew On Fri, Jul 25, 2008 at 6:57 PM, Nguyen Vu Hung wrote:

On Fri, Jul 25, 2008 at 5:29 PM, Bruno Lalande wrote:

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What platform is that?

A very common one: Linux 2.6 with GCC 4.1 or 4.2. The distribution is Kubuntu.

timer().elapsed_max() gives 2147.48 on this platform and indeed, elapsed() returns negative numbers above that time (before returning to 0).

I had thought about the possibility of making a policy-based version of boost::timer, with something like a "heart policy" that would define the way in which the time would be obtained and stored internally. There would be a portable one (the one of boost::timer currently), another one based on boost::date_time, and why not some platform-specific ones (QueryPerformanceCounter on windows for instance). But I never had the time to dig more :-(

I don't mean to hijack the thread but please let me share another way to use timer, with C, not C++ or boots. In the code, not only the time of one test, but average time, and its standard derivation are calculated so we will know how "close" is the average time.

My question: Is there any similar implementation in boost?

The code is as follows:

int count = 30; long long times[count];

for (i = 0; i < count; i++)　｛ time start; gettimeofday (&start, NULL); // do something gettimeofday (&end, NULL); long long time = ((end.tv_sec - start.tv_sec) * 1000000 + (end.tv_usec - start.tv_usec)); times[i] = time; } // and use it printf("mean: %f, stddev: %f\n", mean(times, 20), stddev(times, 20);

double variance (long long *x, int n) { double m = x[0]; double s = 0; int i; for (i = 0; i < n; i++) { double m_new = m + (x[i] - m) / (i + 1); s = s + (x[i] - m) * (x[i] - m_new); m = m_new; } return s / (n - 1); }

double mean (long long *x, int n) { double m = x[0]; int i; for (i = 0; i < n; i++) { m = m + (x[i] - m) / (i + 1); } return m; }

double stddev (long long *x, int n) { return sqrt (variance (x, n)); }

-- Best Regards, Nguyen Hung Vu ( Nguyễn Vũ Hưng ) vuhung16plus{remove}@gmail.dot.com , YIM: vuhung16 , Skype: vuhung16dg Japan through an eye of a gaijin: http://www.flickr.com/photos/vuhung/tags/fav/ _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

-- ___________________________________________ Andrew J. P. Maclean Centre for Autonomous Systems The Rose Street Building J04 The University of Sydney 2006 NSW AUSTRALIA Ph: +61 2 9351 3283 Fax: +61 2 9351 7474 URL: http://www.acfr.usyd.edu.au/ ___________________________________________