Re: [boost] Low-level precision timer proposal

From: Jeff Garland (jeff_at_[hidden])
Date: 2006-05-15 12:03:12

Silex wrote:
> I found out that there's already
> <boost/date_time/microsec_time_clock.hpp>, but on windows it uses
> GetSystemTimeAsFileTime().
> 
> This raises a potential issue: I don't know if
> GetSystemTimeAsFileTime() works at millisecond resolution like
> QueryPerformanceCounter() does, and I don't know if
> QueryPerformanceCounter() returns some kind of epoch.. the docs are
> rather lowly-documented on this.
> 
> I also noticed that getimeofday() wasn't checked for failure in the
> current boost headers.
> 
> I also fell on a page which stated that "On Windows, clock() returns
> the nearest approximation to wall-clock time since the first call to
> this function, based on the Win32 function QueryPerformanceCounter().
> The resolution is typically better than one microsecond.". While I
> doubt it it might be interesting for our problem if it happen to be
> true.

Clocks are highly variable depending on the hardware, OS, etc.  QPC 
clocks have been discussed before, but honestly I think you'll get 90% 
of the what you can get with the current date-time clock.

> After the suggestions & having read the wiki I think we should indeed
> modifiy parts of date_time and template the timer class like
> mentionned. Should I try to give it a go ?

Sure -- I've uploaded some prototype code to that vault under 
date_time/new_timer.zip that I worked on at some point in the past.  It 
should get you going.  Please evolve it and send me issues.

Jeff