Re: [boost] Re: date_time high resolution clock for Win32

From: Aaron W. LaFramboise (aaronrabiddog51_at_[hidden])
Date: 2004-05-18 21:12:04

Reid Sweatman wrote:

>Hardware is definitely involved, and it makes any method based on the Time
>Stamp Counter not nearly as accurate as you might think.  It's all been
>hashed out here before, so rather than repeat it all, I'll just give you the
>reference.  Look back through the Boost Archives for 1999 for a thread
>called "timer classes" with my name and that of Andy Glew associated with
>it, and you'll find some very interesting information (mainly from Andy, who
>was involved with the silicon design).  
>
>Reid Sweatman
>  
>
I found the thread at 
http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/boost/1137286 .  
It is very informative; thank you for the information.

I also found an interesting URL by someone who has done some similar 
research on timing in Windows, 
http://www.wideman-one.com/gw/tech/dataacq/wintiming.htm.  
Unfortunately, most of this is largely inapplicable in Boost.

It still seems to me that, despite its flaws, Intel's RDTSC combined 
with a time source assumed to be relatively reliable, such as the system 
clock, could yield a hybrid clock no worse than the primary system 
clock  The improvement in accuracy might benefit some applications, and 
probably wouldn't hurt.

In any case, there should be no illusions that any timer setup on 
Windows will meet hard real-time constraints.  In fact, even if there 
were some other timer available that did not share these problems, it is 
quite likely it would not offer realistically improved performance 
anyway due to Windows scheduling.  With whatever might be implemented 
for Boost, this needs to be documented.

Aaron W. LaFramboise