Re: [boost] Re: Re: Re: Profiling Library suggestion

From: christopher diggins (cdiggins_at_[hidden])
Date: 2005-02-11 19:30:36

----- Original Message ----- 
From: "Preston A. Elder" <prez_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Friday, February 11, 2005 6:05 PM
Subject: [boost] Re: Re: Re: Profiling Library suggestion

> On Fri, 11 Feb 2005 17:41:16 -0500, Caleb Epstein wrote:
>
>> One subtle difference is that the current implementation uses
>> CPU-cycle timings (via std::clock or Win32 QueryPerformanceCounter)
>> and not wall-clock timings.  Using the xtime_get approach would give
>> you a wall-clock based timer which may not be what you want.
>
> I thought boost::timer (which the high_res_timer is modelled on) used wall
> clock values though.  This makes sense, because if you're using the timer
> to say "X task to Y seconds", you hardly want to tell them how much CPU
> time it spent on it.  It would look odd to use a timer that told the user
> X task took 20 seconds, when its been over a minute, it just got 20s CPU
> time.
>
> This is basically something that needs to be decided, though I suppose
> policies could take care of it (wall_clock or cpu_time for accumulation),
> but do you want to profile how long it took something to run, or how much
> time was spent doing it?  As you say, they're subtly different things.

I am confused. I don't see how measuring time intervals with either 
xtime_get() or QueryPerformanceCounter or std::clock() would differ apart 
from resolution and accuracy.

CD