RE: [boost] Re: [function] timing trivia

From: Hurd, Matthew (hurdm_at_[hidden])
Date: 2004-02-12 19:14:43

> On Behalf Of Pavel Vozenilek
> Subject: [boost] Re: [function] timing trivia
> 
> 
> "Matthew Hurd" <matt_at_[hidden]> wrote
> 
> [snip boost::function benchmark info]
> 
> > Can't explain it.  Boost function can't be faster for the 10 million
> loop
> by
> > more than a millisecond.  I see none of this whacky behaviour with
> release
> > optimized code.
> >
> Can you post complete test code somewhere?
> 
> /Pavel

Probably small enough to post here... (12KB)  Open the .sln, compile and
run the "test" project and you should see something similar to:

This is an Intel P43.2 I'm running on now and I'm getting output like:

---------------------------------------------------------------------
quick time before overhead estimate= 393.5650855126686 nanoseconds
time including previous console output = 1.157412246893155 milliseconds
overhead estimate = 127.8459831920134 nanoseconds
quick time after overhead estimation = 95.25779139797076 nanoseconds
time including previous console output = 1.160907957159062 milliseconds
---------------------------------------------------------------------
                  new timer for checking static carry
---------------------------------------------------------------------
quick time -1.253391992078558 nanoseconds
quick time -5.013567968314233 nanoseconds
overhead estimate = 127.8459831920134 nanoseconds
quick time 2.506783984157143 nanoseconds
quick time -5.013567968314233 nanoseconds
---------------------------------------------------------------------
                  check timing jitter on a simple loop
---------------------------------------------------------------------
---------------------------------------------------------------------
             estimating indirect function call overhead
---------------------------------------------------------------------
---------------------------------------------------------------------
              boost function measurements
---------------------------------------------------------------------
median time = 250.698 microseconds
90% range size = 6.26696 nanoseconds
widest range size (max - min) = 149443 nanoseconds
minimum time = 250.695 microseconds
maximum time = 400.138 microseconds
50% range = (250.695, 250.701) microseconds
50% range size = 6.26696 nanoseconds
stop the optimiser eliding garbage = 3.33328e+017
stop the optimiser eliding garbage = 3.33328e+017
---------------------------------------------------------------------
              direct in-line
---------------------------------------------------------------------
median time = 250.691 microseconds
90% range size = 6.26696 nanoseconds
widest range size (max - min) = 29324.4 nanoseconds
minimum time = 250.688 microseconds
maximum time = 280.013 microseconds
50% range = (250.688, 250.692) microseconds
50% range size = 3.76018 nanoseconds
stop the optimiser eliding garbage = 3.33328e+017
stop the optimiser eliding garbage = 3.33328e+017
Press any key to continue . . .

You see here I look at the median time for boost function and
direct-inline and see only a 7 ns difference which is probably smaller
than I can truly measure I suspect...

At the top of looper.hpp there is 

        #define MAX_FN_LOOP  1e5

which controls the iterations in the timing loop.

If my hacked up untidy code is buggy or if you have some insight I would
love to hear about it.

Regards,

Matt Hurd
_______________________

Susquehanna Pacific P/L
hurdm_at_[hidden]
+61.2.8226.5029
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