I am a problem in writing portable code about computation time
estaimation at various CPU speed.
If a job can done in 2 second on PIII 733Mhz cpu
Can i estimate correctly how long it will take on PIII 900Ghz cpu??
> I am a problem in writing portable code about computation time
> estaimation at various CPU speed.
> If a job can done in 2 second on PIII 733Mhz cpu
> Can i estimate correctly how long it will take on PIII 900Ghz cpu??
Dr. Juergen Hannappel Office: W148 Phone: +49 228 73 2447 FAX +49 228 73 7869
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> > hi all,
> > I am a problem in writing portable code about computation time
> > estaimation at various CPU speed.
> > If a job can done in 2 second on PIII 733Mhz cpu
> > Can i estimate correctly how long it will take on PIII 900Ghz cpu??
> If you talk about the factor 900/733 = 1.227 in speed the estimation
> 1.6288 seconds should be fairly accurate. If you talk about a factor
Hmm, you sound like Scott Nudds ... at least you write "probably"! SCNRQuote:> 1277 which you would get with a 900 Giga-Hertz CPU i would assume that
> it would take longer than 1.6 milliseconds, but probably there will
> never be a 900GHz PIII.
Josef M?llers (Pinguinpfleger bei FSC)
If failure had no penalty success would not be a prize
-- T. Pratchett
At 900GHz, electrons will take three clock cycles to travel a millimeter.
Two ends of a centimeter-wide chip will be 30 clock cycles off! That'll
make circuit design a *...
Providenza & Boekelheide, Inc.
It is almost hopeless to obtain accurate estimates without doing a careful
modeling of the program and the hardware. For some programs the best estimate
would be 2 seconds, and not 733/900*2 seconds. For other programs the latter
would be better. For some hardware, the 900 MHz CPU might actually take
LONGER than 2 seconds (because of some other bottleneck not present in the
700 MHz hardware).
For example, time memcpy(). For small data blocks it will track accurately
the CPU clock speed (because all memory remains in cache during the timing).
For very large data blocks it will track _MEMORY_ clock speed (which is
presumably the same for the two CPUs), because the cache is thrashed by the
copy. Intermediate-sized blocks will be somewhere in between. This ignores the
fact that simple timing may not really time the entire operation (i.e. it may
only time the cache->cache copy, or at most the memory(->cache)->cache copy,
and not the later cache cast-outs to physical memory).
Trying to compare a PIII to a PIV or an Athlon is difficult (at best). Trying
to compare them to a PowerPC is hopeless (for a given clock speed, a PowerPC
6400 can be vastly faster than a PIII...).
> If Moore's law continues to hold, just wait 15 years.
Does anyone benchmarked run-time size of the Apache 2.0 HTTPD web
server on FreeBSD yet ?
I want to have an idea of how big the server can run up to.