Subject: CPU time vs Total time on RS6000

From: Patrick Bultinck <[email-masked]>
Date: Wed, 4 Jan 1995 09:41:27 +0100 (MET)

Netters,

I have noticed a couple of times now that when I run GAMESS on an RS6000 
machine I get quite awful ratios of the CPU time versus the TOTAL time 
for ab initio calculations using GAMESS (conventional SCF, integral 
storage). Do other people have this 
problem too (I'm running only one job at a time, one window active so I'm 
not doing anything but the calcultion) ? Is this present with other 
programs too if implemented on RS6k ? Is this a typical RS6k problem ?
Last but certainly not least : Can I do something about it ???

Thanks for replies,

Send for a summary if you're interested in the replies,

Patrick Bultinck, University of Ghent, Belgium

---

From: "Gerald Loeffler" <[email-masked]>
Date: Wed, 4 Jan 1995 14:15:13 +0100

On Jan 4,  9:41am, Patrick Bultinck wrote:
> Subject: CCL:CPU time vs Total time on RS6000
> Netters,
>
>-- End of excerpt from Patrick Bultinck

Dear Patrick,

without knowing AIX to any noteworthy extent, I can tell you the following:

If you time your application (GAMESS) with time or timex you should at least
get:

	1) real time (i.e. wallclock time)
	2) user time (i.e. CPU time used for the non-kernel-portion of your
	   application, which usually is what you are interested in)
	3) system time (i.e. CPU time used for satisfying requests to the UNIX-
	   kernel made by your application).

The sum of user time and system time is the total CPU time spent on behalf of
your application.

If your application is doing CPU-intensive tasks (like GAMESS is, without any
doubt), then the system time should be negligable and the user time should
nearly be as high as the real time (given that you are essentially alone on the
machine).

If your system time on the other hand is unusually high - as seems to be the
case with you application - then the application generates many exception
conditions, like floating point exceptions, cache misses, thrashing, page
faults, ... . On the other hand, intensive disk I/O won't cause a high system
time, because the system time is a measure of CPU activity - and the CPU isn't
much involved in I/O.

	hope that helped,
	yours
	gerald

--
Gerald Loeffler
PhD student in Theoretical Biochemistry

Email: [email-masked]
Phone: +43 1 40480 612
Fax:   +43 1 4028525
Mail:  University of Vienna
       Institute for Theoretical Chemistry
       Theoretical Biochemistry Group
       Waehringerstrasse 17/Parterre
       A-1090 Wien, Austria

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