execution timing and time(1)

[jec at iuvax.UUCP]

	On of the professors here at IU is trying to get accurate timings
on UNIX for user and system times.  The problem is that I can't figure out
a way to get accurate timings or explain the variations in timing that I
get from time(1).

	Could some one please fill me in on what could account for the
variations in timing?  The following is part of the message I received:

---------

The following timings were generated by repeated invokations of the script:
		|#
		|set NEW = /usr/local/bin/somecommand
		|time $NEW <<HERE
		|<some input>
		|HERE
all within an hour.  The results were
		-----------------------------------------
		|28.4u 3.3s 0:48 65% 96+695k 6+2io 52pf+0w
		|26.2u 2.9s 0:47 61% 96+670k 4+2io 3pf+0w
		|26.1u 2.7s 0:37 76% 96+674k 4+2io 3pf+0w
		|28.9u 3.1s 0:57 56% 96+688k 4+2io 3pf+0w
		|30.2u 3.4s 0:50 66% 96+685k 3+2io 3pf+0w
		|30.8u 3.5s 1:04 53% 96+699k 3+2io 3pf+0w
		|31.5u 4.2s 1:40 35% 95+675k 4+2io 3pf+0w
		|30.6u 4.4s 1:46 32% 96+657k 6+3io 3pf+0w
		|30.7u 3.2s 1:07 50% 96+673k 6+2io 3pf+0w
		|32.1u 3.6s 1:04 55% 96+691k 3+2io 3pf+0w
		|-----------------------------------------
Can you see any factors that would account for a twenty per-cent
variation in user-execution time?

We have similar results from MINOR variations of the object,
using older routines.  The effect seems to be related to
the size of load-image of a particular object.

Again, these are timings for IDENTICAL execution runs.

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