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Path: utzoo!watmath!clyde!cbatt!ihnp4!houxm!homxb!gemini
From: gemini@homxb.UUCP
Newsgroups: comp.arch,comp.sys.misc
Subject: Re: 01/31/87 Dhrystone Results and Source
Message-ID: <2366@homxb.UUCP>
Date: Sat, 7-Feb-87 08:08:10 EST
Article-I.D.: homxb.2366
Posted: Sat Feb  7 08:08:10 1987
Date-Received: Sun, 8-Feb-87 06:28:44 EST
References: <2348@homxb.UUCP> <15203@onfcanim.UUCP> <293@ames.UUCP>
Organization: PC Research, Inc.
Lines: 40
Keywords: Benchmark, C, performance measurement
Summary: Read the instructions
Xref: watmath comp.arch:302 comp.sys.misc:325

>From: dave@onfcanim.UUCP (Dave Martindale)
>Subject: Re: 01/31/87 Dhrystone Results and Source
>
>Does it bother anyone else that the dhrystone benchmark is
>sometimes (if TIME instead of TIMES is used) based on execution
>time of a small number of seconds, measured to the nearest second?
>
>Many of the faster machines execute the benchmark in 10 seconds or less,
>giving a result that may have +- 10% error.  Doesn't it then seem silly
>to quote "dhrystones" as 4-figure numbers?

The TIME define is only for use when a machine doesn't have TIMES, which
isn't many machines (mostly non-UNIX ones).  The instructions say to
use 500000 loops (instead of 50000) for fast machines.  And the report
of the elapsed time, in whole seconds, is just for the purpose of
determining when you have a 'fast' machine on your hands.  The actual
calculation of the figure of merit is done using the granularity
of the TIMES (or TIME) system call.

If this program didn't have to run on so many different OS's, I'd
consider rummaging around and configuring it for the environment.
But since it has to run on DOS, UNIX, VMS, ad nauseum, it'll just
have to be up to the intelligence of the benchmarker to follow the
instructions.

Besides, anybody who quibbles over a 10% difference isn't looking
at the whole picture when selecting a machine.  Dhrystones just
get you looking at the right performance arena.  Other factors
(software, support, migration path, etc.) will get you to the
final decision.

Hypothetical discussion:
Mgr:	"the VAX 8600 and IBM 4381-2 turn about 6000 'stones,
	which should we buy?"
MISmgr:	"Well, i've got IBM stock, get the IBM"
Engin:	"Well, we have 4 zillion lines of code for the 11/780, lets
	get the 8600".

Rick Richardson, PC Research, Inc. (201) 922-1134, (201) 834-1378 @ AT&T-CP
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