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From: kgregory@bbn.COM (Keith D. Gregory)
Newsgroups: comp.lang.c
Subject: Re: Dhrystones
Message-ID: <5096@ccv.bbn.COM>
Date: Thu, 3-Dec-87 10:28:21 EST
Article-I.D.: ccv.5096
Posted: Thu Dec  3 10:28:21 1987
Date-Received: Mon, 7-Dec-87 02:19:34 EST
References: <3368@rosevax.Rosemount.COM>
Reply-To: kgregory@ccv.bbn.com.BBN.COM (Keith D. Gregory)
Organization: Bolt Beranek and Newman Inc., Cambdridge MA
Lines: 29
Keywords: C, performance, useful
Summary: Here we go . . .

In article <3368@rosevax.Rosemount.COM> richw@rosevax.Rosemount.COM (Rich Wagenknecht) writes:
>Could somemone tell me what a 'Dhrystone' (<-sp.?) is?
>Why is it used so often to evaluate compiler performance?
>Is it a good overall indicator of compiler peformance?


Well, we all know that benchmarks are invalid :-)

The dhrystone benchmark produces a number which lets you know how efficiently
your compiler/computer can perform integer operations (as opposed to Whetstone,
which is FP, and yes, I know that the compiler doesn't perform anything except
a compilation :-)

As I see things, there are two uses for Dhrystone:

1 - Compare different compilers for a given machine.  I find this to be very
    useful - although there are certainly many factors contributing to the
    efficiency of compiled code, I've found that Dhrystone figures give a
    fairly accurate comparison of two compilers (as I see it, if a compiler
    writer makes efficient integer procesing code, the system calls will
    probably be efficient too).

2 - Having a number to hang your hat on.
    Let's face it, when I say that my 20MHz 386, running Xenix-386 can turn
    4800 dhrystones/second (and it can :-), that's bound to impress the hexk
    out of someone using a Mac which turns 1000. . .never mind that there
    are vast differences between the two machines/compilers ;-)

-kdg