Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!decwrl!jumbo!sclafani
From: sclafani@jumbo.dec.com (Michael Sclafani)
Newsgroups: comp.arch
Subject: Re: i860 Dhrystones
Summary: ommitted commentary is supplied
Keywords: i860 N10 Floating Point Dhrystones
Message-ID: <13641@jumbo.dec.com>
Date: 21 Mar 89 11:58:56 GMT
References: <39388@oliveb.olivetti.com> <15475@winchester.mips.COM> <95013@sun.Eng.Sun.COM>
Organization: DEC Systems Research Center, Palo Alto
Lines: 60

In article <95013@sun.Eng.Sun.COM>, cramer@sun.com (Sam Cramer) writes:
> Intel is not the only company to do this.  In the "DECstation 3100
> Performance Summary" distributed by DEC, the SINGLE integer benchmark shown
> is Dhrystone 2.1.  The text that accompanies these results contains no
> warning regarding the tendency of Dhrystone to overstate "real-world"
> integer performance.

From the DECstation 3100 Performance Summary / Part 2: Performance Details:

"Dhrystone is widely available, easy to run and is arguably the industry's
most popular Integer benchmark.  Unfortunately, the result obtained is
difficult to fairly compare amongst differing computing architectures and
is almost as sensitive to how the Dhrystone executable image is compiled
and linked as it is to the underlying processor speed.  The benchmark
documentation presents a set of ground rules for building and executing
Dhrystone.  Today, the accepted practice is to run the benchmark under any
environment you wish, as long as the environment is clearly described and
procedure inlining compiler optimization is not employed."

"Dhrystone does not seem to be the best indication of application
performance and is unusual in the following respects:

    + Unusually low dynamic nesting depth of function calls
    + Unusually low number of instuctions executed per function call
    + Large percentage of time spent in "strcpy" and "strcmp" routines,
      processing unusually large character strings
    + Character strings are typically alignable on a word boundary
    + Does not show how the use of shared libraries in real workload
      with multiple concurrent applications effects performance

Results for the Sun-3/60 are not reported because the data in
[Presentation on Benchmarks given at Sun User Group Conference, Dec 5-7,
1988 by Sun Microsystems, Inc.] uses compiler optimization level 4 which
employs procedure inlining.

We include the Dhrystone benchmark in our performance evaluation because
of its popularity, but warn against using it as the sole basis of
comparing system performance and of accepting results that don't
explicitly label how the benchmark was built and what optimizations were
exploited."

The performance summary and technical information are available via
anonymous ftp as compressed postscript from gatekeeper.dec.com in
~ftp/pub:
        ds3100_perf.1a.ps.Z
        ds3100_perf.1b.ps.Z
        ds3100_perf.2.ps.Z
        ds3100_tech.ps.Z

The summary includes Linpack, Whetstone, DR Labs CPU2, Livermore FORTRAN
Kernels, Dhrystone (2.1 AND 1.1), SPICE 2G6, Doduc, Dynamic Graphics TOP
Benchmark, and X11 graphics benchmarks.

Please note that I am not a Digital spokescritter, and any opinions
presented or errors committed are my own.
-- 

Michael Sclafani      \\\  Digital Equipment Corporation
sclafani@src.dec.com  \\\  Systems Research Center, Palo Alto, CA
(415) 854-7569 (home) \\\  (415) 853-2271 (work)