Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!rutgers!apple!vsi1!wyse!mips!mash
From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: i860 Dhrystones
Keywords: i860 N10 Floating Point Dhrystones
Message-ID: <15074@winchester.mips.COM>
Date: 11 Mar 89 08:18:00 GMT
References: <654@cimcor.mn.org> <93088@sun.uucp> <701@pcrat.UUCP> <93452@sun.uucp>
Reply-To: mash@mips.COM (John Mashey)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 40

In article <93452@sun.uucp> garner@sun.UUCP (Robert Garner) writes:
.....
>The judgement so far is that the 22% improvement must be coming from
>the FORTRAN version.  As I've never seen a FORTRAN version of 
>Dhrystone, does anyone at Intel have the source that they could
>post on the net?  Or was the reference to the Fortan
>compiler a typo?  (The Performance brief remarks:
>"Dhrystone was developed in ADA by R. Weicker in 1984.
>Fortran and C versions of the benchmark are more commonly used.")

>It will be interesting to see how pointers and structures are handled.
>Also, which Fortran library routine was used to do the string copies?

If it is indeed true that this is no typo, it is fascinating,
as it is well-known that C's byte-by-byte copy can add 25-30% over
(for example) PASCAL, or anything that has fixed-length character strings.
(On an R3000, 34% of Dhrystone is in strcmp & strcpy.)
Of course it depends on what kind of code-generation is done, also,
i.e., in-line versus out-of-line.

In reading the Intel i860(TM) performacne document, it is interesting
to note that 7 benchmarks are presented:
Dhrystone 1.1 and 2.1, Stanford Integer, SP & DP Whetstone,
and FORTRAN and Coded LINPACK.

Of these, the document claims that Dhrystone was in FORTRAN,
and Stanford and LINPAK were simulated (with zero-wait-state memory;
this makes little difference to Stanford, as it mostly fits in the cache.)

That means, that in terms of published benchmarks that seem apples-to-apples
comparable, the sum total is:  SP & DP Whetstone.

On Feb 27, Green Hills announced it was shipping C and FORTRAN compilers
for the i860, so it does seem a little strange that C wouldn't have been
used.  Maybe it is a typo, and there's some other reason.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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