Subject: re: Perf. of Alpha vs. R10k

From: "Chuck (aka chazix), 508-493-1399 (DTN 223-1399)" <[email-masked]>
Date: Tue, 23 Sep 97 15:43:14 EDT

Greetings,

I don't follow this forum, but a colleague forwarded Dr. van der Spoel's
notes.  Was the Fortran code that was posted (routine FORLJC, with a test
harness) the same code that produced a timing of 31 seconds on a 400MHz
Alpha?

On my system, it runs in less than 4 seconds, either with the options
Dr. van der Spoel gave, or with just "f90 -fast -tune host -non_shared".

(The simpler command is a wee bit better for the given code on my system,
mostly because the rather speculative optimizations at the -O5 level are not
attempted.  As the man page suggests, it's best to test -O5 to make sure it's
an improvement.  That's why -O4 is the default.)

I assume from the cache size that Dr. van der Spoel's system is an
AlphaStation 500/400.  My system is an AlphaServer 4100 5/400, which has
a 4MB backup cache.  Both use an EV5 generation Alpha chip at the same clock
speed, so the bcache and main memory system are the main differences that
would affect the given code.  But I don't think that the larger bcache could
account for the near order of magnitude difference between Dr. van der Spoel's
timings and mine.  Either I'm timing something different, or some other
interesting factor remains hidden.

Regards,
Chuck Schneider
Digital High Performance Computing Expertise Center
Maynard, Massachusetts

(e-mail me directly for best response)

---

From: [email-masked] (Dr. Daniel L. Severance)
Date: Wed, 24 Sep 1997 09:36:30 -0700

On Sep 23,  3:43pm, Chuck (aka chazix), 508-493-1399 (DTN 223-1399) wrote:
> Subject: CCL:re: Perf. of Alpha vs. R10k
>

   Hi,

    It runs in 1.3 seconds on an Indigo2 R10K machine (1 MB cache) with -Ofast,
or 1.8 seconds using the compile options listed.  His 30 second time was
presumably for the whole program.  It sounds like the R10K SGI machines are
still significantly faster than the alpha machines even with the test code.
    The R10K chips were a BIG jump in performance over the previous R4xxx
series
from SGI, so this isn't that far from possibility.
    Take care,
       Dan

-- 
Dr. Daniel L. Severance     [email-masked]       *****************
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