Subject: Perf. of Alpha vs. R10k

From: <[email-masked]>
Date: Thu, 18 Sep 1997 13:09:45 +0200 (MDT)

Hi Netters.

I have recently started working in a group where DEC Alpha machine and SGIs
are used. People tell me that the Alpha's are 2 to 6 times faster
than the SGIs. However when I try it on my MD code, I find that the
R10k (Indigo) is about 30 % faster than a DEC Alpha @ 400 MHz.

I use the following compile options:
(SGI) -n32 -r10000 -mips4 -O3 -OPT:IEEE_arithmetic=3 -SWP:loop_overhead \
       -INLINE:=ON -LNO:opt=1 -LNO:ou_further=3 \
       -OPT:Olimit=0:roundoff=3:alias=typed \
       -GCM:aggressive_speculation -GCM:array_speculation \
       -OPT:cray_ivdep=TRUE 
(DEC)  -fast -O5 -inline speed -tune host -math_library fast -non_shared \
	-speculate all -unroll 2
	
Timings for my MD code are about 23 s on SGI vs 31 s on DEC.

Can anyone point me to compiler options or tools on the Alpha to increase
performance, or should I conclude that the high performance of the Alpha
is just a marketing hype.

Thanks, David.
________________________________________________________________________
Dr. Ir. David van der Spoel	Biomedical center, Dept. of Biochemistry
s-mail:	Husargatan 3, Box 576, 75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
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