AMBER Archive (2004)

Subject: Re: AMBER: amber8 performance problem on Itanium II's

From: Andreas Svrcek-Seiler (svrci_at_tbi.univie.ac.at)
Date: Fri Sep 17 2004 - 03:52:53 CDT

Hi,
> I compiled amber8 (both the serial and REM versions) on the front node
> of an Itanium II (1.3 Ghz) cluster (SDSC). The intel compilers were used
> and the MKL libraries included. However, in comparison with amber7,
> amber8 runs about 4 times slower (~73 ps/day for a 3700 atom system using
> GB=1). The nonbonded cut-off = 12.0 A and used ntt=1 (just as in the
> amber7 runs).

...It's been quite some time since I dug around in egb.f from amber8,
so this is a semi-educated guess:-)
In amber8, there are -technically- two cutoffs, once for the
pairwise (inverse)
effective born radii contributions ("rgbmax", defaults to 25 A) and the
old "cut", for the usual non-bonded interactions. While cut=12 A might be
a bit small, it should be ok for rgbmax (even 9 A seems ok, and even
for nucleic acids). You simulation should be much faster by setting
e.g. rgbmax=12 A and cut= 15 A. See the manual, around page 99.
With the above settings, your MD should run faster than with amber7
(I hope).

I hope that helps,
good luck
Andreas

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