Subject: "Big"jobs on Quantum Chemsitry in Linux plataform

From: Max <[email-masked]>
Date: Thu, 22 Feb 2001 14:06:17 -0600

Hi CCL'ers

IIn the group I'm working on, we have been testing QC computation on
intel arq. computers. Here is a resume of what we have found:

We made computations on several speeds, 400, 500, and 800 MHz PIII
computers, and we observe a nice good comparison with an SGI Octane R1K
for small jobs, say HF 150 functions, but there is a lot of problem to
run a complete job for that kind of job if we want the MP2

The tests include gaussian98, gamess USA, and NWchem4 in the 800MHz
machine, using RedHat 6.2.

The problem with the jobs is that frecuently there is a "nan" result on
the MP2-energy, or the somewhere elseearlier in the computation, and the
job doen't finish well-behaved.

The 800MHz machine has 1GB in RAM, and enough disk to perform the
computation, and it does perform it complete, but with this kind of
output in gaussian, as an example

 5,148.878,0\H,25,1.085054,23,110.165,17,-185.198,0\H,25,1.086148,23,11
 0.493,17,54.162,0\H,25,1.086712,23,109.841,17,-65.099,0\\Version=x86-L
 inux-G98RevA.7\HF=-570.9295579\MP2=nan\RMSD=7.238e-10\PG=C01 [X(C8H16N
 2O2)]\\@

The same kind of results comes from Gamess, or NWchem. Most of the
times, the "nan" is in the SCF optimization cycle :

Cycle   7  Pass 1  IDiag 1:
 RMSU=  9.43D-07    CP:  1.00D+00  1.24D+00
 E=-0.105688403862277D+04 Delta-E=       -0.000000057351
 DIIS: error= 1.53D-05 at cycle   3.
 Coeff: 0.486D+00-0.688D-02-0.148D+01
 RMSDP=1.60D-06 MaxDP=4.70D-05

 Cycle   8  Pass 1  IDiag 1:
 RMSU=  4.05D-07    CP:  1.00D+00  1.86D+00  1.69D+00
 E=                  -nan Delta-E=                  -nan
 DIIS: error=      nan at cycle   4.
 RMSDP=2.65D-01 MaxDP=1.80D+01

I would like to know if this sames behavoir is observed in any other
group using linux on Intel arquitecture.

Please Send any comment to [email-masked], since i'm still waiting
my confirmation to the CCL subscription.

Max
p.s. sorry for my english

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