Subject: Ab initio computational time.

From: Laurence Lavelle <[email-masked]>
Date: Wed, 03 Dec 1997 18:06:20 -0800

Hi,

Not much of a summary as I received one response to my initial posting,
which is listed below. Thanks to Dr. László JICSINSZKY for his 
comments.

Laurence Lavelle

Date: Thu, 27 Nov 1997 21:28:42 -0800

To: [email-masked], [email-masked]

From: Laurence Lavelle <<[email-masked]>

Subject: Ab initio computational time. 

Hi all,

Happy Thanksgiving to those in USA.

I would very much appreciate any estimates (hrs) on the ab initio
computational time of the following system:

single point calculation, 731 basis functions, UHF, MP2, direct SCF

<underline>Hardware:</underline> Dual pentium 200MHz, 256K external
cache, 192MB RAM

<underline>OS:</underline> Windows NT Workstation 4.0 SP3.

<underline>Computational package:</underline> HyperChem 5.02

Although NT uses SMP, HyperChem is not a multithread application so the
"computational system" is a single pentium 200MHz.

I look forward to hearing from you.

Laurence Lavelle

<<<<<<<<

>Date: Mon, 1 Dec 1997 10:26:46 -0500

>From: "CYCLOLAB R&D Lab." <<[email-masked]>

>Subject: Ab initio computational time.

>Sender: "CYCLOLAB R&D Lab." <<[email-masked]>

>To: Laurence Lavelle <<[email-masked]>

>Content-Disposition: inline

>Hi Laurence,

>>single point calculation, 731 basis functions, UHF, MP2, direct SCF 

> Once I've tried to perform an ab initio single point calculation on

>alfa-cyclodextrin (C36H60O30. 390 basis function with STO-3G, direct
scf,

>grad, P100, HC 4.5). It takes about two weeks, but though the
calculation

>did not finish, because some hw errors (the cooler of CPU went wrong),
I

>was very close to the final step.

> The computation time increases in second order, that means, e.g. in 
my

>computer the calculation on your molecule on bases like above would take
~4

>times more than in case of alpha-cyclodextrin (8 weeks). The UHF+MP2
about

>duplicates the calculation time, i.e. -> ~16 weeks. You are using a
P200

>machine, which approximately halves the calculation time comparing with
my

>machine (->~8 weeks), under Win'95. The HC runs ~70 % speed of HC4.5,
that

>means, your time increases with about three weeks (->11 weeks). Some

>slowing factors are within NT4 (about 60 % slower than Win'95 with a
native

>[32bit] application), i. e. my opinion is that your calculation takes
at

>least 10 weeks but not more than 20 weeks.

> Not so inspiring.

> I would propose a solution: cut smaller parts your molecule. In that
case

>you may calculate an approximative result, but much more faster (e.g.
you

>may save dielectric integrals, if you have a large HD. As far as I
know,

>the NT can handle larger than 2 GB HD partitions). Otherwise, I do not
know

>any ab initio calculations such a big molecule. It is enough large for
a

>Cray machine, as well.

> Regards, Laszlo

>-----------------------------------------------------------

>Dr. László JICSINSZKY

>Head of Synth. Dept.

>CYCLOLAB R&D Lab. Ltd.

>H-1525 Budapest, P.O. Box: 435

>XI. Dombóvári út 5-7

>email: [email-masked]

>Tel./Fax: (36-1)-206-51-36 or (36-1)-206-51-37

>-----------------------------------------------------------

<center>

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

Laurence Lavelle, Ph.D.

University of California Los Angeles

Molecular Biology Institute, and Department of Chemistry & Biochemistry 

Laboratory of Structural Biology & Molecular Medicine

Los Angeles, CA 90095-1570, USA

Email:[email-masked]

Phone (Lab): (310) 206-8270

Phone (Office): (310) 825-2083

Fax: (310) 267-1957

http://www.doe-mbi.ucla.edu/people/lavelle/lavelle.html

""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

It will be a great day when schools have all the money they need,

and the military has bake day sales.

In nature's infinite book of secrecy

A little I can read.

</center>