Subject: Re: CCL:Hypechem Hardware Resources

From: Laurence Lavelle <[email-masked]>
Date: Thu, 06 Nov 1997 16:19:47 -0800

<bigger>Hi C.F,

Your question does not state which OS, and if you intend to use other
software at the same time as HyperChem. I will assume (and recommend)
that you are using NT Workstation and no other (large) software.

HyperChem 5.02 is the fastest HyperCube offers for ab initio
calculations. There are however, faster ab initio packages.

HyperChem has options within ab initio that greatly reduce the RAM and
virtual memory requirements. So 64MB of RAM and 200MB virtual memory
would be fine for your calculations. To give you an example of what I
mean by greatly reduced memory requirements with respect to the
2e-integrals: 

For a system with 731 (=m) basis functions.

Not using direct SCF (more memory, less CPU time):

# 2e- integrals = 3.5 x 10^10 and memory required = 571 GB

But using direct SCF (less memory, more CPU time):

The # 2e- integrals = m^2 log m = 1.5 MB

So clearly you would use direct SCF.

However I should also inform you that: The original required memory was
571 GB which on using the (much more) computationally intensive direct
SCF was reduced to ~1.5 MB (depending on the 2e- integral cutoff point)
and finally HC actually limits the total 2e- integral storage to 256KB of
RAM, and if it is larger than 256KB it writes to HD. 

Although I have asked HyperCube why the 256KB RAM limitation, I have had
no reply.  

So you don't need lots of RAM and virtual memory, what you need is
<underline>fast </underline>RAM. In terms of HD's I recommend a fast
(7200-10000RPM), large (~8GB, because you always need storage space) with
0.5 to 1MB buffer. Or start with one 4GB (similar specs) and add another
HD when you need it.

Here comes the bad news. If you want these jobs (70 atoms, using
6311++G** with ~650 basis functions) to converge in two days there is no
PC (with HyperChem) available to do it. Which means you need a large
capital expenditure to buy some non-Intel/AMD/Cyrix  unix/NT machine
(e.g. Digital Alpha 600MHz workstation, etc).

</bigger><bigger>However things would be different if HyperChem was a
multi-threaded application. All the major vendors produce multi-CPU
machines (NCR, HP, SGI, Digital, etc.) not to mention that one can order
a multitude of inexpensive multi-CPU clones. In addition the strongest
HyperChem user base is the PC or PC-workstation/server with MS-Windows as
the OS. Windows NT (Workstation & Server) is one of the few OS's that
utilizes multi-CPU hardware. 

Some of your options are:

Spend 5 to 10 times more on a non-Intel unix/NT machine.

Wait for HyperCube to release a multi-threaded version of HyperChem.

**Buy a PC with a Pentium II, 300MHz processor with 512KB to 1MB L2 cache
and wait twice as long for the results.

**Best option.

Laurence Lavelle

</bigger>At 09:49 AM 11/5/97 -0500, you wrote:

>Hi everybody,

>I am planning to upgrade a machine with the intension to purchase 

>Hyperchem 05. I am interested to obtain highly accurate ab initio

>wavefunctions medium-sized organic molecules (C,O,N,H) at a RHF

>6-311++G**//6-31+G* level of theory).

>Such molecules would have approx 70 atoms (including H), and using

>6311++G** we are talking perhaps of 650 basis functions and perhaps
some

>1200 primitives.

>What sort of CPU, RAM, virtual memory, and HD space should I aim at if
I'd

>like such a job to converge within a few days?

>Thank you very much.

>C.Matta

>McMaster University,

>Hamilton, Ontario, Canada.

<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>