Subject: Gaussian92 on 486 summary

From: Jeremy R Greenwood <[email-masked]>
Date: Tue, 27 Sep 1994 11:09:58 +1000 (EST)

In response to my query regarding run times and memory requirements for
running Gaussian92 on a 486, I received the following replies:

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From: [email-masked]
Subject:  CCL:Gaussian '92 on a 486 -Reply

Hi Jeremy,

Last month I have installed G92 for Windows on my 486/66MHz with 16MB internal
memory and so far I have only tried to do some normal and transition
state optimization jobs on chloro-methanes/ethanes. But run-times are rather lengthy
I'm afraid. For tetra-chloromethane one SCF at the HF/6-31+G(d) level took over 5
hours (about 260 gaussians). Using over 12 heavy atoms will take days I think.

I have 200Mbyte of space on my hard disk but I suppose less will also do.

I am very interested in the reactions you receive, because I am also still figuring out
what will be possible in terms of system size. 
Please summarize to the net or to me

Thanks in advance,

Emiel Rorije   /    [email-masked]   /   [email-masked]
Laboratory for Ecotoxicology
National Institute of Public Health and Environmental Protection
The Netherlands.

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From: [email-masked] (Danne R Rasmussen)
Subject: Re: Gaussian '92 on a 486
Status: OR

Jeremy,

        How is it all going?  I saw your CCL posting and thought I'd drop
you a little line.  I think for a start that turbomol would be better for
running HF and MP2 jobs than GAUSSIAN.  We have the source for turbomol so
you could install a public domain unix (say linux) on your 486/Pentium? and
try to compile turbomol under that system (shouldn't be too hard to get up
and running).

        As for the amount of disk turbomol again is much more efficient
than GAUSSIAN at running semidirect/conventional MP2.  Fulldirect MP2 uses
very little disk but needs heaps of core memory (more expensive) and in
general is slower (because you have to recompute the integrals all the
time) except on vector machines like the vp (where the time to compute the
integrals is negligible).  As you know G92's semidirect MP2 is tunable as
to how much disk you need for optimisations but fixed for frequencies
(unless you do them numerically).  I find that for C13H20 optimisations at
MP2/6-31G* with G92 in high symmetry (D2) I need 2Gb of disk (in order to
do the MP2 in 3 passes).  This is really pushing the limits of a
workstation (RS/6000 m355 with 64Mb).  For the slightly smaller job C9H12
MP2/6-31G* in lower symmetry (C2) I needed only 1Gb of disk to get through
the MP2 in a single pass and it ran in only 20Mb of core.

        Hope this helps,

______________________________________________________________________________
Danne R Rasmussen                                       Phone:  +61 6 249-3771
Research School of Chemistry                                    +61 6 249-2018
Australian National University
Canberra, ACT   0200                                      Fax:  +61 6 249-0750
AUSTRALIA                                       E-mail: [email-masked]

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From: [email-masked] (Csonka Gabor)
Subject: Re:  CCL:Gaussian '92 on a 486

Dear Jeremy Greenwood,

my estimation for a 20 atom molecule with  MP2/6-31g* level of theory
is from 2 to 6 months on a 486/33 MHz. You need at lest 2 GB disk
for that to run confortably. Symmetry can help a lot the 2 month is
valid if you have some symmetry. I did MP2/6-31G* geometry optimization
for 24 atoms (11 heavy) with c3 symmetry on SGI Iris 4000SC 100MHz.
One step took about 6 days. PC is 10 to 15 times slower with g92.
Maybe a 100 MHz pentium can do the job, but as far as I know
g92 is not optimized for pentium, so I expect a rather moderate
performance increase. The MP2 uses lot of disk I/O which are slow on PC-s.
You need the fastest available disk. If you add all the cost
you will easily reach the price of a unix workstation. 
----------------------------------------------------------
Gabor I. Csonka		        Budapest University of Technology
Tel/FAX: (361) 18.12.177	Inorganic Chemistry Dept. Ch. Bldg
[email-masked] 	H-1111, Bp. Szent Gellert ter 4
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From: "Gregory L. Durst - DowElanco R&D" <[email-masked]>
Subject: RE:CCL:Gaussian '92 on a 486

Jeremy,
I would recommend you look at the book "Exploring Chemistry with Electronic
Structure Methods: A Guide to Using Gaussian", by JB Foresman & A Frisch, 
Gaussian Inc., 1993. It's $35, (well...last summer it was $35) and has some 
timings for the test suite of molecules on a Multiflow TRACE 14/300 computer 
with 64 MB RAM. At the bottom of the table they say that a 50 MHz 486 should 
take roughly 10-15 times longer.
(eg. Ethylene geom optimization, tutorial #009, used 3-21G basis set, and
took 2 min 17.7 secs on the TRACE, so figure 20-30 minutes on the 486.)
Hope this helps!
Greg
+-----------------------------------------------------------------------+
|   Gregory L. Durst                   Computational Chemistry          |
|   phone:   317/337-3413              DowElanco  R&D                   |
|   email:   [email-masked]      9330 Zionsville Rd.  Bldg 306/D2 |
|                                      Indianapolis, IN  46268   USA    |
+-----------------------------------------------------------------------+

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From: [email-masked]
Subject: CCL:Gaussian '92 on a 486 (fwd)

Jeremy:
I think that you might be a bit too ambitious here.  While I cannot
speak to the anticipated execute time for a 20 atom mp2/6-31g*
run, I can comment some on the required disk space: You are contemplating
calculations involving on the order of 200 basis functions.  The disk
needed for just the mp2 energy is on the order of 200^3=8e6 64 bit words; 
or about 64 Mbytes.  If you wish to do geometry optimizations, more disk
will be needed, and if you need frequencies at this level (heaven forbid!)
you may need on the order of 10 Gbytes of disk.  I am not sure that it
is possible to put this much storage on a PC, but even if it were, the
bandwidth for getting to/from the disk will be much too slow.  My
guess is that the i/o time will increase the computed time (probably
measured in days) by a factor of 10 or so.  

The PC version of g92 is probably best suited as a teaching tool, at
which it is very good, rather than as production research tool.

Good luck...
Steve Williams
chemistry, asu, boone, nc, usa

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From: "Sophie CREUZET ((33-1-40-01-56-39))" <[email-masked]>

I have no experience concerning Gaussian '92 on a 486, working mainly on
Supercomputer, but concerning the level of theory, I would not recommand
the use of MP2 with a 6-31G* basis set. If you want to use MP2 you should put
polarization functions on all atoms (i.e. 6-31G** in this case) unless
your results might be even worse than at the 6-31G level.