From:	DERMOT BROUGHAM <Dermot.Brougham \\at// dcu.ie>
Date:	Mon, 24 Jan 2000 09:00:36 +0000 (GMT)
Subject:	Summary: PC or UNIX, G98 or Titan

     Dear CCLers,
     I posted the following question quite some time ago, apologies for my
     slowness in sending this summary.
                   Dermot
     
     The question was:
     >I have secured some (moderate) funding to get some hardware and software
     >for QC calculations. I can now go one of several routes, though it is
     >difficult to work out which is better (note there is a site licence here
     >for G98 on UNIX).
     >
     >1. A UNIX box running G98
     >2. A PC running G98 under LINUX
     >3. A PC running TITAN
     >4. A combnation of 2 & 3
     >
     >My first question is which will run quicker given that I will be doing
     >fairly large MP2 & B3LYP calculations and have the same sum to spend
     >whatever route I go.
     >
     >
     >My second question(s) (if I may) is about Titan:
     >1. Does it have a big library of basis sets and can you include basis sets
     >from elsewhere in the input (eg for Ru)?
     >2. Is it recognised, i.e. would I have any trouble publishing results from
     >it?
     >3. I am told the interface is good for both input and visualisation, is
     >this generally accaepted?
     >4. I presume geometry optimization will work on cartesian coordinates and
     >that it can transform to redundant internal coordinates. Can I input in
     >z-matrix format too?
     
     I quickly realised I couldn't run TITAN on PC with LINUX, I should
     have said Jaguar (which is the same code but without the nice windows
     front end of TITAN).
     
     
     The replies included:
     ******************************************************************
     Most flexible would be a PC under Linux, running G98 and, if you could
     afford the additional license, Jaguar from Schroedinger.  That would
     give you the compute functionality, if not the pretty front-end, of
     the Titan solution.
     
     According to Wavefunc's docs, and both their and Schroedinger's web
     pages, Titan is Wavefunction's Spartan front-end on top of
     Schroedinger's Jaguar PS-GVB back-end.   So, the results should be
     acceptable, since it's a known program (jaguar) doing the
     computations, and according to messages in the CCL archive, it's about
     a factor of 10 faster than its (nameless) competitors.
     
     Personally, I prefer the Unix solution, but that's because of being
     familiar with the environment, and for G98 at least, the source-code
     being available, meaning that as better processors, etc, come along,
     you can recompile, tune, and optimize.  It also lowers your chances of
     an OS revision breaking a pre-compiled executable, and leaving you
     stranded until the company builds a new one.
     
     -fred
     
     ******************************************************************
     According to published results Jaguar is found to be 5 to 10 times
     faster as G98 when doing large compuational tasks esp. MPx or DFT. As
     Jaguar is integrated fully into Titan. This product seems to be a
     quite good combination in terms of speed, accuracy and good
     visualisation techniques.
     
     But there are two things which G98 handles better:
     1. There is no source code. You get a fully precompiled version of
     either Titan / or Jaguar.
     2. Not everything g98 does can be done with Jaguar like NMR
     calculations.
     
     Gaussian is the clear recognised standard in this field and you wont
     have any problems publishing results obtained from g98 calculations.
     
     So my recommendations are the following:
     1. A fast PC running NT with Titan and G98W or 2. A fast PC running
     Linux with g98 and Jaguar.
     
     
     Kind regards, Alex
     
     ******************************************************************
     
     I can't speak for Titan but my understanding was that it was a Windows
     product rather than Linux.  You could dual boot to get G98 under Linux
     and Titan under Windows. You can add a copy of GaussView for an
     interface to Gaussian.
     
     Gaussian can do all of 1) and 4). The GaussView interface would do
     both input and visualization.  Can't speak to performance comparisons
     as I have seen none for Titan.
     
     Douglas J. Fox
     Director of Technical Support
     help()at()gaussian.com
     
     ******************************************************************
     
     With a moderate budget, I would suggest a combination hardware-software
     solution from Parallel Quantum Solutions. It is a small company of quantum
     chemistry specialists. They sell 4-16 processor PCs running Linux with
     already-optimized parallelized quantum software installed. Their software
     will read and run G98 input files. They are very fast on MP2 and DFT.
     I have bought and used a system of theirs and I am happy with it.
     See their web page at http://www.pqs-chem.com/
     Best wishes, and I have no commercial interest in the company,
     Brian Teppen
     ******************************************************************
     
     
     I have spoken to Parallel Quantum systems and some of their satisfied
     customers, it does seem like a good option and may be what I do in the
     end.
               Dermot




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