Subject: Re: HyperChem

From: [email-masked] (Thomas Slee)
Date: Thu, 2 Jun 1994 14:06:54 -0400

Dear CCL readers,

Declaration of interest: I work for Hypercube, developers of HyperChem.

It seems appropriate, with the current round of discussion of
HyperChem experiences going on, that I do two things:
1.  Avoid unnecessary interference in this discussion, as an
    interested party, but:
2.  Update and correct purely factual observations where necessary.
With this in mind, here is an update on Dr. Bliznyuk's comments, which
referred to Release 3 of HyperChem.  The current release is Release 4.

|
| Last year we had a chance to try HyperChem v 3.0. This program has
| good graphics and very good molecular editor/builder. 
|

	Thank you! (couldn't resist leaving it in there).

|
| Unfortunately, it is very slow, at least for semiempirical calculations. 
| For example, it takes 35 min. on 486DX2 50MHz with 16 MB of memory to do 
| MNDO 1SCF and gradients for C60 (compare to Sibiq - 10 min.). 
|

Dr. Bliznyuk will be happy to know we have significantly improved the
performance of this kind of calculation.

Calculations on a 486DX2 50 MHz with 20MB of memory show the following:
(C_60, AM1, SCF convergence to 1e-4 kcal/mol, + gradient evaluation),

        HyperChem Release 3.    33 min (my calculation)
        HyperChem Release 3.    35 min (Dr. Bliznyuk's calculation)
        Sibiq                   10 min (Dr. Bliznyuk's calculation)
        HyperChem Release 4.    7 min 30 sec. (my calculation.)

C_60 is a very memory-intensive system for HyperChem's analytical 
energy derivative computation.  Hence some of this time is taken
up with disk access (I suspect this is the cause of the 2 min
discrepancy between the Release 3 calculations).  For a system with
the same number of atomic orbitals but more hydrogen atoms (C_40H_80)
the memory requirements go down by 3Mb and the Release 4 time for
SCF plus gradient becomes 6 min 30 sec.  I have no data from Sibiq
for this system, as we don't have that program in house.

We did do a couple of small calculations checking a demo disk (small 
molecules only) of Sibiq against HyperChem and the results came out 
for C6H10 that HyperChem takes 3.0 seconds for this small system, while 
Sibiq takes 5.3 sec.  Please do not take this as a claim for superior 
performance overall for HyperChem compared to Sibiq; it is quite possible
that in other calculations Sibiq would be faster than HyperChem.  It 
is certainly not my intent to compare the two programs, merely to show 
that the timings I give are consistent with Dr. Bliznyuk's values, and 
that we have indeed speeded up the program significantly.

On the subject of timings, we have carried out test calculations 
similar to the above on a couple of different platforms comparing HyperChem 
and MOPAC 6.  Depending on molecule and compiler, sometimes MOPAC is faster, 
sometimes HyperChem. 

The other point on which I wish to reassure CCL readers is the implicit
suggestion in an earlier posting that HyperChem may give results
inconsistent with MOPAC or AMPAC for NDDO-type calculations.
Our formal testing of HyperChem involves over 1,000 separate calculations.
This testing, and two years of customer experience with the program, have yet
to show a case where HyperChem and MOPAC produce different results
for the same calculation.  The insignificant differences mentioned by 
Antti Poso come, we believe, from MOPAC 6's slightly inconsistent values 
for conversion factors in different parts of the program.

	Tom Slee

-- 
Tom Slee, Hypercube Inc., 419 Phillip St., Waterloo, Ont., Canada, N2L 3X2
E-Mail: [email-masked],  Tel. (519)725-4040,  Fax. (519)725-5193.