Subject: What makes Gaussian fast ?

From: [email-masked] (Teerakiat Kerdcharoen)
Date: Sat, 7 Jan 1995 07:27:17 +0100 (NFT)

Dear cyberchemists,
        I have posted this question a few days ago and I will summarize
the respond and have them posted to the net very soon.
        I just would like to add some informations here as requested by
some readers,

        - The review article which I read that Gaussian scale at N**2.7
not at N**4 is
          Richard A. Friesner (1991) "New Methods for Calculations on
          Large Molecules". Annu.Rev.Phys.Chem. 42: 341-67.

        - My system is Li(I)6(NH3). Dunning's DZP bases are being used
to perform Hartree-Fock calculation.
          The calculation is undertaken on IBM RS6000/550 and here is
the result:
   G92                 30 minutes 59.2 seconds         E = -344.688161
   GAMESS     4 hours  48 minutes                      E = -344.6887325
        
        One can see that the Gaussian is much faster than GAMESS. I have
tried running parallel GAMESS on a cluster and it is still slower than
non-parallel Gaussian.
        The total energy is in Hartree unit. One can see that Gaussian
speed up at the loss of accuracy but I am still satisfied because the
interaction energy (comparative energy) from both programs remain the
same (consistency).
                                                        take care,
                                                        Teerakiat