Subject: Parallel GAMESS benchmark

From: David Heisterberg <[email-masked]>
Date: Fri, 23 Sep 1994 19:57:08 -0400

As a point on the curve, these are times for running a modified
version of the GAMESS bench01 job -- an SCF calculation of sila-
cyclopropane with hydrogens replaced by fluorine and a TZP basis
set.  There are 201 basis functions and 42,057,076 2-e integrals
stored.  The systems are DEC Alpha 3000/300s running OSF/1 in
multi-user mode, with X and full networking running, but no other
users.  They are connected by FDDI and, currently, a Gigaswitch.

 #CPUs    cpu time      real time       efficiency (based on
        node 0 only                                 real time)

  1        1798 sec       2746 sec         1.00
  2         903           1415             0.97
  3         545            988             0.93
  4         442            823             0.83
  7         296            587             0.67
  8         267            562             0.61
 10         235            497             0.55

Geometry optimizations tend to scale up especially well due to the
time spent doing the integral derivatives.  MCSCF hasn't performed
as well for me.  But parallel post-scf is a fairly new development
and I think GAMESS is the only readily-available general purpose
code to attack this problem.

The fairly sharp drop in efficiency from 3 to 4 processors, and
from 7 to 8, is due to the tree-structured communication scheme,
which is at it's best with 2^n - 1 processors.
--
David J. Heisterberg ([email-masked])      Gee, it's so beautiful, I gotta
The Ohio Supercomputer Center           give somebody a sock in the jaw.
Columbus, Ohio                          -- Little Skippy (Percy Crosby)