Subject: GAMESS (Aug-99 version) and MPI...

From: Guillermo Moyna <[email-masked]>
Date: Fri, 29 Oct 1999 16:32:04 -0700

Dear CCL,

I have been using GAMESS on SGI and LINUX boxes for a while now, and
I really like it. In the past, I worried only about the sequential
versions (in versions pre Aug-99), but now I am building a 16 node LINUX
cluster and have been pondering getting both the old (pre Aug-99) and
new version of GAMESS on it.

I ported the old version of GAMESS to use MPI instead of TCGMSG, and it
worked fine - Actually, it worked beautifully. Now, I got the new
version which uses sockets, and after tinkering around a bit, I also got
it to work. I did a comparison using the same input file between the old
(MPI) and new (SOCKETS) versions, and I found that the MPI version was
slightly faster (~ 8%) on the same network.

Now, I thought I could easily compile the new version (to take advantage
of the parallel MP2 calculations) using MPI instead of SCOKETS. I
changet the porting in 'comp', and hacked ddi.src to look for the right
mpif.h header file. It compiled seamelesly, and I got a working binary.
I start it as an 'mpirun' job using 2 nodes, and I can see two mpi jobs
running with ps, but the output file from GAMESS does not says anything
about 2 processors, and also, the job starts only on one node.

Anything huge I'm missing? BTW, I'm using the MPICH implementation of
MPI, PGF77 is my compiler, my 'test' beowulf consists of 4 old pentiums.
Everything works fine with MPI on the old version of GAMESS, or with
sockets in the new version.

Happy Hallowen!

Guillermo

--
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| Guillermo Moyna, PhD
: Department of Chemistry and Biochemistry
. University of the Sciences in Philadelphia
  600 South 43rd Street
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