[molpro-user] Best practices for parallelization

[Ivan Reche]

Hello,

I'm a new user of Molpro 2010 and I'm compiling it to work on a standard
home-made Beowulf cluster.

I've compiled it with global arrays 5.0.2 and mpich2 1.4.1. However, I'm
having some doubts:

1. From what I understood by reading the docs, is there an option to not
use global arrays? Should I use just pure MPICH2 for my setup? Is global
arrays optimized for InfiniBand and other non-conventional networks and, as
such, not recommended to my standard ethernet network?

2. By running some test jobs that came with Molpro and comparing the serial
results with the parallel results, the serial ones were faster in all
cases. Is there a common mistake that I might be causing these undesired
results? What issues should I look for?

3. Let's say that I'm trying to separate my computation in two computers:
foo and bar. If I call molpro in the foo machine like this:

molpro -N user:foo:1,user:bar:1 myjob.com

I get an MPI error complained that it couldn't connect to rank 0. However,
if I switch the orders of the hosts like this:

molpro -N user:bar:1,user:foo:1 myjob.com

It works, but dumps the results in the bar machine. Both machine can login
with "user" using ssh without passwords. What am I missing here? Maybe
using the rank 0 machine for the computation is not recommended?

4. What is the deal with the helper servers? I couldn't understand their
roles by just reading the docs.

Thanks in advance for your time and attention.

Cheers,

Ivan
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