[ESPResSo] Re: Parallel Simulations and System Initialization

[Ulf Schiller]

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Hello Lorenzo:

> Hello,
> And thanks for the suggestions.
> As to the infiniband-adaptor, I am really in a bad shape (had to google
> it up and not sure I understand what that stands for).
> For now, I have re-compiled Espresso with the --without-mpi option.
> However, does this infiniband thing mean that even if I managed to set
> up properly the  environment for the parallel libraries, they would not
> work on my machine in the present situation?

That depends on whether you actually have an Infiniband network on your
system. If so, you also need the support libraries for Infiniband, e.g.
OpenIB. Once you've setup the libraries for your kind of interconnect,
you can build OpenMPI with support for them. The OpenMPI FAQ provides
some more information on this:
http://www.open-mpi.org/faq/?category=building
Once you've a running MPI environment on your system, you can finally
configure and build Espresso (which might need some hand-tuning for
selecting the compiler and mpirun).

> And a final question (definitely not entirely related to Espresso): my
> first target would be to make use of the 2 dual-core processors
> (actually, 4 CPU's) available on my desktop machine.
> Any specific recommendation for a tutorial for an absolute beginner in
> this field to use e.g. OpenMPI on a single multi-core machine rather
> than a cluster?

Documentation for OpenMPI is still somewhat rare. However, the project
homepage http://www.open-mpi.org/ already contains useful information.
In particular, the FAQ might be of help.

Cheers,
Ulf

>> There are two packages that Espresso is known to work with: LAM/MPI
>> and MPICH. However, this will not solve your problems: LAM also
>> requires you to prepare your computer for parallel runs; this has
>> nothing to do with Espresso itself, but is a requirement of the
>> parallel library. In case of LAM, for example, you need to execute
>> lamboot before running your application, and lamhalt after running it.
>> I think MPICH has a mode that does not require an external daemon, but
>> is typical less performant than LAM.
>>
>> The error that you obtain from LAM regarding "OpenIB" indicates that
>> somehow your OpenMPI installation tries to use an non-existing
>> infiniband-adaptor. Maybe you first want to check why OpenMPI wants to
>> use Infiniband...

- --
Ulf D. Schiller   *   Room 1.404   *   Phone +49 6131 379-481
Max Planck Institute for Polymer Research
Theory Group
D-55128 Mainz, Germany                   50° 0' N, 008° 16' E
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