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Subject: Re: [OMPI users] Infiniband requirements
From: Gus Correa (gus_at_[hidden])
Date: 2009-06-25 18:32:32


Hi Jim, list

1) Your first question:

I opened a thread on this list two months or so ago about a similar
situation: when OpenMPI would use/not use libnuma.
I asked a question very similar to your question about IB support,
and how the configure script would provide it or not.
Jeff answerer it, and I asked him to post the answer in the FAQ,
which he kindly did (or an edited version of it):

http://www.open-mpi.org/faq/?category=building#default-build

The wisdom is that OpenMPI will search for IB on standard places,
and will use it if it finds it.
If you don't have IB on a standard place, then you can use the
switch --with-openib=/dir to force IB to be part of your OpenMPI.
If I understood it right, the bottom line is that you
only don't get IB if it is hidden, or doesn't exist.

2) Your second question:

As for the --enable-static question, I don't know the answer.
I defer this one to the OpenMPI developers.
I confess I have no explanation for why "-lrdmacm -libverbs"
are listed amongst the "Wrapper extra LIBS" when OpenMPI is configured
with --enable-static, but those IB library flags are absent
when --enable-static is not used.
(Maybe because the dynamic linker does a smarter search.)

I hope this helps,
Gus Correa
---------------------------------------------------------------------
Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA
---------------------------------------------------------------------

Jim Kress wrote:
> Is it correct to assume that, when one is configuring openmpi v1.3.2 and if
> one leaves out the
>
> --with-openib=/dir
>
> from the ./configure command line, that InfiniBand support will NOT be built
> into openmpi v1.3.2? Then, if an Ethernet network is present that connects
> all the nodes, openmpi will use that network?
>
> Also, is it required to add
>
> --enable-static
>
> to the ./configure command line to make sure Infiniband support is
> available?
> If I do not then the ompi_info --config command yields
>
> Wrapper extra LIBS: -ldl -Wl,--export-dynamic -lnsl -lutil -lm -ldl
>
> Note the absence of -lrdmacm and -libverbs which, I am told, are essential
> for Infiniband support.
>
> Whereas if --enable-static IS included, the ompi_info --config command
> yields
>
> Wrapper extra LIBS: -lrdmacm -libverbs -ldl -Wl,--export-dynamic -lnsl
> -lutil -lm -ldl
>
> And -lrdmacm and -libverbs are now present.
>
> Thanks for your help.
>
> Jim
>
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