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Subject: Re: [OMPI users] non-functional mpif90 compiler
From: Gus Correa (gus_at_[hidden])
Date: 2013-10-01 15:07:42


Hi Damiano

Glad to know you sorted out the problem with
your environment variables.
Home-brewed Open MPI tastes much better
than those six-pack canned RPMs.
Did OpenFOAM (was it OpenFoam?) eventually compile and run?

Thanks Jeff for clarifying where is the hurdle (on Infiniband)
when one tries to build Open MPI as group of static libraries.
I tried to build OMPI static, and had failures in the past.
I eventually gave up, but it was never clear why it would fail
(although the error messages suggested that IB played a role).
However, all my attempts were on machines with Infinband hardware.

Good to know that one can build OMPI static on TCP/IP machines.
And presumably also on (non-IB) standalone machines that will
only use the shared memory features of OMPI).
This may (or may not?) be useful when one intends to run MPI
programs in a single box.
(I wonder if this is what Damiano plans to do.)

I know these questions may be somewhat off-topic,
but from the standpoint of performance,
once upon a time there was a popular wisdom that
static linking produced faster executables
than when linking to shared libraries
(static producing larger executables, though).
Is this "static is faster" view still valid?
Does it apply to Open MPI in particular?
Was it ever true?

Many thanks,
Gus Correa

On 10/01/2013 05:16 AM, Jeff Squyres (jsquyres) wrote:
> If you are using a TCP network for MPI communications,static is fine.
>
> However, if you're trying to use an OS-bypass network such as
> InfiniBand, RoCE, or iWARP, using static libraries can be
> somewhat of a nightmare (because of how the OpenFabrics Verbs
> support libraries work).
> Specifically, I don't see the "openib" BTL plugin in your
> ompi_info output, meaning that your Open MPI installation
> is not capable of using InfiniBand/RoCE/iWARP.
>
> So just be aware that with your current builds,
> you're basically TCP-only.
>
>
> On Oct 1, 2013, at 3:34 AM, Damiano Natali<damiano.natali_at_[hidden]> wrote:
>
>> Hi Gus, today I noticed there was another ompi directory in my path and maybe it gave some strange errors so I put the new ompi installation at the first place in PATH and LD_LIBRARY_PATH before the building and everything went nicely!
>>
>> So, as you and Jeff said, the problem was in having the rigth paths!
>>
>> Thank you very much for your support!
>>
>> Damiano
>>
>> p.s. Building static libraries didn't result in any problem so far!
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