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From: Durga Choudhury (dpchoudh_at_[hidden])
Date: 2006-11-28 20:09:00


Jeff (and everybody else)

First of all, pardon me if this is a stupid comment; I am learning the
nuts-and-bolts of parallel programming; but my comment is as follows:

Why can't this be done *outside* openMPI, by calling Linux's processor
affinity APIs directly? I work with a blade server kind of archirecture,
where each blade has 12 CPUs. I use pthread within each blade and MPI to
talk across blades. I use the Linux system calls to attach a thread to a
specific CPU and it seems to work fine. The only drawback is: it makes the
code unportable to a different OS. But even if you implemented paffinity
within openMPI, the code will still be unportable to a different
implementation of MPI, which, as is, it is not.

Hope this helps to the original poster.

Durga

On 11/28/06, Jeff Squyres <jsquyres_at_[hidden]> wrote:
>
> There is not, right now. However, this is mainly because back when I
> implemented the processor affinity stuff in OMPI (well over a year
> ago), no one had any opinions on exactly what interface to expose to
> the use. :-)
>
> So right now there's only this lame control:
>
> http://www.open-mpi.org/faq/?category=tuning#using-paffinity
>
> I am not opposed to implementing more flexible processor affinity
> controls, but the Big Discussion over the past few months is exactly
> how to expose it to the end user. There have been several formats
> proposed (e.g., mpirun command line parameters, magic MPI attributes,
> MCA parameters, etc.), but nothing that has been "good" and "right".
> So here's the time to chime in -- anyone have any opinions on this?
>
>
>
> On Nov 25, 2006, at 9:31 AM, shaposh_at_[hidden] wrote:
>
> > Hello,
> > i cant figure out, is there a way with open-mpi to bind all
> > threads on a given node to a specified subset of CPUs.
> > For example, on a multi-socket multi-core machine, i want to use
> > only a single core on each CPU.
> > Thank You.
> >
> > Best Regards,
> > Alexander Shaposhnikov
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Jeff Squyres
> Server Virtualization Business Unit
> Cisco Systems
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>

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