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Subject: Re: [OMPI devel] RFC: usnic BTL MPI_T pvar scheme
From: Nathan Hjelm (hjelmn_at_[hidden])
Date: 2013-11-06 10:26:53


On Wed, Nov 06, 2013 at 02:06:15AM +0000, Jeff Squyres (jsquyres) wrote:
> On Nov 5, 2013, at 2:59 PM, George Bosilca <bosilca_at_[hidden]> wrote:
>
> > I have a question regarding the extension of this concept to multi-BTL
> > runs. Granted we will have to have a local indexing of BTL (I'm not
> > concerned about this). But how do we ensure the naming is globally
> > consistent (in the sense that all processes in the job will agree that
> > usnic0 is index 0) even when we have a heterogeneous environment?
>
> The MPI_T pvars are local-only. So even if index 0 is usnic_0 in proc A, but index 0 is usnic_3 in proc B, it shouldn't matter. More specifically: these values only have meaning within the process from which they were gathered.
>
> I guess I'm trying to say that there's no need to ensure globally consistent ordering between processes. ...unless I'm missing something?

There is no need to ensure global consistency unless you declare the pvar to
have a global scope (MCA_BASE_VAR_SCOPE_GROUP, MCA_BASE_VAR_SCOPE_GROUP_EQ,
MCA_BASE_VAR_SCOPE_ALL, or MCA_BASE_VAR_SCOPE_ALL_EQ.)

-Nathan