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Subject: Re: [OMPI devel] BTL add procs errors
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-06-02 12:51:57


George Bosilca wrote:

> We did assume that at least the errors are symmetric, i.e. if A fails
> to connect to B then B will fail when trying to connect to A.

I've not been following this thread closely, but thought I'd add a comment.

It used to be that the sm BTL could fail asymmetrically. A shared
memory could be allocated and processes start to allocate resources
within shared memory. At some point, the shared area would be
exhausted. So, some processes were set up to communicate to others, but
the others would not be able to communicate back via the same BTL. I
think this led to much brokenness. (E.g., how would a process return a
sm fragment to a sender?)

At this point, my recollection of those issues is very fuzzy.

In any case, I think those issues went away with the shared-memory work
I did a while back. The size of the area is now computed to be large
enough that each process's initial allocation would succeed.