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Subject: Re: [OMPI users] Pros and cons of --enable-heterogeneous
From: Eugene Loh (eugene.loh_at_[hidden])
Date: 2010-10-07 18:52:46


David Ronis wrote:

>Ralph, thanks for the reply.
>
>If I build with enable-heterogeneous and then decide to run on a
>homogeneous set of nodes, does the additional "overhead" go away or
>become completely negligible; i.e., if no conversion is necessary.
>
>
I'm no expert, but I think the overhead does not go away. Even if you
run on a homogeneous set of nodes, a local node does not know that. It
prepares a message without knowing if the destination is "same" or
"different". (There may be an exception with the sm BTL, which is only
for processes on the same node and where it it assumed that a node
comprises homogeneous processors.)

Whether the overhead is significant or negligible is another matter. A
subjective matter. I suppose you could try some tests and judge for
yourself for your case.