I do want in fact to bind first to one HT of each core
before binding to two HTs of one core.  So that will
be possible in 1.7?

Thx....John

On 9/11/12 11:19 PM, Ralph Castain wrote:
Not entirely sure I know what you mean. If you are talking about running 
without specifying binding, then it makes no difference - we'll run wherever 
the OS puts us, so you would need to tell the OS not to use the virtual cores 
(i.e., disable HT).

If you are talking about binding, then pre-1.7 releases all bind to core at the 
lowest level. On a hyperthread-enabled machine, that binds you to both HT's of 
a core. Starting with the upcoming 1.7 release, you can bind to the separate 
HTs, but that doesn't sound like something you want to do.

HTH
Ralph


On Sep 11, 2012, at 6:34 PM, John R. Cary <c...@txcorp.com> wrote:

Our code gets little benefit from using virtual cores (hyperthreading),
so when we run with mpiexec on an 8 real plus 8 virtual machine, we
would like to be certain that it uses only the 8 real cores.

Is there a way to do this with openmpi?

Thx....John
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