Quick answer: No, they're not the same.

Reason: If HT is not disabled but the num_proc or slots is set to half the
available cores, the fake/virtual cores might still be used/assigned for
computation. The result/performance could then depend on whether or not its
corresponding real core is also busy or not.

Intel, a while ago, had a white paper detailing how doubling the total vote
count by turning on HT doesn't always lead to twice the (practically
achievable) performance.

Hope this helps. But please wait for someone more knowledgeable to confirm
or correct my answer.

On Tuesday, July 19, 2016, Rémy Dernat <[email protected]> wrote:

> Hi,
>
> I have many nodes with hyperthreading enable.
> I would like to know if modifying the complex value 'num_proc' or 'slots'
> to the half of cores is the same thing that to disable the hyperthreading.
> If not, what is the difference ?
>
> Thanks,
> Best regards,
>
> Rémy
>


-- 

Gowtham, PhD
Director of Research Computing, IT
Adj. Asst. Professor, Physics/ECE
Michigan Technological University

(906) 487/3593
http://it.mtu.edu
http://hpc.mtu.edu
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