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Re: R, openBlas and max thread?

From: zimoun
Subject: Re: R, openBlas and max thread?
Date: Fri, 22 Feb 2019 16:11:40 +0100

Dear Eric,

Thank you for your answer.

On Wed, 20 Feb 2019 at 05:19, Eric Bavier <address@hidden> wrote:

> OpenBLAS will use as many threads as the OpenMP runtime will give it,
> which is by default one per CPU.  I think this default does not take
> into account hyperthreads, which htop shows as a separate "cpu".

Yes for sure, htop shows hyperthreads number of CPU. :-)
Maybe I have wrong, but if hyperthread is activated, then why not use
it by default.
In other words, OpenMP should be set by default at "hyperthread CPU"
and not "physical CPU". I think Debian is doing that for example.

What do you think ?

> You can set the "OMP_NUM_THREADS" environment variable and OpenBLAS
> should pick it up.  I don't know whether R does anything for setting
> OpenMP runtime settings.

I do not know neither.
Hum? R does not seems to use OMP_NUM_THREADS. I do not know.

All the best,

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