[R-SIG-Mac] Fwd: restricting the number of threads used on a dual-core Intel machine

Douglas Bates bates at stat.wisc.edu
Wed Mar 8 16:54:31 CET 2006

---------- Forwarded message ----------
From: Douglas Bates <bates at stat.wisc.edu>
Date: Mar 8, 2006 9:54 AM
Subject: Re: [R-SIG-Mac] restricting the number of threads used on a
dual-core Intel machine
To: Paul Roebuck <roebuck at mdanderson.org>

On 3/8/06, Paul Roebuck <roebuck at mdanderson.org> wrote:
> On Wed, 8 Mar 2006, Douglas Bates wrote:
> > So my question is how does one set this environment variable for the R
> > Console on an Intel Mac or even R running in a terminal on an Intel
> > Mac?  I tried setting OMP_NUM_THREADS=1 in the environment before
> > running R in a terminal on a Mac but that did not seem to have an
> > effect.
> You tried this already?
> <http::gemma.apple.com/qa/qa2001/qa1067.html>

Thanks for the reference.  I guess I wasn't clear about not knowing
the environment variable to set.  On some other systems that use
pthreads the environment variable name is OMP_NUM_THREADS but setting
that to 1 on the Intel Mac didn't have any effect.  (I tried this in a
terminal window using the bash shell so I could be sure that it was
being passed to R.)

So my first question is what environment variable should I set and to
what value.  I probably don't want to set if for all applications
because then applications that are built to be multithreaded with
actually run slower.  I just want to restrict R to using a single

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