[R] R and ATLAS

Peter Langfelder peter.langfelder at gmail.com
Thu May 27 00:17:49 CEST 2010

If you didn't specify an external BLAS when you ran R configure
script, you are not using ATLAS. If you're not sure and you still have
the output of the configure script, at the end it'll say whether it
uses an external BLAS.

Alternatively, you may also want to generate two random 5000x5000
matrices and do their multiplication

a = matrix(rnorm(5000*5000), 5000, 5000)
b = matrix(rnorm(5000*5000), 5000, 5000)
c = a%*%b

While the calculation is running, in a separate terminal, run top and
watch how much CPU R takes. AFAIK standard installation of R is single
threaded and will only use one CPU (up to 100%). ATLAS is
multithreaded and (unless you configured it otherwise) it will use all
available processors, so if you have a 4-core machine, you will see
CPU usage of nearly 400%. Note though that this will not discriminate
ATLAS from other multi-threaded BLASes.



On Wed, May 26, 2010 at 2:16 PM, Jonathan Greenberg
<greenberg at ucdavis.edu> wrote:
> Rhelpers:
> I recently installed the 64-bit version of R on my Debian system, and
> afterwards was asked if it was compiled using ATLAS.  Is there a way
> to test to see if R is using ATLAS?
> --j
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