[R-SIG-Mac] detecting cores

peter dalgaard pdalgd at gmail.com
Fri Feb 5 13:26:35 CET 2016

Sorry, saw the bugzilla item first...

I have

Peters-iMac:IBP pd$ sysctl -n hw.ncpu
Peters-iMac:IBP pd$ sysctl -n hw.physicalcpu
Peters-iMac:IBP pd$ sysctl -n hw.logicalcpu
Peters-iMac:IBP pd$ ssh appleserver
Last login: Mon Dec 14 11:25:08 2015
appleserver:~ pd$ sysctl -n hw.ncpu
appleserver:~ pd$ sysctl -n hw.physicalcpu
appleserver:~ pd$ sysctl -n hw.logicalcpu

both on Mavericks, 10.9.5. As you probably gathered (or remembered), the iMac is Core 2 Duo, so no hyperthreading. 


On 05 Feb 2016, at 13:07 , Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:

> sysctl on 10.11 has options which would enable us to differentiate between logical and physical codes on parallel::detectCores --- however these are not documented in Apple's online man pages, which are for 10.9.  Could someone running 10.9 and someone for 10.10 report if
> /usr/sbin/sysctl -n hw.physicalcpu
> /usr/sbin/sysctl -n hw.logicalcpu
> run in a terminal work and gives the correct result?  (Normally the second will be twice the first taking account of hyperthreading.)
> Thanks in advance.
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Emeritus Professor of Applied Statistics, University of Oxford
> _______________________________________________
> R-SIG-Mac mailing list
> R-SIG-Mac at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-mac

Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

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