[R] Information on the number of CPU's

[tolga.i.uzuner at jpmorgan.com]

Many thanks, that's very helpful.
Regards,
Tolga


----- Original Message -----
From: Prof Brian Ripley [ripley at stats.ox.ac.uk]
Sent: 09/09/2008 20:57 CET
To: Tolga Uzuner
Cc: r-help at r-project.org
Subject: Re: [R] Information on the number of CPU's



On Tue, 9 Sep 2008, tolga.i.uzuner at jpmorgan.com wrote:

> Dear R Users,
> I am on Windows XP SP2 platform, using R version 2.7.2 . I was wondering
> if there is a way to find out, within R, the number of CPU's on my machine
> ? I would use this information to set the number of nodes in a cluster,
> depending on the machine. Sys.info() and .Platform do not carry this
> information.

Correct, since

a) R does not make use of more than 1.

b) It is really not portable, and not even well-defined.  (How many CPUs 
has a hyperthreaded dual Xeon?  Some say 2, some say 4.  Do you want 
CPUs or cores?  If this is a virtualized OS, is the physical number or the 
logical number?)

In the case of Windows, how depends on the Windows version.  The w32api 
(XP or later) call GetNativeSystemInfo will tell you the number of CPUs, 
for some (unstated) definition of 'CPU'.  Later versions have 
GetLogicalProcessorInformation, which can give the number of cores.

> Thanks in advance,
> Tolga Uzuner

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
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