[R] Running R on a 64 bit processor

[Prof Brian Ripley]

Be careful not to use clock speed as a measure of computer performance.
Pentium 4s (and the comparable Xeons) were intended to be run very fast, 
but never managed it.  So a 2.4GHz P4 proved to be slower than a 1GHz 
PIII.

Unless you are running Windows 64, the chip having some 64-bit 
instructions is irrelevant, and even if you were it is irrelevant to 
binary builds of R for Windows (which will actually access less memory 
than is possible under 32-bit Windows XP).

R runs large tasks much better under Linux, and there having a 64-bit CPU
and 64-bit OS pay off once you have 2Gb or more of RAM.

On Fri, 28 Jul 2006, Lewis G Coggins wrote:

> Greetings,
> 
> We recently obtained a new computer in our lab with a Pentium 4 3.86 GHz 
> processor and 4 gb of ram running windows xp with service pack 2.  After 
> installing R on this machine, I ran a bit of code and found that the 
> execution time was actually significantly slower than a machine running 
> windows xp with an older Pentium chip 1.73 GHz and 1 gb of ram.  After 
> speaking with the manufacturer of the new machine, I am told that the 
> processor in the new machine is 64 bit whereas I believe the processor in 
> the  old machine is 32 bit.  I have tried to sort through the 
> documentation on the CRAN page relative to performance of R under the 32 
> vs 64 bit sub architecture, however, I am no computer genius and find some 
> of this stuff extremely confusing. 

Well, it is under the Unix/Linux section, and you are running Windows 
so it does not apply to you.

>  In a CRAN document entitled 
> "Installation and Administration" , there is reference to sub 
> architecture... it reads:
> 
> 8.1 Windows
> Currently the Windows build of R is a 32-bit executable. This runs happily 
> on Windows 64 on AMD64 and EM64T, but is limited to (we are told) a 2GB 
> address space. It will not be possible to build a native version for 
> Windows 64 until suitable compilers are available, and currently 
> (mid-2006) that is not in prospect. 
> So my question is: are there any options to allow R to take advantage of 
> the faster chip, (with 64 bit architecture), and more ram.  I see in the 
> documentation that a linux version of R may be able to take advantage of 
> this chip... is that true what would be involved in making that work?  Are 
> there other options?  As we are beginning to use R more and more around 
> here, we may send this computer back and get a celeron 3.2 GHz chip that 
> has 32 bit architecture... is this an intelligent choice?
> Thanks in advance for considering my question,
> Lew Coggins 
> 	[[alternative HTML version deleted]]
> 
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595