[R] R performance: different CPUs

[Jasjeet Singh Sekhon]

> This would be true of 64-bit builds of R, not 64-bit CPUs.
> [...]
> This doesn't mean that a 32-bit build of R on a 64-bit processor will be 
> slower than a 32-bit build of R on a 32-bit processor.

There is the issue, however, of running a 32bit application on a 64bit
OS.  Under RedHat and SuSE this works transparently and I've not
noticed a performance issue, but under Debian's or Ubuntu's chroot
setup there is in my experience a measurable performance hit.  Of
course, one could simply run 32bit Debian along with 32bit R on an
Opteron.

Cheers,
Jas.

=======================================
Jasjeet S. Sekhon                     
                                      
Associate Professor             
Travers Department of Political Science
Survey Research Center          
UC Berkeley                     

http://sekhon.berkeley.edu/
V: 510-642-9974  F: 617-507-5524
=======================================



Thomas Lumley writes:
 > On Wed, 5 Apr 2006, Jasjeet Singh Sekhon wrote:
 > 
 > >
 > > Hi,
 > >
 > > 64bit CPUs, such as opterons, help significantly with large databases
 > > or if you are running multiple processes.  But there is a speed
 > > penalty if you are not.
 > 
 > This would be true of 64-bit builds of R, not 64-bit CPUs.
 > 
 > On a 64-bit processor you can usually run either 64-bit or 32-bit builds 
 > of R, and the 64-bit one will be able to access more memory but will be 
 > slower.
 > 
 > This doesn't mean that a 32-bit build of R on a 64-bit processor will be 
 > slower than a 32-bit build of R on a 32-bit processor.
 > 
 >  	-thomas
 > 
 > Thomas Lumley			Assoc. Professor, Biostatistics
 > tlumley at u.washington.edu	University of Washington, Seattle