[R] R performance: different CPUs

[Liaw, Andy]

From: 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.

It's my recollection that about a year ago there was still fierce debate
about Debian on x86_64:  One group got a pure 64-bit version to a usable
state sooner than another group that was trying to make a standard
conforming version that would run both 64- and 32-bit apps transparently.  I
don't know how that was resolved in the end, but that basically was enough
for me to steer clear of any Debian-based distro for x86_64.

Andy
 
> 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
> 
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