[R-SIG-Mac] 64bit Tiger performance vs 32 bit Wintel vs 32 bit Linux

[Simon Urbanek]

On Jun 17, 2005, at 3:16 PM, Shea, Ed wrote:

> Has anyone experienced any performance improvements running with a  
> 64bit tiger compiled R.2.* vs the windows and/or Linux versions (on  
> comparable hardware)?

By definition using 64-bit addressing instead of 32-bit is slower,  
simply because all pointers are twice the size and hence twice the  
memory is moved/accessed when dealing with pointers. There is no  
penalty for running 32-bit programs on ppc64 therefore 64-bit  
programs are usually slightly slower than the same 32-bit programs  
and my tests with R confirm this.

It's hard to make any cross-platform claims, because "comparable  
hardware" is a very vague term. If you tell me what you're interested  
in I could run some tests on G5 and amd64 ...

>   Aside from access to more memory, are there any other benefits?

AFAIK, no.

Cheers,
Simon