[R] Mac vs. PC

[Thomas Lumley]

On Fri, 9 Mar 2007, Richard Morey wrote:
> 1. R on Mac was compiled with optimizations for the CPU, with R for
> Windows was not. I could test this by compiling R with the Intel
> compiler, or GCC with optimizations, and seeing if I get a significant
> speed boost.

Yes.  The Mac distribution uses Apple's linear algebra library, which is 
based on ATLAS and uses both cores.  The default Windows distribution 
doesn't use an optimized linear algebra library because there isn't one 
built in to Windows.  You can use ATLAS with the Windows distribution and 
there are even precompiled DLLs around somewhere.

> 2. His R is 64 bit, while mine is for 32 bit windows. (I'm not sure how
> much of a diference that makes, or whether OSX is 64 bit.)

No.

His R isn't 64bit.  It would probably be slower if it were. The main 
reason to want 64bit R is to use lots of memory rather than to be fast.

> 3. Data is getting swapped to the hard drive, and my hard drive is
> slower than his. I chose a slower hard drive to get bigger capacity for
> the price.

This could be true in principle, but I don't think the matrices are large 
enough for it to be the main factor.


His computer won't be twice as fast on most R tasks (though it will still 
be twice as pretty, of course).

 	-thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle