[R] Mac vs. PC

[Richard Morey]

My adviser has a Mac notebook that he bought 6 months ago, and I have a 
PC notebook I bought a month ago. Here are the respective specs, as far 
as I know them:

His:
Mac OSX
1 GB DDR2 RAM
Intel Core Duo, 2 GHz (2MB cache per core)
Unknown HD

Mine
Windows Vista Home Premium 32bit
2 GB DDR2 RAM
Intel Core 2 Duo, 2 GHz (4MB cache)
5400 RPM Hard Drive


We are both running R. As a test to see whose laptop was faster, we 
decided to invert large random matrices. In R language, it looks like this:

N=2000
A=rnorm(N^2)
A=matrix(A,ncol=N)
solve(A)

This creates a matrix of 4,000,000 random normal deviates and inverts 
it. His computer takes about 7 seconds, while mine takes about 14. Why 
the difference? I have several working hypotheses, and it would be 
interesting to see what you guys think.

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.

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.)

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 is not intended to be an OMG MACOS = TEH R0X0R thread. I'm just 
trying to explain the discrepency.

Thanks!