[R] Mac vs. PC

[Gabor Grothendieck]

Such a calculation would be dominated by the time spent inside a call
to an offf-the-shelf C matrix inversion library used by R and is not really
any test of R itself.

On 3/9/07, Richard Morey <moreyr at missouri.edu> wrote:
> 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!
>
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