Mac vs. PC

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Mac vs. PC

richarddmorey
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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Re: 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 <[hidden email]> 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!
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
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Re: Mac vs. PC

Thomas Lumley
In reply to this post by richarddmorey
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
[hidden email] University of Washington, Seattle

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Re: Mac vs. PC

Rod.V
In reply to this post by richarddmorey
2007/3/10, Richard Morey <[hidden email]>:

> 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!
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Hi,

For Windows you can check versions of Rblas.dll linked against the
ATLAS library:
http://cran.r-project.org/bin/windows/contrib/ATLAS/

Rod.

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.