[R] Switching to Mac, suggestions? (was switching to linux)
siegfried.gonzi at stud.uni-graz.at
Tue Dec 14 10:00:53 CET 2004
Jari Oksanen wrote:
>On Mon, 2004-12-13 at 19:53, doktora v wrote:
>>I'm looking to switch to Mac platform. Anyone had any experience
>>with that? I'm expecting on a power G4 laptop later this week.... hope
>Still one comment on speed. I once (and, actually, just now) had to
>analyse a big data set of some 1100 observations using various
>multivariate methods, among them isoMDS of MASS and eigenvector methods
>in vegan library. I made a testsuite of typical analysis sequence for
>this very special data set. So it is non-general, but something that
>matters to me. I have run this data set on crippled (=Celeron) i686
>under Linux and Windows, and on G4 (iBook and iMac) under MacOS X,
>Yellowdog Linux 3 and Ubuntu GNU/Linux 4.10. It may be daring to say
>something about G4 performance based on this special case, but this
>doesn't stop me from saying. For my all sequence, G4 with MacOS X is
>somewhat faster compared to cpu speed than Celeron, but not nearly as
>much as advertised. There were some procedures that run slower per MHz
>than Celeron (isoMDS). However, MacOS X comes with G4-optimized blas, so
>that eigenvector based analysis was faster: 800 MHz iBook run like 1400
>MHz Celeron, and 1000MHz iMac run like 1700 MHz Celeron. I guess the
>boost depends on time you spend in blas. Otherwise you may count that
>your G4 cpu cycles equal i686 cpu cycles, and you are slower since you
>can get faster Intel chips. Vector processor (AltiVec) may be handy, but
>most functions can't use without very tedious and ugly code optimized by
>hand. I've seen claims that gcc 3.4 has some automatic G4 optimization.
>If this is true, you may get some advantage with G4.
It is not directly related to your problem. However, the G4 falls far
behind when speaking of "trigonometric functions". I once had the case
where my old Celeron 1000 MHz laptop (SuSE LInux 8) outperformed --by a
factor of two -- my ibook G4 800MHz any time.
At that time I had to perform off-line calculations. The code was based
on Bigloo which by itself called external C functions.
I posted my observations (note: you can also test the G4/MAC OSX
'trig-functions' by means of the 'Coyote Gulch benchmark', though, my
experience was based on a real-life problem) to some Macintosh mailing
lists. As it turned out my posts have been deleted by the administrator
due to the fact that people insist that the G4 is the last invention
There was only one professor from a Japanese technical university who
took me for serious and we had some private communications.
One thing which I haven't figured out yet: the altivec libraries are
tailored to single precion only - right?
PS: No, I would never trade my ibook for any other laptop.
PSS: And one should quikcly try to forget all the rumors about: "Mac OSX
actually is slow". I happen to use an ibook 800MHz and 640 MB RAM; and
"Panther" OSX 10.3.5 is damn fast and snappy.
PSSS: There exists a library from Motorola for the old 68k proecessor;
that library adresses some of tthe trig-slow-performance issues.
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