Thanks very much for all your advice. To be clear, my OS is window XP. I bought this server last year. It's Dell Precision PWS690. THe processor is Xeon(TM) CPU 3GHZ, 2G RAM. I am not sure how to check more details of processor on my computer. But I went to Dell website and from what I can recall, it seemed that I ordered a Dual-core Intel Xeon 5160 3GHz, 1333FSB, 4MB L2 Cache, 80watts. 

I think from time to time, I will need linear algebra to do things such as Choleskey Factorization, and matrix inverse etc... At the same time, I considered myself quite unskilled on building R by myself. It seems there were lots of details that I can get things wrong. So if there is an existing ATLAS one on R website that I can use, I would be very happy to use it to replace the default one. The reason why I would like to use ATLAS is that R FAQ said :

"The savings can be appreciable: on a 2.6GHz P4 and a 1000 x 1000 matrix svd took 16.2 sec with the standard BLAS and 7.8 sec with ATLAS.  Because ATLAS is tuned to a particular chip we can't use it generally: the optimal routines for a P4 or an Athlon XP are quite different and neither will run at all on a PII."

This seems to me an impressive gain to use the correct ATLAS instead of the default BLAS.  I guess my  Xeon processor is either a P4 or  Core2Duo, but I am really not sure which one to use. Could you please offer me some suggestions?

Again, many thanks for all your advice!

Best,

Hui

Uwe Ligges <ligges@statistik.uni-dortmund.de> wrote: 

Prof Brian Ripley wrote:
> On Tue, 28 Aug 2007, hui xie wrote:
> 
>> hi everyone:
>>
>> I have a Dell Server that has a Xeon processor, and I would like to use 
>> the best ATLAS posted in the R website. I find that R has ATLAS for 
>> core2duo and P4. I am not sure which one of these two is best suited for 
>> Xeon processor, or is that neither of these two is good and I should 
>> stick with the default one that was installed originally?
> 
> And your OS is?
> 
> There are many different 'Xeon' processors with very different 
> capabilities.  

... the earlier similar to P4 and some similar to Core2Duo. You won't 
make use of bigger L2/L3 caches in Xeon processors.

 > You really ought to build ATLAS for yourself if numerical
> linear algebra performance matters to you (and it makes little difference 
> to most people: I think Uwe Ligges quoted 10% for testing all CRAN 
> packages).


Right, it depends on what you are really doing. If most time is spend in 
certain numerical matrix operations, ATLAS is your friend. In all other 
cases, it does not matter so much, as Brian cited correctly.

Uwe Ligges


> 
>> Your advice is very much appreciated!
>>
>> Best,
>>
>> Hui
>>
>>
>> ---------------------------------
>> Park yourself in front of a world of choices in alternative vehicles.
>>
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>>
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> 
> Please do!
> 
> 


       
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