[SciPy-user] numpy/scipy on an Intel(R) Core(TM)2 CPU and CPU THROTTLING

David Cournapeau david@ar.media.kyoto-u.ac...
Sun Feb 18 21:35:11 CST 2007

Nils Wagner wrote:
> David Cournapeau wrote:
>> Nils Wagner wrote:
>>> Hi all,
>>> I am going to install numpy/scipy (svn version)
>>> on an Intel(R) Core(TM)2 CPU. And I would like to build 
>>> everything from scratch
>>> (including BLAS/LAPACK/ATLAS).
>>> Which compiler options/flags should I use for BLAS/LAPACK 
>>> in that case ?
>>> Which fortran compiler g77/gfortran is
>>> currently recommended to build numpy/scipy ?
>>> BTW, I am using openSUSE 10.2.
>>> Nils
>> For Atlas, you should use the flags set by the ATLAS build system. If 
>> you use recent ATLAS sources (3.7.* serie), there are some arch default 
>> for your CPU, I think.
>> cheers,
>> David
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>  Hi again,
> I am confused about CPU THROTTLING.
> How can I switch off CPU throttling on SuSE Linux 10.2 ?
I don't know anything about Suse, but if the command line cupfreq-set 
works, you should try (as root generally) as written in the docs:

cpufreq-selector -g performance

cpufreq works by using so called governor (hence the -g), and the 
performance one is more or less equivalent to disabling cpu throttling, 
as I understand it (note that I don't know much about those things; but 
if I do that on my laptop, it is working as expected).
> I found a command "cpufreq-set" but I don't know how to proceed.
> ATLAS uses gfortran by default but I have used g77 to build BLAS/LAPACK.
ATLAS is written in C, so in my understanding is that the fortran 
compiler is just used to build the Fortran interface to the C 
blas/lapack built by ATLAS. I think the key point is to always keep the 
same compiler (eg if you use gfortran, make sure you always use it for 
all the libraries used by numpy/scipy like umfpack, etc...).

One way to check which one is "better", would be to check other fortran 
libraries you are using, I guess (eg, what is the Suse default: g77 or 
gfortran ?).



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