[R] Experimenting with Rblas.dll

[ripley@stats.ox.ac.uk]

On Tue, 12 Nov 2002, Kenneth Cabrera wrote:

> Dear R-List:
> I was experimenting with ATLAS to compile Rblas.dll again.
> My processor is a PIII (x86 Family 6 Model 8 Stepping) in W2K.
> I compile R from the sources with all the recommended tools, no problem.
> I remake Rblas.dll from sources with cygwin.
                                  ^^^^^^^^^^^
Wrong compiler, if you really used cygwin.

On small problems very small changes in the compiler or the problem can
affect the speed comparisons.  With large problems ATLAS wins hands down.

Very few things people do with R are actaully affected significantly by
the BLAS speed.

> When I use the CRAN compiled version (rw1061.exe) its performance (I use
> kriging function
> on GeoR)  is very similar to the one I compiled.
> I then recompile my version using the Rblas I built, now the performance
> was down in
> relation with the CRAN compiled version. I experiment also with the CRAN
> /ATLAS Rblas.dll
> precompiled version.
> But the thing that I don't understand is that if I use the Rblas.dll
> form the CRAN version (the one in
> the rw1061.exe version) on my compiled version, it is faster!!! than the
> CRAN version and
> of course my compiled version both with and without the Rblas recompiled.
> I wonder ... why?
> I would like to know more about your own experiences in this issue.
>
> Thank you very much!
> Kenneth Cabrera
>
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-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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