[SciPy-dev] scipy and ATLAS (in)dependency

[Fernando Perez]

eric jones wrote:

> of installers for win32.  I think our approach has been to provide 
> Pentium III optimized ATLAS in the Python -- Enthought Edition that we 
> make available.

I think at least on x86, a P-III is a very reasonable baseline for the 'easy' 
distribution, likely to satisfy I'd bet most users.  Those to whom the 
difference between an SSE-2, P-IV optimized ATLAS and a P-III one is truly 
significant, can definitely take care of themselves and build it.  Given that 
scipy.org already provides a number of precompiled ATLASes (thank you!), most 
of the hard part is already solved even for hand-builds.

Quite honestly, these days building scipy even from CVS very easy (assuming 
you have already Numeric and F2PY in place).  Pseudo shell script follows 
(make it a real one simply by defining ARCH and SCIPY_PATH):

ARCH=P4SSE2_2HT  # set to the right string for your arch
PATH_TO_SCIPY=/your/path/to/scipy

#Grab a prebuilt ATLAS from scipy.org, according to your architecture:
wget 
http://www.scipy.org/download/atlasbinaries/linux/atlas3.6.0_Linux_${ARCH}.tgz

# Unpack the tarball, this makes directory Linux_$ARCH:
tar -xzf atlas3.6.0_Linux_${ARCH}.tgz

./install_atlas.py Linux_${ARCH}
# This is a tiny script I wrote for this purpose, which just copies things
# in the right place.  It's trivial, but it saves me from actually having
# to think what to do.  Attached in case anybody cares.

cd $SCIPY_PATH
cvs -q up -P -d  # update CVS
python setup.py install

That's it! And after you've done it once (so atlas is in place), you really 
just need to re-run the last two lines to update/reinstall.  I used to cringe 
(years ago) at the thought of building scipy by hand, but these days it's 
honestly trivial.

But back to the original topic, I really think the P-III ATLAS is an excellent 
compromise point for most users: it keeps the maintainer's burden under 
control and makes a very good (if not tip-top optimal) click-and-run scipy 
install feasible for new users.

Cheers,

f
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