ATLAS now available for Fedora

[Quentin Spencer]

As of today, there are now atlas libraries available in Fedora Extras 
for Fedora Core 4. Like the Debian atlas libraries, there are multiple 
versions that are optimized for different hardware. Here is a list of 
the package names:

atlas         - base version for i386, x86_64 or PPC
atlas-3dnow   - optimized for AMD 3DNow! compatible hardware
atlas-sse     - Optimized for Pentium III
atlas-sse2   - optimized for Pentium 4
atlas-altivec - optimized for PPC with Altivec extensions

The packages are based on the 3.6.0 release of ATLAS, and they provide 
compatible versions of the lapack and blas shared libraries, and they 
should automatically be detected and used by octave in place of the 
existing ones on your system. You should be able to achieve much better 
performance on large vector or matrix operations by simply installing 
one of these packages.

There are some caveats. Because ATLAS relies on compile-time 
optimization, I have used the build records from the Debian packages 
which attempt to achieve reasonable compromises in optimization settings 
so that they will work well on a wide range of hardware. Also, my 
P4-compatible laptop does not seem to gain much from installing 
atlas-sse2 rather than just atlas (though base atlas still shows a 
dramatic improvement over the base blas). A further caveat is that 
because of lack of hardware for testing, I haven't verified whether the 
-sse and -3dnow packages are automatically picked up by the linker. If 
anyone has problems with them, please inform me (a good way to test this 
is to look at the output of "ldd /usr/bin/octave | grep blas").

For users willing to wait for several hours to get optimized versions 
for their computers, the source package has this capability. It is 
explained in the documentation, but I'll briefly summarize how do to it 
here:
1. Get the source package:
http://download.fedora.redhat.com/pub/fedora/linux/extras/4/SRPMS/atlas-3.6.0-7.fc4.src.rpm
2. rebuild it with custom build enabled using:
rpmbuild -D "enable_custom_atlas 1" --rebuild atlas-3.6.0-7.fc4.src.rpm
3. The build process creates a binary called atlas-custom-3.6.0-7.rpm, 
which you can then install.

Because these packages were designed for gcc 4, they probably won't work 
on earlier versions of Fedora, and it may take a fair amount of work to 
modify the package, so I'm not sure if I will ever support earlier versions.

-Quentin



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