ATLAS for Debian ================ Why are optimized packages no longer available? ----------------------------------------------- Before version 3.8.3-25, optimized binary packages were provided. However, due to the fact that most Atlas optimisations are done at build time, it has been decided to remove them and give priority to locally built packages. See section "Building Optimized Atlas Packages on your ARCH" on how to rebuild Atlas for best performances. For more information about linear algebra libraries, see also: http://people.debian.org/~sylvestre/presentation-linear-algebra.pdf How to switch between BLAS/LAPACK implementations ------------------------------------------------- It is trivial to switch between the various BLAS/LAPACK implementations. - BLAS: $ sudo update-alternatives --config libblas.so.3-<multiarch> - LAPACK: $ sudo update-alternatives --config liblapack.so.3-<multiarch> where <multiarch> is the multiarch path for you architecture (e.g. x86_64-linux-gnu for amd64). More information is available here: http://wiki.debian.org/DebianScience/LinearAlgebraLibraries Building Optimized Atlas Packages on your ARCH ---------------------------------------------- Building your own optimized packages of Atlas is straightforward. 1) Get the sources of the package and its build-dependencies: $ apt-get source atlas $ sudo apt-get build-dep atlas 2) Disable CPU throttling if it is enabled. Otherwise Atlas cannot get reliable timings and therefore the optimization will be suboptimal. This can easily be done using the tools from the cpufrequtils package. The state of your CPUs can be checked with: $ cpufreq-info If for any CPU, the governor is not set to "performance", then you can do so by issuing the following command for each of your CPU cores: $ sudo cpufreq-set -g performance -c <cpu#> where <cpu#> is the CPU core number (the first has number zero). See INSTALL.txt from the libatlas-doc package for more details on this issue. 3) Build the package by running the following: $ cd atlas-<UPSTREAM_VERSION> $ DEB_BUILD_OPTIONS=custom dpkg-buildpackage -uc -b where <UPSTREAM_VERSION> is replaced with the appropriate value. If the Atlas build system still complains about CPU throttling issues, despite having set the governors to performance, then you can force Atlas by uncommenting the following line in debian/rules: CONFIGURE_FLAGS += --cripple-atlas-performance 4) When the build finishes (it will take a long time), it should produce a .deb file, whose precise name you can figure out using: $ ls ../libatlas3-base_*.deb Install it using: $ sudo dpkg -i ../libatlas3-base_<VERSION>_<ARCH>.deb> replacing <VERSION> and <ARCH> with the appropriate values. 5) If you don't want the Debian package manager to overwrite your optimized package with a generic one on system upgrades, you can mark the Atlas package to be on hold, with the following command: $ sudo aptitude hold libatlas3-base Don't forget however to periodically check whether a more recent version of the package is available for the Debian suite that you are tracking, in which case you should go again through this procedure. The version check can be performed using: $ aptitude versions libatlas3-base Misc ---- Thanks to David Cournapeau for providing all the patches for the shared libraries managements. -- Sébastien Villemot <sebastien@debian.org>, Thu, 7 Sep 2017 21:50:00 +0200 -- Sylvestre Ledru <sylvestre@debian.org>, Tue, 15 May 2012 18:05:34 +0200
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