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author | Matthew Bauer <mjbauer95@gmail.com> | 2020-04-20 15:49:56 -0500 |
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committer | Matthew Bauer <mjbauer95@gmail.com> | 2020-04-20 15:50:28 -0500 |
commit | f86d582ea7cdf9c969f2294d9dc953f36f2a63e9 (patch) | |
tree | f73e446e2b765a27b8f0140dc4ad88429047beca | |
parent | 3c9c894f836fffa07a8d269f6394bdf2cbfdc940 (diff) |
doc/overlays.xml: add information on BLAS/LAPACK switching
-rw-r--r-- | doc/using/overlays.xml | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/doc/using/overlays.xml b/doc/using/overlays.xml index 26a888368abf..7732e0ac2179 100644 --- a/doc/using/overlays.xml +++ b/doc/using/overlays.xml @@ -137,4 +137,80 @@ self: super: Overlays are similar to other methods for customizing Nixpkgs, in particular the <literal>packageOverrides</literal> attribute described in <xref linkend="sec-modify-via-packageOverrides"/>. Indeed, <literal>packageOverrides</literal> acts as an overlay with only the <varname>super</varname> argument. It is therefore appropriate for basic use, but overlays are more powerful and easier to distribute. </para> </section> + <section xml:id="sec-overlays-alternatives"> + <title>Using overlays to configure alternatives</title> + <para> + Certain software has different implementations of the same + interface. Other distributions have functionality to switch + between these. For example, Debian provides <link + xlink:href="https://wiki.debian.org/DebianAlternatives">DebianAlternatives</link>. + Nixpkgs has what we call <literal>alternatives</literal>, which + are configured through overlays. + </para> + <section xml:id="sec-overlays-alternatives-blas-lapack"> + <title>BLAS/LAPACK</title> + <para> + In Nixpkgs, we have multiple implementations of the BLAS/LAPACK + numerical linear algebra interfaces. They are: + </para> + <itemizedlist> + <listitem> + <para> + <link xlink:href="https://www.openblas.net/">OpenBLAS</link> + </para> + <para> + The Nixpkgs attribute is <literal>openblas</literal> for + ILP64 and <literal>openblasCompat</literal> for LP64. This + is the default. + </para> + </listitem> + <listitem> + <para> + <link xlink:href="http://www.netlib.org/lapack/">LAPACK + reference</link> (also provides BLAS) + </para> + <para> + The Nixpkgs attribute is <literal>lapack-reference</literal>. + </para> + </listitem> + <listitem> + <para> + <link + xlink:href="https://software.intel.com/en-us/mkl">Intel + MKL</link> (only works on x86 architecture) + </para> + <para> + The Nixpkgs attribute is <literal>mkl</literal>. + </para> + </listitem> + </itemizedlist> + <para> + Introduced in <link + xlink:href="https://github.com/NixOS/nixpkgs/pull/83888">PR + #83888</link>, we are able to override the ‘blas’ and ‘lapack’ + packages to use different implementations, through the + ‘blasProvider’ and ‘lapackProvider’ argument. This can be used + to select a different provider. For example, an overlay can be + created that looks like: + </para> + <programlisting> +self: super: + +{ + blas = super.blas.override { + blasProvider = self.mkl; + } + lapack = super.lapack.override { + lapackProvider = self.mkl; + } +} + </programlisting> + <para> + This overlay uses Intel’s MKL library for both BLAS and LAPACK + interfaces. Note that the same can be accomplished at runtime + using <literal>LD_PRELOAD</literal> of libblas.so.3 and + liblapack.so.3. + </para> + </section> + </section> </chapter> |