Make sage.env.cython_aliases more flexible regarding what pkgconfig files for BLAS are required

[tobiasdiez]

While working on #30371, I noticed that cblas is not available for Ubuntu 18.04. In fact, libblas-dev contains a README.if-you-look-for-libcblas with the following content:

    Debian science team maintainers have merged the CBLAS ABI into
    the libblas.so shared object. Everything you need from libcblas.so
    can be found in libblas.so . Please link your program against it
    instead. See also

      https://lists.debian.org/debian-devel/2019/10/msg00273.html
      https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=943712
      https://wiki.debian.org/DebianScience/LinearAlgebraLibraries

So this ticket adds support for other BLAS libraries (openplas, blas) that the user may have installed.

CC: @mkoeppe @dimpase @kiwifb @antonio-rojas @isuruf

Component: build

Keywords: cblas, blas

Author: Tobias Diez, Matthias Koeppe

Branch/Commit: 9c8641a

Reviewer: Matthias Koeppe, Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/30706

[mkoeppe]

comment:2

$ cat build/pkgs/openblas/distros/debian.txt 
libopenblas-dev

[tobiasdiez]

comment:3

Also with openblas the issue remains, as it adds a blas.pc file in usr/lib/.../pkgconfig and thus is not found via -l cblas. Or do I miss something?

[mkoeppe]

comment:4

Are you saying that the .pc files installed on your Ubuntu system are broken?

[tobiasdiez]

comment:5

I wouldn't say broken, but there is no cblas.pc file (but a blas.pc) which is why the check in env.py was not successful without the committed change.

[mkoeppe]

comment:6

Supporting BLAS on various platforms is really tricky. See build/pkgs/openblas/spkg-configure.m4. To interface with system BLAS, in some configurations we create .pc files in $SAGE_LOCAL. If you don't run ./configure and make, you won't have those.

[tobiasdiez]

comment:7

Well, the editable install in #30371 uses only system-wide installed libraries, so things in SAGE_LOCAL don't matter (or do you suggest to set SAGE_LOCAL to say usr before calling configure?).

Would it work to take in env.py the first of the libraries openblas cblas blas that is found using pkgconfig.parse?

[mkoeppe]

comment:8

Replying to @tobiasdiez:

Well, the editable install in #30371 uses only system-wide installed libraries, so things in SAGE_LOCAL don't matter

As I said in #30371, I think it's best to keep the focus narrow -- make #30371 work completely (i.e., pass doctests) when run from within ./sage -sh so that $SAGE_LOCAL is set to a working installation of the Sage distribution.

Of course I do understand that currently technical problems prevent you from completing the build.

Still, make -k can build everything until you get the error with the pip package or whatever is failing. Then for example the .pc files will be available.

Would it work to take in env.py the first of the libraries openblas cblas blas that is found using pkgconfig.parse?

Something like this might work.

Making sage.env.cython_aliases more flexible is a good approach, I would think.

Note that this will need thorough testing across the supported platforms.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

3cfe1c9	Merge branch 'develop' of git://github.com/sagemath/sage into public/build/cblas
ea4a44c	Support different blas libraries

[sagetrac-git]

Changed commit from 23d17ad to ea4a44c

[tobiasdiez]

Description changed:

--- 
+++ 
@@ -1,4 +1,4 @@
-While working on #30371, I noticed that cblas is not available for Ubuntu 18.04. In fact, `libblas-dev` contains a `README.if-you-look-for-libcblas` with the following content:
+While working on #30371, I noticed that `cblas` is not available for Ubuntu 18.04. In fact, `libblas-dev` contains a `README.if-you-look-for-libcblas` with the following content:
 
 ```
     Debian science team maintainers have merged the CBLAS ABI into
@@ -11,4 +11,4 @@
       https://wiki.debian.org/DebianScience/LinearAlgebraLibraries
 ```
 
-So I suggest to migrate/rename cblas to blas. The currently submitted changes worked for an editable install, but they might lead to issues with the build process. So advice how to properly do this migration is  welcome; in fact, feel free to hijack this ticket and push the necessary changes directly.
+So this ticket adds support for other BLAS libraries (openplas, blas) that the user may have installed.