Re: Free AMD Core Math Library (BLAS/LAPACK) + Ada

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Simon Wright writes on comp.lang.ada:
> Thanks for that. We really needed advice from someone who knows.
>
> By way of experiment, I removed liblapack-dev which left
> /usr/lib/liblapack.{a,so} pointing to the now deleted /etc/alternatives/
> files. So I suppose the /usr/lib files get created when
> update-alternatives is run after a new install of libfoo-dev?

Correct but only if libfoo-dev participates in the alternatives system.
Only few libraries do; BLAS is one but I don't know whether LAPACK also
has alternatives.  I'll let you know how I find that out without
installing anything on my system:

- go to http://www.debian.org/distrib/packages#search_contents
- type liblapack.so in the Keyword field
- tick "packages that contain files named like this"
- choose the distribution: in your case , "Stable" (i.e. Debian 6
  "Squeeze").

Results:

/usr/lib/atlas-base/atlas/liblapack.so 	libatlas-base-dev
/usr/lib/lapack/liblapack.so 	liblapack-dev

So there is the answer: two -dev packages provide liblapack.so (the
development-time symlink to the run-time shared library) in different
subdirectories of /usr/lib.  Therefore these two packages can be
installed simultaneously.  Also, no package provides
/usr/lib/liblapack.so.  Therefore the two packages above probably
participate in the alternatives system.  If the two packages are done
correctly:

- installing the first -dev package will initialize the alternatives
  system and create /usr/lib/liblapack.so to point to
  /usr/lib/$package/liblapack.so.

- installing the second -dev package should ask you whether or not to
  change the default to be the new liblapack.so or tell you that it
  updated the alternative without asking (in the output of dpkg).

- uninstalling one of the -dev packages should automatically change the
  alternative to point to the remaining liblapack.so; therefore you
  should never be left with a dangling symlink.

If any of these things fail to happen (and you are sure you did not
tamper with symlinks by hand), please file a bug against the -dev
package that you installed or removed last.

-- 
Ludovic Brenta.