[Pkg-openmpi-maintainers] Bug#455886: Fwd: Bug#455886: mpicc seems missing on buildbots

[Ondrej Certik]

> As far as I can tell, the compilers should work fine as long if you have
> the libopenmpi-dev package installed. Though, we're experiencing some
> problems with multiple MPI implementations installed, see #452047 and
> #451993. It sounds like it affects you as well but I'm not quite sure
> from your report. Do you build against several MPI alternatives?

No, just openmpi. But the builtbots probably (certainly) compiled
something against lam/mpich before, and they just remove (purge) the
packages. And I know that openmpi will not work after that.

>
> In case you build against several MPI implementations, you should pass
> MPICC=/usr/bin/mpicc.openmpi to the configure script. Autotools should
> support that, and you should be specific about what compiler you want.
> If you just build against a single MPI implementation, mpicc should
> exist and work. I can't reprocuce the behavior that they are not
> created.

Unfortunately, that's not the case, see my closed bug report about that:

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=450518

I purged everything (as buildbots do), then installed openmpi, but the
alternatives are broken and the solution is to run:

sudo update-alternatives --remove-all mpicc

for all the mpi* commands.

> The problem mentioned in the bugs above results in broken alternatives
> for linking, so you should get trouble way after configuring. We're

Exactly, see the build log.

> going to upload a package that should fix a part of the problem but the
> real problem is that we're experiencing a bug in update-alternatives
> which does not create the links in a reasonable and reliable way, so
> until that's fixed, I'm not sure if you'll be able to get things to
> work.

Does it mean that libmesh will not be installable because of that? I
would like to fix it, somehow, now.

Would it be please possible to execute that command
(update-alternatives) above in the openmpi before installing?

> I think this problem occurs because g++ is not installed for this
> package (g++ seems to be mandatory).
>
> However, openmi is providing an cxx alternative even when C++ compiler
> is not installed. Is it the right way ?

Do you think that g++ isn't installed? I doubt. But in realite I don't
need g++, but mpicxx. And mpicxx doesn't seem to exist - exactly the
same problem happened to me, when I had lam/mpich installed, then
purged everything and then installed openmpi. The solution is to
execute the update-alternatives command in between - this needs to be
automated.

If what I wrote is true, then I think it's a very serious bug, which
prevents libmesh (and possibly other packages) to build.

Ondrej