Bug#575259: mpi-default-dev doesn't ensure that the right implementation is used

[Thibaut Paumard]

Hi Manuel,

Le 25 mars 10 à 18:07, Manuel Prinz a écrit :

> So, given that the priority in Open MPI changed and we will  
> transition,
> do you think the patch is useful? I do not refrain from applying it to
> mpi-default but my understanding is that we do not need to have it  
> as of
> now.

No, with the prioriy of OpenMPI raised above that of MPICH2, and with  
the idea of switching from LAM to MPICH2 on the other arches, my patch  
does not bring any _immediate_ benefit. It's a proposal for a longer  
term solution, but you seem to have other ideas and you have time to  
let them mature.

> To be clear: I'm very much in favor of having a solution that works
> correctly with whatever MPI implementation is chosen as the local
> default. But u-a can not be used to realize that. Once the sysadmin  
> set
> the default manually, we have lost, no matter how high the priority of
> the mpi-defaults alternative is.

Something to clarify: my understanding is that mpi-default is a  
_Debian_ default, not local default. The problem with the sysadmin  
setting the alternative is not relevant for buildds, and is addressed  
by using the mpicc.default et al. links instead of mpicc. Dealing with  
a local default looks more difficult, requiring a rebuild a little bit  
like kernel modules, which IMHO would be more complex than providing  
the two variant openmpi and mpich2 in the first place.

Regards, Thibaut.