Re: How is mpi-default-dev supposed to work?

[Thibaut Paumard <mlotpot.news@free.fr>]

Hi,

Le 23 mars 10 à 19:40, Lucas Nussbaum a écrit :
> I think that the best way to solve this problem is to explicitely
> conflict with the other implementations in mpi-defaults. I don't see  
> any
> other solution that really fixes the problem we are having and doesn't
> require an upload of all packages using mpi-defaults.

I thought about that a little bit more carefully and I think it is a  
dangerous solution that may lead to many FTBFSes. At least it needs to  
be tested.

The problem is that is that the way dpkg chooses between two  
conflicting packages may not be what we expect. What we want is that  
dpkg always installs the last package selected for installation,  
uninstalling the one installed:
- if mpich2 is installed and installation of mpi-default-dev is  
requested, uninstall mpich2;
- if mpi-default-dev is installed and installation of mpich2 is  
requested, uninstall mpi-default-dev.

Is it what will happen in practice? I'm afraid that the opposite will  
happen: dpkg may well refuse to install the new package because a  
conflicting package is already installed. I believe what we want to do  
requires a combination of Conflicts, Provides and Replaces that will  
be hard if not impossible to put in place.

Regards, Thibaut.