Proposal to (formally/easily) allowing multiple versions of the same library installable

[Martyn Foster]

On 16 February 2015 at 15:12, Kevin Kofler <kevin.kofler at chello.at> wrote:

> Christopher Meng wrote:
> > Maintaining several version of the same library is not easy as you think,
> > basically once a developer wants to install version X while then another
> > people want to deploy things based on version Y, how to crack this nut?
> > You can't just care about runtime.
>
> Then you need to patch one or the other package to work with the same
> version. Only if that is not possible, a compatibility library can be
> considered. But we should always first try to make everything work with the
> same version (if possible, the newer one).
>
>
The requirement to work with multiple versions of a package come up in the
scientific/HPC community very frequently. Its not always about API
compatibility, sometimes exact numerical reproduction is required which
isn't preserved even between minor versions (i.e. an OS update). These
environments usually (increasingly often) use the environment-modules
package (ideally with relocatable packages) to select between libraries or
incompatible subsystems. This is more often done by admins than explicit
support from the OS packagers, but it *can* be done elegantly as part of
the packaging process if there is a will.

Fedora already uses this - admittedly in rather limited ways;

# rpm -qf  /etc/modulefiles/mpi/mpich-x86_64
mpich-3.1-4.fc21.x86_64
# rpm -qf  /etc/modulefiles/mpi/openmpi-x86_64
openmpi-1.8.3-2.fc21.x86_64

Much more comprehensive environments can be built from the methodology.

Cheers, Martyn
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