[Neurodebian-users] keep multiple neurodebian software versions

[Michael Hanke]

Hi,

On Tue, Feb 22, 2011 at 03:46:48PM +0100, marco tettamanti wrote:
> Basically, there are softwares (e.g. mricron/dcm2nii or fsl), for
> which I very much want to use the same version to analyze a specific
> data set, in order to be sure to keep all relevant processing
> parameters constant across the experiment. Under some circumstances,
> this may require having multiple software versions installed, in
> order to benefit from software upgrades for newer experiments but
> still be able to use older versions to analyze, modify or review
> older experiments.

You are pointing to an important issue. We do support co-installation of
FSL, but not for most others. The primary reason is that virtually no
projects actually maintain old versions of their software. You need to
upgrade to get the bugfixes. We have no resource to do the bugfix
backports ourselves. And you really want the bugfixes to make sure you
results are not an artifact of a software bug -- where it would be good
thing if they go away with an upgrade ;-)

But the actual issue is more global than it looks like. Even if you
kept your old version of FSL around it could still change its behavior
over time. The reason is that pretty much all software relies on
computational and other 3rd-party libraries. Those libs are installed on
the system and change independently from the "frontend" software itself.
Consequently, just keeping FSL's version constant doesn't help you much.

One solution is to snapshot your whole analysis environment and archive
it together with the data of any study. You can easily do that with
Virtual Machines (like ours), or chroots if that is enough. The
advantages of VMs are that you can take them out some years later, boot
them up and run a re-analysis in exactly the same environment -- even
after your original machine died, or you moved to another lab and don't
even have access to it anymore.

Given that it is very cheap to snapshot the whole system and very time
consuming to maintain co-installable software with countless versions and
dependencies we generally favor to former for practical purposes.

Does that make sense?


Michael


-- 
Michael Hanke
http://mih.voxindeserto.de