Re: License Problem and Other Questions defining new package Geant4 from CERN for Partical Physcis Simulation

[Leo Prikler <leo.prikler@student.tugraz.at>]

Hello Sebastian,
Am Donnerstag, den 18.02.2021, 15:04 +0800 schrieb Sebastian:
> Dear developers at Guix,
> 
> I am a physics student willing to use  the Geant4 simulation toolkit
> from the European Organization for Nuclear Research (CERN). 
> https://geant4.web.cern.ch/
> The Geant4 code is distributied under its own licence, Geant4
> Software License Version 1.0. 
> https://geant4.web.cern.ch/license/LICENSE.html
> Let's call this license G4SL1.0. After some searching, finding it is
> NOT listed by FSF or GNU in their license list.
> https://www.gnu.org/licenses/license-list.html
> But from a personal perspective, G4SL1.0 do seems like a free
> software license.
> So, may it be included into the Guix proper (gnu packages)?
You should drop a mail to licensing@fsf.org.  On a quick glance, it
appears as though the Geant4 devs had a look at the original BSD
license and thought to themselves "I want that, but harder".

> I am currently testing the package under a custom channel,using
> cmake-build-system.
> https://git.nju.edu.cn/nju/chngix/-/blob/master/gix/packages/geant4.scm
> 
> Here is another problem:
> during configuring command "cmake" on a non-Guix system, 
> -- Geant4 has been pre-configured to look for datasets in the
> directory:
> -- /usr/local/share/Geant4-10.7.1/data
> the user needs to download datasets and unpack them under that
> directory.
> https://geant4.web.cern.ch/support/download
> Or, set flag -DGEANT4_INSTALL_DATA=ON to automatically download the
> datasets during building.
> On Guix however,
> -- Geant4 has been pre-configured to look for datasets in the
> directory:
> -- /gnu/store/byprhqa1qq6s0ksgdpjgwv58ak25kprd-geant4-
> 10.07.p01/share/Geant4-10.7.1/data
> the building process is sandboxed, and does not allow download during
> building that causing non-repuduciable build result.
> Cmake flag  GEANT4_INSTALL_DATADIR defaults to "share", a path
> relative to CMAKE_INSTALL_PREFIX,
> and it can be set to define the directory storing datasets other than
> ....../share, but datastes should always be under
> "GEANT4_INSTALL_DATADIR/Geant4-10.7.1/data".
> https://geant4-userdoc.web.cern.ch/UsersGuides/InstallationGuide/html/installguide.html#geant4buildoptions
> But the (source origin) denotes "a file" only,
> https://guix.gnu.org/manual/en/html_node/package-Reference.html
> is it possible to define a package fetching multiple files and
> extracts them into the desired directory, using the Guix package
> definition?
The "proper" way of fixing this would be to patch Geant, so that it
takes data from a configurable directory or path (e.g.
GEANT4_DATA_PATH), so that this can be set through a native-search
path, or alternatively honor XDG_DATA_DIRS, depending on what makes
more sense.

However, if fixing the narrower problem of lacking some important files
is all, that is needed, you can specify an origin to the data as an
input.  Assuming that you add ("geant-data" ,(origin ...)) to your
inputs, you then simply need to add a phase, which recursively copies
(assoc-ref inputs "geant-data") to wherever you need it.  

Note, that either way you should probably make it so that you're not
relying on such a specific version in your install paths.

> I am not familiar with trivial-build-system. 
> The build and install of the geant4 without datasets using cmake-
> build-system seems to be successful. 
> Your help would be much appreciated.
This should be doable with cmake-build-system.  Alternatively, if you
want the data as an extra package, you can use copy-build-system for
it.

Regards,
Leo