Offline Leads Meeting Notes: 8/14/24

Attendees: Michael Kirby, Thomas Junk, Erica Snider, Katherine Lato

LArSoft status:

• Spack status – see below.
• We want the offline leads and spokespeople to start thinking about what you want from LArSoft in the coming year. Will start the process of drafting next year’s work plan soon.
• GPU work on hold since labor shifted to Spack
• Geometry refactoring, Pixel detectors in geometry
• Infrastructure updates
• Refactoring event generators – waiting for Spack…
• Documentation updates – 
  • https://larsoft.github.io/LArSoftWiki/Supported_platforms 
  • https://larsoft.github.io/LArSoftWiki/Developing_LArSoft_with_Containers 
  • https://larsoft.github.io/LArSoftWiki/LArSoft_with_SPACK 

The main focus of the meeting was on the status of Spack. 

• As of the time of meeting, we did not have much new information since the August 6th LArSoft Coordination Meeting aside from the following update from Marc Paterno:
• The team is working to finalize a plan, with an associated document, for how we are to provide pre-built software through a Spack environment, what we call “standard builds”. This takes the place of UPS packages grouped into “umbrella products” or “distributions”. The document also describes new procedures and processes for managing releases, and the division of responsibilities between experiments and the SciSoft team should experiments wish to exploit the added flexibility in building releases that Spack provides.
• The team recently started testing a method for building standard releases that avoids issues of Spack “re-concretizing” already-built products. This re-concretizing is the last significant issue with Spack that is blocking migration.
  • [Discussed this point with Marc after the meeting. The candidate solution involves creating a sub-environment of low-level libraries, then telling Spack that they are not re-buildable. This approach worked in a small scale test, and is now being tested on a large software suite (not LArSoft).]
• The team has developed a beta version of a download-and-setup script that with only two commands installs spack and sets up a personal environment ready for development

• Q:  Is there  “added flexibility” because it allows experiments to build against any compatible version of any dependent product?
  • A:  Essentially yes. UPS locks you into specific versions. Spack does not. This is something DUNE has been requesting for a long time. It has many benefits, but also some notable costs. 
  • Along the lines of added flexibility, there has long been a work plan item to decouple the version of GENIE from LArSoft. We will complete this work after the migration. Can then compare two versions of GENIE in exactly the same LArSoft release.
• Q:  Is progress on the migration moving faster since moving the project into DSSL?
  • A:  [Update since the meeting:  as noted above, there is potentially significant progress on solving the main problem that has plagued Spack for a long time. Also, there has been progress in recent weeks in several areas that are relevant to LArSoft. So maybe.]

Please email Katherine Lato or Erica Snider for any corrections or additions to these notes.