Conference notes for 2025 10 07

Lmod Zoom Meeting October 7, 2025

attendees:

• Robert McLay (TACC)
• Matthew Cawood (TACC)
• Bart Oldeman (Digital Research Alliance of Canada)
• Bob Dröge (Univ. of Groningen)
• Davide Grassano (CECAM)
• James Carpenter (Univ. of Birmingham)
• Kurt Lust (Univ. of Antwerp, LUMI User Support Team)
• Lara Peeters (Ghent University)
• Kenneth Hoste (Ghent University)
• Loris Ercole (CECAM)
• Pedro Santos Neves (Univ. of Groningen)
• Simon Branford (Univ. of Birmingham)
• Vladislav Mogilev (Univ. of Birmingham)
• Lev Gortenstein (Globus, Univ. of Chicago)
• Shelley Johnson (UVM)
• Alan O'Cais (freelancer)
• Adam Huffman (University of Oxford)

Notes

• My Last Meeting where I run the meeting
• My last day working is October 10th (4 days left!)
• Acknowledge Bill Barth
  • Friend, Co-worker and the one that started the Lmod Adventure
  • He asked: Can we switch compiler, mpi stacks with the hierarchy?
  • => Lmod
• New features since SC '24
• Irreversible functions
  • Allows sites to set variable when a module is unloaded.
  • load{"A","B", mode={"unload"}), setenv("A","a", mode={"unload"}}
• Lmod Internal documentation
  • https://lmod.readthedocs.io/en/latest/440_lmod_overview.html
  • Now provides a walking tour through the code for module load foo/1.0
  • Amazing work by Matthew Cawood to force/convince different AI Agents to deliver readable docs.
  • Detailed overview of how things like mcp and mname work. The core magic of Lmod.
• Big Cache Adventure
  • result of discussions in Jülich at EUM'25
  • Juelich with 100 dependent modules took a long time to load.
  • Thought that the spider cache needed to contain all modules.
  • Wrong!
• Improvements instead of Big Cache:
  • Dependent tree is now stored in ModuleTable Env. Var.
  • Do not reload spider cache for every dependent load
  • Now use posix.syslog calls instead of logger program if it can.
• Lmod 9.0 release
  • blocked by bug with Tcl modules
  • will include breaking change w.r.t. locations of saved collections
• people who report problems will be asked to provide reproducers
• Lmod's greatest feature: "It just works."
• Q/A

Next Meeting: Matthew January 2026