DD4hep Meeting December 11th, 2025

Present:     Andre, Markus

Apologies: Juan, Peter, Thomas

Link to minutes of previous meeting

Merged PRs

• PR1536:       Remove unnecessary check (Thomas)
  ISSUE1529: Next podio tag will break EDM4hep reader (Thomas)

• PR1534:      VolumeBuilder fix to handle case where volume is created with constructor (Ben)
  PR1533:      Fix assembly handling in VolumeBuilder according to LHCb XML syntax (Markus)
                       All followup of to issue 1524.
                       ---> Real backwards compatibility with check of full detector checksum is not really simple

• PR1532:      Delay creating surfaces with the SurfaceManager plugin until it's needed (Juan)

• PR1531:      Remove unused variable to prevent a compiler warning (Juan)

• PR1530:      Fix the EDM4hep reader since frame.get throws if a collection is not found (Juan)

Closed PRs, closed issues and fixed problems

• None

Pending Problems

• ISSUE1297:  Possible to dump all available readout elements?
                        ==> Possibly a copy of unsolved ISSUE580 from Valentin about enumerating all sensitive cells.
• ISSUE1320:  Replacing a Handle<Segmentation> which contains a MultiSegmentation with the underlying Segmentation
                        ==> Unclear what he really means.
• ISSUE1335:   Uniform random picking of points on detector surfaces for noise studies
                         This problem is linked to #1297 and #580.
• ISSUE1373:  Add GeneratorInfo to EDM4hepReader (Andre)
• ISSUE1443:  Make user particle handler extensible
                         ---> Maybe we should take advantage and re-collect requirements.
• ISSUE1458: XML file vs TGeoStored geometry in GenFit
• ISSUE1487: The test t_DDDigi_sim_test_weighted_deposit_overlay can fail (Juan)
    ---> Unstable test 
• ISSUE1489:  using SkinSurfacequestion
                        ----> Issue re-opened by Sara Eno
                        ----> Does she have a problem with the interface ?
• ISSUE1492:  Readout segmentation for multiple cylinders with offset axes question
                        ----> Unclear code in CylindricalGridPhiZ.cpp line 80
                        ----> Try special case where axis is identical to beam axis.
• ISSUE1501: Bug/Feature: Condense duplicated particle contributions in calorimeter question
• ISSUE1514: How to convert Geant4TrackID into MCParticle Parent ID

• ISSUE1515: How to apply the step_length_max limit to neutral particles?
                        ----> Issue opened by Andreas Loeschke
• ISSUE1520: Missing segmentation in the box of straws (Juan)
                        -----> This detector has intentionally no segmentation, because the sensitive volumes should not enter the volume manager since there are so many....
                         Sensitive detector is attached to main gas volume, which perhaps is wrong: It should not be attached to any volume.
                         There are 2 tests related to BoxOfStraws. Not both seem to fail. Maybe the problem is related to the DDSim setup in the second test?
  
                         "NoSegmentation" segmentation added.
                         Did this improve anything for the reliability of the tests ?

New:

• ISSUE1535: How to add new output variables in Hitsquestion (matclim -> DD4SHip)
• ISSUE1537: G4Kernel configuration error (gondiaz)
                        DDG4 or ddsim issue ?

Pending PR:

• PR1240:        Add multithreading support to ddsim
• PR1314:        Cylinder segment surface (Armin Ilg)
• PR1503:        [WIP] Add flag for fast simulation to MCParticle (Thomas)

Round Table

Juan:.     NTR
Markus:  NTR
Peter:      Started looking into issue opened by Andreas 1515.
Andre:     New release V01-34. LCG view 108a_LHCb_Core

AOB

Next meeting:   January 15th, 2026