DD4hep Developers Meeting

Thursday 19 Nov 2026, 15:30 → 16:00 Europe/Zurich

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Andre Sailer (CERN), Markus Frank (CERN)

Please Join DD4hep developer's meeting via Zoom

DD4hep Meeting November 5th, 2026

Present:      Andre, Markus, Peter

Apologies:  Juan, Thomas

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Link to minutes of previous meeting

Merged PRs

• PR1695:  Fix concurrent DDDigi container combining (Juan)
     ---> Missing locking caused crashes
• PR1700:  Geant4Action: get event action by name without splitting. (Andre)

• PR1701:  CI: build and test k4geo against DD4hep (Juan)

• PR1702:  fix(Geant4ParticleHandler): avoid duplicate track-equivalents map at end of event (Wouter)
     ---> memory saving mechanism
• PR1703:  Speed up the placement path search in the SurfaceManager map build (Joshua Beirer)
• PR1704:  SurfaceManager: enter each surface only once into the type and world maps (Joshua Beirer)
• PR1705:  Fix RICH tests with ROOT object auto-registration disabled (Juan)
• PR1706:  Fix bug in Volume divisions (Markus)
• PR1707:  Multiple commits: doc, Geant3 geometries, structure creation plugin (Markus)
• PR1712:  Thread safety fixes (Giovanni Machiori)

Closed PRs, closed issues and fixed problems

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• ISSUE1568: Sim hits between two sensitive volumes (Alexander Tuna)
                        ---> See PR1690
• ISSUE1693: Incorrect number of events saved to EOS when running with multithreading (IDEA o1 v4)bug (Andrea da Vita)
                        ---> See PR1700
• ISSUE1711: DetElement::nominal() and VolumeManager::getVolumeManager() are not thread-safe on first access
                       (ddsim crashes / wrong positions in MT mode)bug (Giovanni Machiori)
                        ---> See PR1712

Pending Problems

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• ISSUE1335: Uniform random picking of points on detector surfaces for noise studies
                         This problem is linked to #1297 and #580.
• ISSUE1458: Possible discrepancy between xml file and geometry converted into root file
• ISSUE1501: Bug/Feature: Condense duplicated particle contributions in calorimeter question
• ISSUE1633: Decouple DD4hep Readers/Writers into Separate Source and Injection/Build Stagesenhancement (Simon Gardner)
• ISSUE1643: Non-determinism in hit ordering when multiple detectors share readoutbug (Wouter)
• ISSUE1657: DDG4 reduces the generator status to 16 bits and gives no warning (Marco Meyer-Conde)
     ---> What to do here ?
• ISSUE1667: LCIO output not writing runParameters (Andre)
• ISSUE1671: CI: replace macOS brew install with lcgcmake installenhancement (Andre)
• ISSUE1683: Bug about the thickness in DiskTracker_geo.cppbug (Fangyi Guo)

Pending PR:

• PR1606:   feat: AdePT physics list plugin for e+/e-/gamma offload to GPU [WIP] (Wouter)

• PR1626:  feat: add support for python geometry plugins (Wouter)
• PR1658:   [DRAFT POC] Add Arrow IPC stream writer for EDM4hep output (Wouter)
          ---> What is arrow IPC
• PR1664:   feat: honor DD4HEP_LIBRARY_PATH for plugin search (Wouter)
          ---> MacOS is non-trivial!
• PR1672:  Add cvmfs/LCG-based macOS workflow (Wouter)
• PR1682:  AssimpWriter: Drop need for rootcsg (Andre)
     ---> PR started, but still problems with assemblies. Problem was always present in rootcsg.
• PR1692:  fix(Geant4InputHandling): start a tracked parent-less particle at its own production point (Joshua Beirer)
     ---> Does this not do the gun as well ?

New:

• PR1702:  fix(Geant4ParticleHandler): avoid duplicate track-equivalents map at end of event (Wouter)
• PR1709:  fix: avoid printing every constant on failed getRefChild (Dimitry Kalinkin)
• ISSUE1708: Add SetCheckPrimaryMass to plugin interfaceenhancement (Andre)
• ISSUE1710: ddsim selects EDM4hep reader for HepMC3 ROOT input named .hepmc3.root, then reports misleading podio_metadata errorbug (K.Kauder)

Round Table

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Andre:            NTR
Markus:         NTR
Thomas:        NTR

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Next meeting:   November 19th, 2026

15:30 → 15:50 Around the table