DD4hep Meeting August 27th, 2026

Present:     Andre, Juan, Markus, Thomas

Apologies: Peter

Link to minutes of previous meeting

Merged PRs

• PR1240  Add multithreading support to ddsim (Wouter)
          ---> probably longest pending PR

• PR1617  Make EventSeeder run before primary generation (Andre)

• PR1656  Removed .py extension from the g4PolarAngleScan help text (Andreas Loeschcke Centeno)
          ---> Cosmetics, corollary of PR1649

• PR1661  Geant4Output2EDM4hep: always use the metadata category for metadata (Andre)

• PR1662  Improve Geant4RegexSensitivesConstruction::collect_volumes to avoid duplicate regex searches (David Lange)

• PR1665  remove redundant calculations from i_collect and scanPhysicalVolume  (David Lange)

Closed PRs, closed issues and fixed problems

• ISSUE1659: EDM4hep writer creates two categories for metadata (Thomas).

Pending Problems

• 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
• ISSUE1568: Sim hits between two sensitive volumes (Alexander Tuna)
• ISSUE1633: Decouple DD4hep Readers/Writers into Separate Source and Injection/Build Stagesenhancement (Simon Gardner)
• ISSUE1635: ddsim crashes when given a particle outside world volumebug (Andre)
• ISSUE1643: Non-determinism in hit ordering when multiple detectors share readoutbug (Wouter)

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
• PR1663:   Geant4Output2EDM4hep: get run from worker context (Andre)
          ISSUE1660: OutputAction and contextsbug (Andre/Thomas)
• PR1664:   feat: honor DD4HEP_LIBRARY_PATH for plugin search (Wouter)
          ---> MacOS is non-trivial!
• PR1666:   Modified FCC MDI Synchrotron Radiation Mask geometry (Who is neskongarr?)

New:

• ISSUE1657:  DDG4 reduces the generator status to 16 bits and gives no warning (Marco Meyer-Conde)

Round Table

Andre:            Perhaps new tag after multi-threading issues are sorted out.
Juan:              NTR
Markus:         NTR
Thomas:        NTR

Next meeting:   September 17th, 2026