DD4hep Meeting June 5th, 2025

Present:     A.Sailer, M.Frank, F.Gaede, P.McKneown

Apologies: A.Tolosa Delgado, T.Madlehner

Link to minutes of previous meeting

Merged PRs

• PR1449:    Prevent new TColor allocation in VisAttr::color()  (Dmitry Kalinkin)

• PR1450:    Gcc15 bind (Andre)
  PR1453:    Gcc15: fix checksum access errors, non-void return (Andre)
                     (See also ISSUE1452, 1451)

• PR1455:    TGeoTrd1 generic surfaces (Armin Ilg)
                     -- Have surfaces for TGeoTrd1's that are not in y direction

• PR1456:    fix: avoid exit codes in thisdd4hep.sh for set -e support (Dmitry Kalinkin)

Closed PRs, closed issues and fixed problems

• ISSUE1199: Persist hepmc vertex status code into output
• ISSUE1451: Compilation error with gcc15, c++23
  ISSUE1452: Problem in OpaqueDataBlock
                        -- Compiler error found by gcc15
                        -- Bad return screwed up program stack
• ISSUE1457: CMake Error in Installing: Target ROOT::ROOTHistDraw
                       + cling compile error std::any
                       -- Using bad ROOT build (need to set CMAKE_CXX_STANDARD=17 in ROOT as well)

Pending Problems

• ISSUE1285:  Memory Consumption of Sensitive Detectors
                        ==> Should be handled as illustrated in PR1288. Intrinsic problem of the Geant4VolumeManager;
• ISSUE1297:  Possible to dump all available readout elements?
                        ==> Possibly a copy of unsolved ISSUE580 from Valentin about enumerating all sensitive cells.
• ISSUE1319:  Problem with regexSensitiveDetector and volume IDs
                        ==> Interesting use case for reg-ex sensitive detectors
                               having a VolumeMgr equivalent.
• 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.
• PR1240:        Add multithreading support to ddsim
• PR1304:        SurfaceManager: lazily construct surface maps on demand (Leonhard Reichenbach)
• PR1314:        Cylinder segment surface (Armin Ilg)
• ISSUE1373:  Add GeneratorInfo to EDM4hepReader (Andre)
• ISSUE1443:  Make user particle handler extensible
                         ---> Maybe we should take advantage and re-collect requirements.
  
  New issues:
• PR1454:    CI: add gcc15 dbg dev3 builds (Andre)
                     -- Contains debug builds and tests

Round Table

Andre:        NTR
Markus:     NTR
Peter:         Related to fast-simulation: Need for machine learning to tell Geant4 that whole subdetectors are sensitive, not only certain layers e.g. in a calorimeter.
                   Possibility:
                   1) Remap a certain subdetector to a non-standard Geant4SensitiveDetector instance.
                   2) In Geant4DetectorSensitivesConstruction or equivalent assign this Geant4SensitiveDetector instance to all volumnes of such a subdetector.
Frank:         NTR

AOB

Next meeting:   June 19th, 2025