DD4hep meeting 03/12/2020
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A.Sailer, C.Vuosalo, M.Frank, I.Osborne, M.Petric

1)   Pending problems

1.1  Pending problems reported by Sang Hyun Ko:
   - Cannot setup Birk's constant as material property.
   - No analogy to G4PVParametrized. Unclear if a solution is possible.
1.2  Change of unit system to Geant4 units: Issue 753 on Hold.
1.3  New issue with G4 primaries

2)   Closed issues and fixed problems

- PR for module writing DDG4 data with EDM4hep and PODIO merged.
- Proper G4 conversion of TGeoScaledShape implemented for Geant4 > 10.03

- Reflection Rotations: According to Gabrielle fixed and understood.
  Issue got closed.

- Possible improvements for checking/linker compiler flags for different compilers (gcc, clang)
- Fixes to multi-threading issues concerning expression evaluation.

4) Round table
   Andre:     Problems with the HEPMC reader (HEPMC-2) Geant4ReaderHepMC.
              Problems found with clashing units and secondary vertices.

                          Need to see if other people stumble over the problem before removing
                          the component. The idea is to remove this reader and only use
              the also supplied HepMC-3 reader. Frank needs to comment on the
              usage of this reader in ILC software.
   Carl:      Reflections and multi-threading issues are fixed.

   Frank:     (message)
              working on finalizing https://github.com/AIDASoft/DD4hep/pull/740
              - need to cleanup the treatment of units
              - should be done later today
   Ianna:     Milestones are finally met. They though still see some issues

              with race conditions.
   Marko:     -- Fixed units business. Two lessons learned:

                 1) Do not use G4SystemOfUnits.hh. Use CLHEP/Units/SystemOfUnits.h
                 2) Never say "using namespace CLHEP".
              -- Preparing new release.
   Markus:    All already mentioned.

5) AOB
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Next meeting in 2 weeks: 14/01/2021