Geant4: document RunManager perforamnce issue and allow multithreading with one worker
Follow-up of !943 (closed).
- Fixes a missing override in run managers
- Allows multithreading with one worker (emit warning)
- Add test for MT with one worker
- Updates documentation to inform users about this issue
Two questions remain:
- Should the
multithreading=true
+worker=1
log message be a warning if it is a legitimate use-case? - Should the test for this case be part of GeometryBuilderGeant4? It's actually just a copy of a DepositionGeant4 test with adjusted mt settings