I found that a Geant4 (4.3.0) program sometimes enters an infinite loop when a gamma ray (or a geantino) is injected into the boundary of G4BREPSolidPolyhedras adjacent to each other parallel to the boundary plane. It just repeats transportations between the two G4BREPSolidPolyhedras with 0 step lengths. An example modified from N01 can be downloaded from the provided URL. I also tried the same test replacing the G4BREPSolidPolyhedras by G4Boxes and had no problem with G4Boxes.
Thanks for the report. The problem is under investigation.
Radovan is going to investigate on this.
Fix commited into CVS HEAD, description follows: revision 1.2 date: 2001/05/09 15:52:31; author: radoone; state: Exp; lines: +44 -23 Fixed problem reported in Bugzilla with No. 185 Added the additional check in CheckPointOnSurface method which helps to resolve endless looping of G4Navigator in case the track is passing through a point, edge or surface shared by two solids. This problem occured when G4Navigator was trying to transport a particle when exiting a solid. After this fix the transportation will perform a few zero steps and continues stepping instead of looping around the same point. Radovan Chytracek
Resolved
Fixed
