I have modified Geant4 to use a quasi random number generator instead of the classical James Random pseudo random generator. This quasi random number generator generates numbers between 0 and 1, like the classical generator. When I am launching a particular GATE simualtion the following exceptions are thrown after a bit of a while. G4ParticleChange::CheckIt : the global time goes back !! Difference: 8501.7019[ns] G4ParticleChange::CheckIt ----------------------------------------------- G4ParticleChange Information ----------------------------------------------- # of 2ndaries : 0 ----------------------------------------------- Energy Deposit (MeV): 0 Track Status : Alive True Path Length (mm) : -2.55e+06 Stepping Control : 0 Mass (GeV) : 0 Charge (eplus) : 0 Position - x (mm) : 4.01e+05 Position - y (mm) : -4.43e+05 Position - z (mm) : 2.48e+06 Time (ns) : 1.88e+08 Proper Time (ns) : 0 Momentum Direct - x : -0.157 Momentum Direct - y : 0.174 Momentum Direct - z : -0.972 Kinetic Energy (MeV): 0.14 Polarization - x : 0 Polarization - y : 0 Polarization - z : 0 Track Weight : 0 Touchable (pointer) : 0x17f7930 *** G4Exception : 200 issued by : G4ParticleChange::CheckIt momentum, energy, and/or time was illegal *** Event Must Be Aborted G4VParticleChange::CheckIt : the true step length is negative !! Difference: 2.55e+06[MeV] G4VParticleChange::CheckIt ----------------------------------------------- G4ParticleChange Information ----------------------------------------------- # of 2ndaries : 0 ----------------------------------------------- Energy Deposit (MeV): 0 Track Status : KillTrackAndSecondaries True Path Length (mm) : -2.55e+06 Stepping Control : 0 Mass (GeV) : 0 Charge (eplus) : 0 Position - x (mm) : 4.01e+05 Position - y (mm) : -4.43e+05 Position - z (mm) : 2.48e+06 Time (ns) : 1.88e+08 Proper Time (ns) : 0 Momentum Direct - x : 0.157 Momentum Direct - y : -0.174 Momentum Direct - z : 0.972 Kinetic Energy (MeV): 0.14 Polarization - x : 0 Polarization - y : 0 Polarization - z : 0 Track Weight : 1 *** G4Exception : 100 issued by : G4VParticleChange::CheckIt step length and/or energy deposit was illegal *** Event Must Be Aborted
The QRNG has been added to CLHEP. The QRNG algorithm used is Sobol and is implemented in the GSL (GNU scientific librairy)
The exception indicates that some process propose "negative" step length. The problem may be caused by a bug in the proces or modification in random number genereation. But, no further information can be obtained by this report and I can not investigate this problem.
Could you please provide more information about the problem, to enable us to reproduce it ? Best regards, JOhn Apostolakis
No more info about this. Ticket being closed.
