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None Infinite loop in novice/exampleN04 using geant4.8.1-patch01!!! 

Keywords: nan, deadloop
Forum: Hadronic Processes
Date: 11 Sep, 2006
From: G.F. Cao <G.F. Cao>

Dear G4 Experts,
  We encountered a dead-loop in our detector simulation using Geant4.8.1.p01 (hadronic
package QGSP). It seems our problem is related to AntiProtonInelastic process. We find that for some low-energy anti-proton, its momentum and direction become to NAN when 
the program goes to infinite loop. In order to check if the problem is from our side, I did a test using novice/exampleN04 provided by geant4.8.1.p01. First, I did several changes in the eaxmple for antiproton tracking.

1) comment out StackingAction in exampleN04.cc, all scondaries will be reacked:
  // G4UserStackingAction* stacking_action = new ExN04StackingAction; 
  // runManager->SetUserAction(stacking_action); 
2) in ExN04PrimaryGeneratorAction.cc
   #include "Randomize.hh" 
   G4ParticleDefinition* particle = particleTable->FindParticle(particleName="anti_proton");
   set fParticleGun->SetParticleEnergy((51+G4UniformRand()*50)*MeV); 
3) use exampleN04.in as macro file:
  # /mydet/RoIangle 10 deg
  # /mydet/reqmuon 1
  # /mydet/isomuon 1
   /control/verbose  1
   /run/verbose      1
   /tracking/verbose 0
   /run/beamOn 1000000

As a result, the same situation was found. The program went to infinite loop at event 44990. See the tracking information below with /tracking/verbose 6

*********************************************************************************************************
* G4Track Information:   Particle = anti_proton,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng     Volume     Process
    0      0 fm      0 fm      0 fm   67.9 MeV     0 eV      0 fm      0 fm    expHall_P    initStep

 >>DefinePhysicalStepLength (List of proposed StepLengths):
    ++ProposedStep(PostStep ) = 36918.282 : ProcName = AntiProtonInelastic (No  ForceCondition)
    ++ProposedStep(PostStep ) = 208773.54 : ProcName = hElastic (No ForceCondition)
    ++ProposedStep(PostStep ) = 8.8941426 : ProcName = hIoni (No ForceCondition)
    ++ProposedStep(PostStep ) = 1.7976931e+308 : ProcName = msc (Forced)
    ++ProposedStep(PostStep ) = 1.7976931e+308 : ProcName = Transportation (Forced)
    ++ProposedStep(AlongStep) =  50260.06 : ProcName = hIoni (CandidateForSelection)
    ++ProposedStep(AlongStep) =  8.894141 : ProcName = msc (NotCandidateForSelection)
    ++ProposedStep(AlongStep) =  8.894141 : ProcName = Transportation (CandidateForSelection)
... ...
... big skip
#Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng     Volume     Process
   80  -20.4 cm   34.8 cm  -2.44 mm   2.13 MeV    12 MeV  1.26 mm   42.4 cm   trackerLayer_phys       hIoni

 >>DefinePhysicalStepLength (List of proposed StepLengths): 
    ++ProposedStep(PostStep ) = 0.05207071664281887 : ProcName = AntiProtonInelastic (No ForceCondition)
    ++ProposedStep(PostStep ) = 40.82619179226723 : ProcName = hElastic (No ForceCondition)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = hIoni (No ForceCondition)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = msc (Forced)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = Transportation (Forced)
    ++ProposedStep(AlongStep) = 0.05316910600208757 : ProcName = hIoni (CandidateForSelection)
    ++ProposedStep(AlongStep) = 0.05186068454676943 : ProcName = msc (NotCandidateForSelection)
    ++ProposedStep(AlongStep) = 0.05186068454676943 : ProcName = Transportation (CandidateForSelection)

 >>AlongStepDoIt (process by process):    Process Name = Transportation

    ++G4Step Information 
      Address of G4Track    : 0xa346b20
      Step Length (mm)      : 0.05186068454676943
      Energy Deposit (MeV)  : 0
      -----------------------------------------------------------------------
        StepPoint Information               PreStep            PostStep
      -----------------------------------------------------------------------
         Position - x (mm)   :   -204.2736407465781  -204.3178574956753
         Position - y (mm)   :    348.4945252611842   348.5195802058862
         Position - z (mm)   :   -2.436856962280072   -2.42652936189449
         Global Time (ns)    :    4.329706447170537   4.332279994268195
         Local Time (ns)     :    4.329706447170537   4.332279994268195
         Proper Time (ns)    :    4.086523306909923   4.089091033453018
         Momentum Direct - x :  -0.8524280729078487 -0.8527845550176441
         Momentum Direct - y :   0.4834347442858566  0.4828056277504221
         Momentum Direct - z :   0.1991412276146746  0.1991412276146747
... ...
... small skip
... the first nan appears
 >>PostStepDoIt (process by process):    Process Name = AntiProtonInelastic

    ++G4Step Information
      Address of G4Track    : 0xa346b20
      Step Length (mm)      : 0.05207071664281887
      Energy Deposit (MeV)  : 2.05859873404215
      -----------------------------------------------------------------------
        StepPoint Information               PreStep            PostStep
      -----------------------------------------------------------------------
         Position - x (mm)   :   -204.2736407465781   -204.319970104144
         Position - y (mm)   :    348.4945252611842   348.5154997473365
         Position - z (mm)   :   -2.436856962280072  -2.425683387001505
         Global Time (ns)    :    4.329706447170537   4.332279994268195
         Local Time (ns)     :    4.329706447170537   4.332279994268195
         Proper Time (ns)    :    4.086523306909923   4.089091033453018
         Momentum Direct - x :  -0.8524280729078487                 nan
         Momentum Direct - y :   0.4834347442858566                 nan
         Momentum Direct - z :   0.1991412276146746                 nan
         Momentum - x (MeV/c):   -53.88345198779397                 nan
         Momentum - y (MeV/c):    30.55874584714016                 nan
         Momentum - z (MeV/c):    12.58806123120922                 nan
         Total Energy (MeV)  :    940.3991873554132   938.3405886213711
         Kinetic Energy (MeV):    2.126887355413274 0.06828862137112379
         Velocity (mm/ns)    :    20.15144179563204   3.616776901458536
         Volume Name         :    trackerLayer_phys   trackerLayer_phys
         Safety (mm)         :   0.7969176405153779  0.8333978912969117
         Polarization - x    :                    0                   0
         Polarization - y    :                    0                   0
         Polarization - Z    :                    0                   0
         Weight              :                    1                   1
         Step Status         :      AlongStep Proc.       PostStep Proc
         Process defined Step:                hIoni AntiProtonInelastic
      -----------------------------------------------------------------------
... ...
... small skip
#Step#      X         Y         Z        KineE    dEStep   StepLeng  TrakLeng     Volume     Process
   81  -20.4 cm   34.9 cm  -2.43 mm   68.3 keV  2.06 MeV  52.1 mum  42.4 cm    trackerLayer_phys  AntiProtonInelastic

 >>DefinePhysicalStepLength (List of proposed StepLengths):  
    ++ProposedStep(PostStep ) = 44.52449073783492 : ProcName = AntiProtonInelastic (No  ForceCondition)   
    ++ProposedStep(PostStep ) = 36.7761184247093 : ProcName = hElastic (No ForceCondition)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = hIoni (No ForceCondition)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = msc (Forced)
    ++ProposedStep(PostStep ) = 1.797693134862316e+308 : ProcName = Transportation (Forced)
    ++ProposedStep(AlongStep) = 0.000767365494101051 : ProcName = hIoni (CandidateForSelection)
    ++ProposedStep(AlongStep) = 0.0007558743340329251 : ProcName = msc  (NotCandidateForSelection)

The program stopped here.

  How to solve this problem? Momentum is nan, why?

Thanks in advanced.

Guofu

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1 None: Re: Infinite loop in novice/exampleN04 using geant4.8.1-patch01!!!   (Vladimir IVANTCHENKO - 12 Sep, 2006)
(_ None: Re: Infinite loop in novice/exampleN04 using geant4.8.1-patch01!!!   (MaTao - 22 Mar, 2007)
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