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Forum: Fields: Magnetic and Otherwise
Re: None Crazy Point in G4Field::GetFieldValue() (Tom Roberts)
Re: None Re: Crazy Point in G4Field::GetFieldValue()
Date: 17 Dec, 2005
From: Tom Roberts <Tom Roberts>

Thank you. I downloaded the Geant4 7.1p01 source, built it and my program (no errors), and re-ran my test. Now instead of a segment fault it loops forever on the same event. Here are the last few lines of my customized steppingVerbose print (in UserSteppingAction()):
=================== Event 167408188 ==================
=========== Event 167408188 Track 1 pi+  Parent 0 =========
 Step   X(mm)   Y(mm)   Z(mm)    T(ns)      Px,Py,Pz (MeV/c)       StepLen This Volume      Process
... 
   46   -53.2    83.0  3856.5    13.55      8.8     20.2    424.0   100.00 vacuum2          StepLimiter
   47   -52.2    85.3  3905.7    13.72      8.7     19.9    424.1    49.32 vacuum2          Transportation
   48   -51.8    86.7  3928.2    13.80     -2.3     -6.0   -114.4    22.53 pipe2            PionPlusInelastic
   49   -51.9    86.1  3922.1    13.83      nan      nan      nan     6.18 pipe2            hIoni
Following this is an endless number of diagnostic prints stating there is a nan in point[] to G4Field::GetFieldValue() -- that is within a step so I could not even kill the track if I tried.

In the prints above, the nan-s came from step->GetTrack()->GetMomentum(), "This Volume" comes from step->GetPreStepPoint(), and "Process" comes from step->GetPostStepPoint(). vacuum2 has material=Vacuum, and pipe2 has material=Al. I'm using the physics use case LHEP_BIC. There is a fringe B field ~0.03 Tesla here.

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1 Feedback: Re: Crazy Point in G4Field::GetFieldValue()   (John Apostolakis - 18 Dec, 2005)
1 None: Re: Crazy Point in G4Field::GetFieldValue()   (Tom Roberts - 21 Dec, 2005)
(_ None: Re: Crazy Point in G4Field::GetFieldValue()   (Tom Roberts - 03 Jan, 2006)
(_ Warning: Re: Crazy Point in G4Field::GetFieldValue()   (Peter Gumplinger - 04 Jan, 2006)
(_ None: Re: Crazy Point in G4Field::GetFieldValue()   (Tom Roberts - 04 Jan, 2006)
3 None: Re: Crazy Point in G4Field::GetFieldValue()   (vnivanch@mail.cern.ch - 18 Dec, 2005)
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