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Forum: Physics List
Re: Question ionIoni at low energies
Re: Idea Re: ionIoni at low energies (Vladimir Ivanchenko)
Re: None Re: ionIoni at low energies
Re: Idea Re: ionIoni at low energies (Michael H. Kelsey)
Re: None Re: ionIoni at low energies
Date: 03 Jul, 2013
From: Michael H. Kelsey <Michael H. Kelsey>

m.balmer@lancs.ac.uk writes:
> Thanks for the tip with the debugger (also to those who emailed me
> offline).

Hi, Matt.  It looks like you are still using a non-debug installation of
G4.  If you do move forward to patch-02 (recommended), then in CMake you
want to change the build type to "Debug",

 cmake -DCMAKE_BUILD_TYPE=Debug <all your other stuff here>

What this will do is allow you to see exact line numbers, and the parameters
passed to functions, in the GDB traceback.  It also allows stepping through
the exectuable at runtime to isolate where a problem occurs.

> 1) I am tracking a neutron into a liquid scintillator, in this case the
> following material:
> 
>   fScint=new G4Material("Scint", 0.92*g/cm3, ncomponents=4);
> 
>   fScint->AddElement(fC, fractionmass=0.857);
>   fScint->AddElement(fH, fractionmass=0.104);
>   fScint->AddElement(fO, fractionmass=0.029);
>   fScint->AddElement(elL6, fractionmass=0.01);
> 
> but I have seen the same crash with Boron-10 loading too. Same scenario,
> neutron capture of neutron in boron-10, then boron-12 decay causes
> crash.
> 
> 2) The crash occurs when I get a 8Li particle appearing in the tracking.
> These are very low energy particles and the crash seems to occur when
> they decay.

Interesting.  Both of these isotopes decay to "8-Be", which of course
immediately falls apart into two alphas.  I wonder if it's that latter which
is causing your problem.

> Running gdb debugging, I see the following:
[...]
> Program received signal SIGSEGV, Segmentation fault.
> 0x00007ffff5053c3a in G4NuclearDecayChannel::DecayIt(double) () from ~/Geant/geant4.9.6-install/lib/libG4processes.so
> (gdb) backtrace
> #0  0x00007ffff5053c3a in G4NuclearDecayChannel::DecayIt(double) () from ~/Geant/geant4.9.6-install/lib/libG4processes.so
> #1  0x00007ffff50598f9 in G4RadioactiveDecay::DoDecay(G4ParticleDefinition&) ()
>    from ~/Geant/geant4.9.6-install/lib/libG4processes.so
[...]

This is where a "Debug" build of GEANT4 itself will be helpful.  You'll be
able to inspect that G4ParticleDefinition to see what particle it is, ad
also see if the G4NuclearDecayChannel object is correct, or is maybe a null
pointer.

I know that re-doing an installation is a pain, but there is one thing you
can do "efficiently."  First, apply the |cmake| command I quoted above to
change the build type.  Then, do |make clean| followed by |make install|.
You do *NOT* have to wipe out directories or anything else.  Those two
commands will just get rid of your current .o files and make new ones, with
debugging symbols.

If you then recompile and relink your application, you should get a fully
instrumented debuggable executable.

      -- Michael Kelsey

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1 None: Re: ionIoni at low energies   (matt_b - 04 Jul, 2013)
(_ None: Re: ionIoni at low energies   (Mike Kelsey - 04 Jul, 2013)
(_ None: Re: ionIoni at low energies   (matt_b - 05 Jul, 2013)
1 Idea: Re: ionIoni at low energies   (Vladimir Ivanchenko - 05 Jul, 2013)
1 Sad: Re: ionIoni at low energies   (matt_b - 09 Jul, 2013)
2 None: Re: ionIoni at low energies   (Mike Kelsey - 05 Jul, 2013)
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