Hi, It seems that the code here: http://www-geant4.kek.jp/lxr/source/processes/hadronic/models/parton_string/hadronization/src/G4LundStringFragmentation.cc#L509 can cause a (nearly) infinite loop. In particular, I have this stack from gdb: #0 0xf0773f2b in G4VLongitudinalStringDecay::SampleQuarkPt () from /afs/cern.ch/atlas/software/builds/AtlasSimulation/15.1.0/InstallArea/i686-slc4-gcc34-opt/lib/libG4processes.so #1 0xf076e36f in G4LundStringFragmentation::Sample4Momentum () from /afs/cern.ch/atlas/software/builds/AtlasSimulation/15.1.0/InstallArea/i686-slc4-gcc34-opt/lib/libG4processes.so #2 0xf076f38e in G4LundStringFragmentation::SplitLast () from /afs/cern.ch/atlas/software/builds/AtlasSimulation/15.1.0/InstallArea/i686-slc4-gcc34-opt/lib/libG4processes.so #3 0xf076ff2a in G4LundStringFragmentation::FragmentString () from /afs/cern.ch/atlas/software/builds/AtlasSimulation/15.1.0/InstallArea/i686-slc4-gcc34-opt/lib/libG4processes.so #4 0xf0769b6b in G4ExcitedStringDecay::FragmentStrings () Which has been running for ~70 hours in Sample4Momentum (in and out of SampleQuarkPt). It seems as though this could happen with a very small initial mass. The last output in the log file was: G4PDGCodeChecker::CheckPDGCode : ??? Illegal PDG encoding for nucleus PDG code=1000010011 Particle H1[21221.8] has a strange PDGEncoding (not clear where this message is coming from, but that PDG code is an excited proton...). This occurs running G4 9.2 patch01 on slc4, gcc346, 32-bit, built against CLHEP 1.9.4.2. I'm using the FTFP_BERT physics list - and I have never seen this message or problem running QGSP_* (in case it helps). Could one of the G4 experts take a look? Thanks, Zach
Thanks for reporting. I think this is actually two reports. The strange PDGCode has nothing to do with the loop you observe. I have a fix for the near infinite loop. Eventually this will get of the loop, but the code was often trying many times to find a acceptable value, and you must have hit a very bad one. If testing goes well, this should still be included in the beta release 9.3.beta. For the PDGCode, this is actually the code for a nucleus, but apparently an invalid code. This should be followed in a separate report, I will create this.
