Bug #23816
Random Number Generator not Seeded in GenieHelper tool
100%
Description
The random number generator in the class in nugen responsible for emulating the FNAL beam spill timing is not seeded. This means that all neutrino generation times in a set of MC files will be identical.
The base class implementing the timing is here (nugen:source:nugen/EventGeneratorBase/GENIE/EvtTimeShiftI.cxx#L18) -- the un-seeded random generator is constructed at line 18.
The instance of this virtual class that specializes to the FNAL beam timing is here (nugen:source:nugen/EventGeneratorBase/GENIE/EvtTimeFNALBeam.cxx). It uses the default constructed random number generator and does not update it to be a seeded one.
History
#1 Updated by Gianluca Petrillo 11 months ago
- Description updated (diff)
That is all true (TRandom3 is initialised with seed 4357 by default).
Just a reminder that all this machinery is broken anyway because it ignores the correlation between the time of the interaction and the distance of the interaction from the target.
#2 Updated by Robert Hatcher about 1 month ago
- % Done changed from 0 to 100
- Status changed from New to Resolved
While this redmine issue is long outstanding (2019-12-30), I think the fix is as well (made 2020-01-15)
https://cdcvs.fnal.gov/redmine/projects/nugen/repository/changes/nugen/EventGeneratorBase/GENIE/EvtTimeShiftI.cxx?rev=master
See the change 178c268f
I'd forgotten that this problem was entered as a Redmine issue; updating this to 100% done and resolved. Will close unless I hear feedback otherwise.
#3 Updated by Robert Hatcher about 1 month ago
- % Done changed from 100 to 70
- Status changed from Resolved to Assigned
#4 Updated by Robert Hatcher about 1 month ago
- % Done changed from 70 to 100
- Status changed from Assigned to Resolved
The corresponding change in GENIEHelper was pushed as https://cdcvs.fnal.gov/redmine/projects/nugen/repository/revisions/e1c43a11e13cc6f5f41d42d3d892388020f2b58e