.. external_issues:

Known external issues
=====================

These are known problems which are completely unrelated to the genie-reader code,
but can be encountered during the simulation:

``grwght1p`` can only process more than 1 event
-----------------------------------------------

``grwght1p`` is a GENIE Reweight application, responsible for calculating systematics weights. ``grwght1p`` can only process >1 events and will crash if GENIE Generator file with only one event os provided as input. To prevent this problem, if you are planning to calculate systematic weights in genie-reader simulation, you shoud always generate files with at least two events. This issue does not affect geneation without systematics weights, as ``gevgen`` can in fact produce files with just one event.

Limited file size (number of events)
------------------------------------

It was found that the maximum file size (number of events per file) when running ``genie-reader`` simulation in IceCube CVMFS environment has to be reduced compared to the previous oscNext simulations which used ``GENIE-IceTry``. Going over the maximum size leads to the segmentation violation.
As an example, while files of 300000 events were used before, for ``genie-reader`` simulation with the same settings the size had to be scaled down to 100000 events in order to avoid the error.
In ``genie-reader`` requested number of events is number of neutrino interactions, while in ``GENIE-IceTry`` it was number of flux neutrinos, so actual number of events stored in the file (neutrino interactions) was smaller.
``GENIE-IceTray`` also used different types of objects to store event information, which might be the cause for the different maximum number of events.