I should add that in order to see the diagnostic messages I suggest to add,
you must run MG5_aMC in debug mode, that is:

cd <MG5_aMC_root_dir>
./bin/mg5 --debug
[...]

On Tue, Jul 25, 2017 at 12:26 AM, Valentin Hirschi <
<email address hidden>> wrote:

> So there seems to be two different issues in this thread:
>
> ----------
> 1) Sometimes, the split event files show "empty events" which crash
> Pythia8.
> I cannot reproduce this issue, even when starting from the
> 'unweighted_events.lhe' file provided by nicolas.neill.
> So, at this stage, we cannot bring any further help. If you encounter
> similar issue (i.e. not just Pythia8 crashing, but crashing because it
> didn't accept any event, and then looking into the source .lhe file fed to
> PY8, you see empty events there), then please go to the file
>
>
> <MG5_aMC_root_dir>/madgraph/interface/madevent_interface.py, around line
> 4106,
>
> change:
>
>
> n_splits = lhe_file.split(partition=partition, cwd=parallelization_dir,
> zip=True)
>
> into:
>
> misc.sprint("Original evt file:", pjoin(self.me_dir,'Events',
> self.run_name,PY8_Card.subruns[0]['Beams:LHEF']))
> misc.sprint("Partitions asked for":, partition)
> n_splits = lhe_file.split(partition=partition, cwd=parallelization_dir,
> zip=True)
>
> And then send us the event file pointed at by the first printout line
> and what the 'partition' variable is. This should allow us to straight-
> forwardly reproduce the issue.
>
> ---------
> 2) The second issue 'Nelson Vanegas-Arbelaez' is having is probably
> completely unrelated and happens both with and without parallelization.
> In this case it is probably an issue during Pythia8 run itself.
> I suggest you look inside the Pythia8 log file in:
>
> NewBckgndWZ/Events/run_02
>
> And going to the end of it, it is likely that you will find an error
> report from PY8. If not, then forward this log by attaching it here to this
> thread.
> If you find an error however, and you believe it is not directly related
> to the way MG5_aMC produced the event file, then directly address this
> error to Pythia8 authors.
>
> --
> You received this bug notification because you are a bug assignee.
> https://bugs.launchpad.net/bugs/1674341
>
> Title:
>   Pythia8 shower failed since it did not accept any event from the
>   MG5aMC event file
>
> Status in MadGraph5_aMC@NLO:
>   New
>
> Bug description:
>   Hi,
>
>   I'm trying to generate a matched jet sample using pythia8 and MG
>   2.5.3, but I'm getting the following error:
>
>   Command "generate_events run_01" interrupted with error:
>   InvalidCmd : Pythia8 shower failed since it did not accept any event
> from the MG5aMC event file.
>
>   I'm doing the following for the generation:
>
>   generate p p > z, z > e+ e- @0
>   add process p p > z j, z > e+ e- @1
>   add process p p > z j j, z > e+ e- @2
>   output ~/mgoutput2/zjj_matched_MG253
>   launch
>   shower=pythia8
>   detector=delphes
>   set run_card ickkw 1
>   set run_card auto_ptj_mjj True
>   set run_card xqcut 20
>   set pythia8_card JetMatching:qCut 30
>
>   The same process with MG 2.3.3 and pythia 6 works fine.
>
>   I'm attaching the end of one of the log files
>   (Events/run_01/PY8_parallelization/split_0/PY8_log.txt). If I don't do
>   matching, the showering with pythia8 is working fine.
>
>   Thanks in advance,
>
>
>   Nicolas.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/mg5amcnlo/+bug/1674341/+subscriptions
>



-- 
Valentin