nsplit_jobs in shower_card.dat

Asked by Richard Ruiz on 2018-11-06

Hi Folks,

I have a quick question about parton showering with mg5amc. In the file Cards/shower_card.dat, there is the line:
nsplit_jobs = 1 # N jobs to run in parallel (< 100!!)

This just literally splits the "unweighted" lhe output of mg5amc into a smaller number of unweighted files, yes? As in, the the individual event weights are related by:

(weight for unsplit event) * nsplit_jobs = (weight for split event)

cheers

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Paolo Torrielli Edit question
Last query:
2018-11-06
Last reply:
2018-11-07

Dear Richard,
what that command does is to take the unweighted .lhe file that is to be showered,
split into nsplit_jobs unweighted files, each with nevent/nsplit_jobs events (I guess
that if nsplit_jobs is not a divisor of nevents the code does not attempt to split, and
outputs a warning). The events (including their weights (all equal up to a sign)) are
unchanged in the splitting procedure.
At this point, each of these files gets showered in parallel, and eventually distributions
get recombined in a unique plot.
Cheers.
Paolo

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