Is the event generation from a lhe file using pythia random when used multiple times?

Asked by Olivier Dupon on 2020-06-26

Dear MadGraph experts,

I currently want to generate around 300k events from models used in MadGraph. For this I have to use a stand-alone pythia program. My current idea is to let MadGraph generate an 30k lhe file which I want to then let run through pythia 10 times parallel.
The question I have for this, however, is whether this will be random or will just generate the same 30k events 10 times since iseed is already set in run_card and the general data about the events is already given.

Kind regards
Olivier Dupon

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Solved by:
Olivier Mattelaer
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If you run like this
multi_run 10
set nevents 30k

Then you will certainly have 10 independent sample.
If you create 10 different directory and run like this
set nevents 30k

Then your events will be correlated in all the different directories. In that case, you will need to set the seed manually to a different value in each directories to avoid correlations.



Olivier Dupon (odupon) said : #2

Thanks Olivier Mattelaer, that solved my question.