Set random seed for Delphes

[mhabedan]

Feature details

Hi!

For reproducibility of results, it would be very helpful if the random seed that can be set for MadAnalysis was propagated to Delphes. Otherwise results may differ significantly between to directly repeated runs.

Output without setting random seed:

Have there been any attempts in that direction already?

Cheers,
Martin

Implementation

One way to make Delphes recognise a random seed is by adding

set RandomSeed <number>

to the Delphes card. This would unfortunately mean that the Delphes cards have to be edited dynamically.
Probably there's a smarter way to do it but unfortunately I'm new to using Delphes, so I'm not aware of anything.

Output when setting random seed like this:

How important would you say this feature is?

2: Somewhat important.

Additional information

No response

[jackaraz]

Hi Martin that is up to the user to set the card as they like. We only offer random seed settings in SFS through the interface. Delphes is a third-party party, so it is up to the user.

[mhabedan]

Hi Jack!

I think the question is a bit what you classify as "user" in this case. And in either case, I'd argue that MA's output becomes less opaque if the random seed is also set for Delphes.

If the user wants to implement a new analysis in MadAnalysis and provide the corresponding Delphes card, true, they can set the random seed in the Delphes card. But then the random seed is fixed for good for this Delphes card, which is certainly not desirable.

For people who are even more "end users", i.e. who only want to run already existing analysis implementions in MA, it's even more unclear what is happening. They certainly won't expect to have to set a random seed in a Delphes run card deep in the MA install directory (as opposed to a setting in a MA run card), only to get reproducible results. In particular, as MA has an option to set the random seed, it's just not propagated to Delphes. That was very unintuitive to me when I started using MA.

Edit: Just as an addition - yes, Delphes is third-party software but MA steers Delphes for the user so that the "end user" doesn't have to touch Delphes at all. Given that, I think it's fair for the user to expect that MA steers all necessary features of Delphes, including setting the random seed.

[jackaraz]

Hi Martin, please go ahead if you would like to add a command for ma5 to modify the delphes card with a fixed seed. It can be something like

set main.recast.random_seed  = <value>

which then automatically triggers a modification in the card during the run without altering the original card and uses the modified version instead. Unfortunately, we currently lack the manpower to implement and test this.

Cheers