Support Allpix Squared format

[MarcoRiggirello]

Allpix Squared is a very common Monte Carlo simulation framework for silicon detectors.

Unfortunately, their output format is not a trivial one, hence one needs to write the custom parser. Since it is a very popular package, can it be possible to integrate the parser in UnROOT?

I'm willing to help if the task is doable by someone who never contributed to this package. Thank you for the good work

[tamasgal]

I think it would make sense to write a nice I/O library which also contains some other related helper functions, don't you think?

We try to keep UnROOT small ;)

We have a similar I/O library in KM3NeT which uses UnROOT under the hood and hides a couple of complicated streamer logic and branch structures behind easily usable types and functions: https://git.km3net.de/common/KM3io.jl or the GitHub (read-only) mirror https://github.com/KM3NeT/KM3io.jl

[MarcoRiggirello]

Actually makes lot of sense. Before today I only used NanoAOD files that work out of the box, hence I never thought about having a separate library 😅

Thanks for the explanation!

[Moelf]

is the output still root files in TTrees? I just haven't heard of that format until today

[MarcoRiggirello]

Yes, they are indeed TTrees where each event is a vector of Allpix objects (custom classes).

[Moelf]

in that case, if one wants to, one can implement https://juliahep.github.io/UnROOT.jl/stable/advanced/custom_branch/ for the custom classes

[MarcoRiggirello]

BTW, I just found out that examples to convert their format to a flat NTuple do exist. The flat ntuples can be read by UnROOT without any issue. Good!

And thank you for clarifying the best practice of having the stramer logic separate from UnROOT! I learned something new :)