Add positivity observables

[cschwan]

Do we want a generator in this repository for the positivity observables? This would be basically https://github.com/N3PDF/pineappl/blob/master/examples/python/positivity.py.

[felixhekhorn]

Maybe this is the more suitable place then pineappl examples, even more if this will become a proper dataset (in the NNPDF sense)

[cschwan]

That was my train of thought also. I'd volunteer to take care of it, if you're busy with other projects.

[alecandido]

We're slowly completing most of the chores, but still I would not do it before ~10 days. If you can start, do it :)

Were you thinking something about a new backend (like yadism, mg5, and conversions the moment we'll get there), a new subcommand, or just moving the script?

[cschwan]

We're slowly completing most of the chores, but still I would not do it before ~10 days. If you can start, do it :)

Were you thinking something about a new backend (like yadism, mg5, and conversions the moment we'll get there), a new subcommand, or just moving the script?

I was thinking about making it a new backend, which isn't too complicated given that we already have that script.

[alecandido]

Indeed, I just wanted to understand.

At the end, a backend is not doing so much:

• __init__: used to load backend specific runcards, or define variables, if needed
• run: used to compute the actual numbers and dump in a backend specific format (but here might be even skipped) ❌
• generate_pineappl: here goes the script ✔️
• results: used to display the comparison (I guess it can be left empty in the first shot) ❌
• collect_versions: not needed, this backend would be fully integrated in the runner ❌

[cschwan]

OK, thanks for your pointers, let me try to implement it!

[felixhekhorn]

* `collect_versions`: not needed, this backend would be fully integrated in the runner x

then it should be the runner version

[alecandido]

runner version is included always by default:
https://github.com/NNPDF/runcards/blob/500e06c14cf2b42c2897fd6360fc0df347af6516/runcardsrunner/external/interface.py#L110-L116

(even though maybe we can even drop pygit2 at some point, and try to use the poetry-dynamic-versioning provided one, they should coincide)

[felixhekhorn]

yes, I meant just not to leave it empty or something, but put the version twice (such that one can guess the generator, i.e. if they are the same the generator is built-in)

[alecandido]

No, why twice? It is redundant, and runner is runner, so leave it empty.

Consider that there is no standard field for external, yadism add a yadism_version, and mg5 add an mg5_version. Here there is nothing but the runner, so leave it empty.

[alecandido]

If you want to log the generator used let's add a separate field, and make it explicit (even though it might already be logged somewhere, but I'm not sure).