Remove compatibility with 3.1

[Zaharid]

As per https://docs.nnpdf.science/releases.html#id4
having published the 4.0 paper we no longer need to support 3.1-era runcards and fits. To some approximation that means rm -rf nnpdfcpp but I think also things like the complicated backwards compatibility support for experiments (which has been very useful) would no longer be needed, leading to some opportunities for simplification.

It would be probably good to tag the code with the last version supporting 3.1 compatibility.

[Zaharid]

@enocera @scarrazza Is there a reason why we would want to keep the nnpdfcpp directory any longer? Apart from moving the data around and so on.

[scarlehoff]

Beyond removing nnpdfcpp we should also remove all the extra files the fit creates which are not needed (as all information is in the .json file)

[Zaharid]

I am wondering if we should wait until the paper is actually published for this.

In the meantime here what has been collected so far

• Tag code.
• Delete nnpdfcpp (easy, but requires changing builds as well).
• Amend documentation (easy, should be mostly removing stuff, but needs to be done together with each change)
• Remove old fit format data (easy, but requires some work and an issue).
• Remove compatibility with experiments (hard, as there is a bit of tricky code involved cc @siranipour ).
• Possibly simplify closure test commondata cc @RoyStegeman (probably hard).
• Update recommended examples here https://docs.nnpdf.science/vp/examples.html?highlight=example%20resources

[scarlehoff]

I am wondering if we should wait until the paper is actually published for this.

You mean you would like to have the "published tag" in which compatibility with 3.1 is kept?

[Zaharid]

I mean having the paper accepted in a journal.

[scarlehoff]

Yes. With a companion "published tag". Because otherwise it makes no difference for the code.

[Zaharid]

Yes indeed. If everything goes well that tag won't be very different from the current one.

[Zaharid]

Another thing that would need to be done is changing the 3.1 resources, which we would not necessarily support any longer here https://docs.nnpdf.science/vp/examples.html?highlight=example%20resources