Code review comment for lp:~maddevelopers/mg5amcnlo/v3_syntax_handler

Hi Olivier,

I started to play with it and I noticed that if I do

generate p p > t t~ QCD=1 QED=1 [/*QED*/]

I get

/Interpreting 'QED=1' as 'QED<=1'//
//Interpreting 'QCD=1' as 'QCD<=1'//
//Command "generate p p > t t~ QCD=1 QED=1 [QED]" interrupted with error://
//Exception : Potentially ambigious syntax detected. Note that the
syntax of paper 1804.10017 (used in 3.0.x) is not used anymore (since
version 3.1.0).//
//    If you want to follow the syntax of that paper, you can just
replace "QED" by "aEW" and "QCD" by "aS".//
//    More information here: http://amcatnlo.cern.ch/co.htm//
//    If you know the current meaning of the syntax you can bypass this
crash by running (once per machine) this command://
//     set acknowledged_v3.1_syntax True --global//
//Please report this bug on https://bugs.launchpad.net/mg5amcnlo//
//More information is found in 'MG5_debug'.//
//Please attach this file to your report./

and the code stops, that I think it is what we want.

If instead I do

generate p p > t t~ QCD=1 QED=1 [/*QCD*/]

I obtain:

/Potentially ambigious syntax detected. Note that the syntax of paper
1804.10017 (used in 3.0.x) is not used anymore (since version 3.1.0).//
//If you want to follow the syntax of that paper, you can just replace
"QED" by "aEW" and "QCD" by "aS".//
//More information here: http://amcatnlo.cern.ch/co.htm//
//
//Order QED is not constrained as squared_orders. Using: QED^2=2//
//Order QCD is not constrained as squared_orders. Using: QCD^2=2//
//WARNING: Use of multiparticles is non-trivial for NLO process
generation and depends on the orders included, the process considered,
as well as the PDF set chosen. See appendix D of arXiv:1804.10017
[hep-ph] for some guidance. /

and the code keeps running.

If I am not wrong, this is not what we wanted. If I remember correctly,
the first output should always appear unless one is either not
specifying QCD=* QED=* or setting QCD=99 AND QED=99 together with [QCD QED].

Marco: should also QCD=99 AND QED=99 [QCD] or QCD=99 AND QED=99 [QED]
raise an error?

Cheers
Davide

On 14.04.21 15:15, Olivier Mattelaer wrote:
> Any comment on this?
>
> I think that it does not make that much sense to wait months before releasing it (otherwise this will be even more uglier).
>
> Olivier