Qgraf–r computes particle
number conservation rules (both
additive and multiplicative)
for many types of QFT models.
It is then able to identify (un)physical processes that break
those rules, thereby ruling out the existence of matching
Feynman diagrams for every order of perturbation theory.
Additionally, it ‘solves’ inclusive
processes with a fixed number of external fields,
some of which ‘unknowns’ — that is, it can
find the matching noninclusive processes that satisfy the
number conservation rules it has computed itself.
For example, it can produce a list of the n–point
functions allowed by those rules (for n fixed, and not too
large).
The information produced by Qgraf–r
may also be used to partly crosscheck the input modelfile.
For instance, if some of the rules of the (intended) model are
known in advance, and if they are not compatible with those
computed by the program, then the model description is very
likely incorrect.
Most of the theory behind Qgraf–r is
described in these papers:

From Feynman rules to conserved quantum numbers, I
Comput. Phys. Commun. 214 (2017) 83–90
https://doi.org/10.1016/j.cpc.2017.01.025
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paper I shows that there are efficient algorithms for
computing the (particle) number conservation rules of a QFT
model — more precisely, for computing a complete
system
of those rules;
moreover, it shows that that system follows easily from the
simple, combinatorial requirement that Feynman graphs must be
built up from the vertices and freeparticle propagators of
the model.

From Feynman rules to conserved quantum numbers, II
Comput. Phys. Commun. 215 (2017) 13–19
https://doi.org/10.1016/j.cpc.2017.01.027
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paper II shows how the form of pairing graph (a classic graph
that describes the propagator types of the respective model),
and specifically the (non)bipartiteness of its connected
components, may impose nontrivial constraints on the form of
the (particle) number conservation rules (eg on whether
additive charges exist);
in addition, it shows that the algorithms described in paper I
may often be improved.

From Feynman rules to conserved quantum numbers, III
Comput. Phys. Commun. 260 (2021) 107740
https://doi.org/10.1016/j.cpc.2020.107740
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paper III shows that, for ‘most’ of the common QFT
models, there exist Feynman graphs for a complete correlation
function
⟨F⟩
if and only if
F
is compatible with the particle number conservation rules of
the respective model (the nontrivial part is the sufficiency
of that condition);
moreover, it presents the general form of those rules for the
usual type of QFT models (without propagator
mixing).