Qgraf is a computer program that generates connected Feynman diagrams for various types of QFT models — it is a research tool created with the obvious aim of contributing to extend the range of feasible, perturbative QFT calculations. Diagrams are represented by symbolic expressions only; nevertheless, if some kind of graphical representation is required, have a look at the external links.

• Latest version: qgraf-3.5.0 (2021).
  Please report any error you may happen to find.

• Programming language: Fortran 2008 for version 3.5.0, and Fortran 77 for earlier versions.
  Executables/binaries are not distributed, the program has to be compiled and linked.
  Employing GNU's gfortran for that task should be straightforward, eg there should be no
  need to specify a Fortran standard (see eg file qgraf-3.5.0.pdf).
  There are executable/binary versions of GFortran for several operating systems, see the
  GFortranBinaries webpage.

• The features added in the last three versions include (eg):
  improved treatment of duplicate vertices (3.3);
  a way of restricting the configuration of external lines (3.3);
  the ability to require/disallow bridge-type propagators with certain momenta (3.3);
  an option to select diagrams with non-factorizable cycle spaces (3.4);
  an option to select 1–vertex irreducible diagrams (3.4);
  the ability to generate multiple output files in the same run (3.5).

• Current plans: qgraf-3.4 should be available and supported for some time yet (minimal
  fixes as need be); the long term status of qgraf-3.5 is uncertain at this moment, but it
  will not be ‘stable’ like version 3.4 (as there will likely be a version 3.6); qgraf-3.1
  should be considered obsolescent, although it is still available for automatic downloads.
  The next release will probably occur in late 2021.

Qgraf is based on the method described in the following paper:

• Automatic Feynman graph generation
  P. Nogueira
  J. Comput. Phys. 105 (1993) 279–289
  https://doi.org/10.1006/jcph.1993.1074
  

  ▻ show outline ▻ hide
  this paper presents a concise description of an orderly algorithm for generating Feynman graphs, on which Qgraf is based; in addition, it presents a diverse set of numbers — either the numbers of graphs in certain sets or the sums of the respective symmetry factors — which may be employed to cross-check the correctness of that program.

The diagram generation with mixed propagators can be reduced to the usual one:

• Feynman graph generation and propagator mixing, I
  P. Nogueira
  Comput. Phys. Commun. 269 (2021) 108103
  https://doi.org/10.1016/j.cpc.2021.108103
  

  ▻ show outline ▻ hide
  given a QFT model with mixed propagators, this paper shows how to construct a modified model without such propagators, whose Feynman graphs may be easily transformed into the graphs of the original model; moreover, it explains in detail why that approach works.