• Latest version: qgraf-4.0.5 (2024-Sep)
  Please report any error you may happen to find.

• Programming language(s): Fortran 2008 (starting with qgraf-3.5), Fortran 77 (for earlier versions).
  Executables/binaries are not distributed, the program has to be compiled and linked. Employing GNU Fortran for that task should be straightforward, see eg the latest documentation. There are executable/binary versions of GFortran for several operating systems, as described in the GFortranBinaries webpage.

• The features added in the last two versions include (eg):
     the partition statement (3.6);
     an extended language for describing input models (3.6);
     a more general loops statement (3.6);
     special directories, automatic deletion of output files (4.0);
     wide(r) input files, a statement continuation mark (4.0);
     the momentum-loop construct (4.0);
     an application programming interface (4.0).

• Current plans: versions 3.4 and 3.6 are stable, and should be available and supported for some time yet (minimal fixes as need be); in contrast, qgraf-4.0.5 is a development version, although it is very nearly ready for actual use. I will be back online in a few days, sorry.

• Notice: for better future-proofing, packages that try to download this program should do so by using the URL that includes the links/ directory (as described in any recent manual, section ‘Automatic downloads’ or similar title), or at least using it as an alternative URL.

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

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

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  This paper presents a concise description of an orderly algorithm for generating Feynman diagrams, on which Qgraf is based. In addition, it presents a diverse set of numbers — either the numbers of diagrams in certain sets or the sums of the respective symmetry factors — which can be employed to cross-check the correctness of Feynman diagram generators.
   

This other paper shows that the diagram generation with explicitly mixed propagators can be reduced to the usual one.

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

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  Given a QFT model M with explicitly mixed propagators, this paper shows how to construct a model M^⁎ without that kind of mixing, such that the Feynman diagrams in M can be easily derived from the diagrams in M^⁎ (by field re-naming, to be precise). Moreover, it explains in detail why the method works; for example, it shows that if a diagram D^⁎ in M^⁎ gives rise to diagram D in M then D and D^⁎ have identical symmetry factors.