I keep finding references to $G$-Set graphs and I cannot find a definition anywhere.


They are usually mentioned at the same time as the random graph generator "rudy," so I believe they refer to a method of generating graphs but I cannot find out any more than that. 


I apologise in advance if I have missed something obvious.



What is a G-Set Graph?
I believe these are the 57 graphs labelled $G\_1$ to $G\_{57}$ in Table 7 of a preprint by Helmberg and Rendl (<http://opus4.kobv.de/opus4-zib/files/306/SC-97-37.pdf>). As you thought, they were generated by rudy, and the table lists the data needed to get them from that program. 


Apparently, these graphs are accepted as standard test cases for some kinds of problems. In particular, a paper by S.J.Benson, Y.Ye, and X.Zhang <http://dx.doi.org/10.1137/S1052623497328008> says: "Our experiments used a machine-independent graph generator, called rudy, created by G.Rinaldi. We tested the maximum cut semidefinite program on the G set of graphs used by Helmberg and Rendl [12]. This set of problems becomes a standard test set for graph optimization."


