TITLE: Repository of graph classes that are tough to test non-isomorphic pairs from isomorphic pairs
QUESTION [5 upvotes]: (1) Which graph classes are extremely tough to test for graph non-isomorphic pairs from isomorphic pairs?
(2) Is there a repository of adjacencies from such classes?

REPLY [5 votes]: There is a move towards creating a "standard" benchmark set for graph isomorphism, but it didn't happen yet.  Meanwhile, the largest collection that includes hard graphs as well as easy graphs is here. To make examples of difficult nonisomorphic pairs, take two graphs with the same parameters and randomly label them. For difficult isomorphic pairs take two random labellings of the same graph.
The graphs here that will cause trouble to most programs are in the classes ag, cfi, had, latin-sw, pg, pp, f-lex.