To give some more context: The function *mk_acyclic_graph* (I'm very unhappy with that name, by the way, but also by the idea of the function itself of course) explores the landmark graph starting from every node one after the other (skipping those nodes for which it previously found that it cannot be part of any cycle). It marks nodes encountered as visited and procedes until a previously visited node is encountered. If this happens, it removes the first weakest ordering on the path from the visited node back to itself. Hence, this choice depends on the order in which these landmark nodes are considered/expanded and this might change in the different versions due to the use of an unordered set as the data structure. The reason why a different amount of orderings is removed is, because cycles can overlap in the set of orderings they consist of, and hence it is possible to get rid of multiple cycles at once by removing a single ordering. Since the choice by the implemented algorithm is greedy and it simply removes the firstweakest ordering, this does not have to be the same number over all for two different versions.
