- /**
- * @brief The "relevant" portions of the unfolding that must be kept around to ensure that
- * UDPOR properly searches the state space
- *
- * The set `U` is a global variable which is maintained by UDPOR
- * to keep track of "just enough" information about the unfolding
- * to compute *alternatives* (see the paper for more details).
- *
- * @invariant: When a new event is created by UDPOR, it is inserted into
- * this set. All new events that are created by UDPOR have causes that
- * also exist in U and are valid for the duration of the search.
- *
- * If an event is discarded instead of moved from set `U` to set `G`,
- * the event and its contents will be discarded.
- */
- EventSet U;
-
- /**
- * @brief The "irrelevant" portions of the unfolding that do not need to be kept
- * around to ensure that UDPOR functions correctly
- *
- * The set `G` is another global variable maintained by the UDPOR algorithm which
- * is used to keep track of all events which used to be important to UDPOR
- */
- EventSet G;
-
- /// @brief UDPOR's current "view" of the program it is exploring