Change Summary:

This seems to work pretty well for me.  The one downside is that event order gets wonky due to the cache.  This is because we don't have any tie-breaker for events of the same tick/priority, and as a result, the order of those events is somewhat random.  So, we can leave things as they are or accept the cache.  We should consider if we want to do something for tie breaking.  In theory, we want this for a multithreaded simulator, but it may be better to do the tie breaking not in the event queue itself, but in the the events that actually cause the problems.