That's awesome! I knew there were faster approaches to ref-counting, but I didn't know about that one, "sloppy counters".

The most common approach to speeding up ref-counting is to ref-count bigger objects — modules rather than individual variables, say.

The simplest way to speed up ref-counting transparently is to statically analyze the code and remove redundant increment and decrement operations. This can be tricky in practice, and I haven't heard of anyone actually doing it.