From a bug report, when the hero has
precisely 24 movement points, fast monsters will move twice and then the
hero will move twice, instead of being interleaved. The hero will get 24
additonal movement points approximately one turn out of three when wearing
speed boots (or when using spell of haste self or potion of speed) and can
also get 18 additional points twice in succession, with a net of 24 after
12 of them are used on the first turn. But hero might not be starting at
zero at the time, so I'm not sure how often this is actually noticeable.
He apparently got a report about this for <some variant> and had some
user-contributed instrumentation in place that made it easier to replicate.
This fix is the one he suggested.
projects / nethack / commit