[Python-Dev] Issue 2986: difflib.SequenceMatcher is partly broken

[Eli Bendersky]

> Rather than reverting to Tim's
> undocumented vision, perhaps we should better articulate it by
> separating the general purpose matcher from an optimised text matcher.
>

For what it's worth, my benchmarking showed that modifying the
heuristic to only kick in when there are more than 100 kinds of
elements (Terry's option A) didn't affect the runtime of matching
whatsoever, even when the heuristic *does* kick in. All it adds,
really, is the overhead of a single 'if' statement. So it wouldn't be
right to assume that somehow modifying the heuristic or allowing to
turn it off will negatively affect performance in the special case Tim
originally optimized for.

Eli