[m-rev.] for review: speed up find_edit_distance

[Julien Fischer]

On Thu, 25 Jan 2024, Zoltan Somogyi wrote:

> Speed up find_edit_distance.
> 
> library/edit_distance.m:
>     Speed up the find_edit_distance predicate by
>
>     - changing it to operate on arrays instead of maps, and
>     - reusing the *same* three arrays over and over.
> 
> diff --git a/library/edit_distance.m b/library/edit_distance.m
> index c54bae746..3c6bfc110 100644
> --- a/library/edit_distance.m
> +++ b/library/edit_distance.m

...

> @@ -166,77 +169,112 @@ find_edit_distance(Params, SeqA, SeqB, Cost) :-
>          % RowNum here iterates from 0u up to LenB - 1u.
>          % And just as in the gcc code j iterates from 0 up to len_s-1,
>          % J here iterates from 0u up to LenA - 1u.
> -        map.init(RowTwoAgo),
> -        init_row_zero(DeleteCost, 0u, LenA, map.init, RowOneAgo),
> +        %
> +        % The Mercury compiler uses this predicate mostly when constructing
> +        % "did you mean" addendums for diagnostic messages reporting
> +        % failed name lookups. In modules that are large themselves, or
> +        % (more likely) in modules that import many other modules, the set of
> +        % names to which we want to compare the name whose lookup failed
> +        % can be quite large. In such sitations, the code constructing

s/sitations/situations/

That looks fine otherwise.

Julien.