There could be a lot more done if we target luajit only. Or if we port
this to C. But for now let's keep it this way. It's 2-3x faster than
before, and the issue is mostly only on very big inputs, which are not
that common in practice.
Previously computing scores allocated two matrices of lua tables per
call. With hundreds of thousands of items this made fuzzy matching in
console.lua GC-bound.
When only the score is needed, keep two reused rolling matrix rows,
making repeated scoring allocation-free. positions() still keeps all
rows since tracing back the matched positions requires them.
fzy.filter() of 300000 items drops from 1013 ms to 356 ms (on my setup)
for a worst-case single-character needle, and a standalone score() call
no longer allocates at all.
Kacper Michajłow
e2eaf31ce2