Querying number of distance evaluations about nearestneighbors.jl

[KristofferC]

That's a good idea!

There used to be a "debug" mode that you could activate that added some stats but it was removed in https://github.com/KristofferC/NearestNeighbors.jl/pull/98/files#diff-3d112593fe19c53f85f19846cc9d0406c17b39736378b65e7d12821d20207302.

With more experienced eyes, I think a better alternative is to allow one to pass something like a

struct EvaluationData
    n_distance_evals
    n_tree_intersection_evals
    ...
end

to inrange and knn and have that struct be populated. By default that argument would just be nothing and unused.

[fcdimitr]

I made a minor modification on my fork to include a global counter:

master...fcdimitr:NearestNeighbors.jl:master

It works correctly, and some preliminary benchmarking shows that it does not affect the running time.

In any case, I agree that a more structured approach to collecting statistics should be preferred.