hash_count

For each query position, how many indexed points lie within a radius of it, searched through the spatial hash the hash and hash_starts kernels build. An exclusive scan of the counts gives the offsets hash_gather writes each query's neighbour list at; core.pairs runs the three in that order. Exact.

It reads pts, order and range (the index), qpts (xyz a query) and the params buckets, inv_cell, radius and skip_self (1 leaves out the point whose index is the query's, for queries that are the indexed points), and writes counts, one a query. Dispatch over the queries.