hash

The first step of a spatial hash over a run of points: the bucket of the cell each point stands in. The sort kernel orders the points by bucket, and hash_starts then states where each bucket's points start and end in that order. The keys, the order and the bucket spans, with the cell size, are the index hash_count, hash_gather, hash_nearest, hash_repel and hash_hook search. core.spatial builds the index with it. Exact: the same points give the same keys.

It reads pts (xyz a point) and writes keys, one a point; the params are buckets (a power of two) and inv_cell (one over the cell side).

Over a live count (COUNT=device, see the abi README) n is the capacity and the first domain_count slots are live. A slot at or past the live count holds the key 0x7fffffff, which is past every bucket: the sort (over the same live count, or over the capacity) places it after every live key, and hash_starts over the capacity states every bucket's span over the live points only. It binds 3 storage buffers (2 in the plain variant).