jump

One round of pointer jumping over a run of links, three ways:

• rank (MODE rank): list ranking. Repeated rounds give each element its root and its distance to it, for chains and trees. Both live in the double-buffered parent/parent_out and value/value_out pairs; the caller swaps them between rounds.
• min (MODE min): doubling of the smallest label within reach. After ceil(log2 n) rounds, every element on a cycle holds the cycle's smallest label.
• label (MODE label): label propagation over pairs, in place. Iterated to changed = 0 it labels each connected set of elements with its smallest label.

changed counts what the round altered; the caller zeroes it before a round and reads it after, so iteration with a stop is one dispatch and one count per round. Integers are 32-bit words and every mode is exact: the final labels do not depend on the order invocations ran in.

The label mode reads the pairs from la and lb; rank and min read parent and value and write parent_out and value_out. core.boundary orders its loops with min and rank rounds, curve.chain_ranks ranks chains with it, and core.islands labels connected sets with the label mode.

Over a live count (COUNT=device, see the abi README) the elements (rank, min) or the pairs (label) are the first domain_count slots of a capacity n, and the n param is not read. In rank and min mode a slot at or past the live count links to itself with the value 0. It binds 8 storage buffers (7 in the plain variant).