Seeding the merge heaps was 3.06s of a 5.93s regroup on the reference
18,143-face library — more than half the pass, spent before a single
merge was considered.
Every component scanned the whole pair list looking for the pairs that
were its own: 475 components against 804,499 pairs, 382 million set
lookups to place 804,499 of them. A pair can only ever join two faces of
one component, since that is what a component is, so the union-find that
finds the components can file the pairs at the same time and hand each
agglomeration the list it needs.
The membership set inside agglomerate goes with it — it existed only to
run that filter — and the heap can be sized up front now that the pair
count is known.
Ordering is preserved deliberately: pairs are filed in the order they
arrive, which is the global (i, j) order, so the seeded heap breaks its
ties exactly as before and the merge order is unchanged. Same 2,518
groups holding the same 16,246 faces on the reference library, at 3.5s
rather than 5.9s.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dtourolleandClaude Opus 5
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