- fast_bridge.py: states as 210-bit integer edge-bitmasks (compact memory,
O(1) set ops); build a NetworkX graph only once per state for the planar
embedding; parity-subgraph bridges via one iterative DFS per state instead
of per-edge subgraph copies. Validated identical orbits to the slow version;
throughput ~5170 states/s vs ~1100 (graph.copy was 66% of old runtime).
- fast_decide.py: integrated, gated ELG-witness check (only even-class
sources with all-opposite-class neighbourhoods are tested with the
ground-truth is_even_level_graph, then parity match). Witness detection
validated (ELGs -> True, T*_9 -> False).
- Feasibility finding: bridge orbits are ~100x smaller than full E/O orbits
but still 1e5-1e6 states per labelling (partitions 0,1 of dual 0 exceed
310k and 685k without exhausting), x ~150 valid parity partitions per dual.
Exhausting every orbit -- required for a conclusive NEGATIVE -- is
computationally infeasible. A conclusive POSITIVE (witness ELG) remains
reachable; none found so far.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
