`frac > RATIO * best_frac` cannot be satisfied once best_frac passes 1/RATIO - above
0.667 for a ratio of 1.5, which is ordinary for good rotation data. Above that the two
guards do not raise the bar, they close the branch: no axis multiple and no
lower-symmetry setting can displace the incumbent however much better it fits, so a
genuine superstructure is kept as its sub-cell and its satellite rows go unindexed,
silently.
The obvious repair - restate the bar on the fraction left UNINDEXED, which is well
defined over the whole range - was implemented and measured. It regressed the
37-crystal battery from 34/37 to 32/37 correct space groups: a C2 lattice fell to P1,
and a P2 case went to C222 keeping 2923 of 22440 reflections with CC1/2 in the last
shell at -35%. The indexed fraction is too noisy to carry a looser test.
So the unreachable-but-safe form stays, and the limitation is recorded at the comparison
rather than left to be rediscovered. Fixing it properly needs the selection to be
decided on something better than the indexed fraction.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5
5727cb68a4