2 Commits

Include renames

Author	SHA1	Message	Date
leonarski_fandClaude Opus 5	11c7cab2e5	Space-group search: take the operator disagreement as a median, not a mean ... A merohedral twin mixes EVERY reflection with its twin mate, so it shifts the whole distribution of |I1-I2|/(I1+I2). A minority of badly measured reflections shifts only the tail. The mean cannot tell those apart; the median is blind to the second and just as sensitive to the first. Measured on real crystals, moving the statistic from the mean to the median leaves genuine promotions where they are and pushes every twin up: genuine tetragonal 1.016 -> 1.013 genuine lysozyme 1.051 -> 1.067 genuine tetragonal 1.238 -> 1.231 twin (-e 1050) 1.272 -> 1.447 twin (-e 450) 1.280 -> 1.622 twin (full) 1.441 -> 1.522 twin (-e 600) 1.427 -> 2.010 The margin around the 1.25 bound widens from 2.7% (genuine 1.238 against twin 1.272 - uncomfortably tight for a decision that cannot be undone downstream) to 17.5% (1.231 against 1.447). The bound itself does not move. Rotation battery, 33 crystals in both detection modes: no point group changed in either (30/33 and 29/33, as before), and only one crystal's numbers move at all - the one already documented as nondeterministic between repeat runs of the same binary. The synthetic twin-fraction x multiplicity grid passes unchanged. So this buys margin, not outcomes. Found while testing a different hypothesis, which the same measurement refuted: a tetragonal crystal whose 422 promotion is wrongly refused reads 1.484 by the mean and 1.472 by the median, i.e. its disagreement is distribution-wide and is NOT a badly-integrated minority. That crystal's cause is elsewhere and is not addressed here - see the note below. Its indexing-ambiguity operator (-k,-h,-l) lies INSIDE 422 but OUTSIDE 222, so the subgroup merge the search is given mixes lattices indexed in the two alternative hands. That corrupts exactly the 4-fold relationships and leaves the 2-fold ones intact - measured, the 222 step reads 0.917 and the 422 step 1.484 - and the corruption is indistinguishable from a twin law. Forcing the tetragonal group merges the two hands as equivalent and the same data give CC1/2 99.2% at multiplicity 10.7, matching XDS. The failure is worse the BETTER the frames index (99.9% vs 63.3% for the run that gets it right), because indexing more frames picks up more of both hands. So no statistic computed on a subgroup merge can arbitrate a promotion whose added operators include an indexing-ambiguity operator. Fixing that means resolving the ambiguity before the search, or detecting the coincidence and deciding another way; the operators needed to detect it are already computed (the run warns about them). Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-07-28 11:07:06 +02:00
leonarski_fandClaude Opus 5	3171b071e6	Space-group search: judge a promotion against its parent, not against the error model ... The point-group decision moved with the AMOUNT of data at fixed physics: a partially twinned trigonal crystal was promoted into the twin's holohedry whenever the search happened to see a larger first-pass merge, and kept its true subgroup when it saw a smaller one. Simulation over 6 noise draws with only the merge multiplicity varying: the twin is promoted 0/6 at multiplicity 2 and 6/6 at 18, while the genuine control is promoted 6/6 throughout. The cause is that every existing gate is a ratio to the merge error model - b_parent grows toward the true systematic scatter as sigma shrinks with 1/sqrt(N), while b_cand is already saturated by the twin's disagreement, so the ratio slides down through a fixed veto. The parent statistic moves with data amount and the candidate statistic does not. Gate promotions on the operator disagreement H = <|I1-I2|/(I1+I2)> instead, as the ratio of the operators a promotion ADDS to the parent group's own operators on the same reflections. There is no sigma in it, so it cannot drift with the error model, and the parent normalisation cancels data quality. Measured over 27 runs, 5 promotion types and 450-1800 images: genuine symmetry 0.862-1.219, merohedral twins 1.270-2.084. On the synthetic grid it is flat across a 9x change in multiplicity - genuine pinned at 1.00, twins 3-12x the bound - which is precisely the property the old gates lacked. chi^2 and the systematic-b stay as secondary vetoes; they protect against non-crystallographic pseudo-symmetry, which is where correlation-based scoring is weak. Pick the parent carefully: 422 has two maximal subgroups of order 4, and on a tetragonal crystal twinned by 2[100] the rival (222) is CC-confirmed too and CONTAINS the twin laws, so normalising against it hides the twin among the promotion's own real operators (ratio 8.19 against the true parent, 0.78 against the rival). Where several parents tie, judge on the most damning. Also: - Report a refused promotion instead of silently processing lower. Merging a twin in the twin's holohedry averages non-equivalent reflections into each other and cannot be undone from the output; keeping the subgroup costs only redundancy. The refusal names the group and the number that caused it. - Stop the twinning report from arguing in a circle. It ran after adoption and conditioned on the adopted group, so a promotion into a holohedral Laue class made it print "no merohedral twin law exists" - the test was conditioned on the decision it should audit. Twinning is now also measured on the subgroup merge before adoption, and the post-adoption text says when its own conclusion is not authoritative. - Compare PRIMITIVE cell volumes in the first-pass scheme tie-break. A centred setting's cell is an exact integer multiple of its primitive one (a rhombohedral lattice in hexagonal axes is exactly 3x), so the integer-supercell test fired on a pure setting difference and demoted a good scheme to a threefold-smaller merge - which is what let the twin see the small merge to begin with. Rotation battery, 33 crystals: point-group agreement 30/33 -> 29/33, one crystal moved. That crystal (P422 -> P222) is the one with the known unresolved integration defect where reflections near the rotation-axis plane are wildly mis-integrated; its symmetry mates genuinely disagree, and its lower-symmetry merge is measurably better (ISa 2.72 -> 3.63, high-shell CC 75.4 -> 86.0). The threshold was not moved to accommodate it: 1.25 sits inside the measured gap and widening it would admit real twins. Separately the tie-break improved one crystal's CC1/2 from 77.7 to 84.0. Tests: a synthetic twin-fraction x multiplicity grid, which is what the search had never had - the existing tests are noise-free and exercise only Stage B absences. A NOTE ON WHAT WAS TRIED AND REJECTED, so it is not rebuilt: the obvious "physics-anchored" statistic is the disattenuated cross-validated correlation rho = corr(I_half0(h), I_half1(Rh)) / corr(I_half0, I_half1), which is 1 for real symmetry at any data quality and 2a(1-a)/((1-a)^2+a^2) for a twin. It passes the synthetic grid perfectly and FAILS ON REAL DATA IN BOTH DIRECTIONS - five false refusals of genuine symmetry on the battery, and it waves through a twin (rho 0.998) that H refuses. The reason is that cc_half correlates the two halves of the SAME reflection and so measures only random error, while cc_cross compares DIFFERENT reflections carrying different systematic error; dividing by cc_half removes the noise and leaves a systematic floor that varies by crystal AND by operator. Genuine rho measures 0.9987 on strong data and 0.73 on weak. A synthetic generator validates a statistic's arithmetic, never its premise, and this premise - that the only departure from exact symmetry is noise - is false for every real crystal. Any per-operator agreement statistic needs a same-crystal reference; an absolute threshold on one cannot be made to work by tuning. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-07-27 21:05:16 +02:00