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Space-group search: judge a promotion against the worst of its tied parents

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A candidate can have several confirmed subgroups of the same order - 422 has
both 4 and 222 - and on a twinned crystal the rival is not a harmless
alternative: a P4 crystal twinned by 2[100] has 222 confirmed too, and 222
CONTAINS the twin laws, so its own merge b is already ballooned. The H test
already answers to every tied parent; the systematic-b veto and rescue took
whichever one the enumeration happened to list first (222 before 4, by space-
group number), which disabled the veto on exactly the case it exists for. Take
the smallest parent b, which is the conservative direction for both tests.

The refusal message also quoted the raw parent b rather than the floored value
the veto actually compared against.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
This commit is contained in:
leonarski_f
2026-07-30 10:52:05 +02:00
co-authored by Claude Opus 5
parent 609650b061
commit 72cd91ccc3
1 changed files with 10 additions and 3 deletions
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image_analysis/scale_merge/SearchSpaceGroup.cpp
+10 -3
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@@ -517,7 +517,6 @@ SearchSpaceGroupResult SearchSpaceGroup(
// (imperfectly scaled data) and VETOES a twin whose chi^2 now looks self-consistent but whose b
// balloons - the chi^2 ratio alone no longer separates them.
double parent_b = -1.0;
const PointGroupInfo *parent_pg = nullptr;
// Every confirmed subgroup of the largest order below this candidate. There can be more than one
// - 422 has both 4 and 222 - and on a twinned crystal the rival is not a harmless alternative: a
// P4 crystal twinned by 2[100] has its two twin 2-folds confirmed, so 222 is CC-confirmed too and
@@ -535,8 +534,13 @@ SearchSpaceGroupResult SearchSpaceGroup(
if (s.order > parent_order) {
parent_order = s.order;
parent_b = s.b_extra;
parent_pg = s.pg;
parents.clear();
} else {
// Tied parent. The b tests answer to the most damning of them, exactly as the H
// test below does: the SMALLEST parent b is the one that makes the veto easiest to
// trip and the rescue hardest to pass, and a rival subgroup that already contains
// the twin laws has its own b ballooned - taking it would hide the twin.
parent_b = std::min(parent_b, s.b_extra);
}
parents.push_back(s.pg);
}
@@ -611,8 +615,11 @@ SearchSpaceGroupResult SearchSpaceGroup(
+ "x the parent's (bound " + FormatDouble(opt.max_operator_h_ratio, 2)
+ ") - the added operator relates unequal intensities, as a twin law does";
else if (b_refused)
// Against the FLOORED parent b, which is what the test compared - quoting the raw
// parent b reads as a far bigger balloon than the one that actually tripped the veto.
refused_why = "its merge's systematic error b is " + FormatDouble(c.b_extra, 3)
+ " against the subgroup's " + FormatDouble(parent_b, 3)
+ " against the subgroup's "
+ FormatDouble(std::max(parent_b, opt.min_systematic_b_for_veto), 3)
+ " (bound " + FormatDouble(opt.max_systematic_b_veto, 2)
+ "x) - the added operator forces unequal intensities together";
else if (std::isfinite(c.chi2) && std::isfinite(chi2_ref))