ReindexMergedIntoAsu swapped I(+)/I(-) whenever the reindexed index came out on
the minus side of its Friedel pair. That is right only for a row that started on
the plus side, which is every row when merge_friedel is set - and none of the
problem cases.
With the mates kept apart, the merge stores the plus mate at +hkl_asu and the
minus mate at -hkl_asu (Merge.cpp), while RotationScaleMerge attaches I_plus /
I_minus in the plus convention on both rows alike, keying the lookup at
plus=true. An alternative-indexing operator is rotation-type, so op(-x) == -op(x)
and the two mates always land on opposite sides: testing key.plus alone therefore
swaps exactly one row of every pair, whichever way the operator went. The pair
ends up self-contradictory, and the mmCIF's pdbx_I_plus / pdbx_I_minus and the
F(+)/F(-) columns are swapped on half the rows.
Reached by "rugnux -A --model model.pdb" - -A clears MergeFriedel - on a crystal
whose indexing ambiguity the model resolves, which is the one path that both
keeps the mates apart and reindexes.
The swap now fires on was_plus != key.plus. With merge_friedel every row is
stored at the ASU representative, so was_plus is always true and this reduces to
the previous test; the existing change-of-hand case is unchanged.
The test that covered the merge_friedel=false path checked only I, so it passed
either way. The new one builds both mates of a pair and asserts they still agree
about which intensity is which afterwards - an invariant that holds however the
operator moves the hand, so it fails on the old code for either direction.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016L1qig74oYQzfUJJZbbxFh
leonarski_fandClaude Opus 5
ab14ca10e8