Two whole-dataset sorts sat on the main thread at the end of a rotation run:
WilsonOutliers orders every full by resolution, and the unmerged MTZ is put
in H K L M/ISYM BATCH order by Mtz::sort(5) - together about 2 s of one
thread on a 1.4 M-observation set.
ParallelSort (common/ParallelFor.h) sorts one piece per worker and merges
them pairwise. It is only for comparators that are a strict total order,
where the sorted sequence is unique and the result is the serial sort's bit
for bit: WilsonOutliers already breaks ties on the index, and the unmerged
writer now sorts the rows itself on the five key columns and then the row
number - the order Mtz::sort's stable sort gives - and sets sort_order as it
did. An empty table still fails the way Mtz::sort does.
md5-identical p.hkl, p.mtz and p_unmerged.mtz; 44.4 -> 43.6 s on a 16M set.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D1G8gJVAy6gp1K5Dz3NE5C
leonarski_fandClaude Opus 5.5
59d92a7238