Cleanup removed each duplicate vertex with List.RemoveAt from the middle
of the list, so a polygon cost O(duplicates x vertices). Shape.ToPolygon
emits a duplicate at every entity junction and flattened arcs to 1000
points, so building the Drawing for a large arc-heavy part spent seconds
shifting memory: one 1 MB PEP nest took 12.7 s to convert and 11.2 s to
read back, a quarter of a 300-nest archive import's total time.
The single pass compares each vertex with its original predecessor, as
the back-to-front loop did, so tolerance-equal runs collapse identically
and the output is unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ajandClaude Opus 5.5
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