[geos-devel] Why many calls to signOfDet2x2 and addIntersections

[Martin Davis]

Just for grins, I disabled the self-intersection check and reran the SineStarX2 test.  Times are below - they are up to 10 times faster!

I've been thinking a bit about this annoying requirement to test for self-intersections before performing any functions.  Strictly speaking, this is only required for linestrings (which can self-intersect) and *between* different rings of polygons - but not between a ring and itself (OGC rings can't self-intersect).  Currently JTS just checks *everything* for self-intersections.  Since many cases involve only polygons without holes, being a bit smarter about what gets checked could produce a substantial performance improvement.

I'll spend some time thinking about how to change JTS to implement this.. It's not totally trivial, but might not be too bad.

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Martin Davis, Senior Technical Specialist
Vivid Solutions Inc.
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