Upgrade Clipper library
Currently we use v4.8.5 of the ClipperLib for some of the geoprocessing like Clip and Dissolve.
With large files Clipper is much faster then GEOS (GDAL/OGR).
Version 6.4.2 is now available at https://sourceforge.net/projects/polyclipping/files/
This might solve some problems I'm seeing now.
Implementation is finished.
I've upgraded to v6.4.2 and made the necessary changes in the calling functions: Polygons are renamed the Path and more small changes.
The result of clipping a large shapefile with 680.000 shapes is now:
It took only 2:35 minutes. GEOS needed for the same file 2:44:24 hours!
The result does have a lot of invalid shapes (self-intersecting). I'll have a deeper look how to prevent that.