Hi Ticker, the code is getting more complex with each patch and I don't fully understand why because the unit tests never changed. I doubt that a warning message like "Possible ambiguous balloon allocation at ..." will help anyone except you ;) I am not sure if you are wasting your time here. I've almost dropped the idea that ShapeMergeFilter could merge to the max, so I wonder in what situation you face those degenerated polygons? If the only "normal" source is the joinWays() algo in MultipolygonRelation I fully agree that we should change that first. We just have to decide which version we use: trunk or the faster-mp branch or the low-res-opt branch. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Freitag, 11. Juni 2021 16:11 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] low-res-opt branch: error message from ShapeSplitter for self-intersecting multipolygon Hi Gerd I've improved ShapeSplitter so it can cope with more cases when there are multiple lines at the same point on the cut-line. Any problems will generate a single log.error, with reasons as log.warn and more information as log.info and gpx traces if log.debugEnabled() Ticker