Hi. After long time i am returning to the issue of long generation time for tiles with large polygons. I have avoided interfering with the discussion as i am not in the position to help on the technical details. The original tile for which there was an issue was used in the following test, can be found here: https://files.mkgmap.org.uk/detail/502 On my computer, compiling the split data (from link above): with version mkgmap-faster-mp-r4706 it takes around 2 minutes 40 seconds, output size 13520896 bytes. with version mkgmap-r4745 it takes around 25 minutes and 30 seconds, output size 13516800 bytes. This is a great change! With an earlier version of the mkgmap-faster-mp i have compiled maps with no problem, but with 4706 i get the following error in one case. (split data can be uploaded in case you want, 77700020*.pbf). What could be the issue? Mkgmap version 4706 Time started: Sat Jun 05 08:09:29 CEST 2021 ALLVARLIG (global): Unexpected error java.lang.ArrayIndexOutOfBoundsException: -1 at java.util.ArrayList.elementData(ArrayList.java:422) at java.util.ArrayList.get(ArrayList.java:435) at uk.me.parabola.mkgmap.reader.osm.MultiPolygonRelation.getLargest(MultiPolygonRelation.java: 674) at uk.me.parabola.mkgmap.reader.osm.MultiPolygonRelation.processElements(MultiPolygonRelation.java: 640) at uk.me.parabola.mkgmap.reader.osm.ElementSaver.addRelation(ElementSaver.java: 163) at uk.me.parabola.mkgmap.reader.osm.bin.OsmBinHandler$BinParser.parseRelations(OsmBinHandler.java: 215) at crosby.binary.BinaryParser.parse(Unknown Source) at crosby.binary.BinaryParser.handleBlock(Unknown Source) at crosby.binary.file.FileBlock.process(Unknown Source) at crosby.binary.file.BlockInputStream.process(Unknown Source) at uk.me.parabola.mkgmap.reader.osm.bin.OsmBinHandler.parse(OsmBinHandler.java: 54) at uk.me.parabola.mkgmap.reader.osm.OsmMapDataSource.parse(OsmMapDataSource.java: 166) at uk.me.parabola.mkgmap.reader.osm.OsmMapDataSource.load(OsmMapDataSource.java: 141) at uk.me.parabola.mkgmap.main.MapMaker.loadFromFile(MapMaker.java:165) at uk.me.parabola.mkgmap.main.MapMaker.makeMap(MapMaker.java:58) at uk.me.parabola.mkgmap.main.Main.lambda$processFilename$1(Main.java: 290) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java: 1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java: 624) at java.lang.Thread.run(Thread.java:748) ALLVARLIG (global): Exiting due to unexpected error Number of ExitExceptions: 1 Time finished: Sat Jun 05 08:09:42 CEST 2021 Total time taken: 13 seconds Regards Karl