Hi Ticker, I've committed the patch as is. I've not seen big changes in performance, but I've used a different (already existing) set of files which was created with my own style. For me, Mdr11.preWriteImpl() is the most problematic part reg. OOM errors. Maybe look at the code which uses LargeListSorter. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Dienstag, 11. Mai 2021 13:27 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] MDR building out-of-memory Hi Gerd Here is updated version of patch. Changes from last: Uses your cache code for region and country (in 2 places). For British Isles, there are 190 regions and 7 countries, so I don't think the extra memory will be a problem and there should be some performance benefit. Delays allocating cities until it can use sortKeys.size() for initial allocation. For above map this is 0.07% too big, so I don't think trimToSize() is worthwhile. Shares the Sort object between the 4 methods. Ticker