[mkgmap-dev] Memory limits for mkgmap and splitterFrom Lambertus osm at na1400.info on Tue Aug 4 17:36:01 BST 2009
Chris Miller wrote: >> Ah, this might explain the 'POI only' tiles I have without good reason >> in the NE USA and Canada. Is there a possibility for a quick fix for >> this behavior, as this would be most welcome...? :-) > > Not really... currently the limitation is that each node, way and relation > can only belong to a maximum of 4 areas. This is because during the split > each area is given an ID from 1-255 (8 bits) and up to 4 areas are squeezed > into a single 32 bit integer for each node/way/relation. This is really important > to save memory for the nodes and ways, so to support more than 255 areas > would require a lot more memory. What happens with > 255 areas is that multiple > areas map to the same 8 bits and so get mixed up with each other without > warning - there's no bounds checking on the bit manipulation. About the only > 'quick fix' is to refuse to split more than 255 areas, or to split them in > multiple full passes which will take significantly longer. In the meantime > your best bet is to split your areas.list file into two by hand, making sure > there's < 256 areas in each. Then run the splitter twice, once for each area > file you created. > Crap, this means I'll have to split North America into two sections using Osmosis. At ground level this means broken routing between the sections and that some cities/villages will be divided into two... Thanks for the thorough explanation. > Currently there's another limitation in that a relation can only appear in > a maximum of 4 areas - hence all the "Relation 123 in too many areas" message > you probably see when splitting. The result of this is that the relation > only gets written to the first 4 areas it encounters and won't appear in > any additional ones. I think I can fix this one fairly easily, I'll take > a look in the next few days. > That'll be great. Tia.
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