[OSM-dev] Osmium - Saving nodes to memory, so they are accessible when processing ways?

Pris Matic prismatic.project at gmail.com
Mon Aug 29 18:34:45 BST 2011


I need node geometry (lat,lon) information available as I process the ways
in an OSM file through an Osmium handler (I'm using C++). The FAQ says I can
use a few ways to store the nodes while processing. I just wanted a bit of
clarification... The docs say that mmap and FixedArray both require 64-bit
systems to address enough memory for all the nodes (I'm not working on the
planet dataset, but for arguments sake let's assume I am). They also say
that mmap writes to file -- so I understand that I need 64-bit for
FixedArray to address all that memory, but if mmap writes to file, shouldn't
it work on systems with less memory? I don't know where the cut off is --
ie. how much memory is addressed before it starts writing to file. It would
be great if someone could explain this a bit further.

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