Comment by karussell
1 year ago
> the entire planet would likely need 384GB of RAM
Unlikely. Even with turn costs enabled 256GB (or less) are sufficient. You could also try to disable CH as for bike often no long routes are required (you could disable them). Here we have written down a few more details: https://www.graphhopper.com/blog/2022/06/27/host-your-own-wo...
Hey karussell, I really appreciate all the hard work you’ve put into Graphhopper. I wouldn't be able to create this project without GH. I have a question about memory usage during the import stage (specifically in the OSM Reader's preprocessRelations function). I'm using a HashMap<Long, List<Long>> to map way IDs to OSM bike route relation IDs, which means allocating lots of arrays. Could this be causing me to run out of heap memory faster or am I off base here?
I thought I would be able to compute the graph with 64GB of ram but it kept crushing before CH and LM stage. After switching to a 128GB instance, it finally worked, hitting around 90GB at peak memory usage. For context, I was using 3 profiles - one with CH and two with LM, plus elevation data and used all of the tips from deploy.md
Love your project!
Maybe you already considered, but there are a number of collection libraries out there that are optimized for holding Java primitives and/or for very large sets of data, which could help you save significant memory. Eclipse Collections [0] and Fastutil [1] come to mind first, but there are many out there [2]
[0] https://github.com/eclipse-collections/eclipse-collections [1] https://fastutil.di.unimi.it/ [2] https://github.com/carrotsearch/hppc/blob/master/ALTERNATIVE...
Thank you! I'm a total Java noob - actually, this is the first project where I've written any Java code (had to slightly modify the Graphhopper source code to suit my needs). Those libraries look very interesting. I'm saving this post for another battle with processing maany GBs of OSM data :D
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> Could this be causing me to run out of heap memory faster
Yes, definitely.
> I thought I would be able to compute the graph with 64GB of ram but it kept crushing before CH and LM stage.
For normal GraphHopper and just the EU the 64GB should be more than sufficient.