[mkgmap-dev] New splitter version available

Sat Aug 8 09:34:26 BST 2009

I've checked in some more updates to the splitter. You can either check it 
out of Subversion and build it yourself, or download a copy from http://redyeti.net/splitter.jar.

Here's what's new/changed:

- Removed the 4 areas per way restriction. Now all ways will be split correctly 
regardless of how many areas they are in.
- Added a --max-areas parameter. This allows you to trade off speed against 
memory usage.
- Improved the logging to make it clearer what is happening, and to provide 
feedback of progress during the split.
- The default ant target is now 'dist'.
- A couple of minor performance improvements.

Some further explanation of --max-areas is probably required. By default 
this is set to 255, meaning that up to 255 areas will be processed on a single 
pass over the XML when splitting. However if your map is going to split into 
say 387 areas, rather than doing one pass of 255 areas and a second of 132 
the splitter will balance the passes at 184 and 183 areas each. This is because 
the amount of memory used by a given pass is proportional to the number of 
areas being processed multiplied by --max-nodes, so the lower the number 
of areas for a given pass the better. There is no performance cost associated 
with this balancing.

As for the 4 areas per way restriction... I managed to come up with a way 
to handle the few ways that exceed this limit with some special-case code. 
There is a slight performance and memory cost associated with this, but with 
the current data it is negligible. If in the futher there end up being a 
huge number of ways covering more than 4 areas we might have to rethink how 
this works, but for the medium term at least I think we'll be fine.

As always, please give this new version a try and let me know what you think 
or have any problems/questions.

Chris