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[mkgmap-dev] Binary format update

From Scott Crosby scrosby at cs.rice.edu on Thu Sep 16 22:37:33 BST 2010

> Ok, that means we cannot use the common planet dumps for this and a
> separate step (geographical sorting) is needed which maybe eats up the
> advantage to skip the tile splitter step. Just keep the idea in mind and
> give it a try when the geographical sorting is available.

I designed the format to support that feature, but I have no idea
when, or if, I'll have time to program it. One advantage is that the
sorting process only has to be done once.

>> I've got a question though, why can't mkgmap generate different areas
>> in parallel? It seems like it should be possible and it would make it
>> a lot faster to render maps.
> mkgmap already works in parallel if you specifiy multiple osm files
> which are usually generated by the tile splitter (see parameter
> --max-jobs). The advantage of my idea would be to skip the tile splitter
> step.

Are you sure?

If I try it on a quad-core hyperthreading CPU, I only see about 2-3
cores used and 5 idle. (Invoked with '-c template.args and

There's also this code in MapMaker.java:

	 * Load up from the file.  It is not necessary for the map reader to completely
	 * read the whole file in at once, it could pull in map-features as needed.
	private LoadableMapDataSource loadFromFile(CommandArgs args, String
name) throws
			FileNotFoundException, FormatException
		LoadableMapDataSource src;
		// work around non-reentrancy of GType priority stuff
		// by serialising the map reading
		synchronized(MapMaker.class) {
			src = MapReader.createMapReader(name);
			log.info("Started loading " + name);
			log.info("Finished loading " + name);
		return src;

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