Hi Johann,
As a lot of the processing has to be done in sequence, the opportunities for using multiple threads are somewhat limited. However, the attached patch parallelises:
1 - processing of ways from OSM form to MapLine/MapRoad.
2 - processing of cities
3 - processing of POIs
4 - processing of polylines and polyshapes within each division
In this situation (a lot of sequential processing), wouldn't it be an better approach to start several processes of mkgmap with different tiles?
This could be fully parallelized without dependencies.
Afterwards the different tiles had to be merged into an single img file. This process could be started in another extra process with the finishing of the first tile.
That's fine as long as you have the memory available and are processing more than one tile. I wrote the patch as I was intrigued as to how much performance gain could be achieved using multi-threading. It's not a stunning improvement but certainly good enough to consider doing more work on it. Cheers, Mark