Folks, OK, so the parallelisation code has not been very successful so far but we can still speed up mkgmap. You have probably noticed that it spends a huge proportion of its time in Math.acos() which is being called from Coord.distance(). The attached patch renames distance() to slowDistance() and introduces a new quickDistance() function that is based on the code that was in the MultipolygonRelation class. I have tested quickDistance() against slowDistance() and for maps in the UK and Germany it produces distances that are very similar (within 0.5% or better). It is substantially faster and so I believe we should change to using it as long as it doesn't introduce any issues. So please try out this patch and report: a - if any breakage is observed b - performance increase/decrease Cheers, Mark