[mkgmap-dev] [PATCH v1] quick distance calculation

Sat May 16 18:54:31 BST 2009

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
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