[mkgmap-dev] Short Arc Problem? Error 3 Mapsource, Problem on Calculating this route Basecamp.

Fri Jan 4 19:17:11 GMT 2013

> I've now tracked down the problem. The tertiary way 114405617 and its
> copy C114405617 share the list of Coord objects. Not just the actual
> Coord's (which is correct) but the ArrayList too. Code in
> addRoadWithoutLoops() replaces the nodes that have a highwayCount
> greater than 1 with CoordNode objects.  If the tertiary way is
> processed first then it will end up properly routable. When the copy
> is processed however, the nodes have already been replaced and have no
> highwayCount, so it appears to have no connection to other roads to
> the code. So you end up with a road without the correct routing
> information which happens to crash MapSource.
>
> The previous workaround removed the piece of road that ended up without
> routing information. Sometimes that would be the MP copy and sometimes
> the original road - it just depends on which is done last.
>
> Two solutions I can think of
> 1. Always ensure you have a (shallow) copy of the list.
> 2. Fix up the addRoadsWithoutLoops() to recognise that a way has
> already been processed and do everything that would have been done
> anyway.
>
> I favour 1) hoping that there is no intentional sharing of lists
> anywhere.
>
> Attached is a patch that copies the list in the Way constructor. I'll
> check all call sites to make sure there is no duplicate copying
> later. This patch is instead of the previous workaround.

Steve,

I could also create a copy of the points list in the mp algorithm (I 
would call it a bug that it hasn't been done :-).

But having a look at the signature of the constructor I would expect 
that it takes a copy of the points list. On the other side copying the 
points list will create some temporary lists but I think that's ok.

I have removed three copies of the points list that are unneccessary 
now. See attached patch Routing_error3.patch.

>
> This kind of tagging that produces the problem is particularly common in
> Spain, in the UK I couldn't find any examples and in Germany there are
> only a few; perhaps one per tile. In fact the only German example I
> tried to trace had been changed since I downloaded it and was no longer
> a problem. Every Spanish example I looked at was a sure routing failure
> however.
>
> ..Steve
>

What do you think of Felix proposal to add a special handling for 
highways in multipolygons? I doesn't feel good to me but I could add it 
if required.

WanMil
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