[mkgmap-dev] highway count not fixed yet... - merge-roads-branch

Sun Sep 29 14:24:22 BST 2013

Hi Gerd,

I've commited the changes to the merge_road branch.

setHighwayCount() still need to be changed.
In case the merged road has the same id as the duplicate road you have 
the same problem again.

            <<<<<<<<<<< (not counted due to same id)
x>>>>>>>>>x>>>>>>>>>>>x
1         1           1

should be

            <<<<<<<<<<<
x>>>>>>>>>x>>>>>>>>>>>x
1         2           2

I still don't understand how you want to check which node is a routing 
node. It's easy for the first and the last node but how to proceed with 
the nodes inbetween?

WanMil

> Hi WanMil,
>
> thanks for the ascii graphics, I think that explains what goes wrong with
> Felix' style.
> I still don't see a need to change the setHighwayCount() method
> as long as we call it after the mergeRoads().
>
> Why don't I like the usage of the highway count?
> Well, in some places we increment the counter
> for the 1st and last point of a way and the
> comment says
> // make sure the way has nodes at each end
> If that is really needed, I'd prefer to set a flag
> instead of messing up the counter.
>
> Gerd
>
>  > Date: Sun, 29 Sep 2013 13:01:17 +0200
>  > From: wmgcnfg at web.de
>  > To: mkgmap-dev at lists.mkgmap.org.uk
>  > Subject: Re: [mkgmap-dev] highway count not fixed yet... -
> merge-roads-branch
>  >
>  > > WanMil wrote
>  > >> Hi Gerd,
>  > >>
>  > >> in my opinion recalculating the highway counter after removing the
> short
>  > >> arcs should fix all problems, shouldn't it?
>  > >
>  > > Don't think so. All routines that replace or add points after that must
>  > > make sure that they maintain the correct highway count.
>  > >
>  >
>  > Ok, which routines perform such modifications? I couldn't find any such
>  > modifications of MapRoad instances after the StyledConverter.
>  >
>  > >
>  > >
>  > > WanMil wrote
>  > >> I've added three changes to the patch:
>  > >> 1. When calculating the highway count ways with duplicate id are not
>  > >> considered. This avoid that all points of a duplicated way are
> preserved
>  > >> by all filters.
>  > >> I think this should be modified a bit. For the first and last point of
>  > >> those ways the highway count should be increased and also all points
>  > >> where another way is connected. I have no use case where this matters
>  > >> but I think it is the "correct" counting?
>  > >
>  > > No, it just increases the possibility that the counter overflows.
>  >
>  > Maybe that's true for the trunk but in the branch there are real cases
>  > where it matters.
>  >
>  > Assume the following two ways:
>  >
>  > x>>>>>>>>>x===========x
>  > 1 2 1
>  >
>  > (x = Node; >> oneway line; === oneway=no; highway count below nodes)
>  >
>  > The style might duplicate the oneway=no way into to oneway=yes ways
>  >
>  > >>>>>>>>>>>
>  > x>>>>>>>>>x<<<<<<<<<<<x
>  > 1 2 1
>  >
>  > The merger might merge two of the ways:
>  >
>  > <<<<<<<<<<<
>  > x>>>>>>>>>x>>>>>>>>>>>x
>  > 1 1 1
>  >
>  > As a result the highway count of the 2nd and 3rd node is wrong. It
>  > should be 2 instead of 1. And AFAIK this difference matters.
>  >
>  >
>  > > Maybe we should not use this counter at all. The information that
>  > > it "hides" is that a point connects two or more roads.
>  > > I think a better solution would be to have a method markRoutingNodes()
>  > > which uses the counter and sets a bit flag in the coord instance.
>  > > This routine would replace setHighwayCounts() and resetHighwayCounts().
>  >
>  > I don't understand the advantage? I think maintaining the highway count
>  > is the same like markRoutingNodes(). How do you want to know when to
>  > call markRoutingNodes()?
>  >
>  > >
>  > >
>  > > WanMil wrote
>  > >> 2. I have added the problematic point in the error message of the
>  > >> MapBuilder in case a node is not a CoordNode. Just having the way id
>  > >> might not be enough information and the way also might have been
> merged.
>  > >>
>  > >> 3. I have moved the recalculation of the highway counters after the
>  > >> merge procedure. This should not change anything but it avoids a
> problem
>  > >> with merging...
>  > >
>  > > This is a good idea. Maybe do it before and after? That also means that
>  > > decHighwayCount() is obsolete, doesn't it?
>  >
>  > decHighwayCount() is obsolete as long as the highway counters are
>  > recalculated after mergeRoads(). When recalculating the highway count
>  > after mergeRoads() the RoadMerger does not care about (correct) highway
>  > counts (maybe a perf improvement might require correct highway counts
>  > but I don't know if the improvement is neccessary).
>  >
>  > >
>  > > Gerd
>  > >
>  > >
>  > >
>  >
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