[mkgmap-dev] Unit tests in trunk fail

Sun Jan 5 14:19:43 GMT 2014

Hi Gerd,

the SimpleTest also randomly fails because the number of resulting lines 
is sometimes different.

You are right that the roadmerger does not change the number of lines in 
roundabouts. But there are other ways similar to roundabouts:
http://www.openstreetmap.org/?mlat=51.25946&mlon=6.74760&zoom=17#map=19/51.25990/6.74788
I guess such ways are responsible for different number of lines.

Anyhow I have found a quite easy way to make the RoadMerger stable.
When creating the list of roads I copy all start and end points to a 
list. This list is stable. Step by step I go through this list to find 
merge candidates. No matter if we allow to merge ways to a closed way 
this procedure is stable.
Sorting at the end is still required because the roads are copied from 
the IdentityHashMap to the resulting list and this is not stable.

Attached patch also contains the creation of a debugging file at the end 
of the RoadMerger.merge procedure. The output contains informations 
about the roads which makes it easy to compare two runs of mkgmap.

Please give it a check if that solves your problem. I will have a look 
on the tests and if the performance is still acceptable using the patch.

WanMil

> Hi WanMil,
>
> it's a unit test regarding the style finalizer section which fails and I
> don't know why.
>
> reg. RoadMerger:
> it makes no sense to create closed ways because we would split them
> again later in StyledConverter.
> I don't understand the idea about roundabouts.
> If one is divided into 4 parts you can do 2 merges without closing it,
> no matter which
> parts you connect first, and you should always get 2 remaining parts.
> Assumes part a,b,c and d:
> a+b and c+d or
> a+b and a_b + c or
> b+c and d+a  or
> b+c and b_c + d or
> b+c and a + b_c or
> ...
>
> Gerd
>
>  > Date: Sun, 5 Jan 2014 12:37:09 +0100
>  > From: wmgcnfg at web.de
>  > To: mkgmap-dev at lists.mkgmap.org.uk
>  > Subject: Re: [mkgmap-dev] Unit tests in trunk fail
>  >
>  > Hi Gerd,
>  >
>  > I think I found the problem:
>  >
>  > // check if merging would create a closed way - which should not
>  > // be done (why? WanMil)
>  > if (cStart == cOtherEnd) {
>  > return false;
>  > }
>  >
>  > The RoadMerger avoids to create closed roads. In case the roads are not
>  > merged in exactly the same order this is the reason for different merge
>  > results due to roundabouts. In case a roundabout is divided in multiple
>  > ways the number of merged ways is random.
>  >
>  > At the moment I have no time to check that more in detail but I think
>  > the code listed above can be removed.
>  >
>  > WanMil
>  >
>  > > Hi WanMil,
>  > >
>  > > please have a look, I don't fully understand why.
>  > >
>  > > Gerd
>  > >
>  > >
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>  > >
>  >
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