[mkgmap-dev] tile takes very long time to generate

Wed Mar 31 10:10:31 BST 2021

Hi Gerd

Looking at the Polish format (cGPSmapper-UsrMan-v02.4.pdf), my
understanding is that a polygon definition with multiple Data#
statements at the same level defines a single outer with multiple
inners (Page 20 and 74/5).

Touching inner or outer rings is a slightly different problem and, I
think, the current code has made all its choices about this before the
complexity of geometry determination.

I wasn't suggesting stopping on errors, but if there are only 2 way
elements ending at a Coord, and one is explicitly marked "inner" and
the other "outer" then I think this can be errored and chucked.

Ticker  

On Wed, 2021-03-31 at 07:57 +0000, Gerd Petermann wrote:
> Hi Ticker,
> 
> I don't know what data we see when MultipolygonRelation is used with
> polish input, but I am sure that there is no info about roles.
> 
> I also thought about using the info about the area size as a quick
> indicator before doing complex tests.
> 
> The missing unit tests are my real problem. I've not (yet) found a
> good way to test the result. I'd like to have a test that allows to
> rotate or reverse rings so that we find errors with handling of the
> closing node.
> 
> I think we need the complex and somehow tolerant tests for the
> boundary calculations, we cannot simply stop on error. I know that
> some admin boundaries have very special cases (France), they are not
> exactly correct reg. the rules for touching outer rings.
> 
> 
> So, I started to use already tested code where possible, e.g.
> IsInUtil. See attached patch. Run times seem similar to the existing
> code in trunk.
> Just experimental so far, but at least a lot less code...
> 
> Gerd
> 
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> Gesendet: Dienstag, 30. März 2021 15:17
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] tile takes very long time to generate
> 
> Hi Gerd
> 
> I'm revising my opinion about considering the geometry to determine
> inner and outer.  All the different BitSets, containsMatrix etc logic
> is too complex, and if it then conflicts with the explicit definition
> of the MP it just gets worse.
> 
> I'd simpify it along these lines:
> 
>  split the polygon/joinedWay list:
>    error: the explicit conflicting inner/outer
>    inners: at least one inner element
>    outers: all the rest
> 
>  for each inner
>    find a larger_area outer that contains a part of it
>      add to the outer.listOfInners
>      error if more than one
> 
>  for each outer
>    cut out listOfInners
>    apply tags
>    output to the wayMap
> 
> This copes correctly with outer with inner hole that
> contains another outer. If, in the above logic, more than one larger
> outer is found, then choosing the smallest would allow this nesting
> to
> any level.
> 
> Ticker
> 
> On Thu, 2021-03-18 at 10:21 +0000, Gerd Petermann wrote:
> > Hi all,
> > 
> > I still struggle with the unit test because it's hard to say what
> > we
> > want to get in special cases.
> > The current code doesn't really work in the way that I expected. I
> > always thought that roles like "inner" and "outer" are completely
> > ignored and that mkgmap calculates and uses the correct roles. This
> > is only partly true. See attached file with MP were a forest
> > contains
> > a lake that contains a forest.
> > For a nested polygon where the innermost ring has wrong role
> > "inner"
> > this doesn't work as expected. The forest  in the lake is ignored.
> > With the correct role "outer" it is not ignored. No idea if this is
> > intended or an error. Fortunately nested MP are very rare.
> > 
> > Gerd
> 
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