[mkgmap-dev] new splitter branch solve-parallel

Wed Jun 30 20:21:19 BST 2021

I feel of all tiles are 85 percent of max then stop. If 5percent of tiles
are less the 75 percent max then maybe stop after 30 seconds. If more then
10 percent AND more then 10 tiles are less then 75 percent continue.

On Wed, 30 Jun 2021, 19:09 Gerd Petermann <GPetermann_muenchen at hotmail.com>
wrote:

> Hi all,
>
> I've started this branch to further improve the split results.
> Splitter has two different algorithms to find good splits.
> 1) Algo FULL tries first to split in the middle and then continues with
> the next positions (mid+1, mid-1, mid+2, mid-2, ...)
> The resulting parts are split again recursively. This should find the best
> possible split but can take very long when the only good split starts far
> from the middle.
>
> 2) Algo SOME uses some heuristics to test only some of the possible
> splits. This is typically much faster but sometimes doesn't find any
> solution and sometimes the FULL algo finds a better solution.
>
> The trunk version tries first the one that is more promising and - if that
> fails to find a good split - tries the other. So, sometimes the FULL algo
> works for 2 minutes and then SOME finds a good result in a few seconds.
>
> This branch executes both algorithms in parallel and uses the better
> result.
>
> One of the open problems is to decide under what conditions the execution
> should stop.
> If the SOME algo finds a good solution within 20 secs should we still
> continue the FULL algo to find the best solution? If yes, how long?
> I'm playing with this, any input is welcome.
>
> Gerd
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