perf(isochrones): improve isochrones performance

[rtroilo]

Replacing ConcaveHullOpenSphere with jts own ConcaveHull algorithm

Pull Request Checklist

• 1. I have rebased the latest version of the master branch into my feature branch and all conflicts
  have been resolved.
• 2. I have added information about the change/addition to functionality to the CHANGELOG.md file under the
  [Unreleased] heading.
• 3. I have documented my code using JDocs tags.
• 4. I have removed unnecessary commented out code, imports and System.out.println statements.
• 5. I have written JUnit tests for any new methods/classes and ensured that they pass.
• 6. I have created API tests for any new functionality exposed to the API.
• 7. If changes/additions are made to the ors-config.json file, I have added these to the ors config documentation
  along with a short description of what it is for, and documented this in the Pull Request (below).
• 8. I have built graphs with my code of the Heidelberg.osm.gz file and run the api-tests with all test passing
• 9. I have referenced the Issue Number in the Pull Request (if the changes were from an issue).
• 10. For new features or changes involving building of graphs, I have tested on a larger dataset
  (at least Germany), and the graphs build without problems (i.e. no out-of-memory errors).
• 11. For new features or changes involving the graphbuilding process (i.e. changing encoders, updating the
  importer etc.), I have generated longer distance routes for the affected profiles with different options
  (avoid features, max weight etc.) and compared these with the routes of the same parameters and start/end
  points generated from the current live ORS.
  If there are differences then the reasoning for these MUST be documented in the pull request.
• 12. I have written in the Pull Request information about the changes made including their intended usage
  and why the change was needed.
• 13. For changes touching the API documentation, I have tested that the API playground renders correctly.

Fixes #1573.

Information about the changes

• Key functionality added:
• Reason for change:

Examples and reasons for differences between live ORS routes, and those generated from this pull request

Required changes to ors config (if applicable)

[aoles]

Some preliminary benchmarks are available here. Compared to the current master branch it looks quite promising. Apart from faster query times, the produced geometries seem to be more accurate as well. In particular, there seem to be less artifacts around long highway stretches.

[jhaeu]

Hi @aoles - the test combinationsAsGeojsonFiles was only a means to write isochrones results to files to make them visually comparable after code changes. But I think, the test could/should now be removed or at least @Disabled , it does not assert anything and it should not write files in the ci environment...?

[aoles]

Thanks @jhaeu! Sure, I have already addressed your concerns in bce8ff5 👍

[MichaelsJP]

@rtroilo @aoles @jhaeu Is this ready for review?

[aoles]

A comprehensive benchmark of 60 min car isochrones split into 3, 6, and 9 intervals across 100 locations in the DACH region suggests an average performance gain of around 25%.

Additionally, there seem to be an overall improvement to the geometries. Consider the following examples, where

• red is the new geometry produced by this feature branch
• blue is the current reference computed with the master branch.

^{Location 2}

^{Location 3}

^{Location 5}

^{Location 7}

^{Location 9}

[sfendrich]

LGTM!