RRTstar crashes when run on DubinsStateSpace

[ompl]

RRTstar crashes when run on DubinsStateSpace

[mamoll]

Original comment by Mark Moll (Bitbucket: mamoll, GitHub: mamoll).

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Dubins distance is not a metric. The default nearest neighbor data structure that RRT* uses assumes a metric, so you need to change the nearest neighbor data structure type:

#!c++

ompl::geometric::RRTStar* rrtstar = new ompl::geometric::RRTStar(setup.getSpaceInformation());
rrtstar->setNearestNeighbors<ompl::NearestNeighborsSqrtApprox>();
setup.setPlanner(ompl::base::PlannerPtr(rrtstar));

The reason you don't see the crash without your changes is that the default planner doesn't use a nearest neighbor structure.

See also http://ompl.kavrakilab.org/blog/?p=18. Let me know if this fixes things.

[mamoll]

Original comment by Luis G. Torres (Bitbucket: [Luis Torres](https://bitbucket.org/Luis Torres), ).

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That did the trick! Thanks for your help, Mark; I should've looked more closely at the documentation for the DubinsStateSpace.

[mamoll]

Original comment by Luis G. Torres (Bitbucket: [Luis Torres](https://bitbucket.org/Luis Torres), ).

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I needed to use a different nearest neighbors structure, since DubinsStateSpace's distance function does not define a proper metric. I wonder if there would be a way to indicate within a StateSpace class whether its distance function defines a metric, so that if the wrong nearest neighbor structure is used, an exception could be raised.

[mamoll]

Original comment by Mark Moll (Bitbucket: mamoll, GitHub: mamoll).

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Yes, something like that would be good to have. Better yet, the default nearest neighbor data structure could be automatically selected to be compatible with the properties of the state space. Let me think about that. Thanks for the suggestion.