[mlpack] Numeric sensitivity of RangeSearch

[Ryan Curtin]

On Tue, Mar 25, 2014 at 04:35:18PM +0800, Li Dong wrote:
> Dear all,
> 
> I have used RangeSearch to search neighbours on the sphere surface.
> Previously, the radius of sphere is set to 1, so the Cartesian
> coordinate range (I convert spherical coordinate to Cartesian
> coordinate for searching) is from -1 to 1. In real applications, the
> radius of the Earth is around 6.371e6, and the Cartesian coordinate
> range is also from -6.371e6 to 6.371e6. The problem that I am facing
> is when radius is 6.371e6, many neighbours are not found by
> RangeSearch.
> 
> I have uploaded the result comparison in
> https://gist.githubusercontent.com/dongli/9634592/raw/cb3e6cdf85758594be15fabd7fa61d73ac4ecf3e/rangesearch_numeric_problem.png,
> where the blue circle represents the range (approximately), and red
> points are the neighbours. The only difference is the radius.

Hi Li,

I have tried to generate a similar example, running range search first
on a similar-looking dataset normalized to [-1, 1], and then
renormalized to [-6e6, 6e6], but the results were the same.  Can you
give more information on your dataset or some way to reproduce the error
so I can look into it further?

Thanks,

Ryan

-- 
Ryan Curtin    | "I like this game."
ryan at ratml.org |   - Coach