Ignacio Vera created LUCENE-8583:
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Summary: Make GeoUtils#orientation method more stable
Key: LUCENE-8583
URL: https://issues.apache.org/jira/browse/LUCENE-8583
Project: Lucene - Core
Issue Type: Improvement
Components: core/other
Reporter: Ignacio Vera
The method GeoUtils#orient is problematic when called with points that are
almost collinear but not quite. In that case the sign of the determinant is not
reliable, so for example calling the method with points (a, b, c) and with (c,
b, a) gives the same orientation.
There is a complex implementation described here
(https://www.cs.cmu.edu/~quake/robust.html) where the method becomes more
reliable. I have been playing with such implementation and still is not 100%
reliable.
My proposal is not to be fully precise and define a precision constant for this
method. Therefore whenever the value of determinant is small to that precision,
we consider the points to be collinear. In this case the results of the method
are reliable.
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