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From "Matt Juntunen (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (GEOMETRY-11) Replace tolerance with GeometryContext
Date Sat, 22 Dec 2018 03:57:00 GMT

    [ https://issues.apache.org/jira/browse/GEOMETRY-11?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16727203#comment-16727203
] 

Matt Juntunen commented on GEOMETRY-11:
---------------------------------------

Yeah, the name is not so great. It should be something that implies that the class contains
state that is used as a basis for comparing doubles. Perhaps we could make {{Precision}} instantiable
and use that. You could then just use it for the static methods or create an instance with
your own epsilon and ulps values. Thoughts?

> Replace tolerance with GeometryContext
> --------------------------------------
>
>                 Key: GEOMETRY-11
>                 URL: https://issues.apache.org/jira/browse/GEOMETRY-11
>             Project: Apache Commons Geometry
>          Issue Type: Wish
>            Reporter: Matt Juntunen
>            Priority: Major
>             Fix For: 1.0
>
>
> All of the partitioning-related concrete classes (ex: Plane, PolygonsSet, PolyhedronsSet,
etc) use a double value named tolerance in order to address issues with floating point accuracy.
For example, when determining if a point lies in a plane, the point does not need to lie exactly
on the plane but just be within +- tolerance distance from it. Code testing values against
each other using this toleranceĀ isĀ repeated throughout the code base (ex: x >= y - tolerance).
We should abstract the concept of the tolerance into a GeometryContext class and provide methods
for testing values against each other using the tolerance. This will reduce the chance of
bugs and will also allow for more sophisticated handling of floating point accuracy later
on.
> The GeometryContext class would be similar to the MathContext class used by BigDecimal
but would contain the logic for making comparisons in addition to the configuration for the
comparisons.
> {code:java}
> public class GeometryContext {
>    public GeometryContext(tolerance){...}
>    public double getTolerance(){ ... }
>    // return -1, 0, +1
>    public int compare(double a, double b) { ... }
> }{code}



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