[
https://issues.apache.org/jira/browse/NUMBERS-90?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16752918#comment-16752918
]
Matt Juntunen commented on NUMBERS-90:
--------------------------------------
These classes are meant to replace the usage of {{tolerance}} values in
commons-geometry. When users create instances of classes like {{Plane}} and
{{Line}}, they currently pass in a tolerance double value that essentially
defines the "thickness" of the hyperplane. For example, if the distance of a
point from the hyperplane is less than the tolerance, then the point belongs to
the hyperplane. The value is also used in various other floating point
comparisons and is exactly like the absolute epsilon in the
{{EpsilonDoublePrecisionContext}} class in this PR. I wanted to move away from
passing raw double values as tolerances in commons-geometry and instead use
classes so that 1) we could avoid all of the duplication of expressions such as
{{if (Math.abs(a - b) <= tolerance)\{ ... }}} and 2) so that the library could
be extended later with other floating point comparison strategies. Users could
then choose the comparison strategy that works best for the types of numbers
used in their applications.
So, all of this to say, these classes can't be internal. Users will need to
create instances of them to pass to other commons-geometry types.
{quote}Assuming you have two *very* large cubes next to each other, how do
define whether they have a common face?
{quote}
The logic is the same for any size of cubes. In order to help avoid floating
point comparison issues, users need to choose an appropriate tolerance value
(current behavior) or precision context (after this PR and GEOMETRY-11) for
their particular application.
> DoublePrecisionContext
> ----------------------
>
> Key: NUMBERS-90
> URL: https://issues.apache.org/jira/browse/NUMBERS-90
> Project: Commons Numbers
> Issue Type: New Feature
> Reporter: Matt Juntunen
> Priority: Blocker
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> We should add a new class to commons-numbers-core that encapsulates
> configurable strategies for comparing doubles. This is required for
> GEOMETRY-11. Here is what I'm picturing:
> {code:java}
> // abstract class for the general concept of comparisons
> public abstract class DoublePrecisionContext implements Comparator<Double> {
> public abstract boolean equals(double a, double b);
> public int compare(double a, double b) { /* ... */ }
> public int compare(Double a, Double b) { /* ... */ }
> }
> // ...
> // concrete class implementing a specific strategy
> public class EpsilonUlpDoublePrecisionContext extends DoublePrecisionContext {
> public EpsilonUlpDoublePrecisionContext(double eps, double maxUlps) { /*
> ... */ }
> @Override
> public boolean equals(double a, double b) { /* ... */ }
> } {code}
> Pull request: https://github.com/apache/commons-numbers/pull/28
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
