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https://issues.apache.org/jira/browse/LUCENE-9139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17017853#comment-17017853
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Adrien Grand commented on LUCENE-9139:
--------------------------------------
The subtraction by-ay is indeed not accurate already in spite of the promotion
from floats to doubles since their exponents differ by more than the number of
mantissa bits of a double. And things might get worse with the multiplications.
I wonder if your proposal would actually address the problem though, the
problem is not that much the absolute values of the coordinates, but rather
their relative values. For instance I believe you could have the same issue if
we had some coordinates that are close but not equal to zero?
I haven't looked at the test, but how does it know that these lines don't
intersect, is it using better logic?
> TestXYMultiPolygonShapeQueries test failures
> --------------------------------------------
>
> Key: LUCENE-9139
> URL: https://issues.apache.org/jira/browse/LUCENE-9139
> Project: Lucene - Core
> Issue Type: Test
> Reporter: Ignacio Vera
> Priority: Major
>
> We recently have two failures on CI from the test method
> TestXYMultiPolygonShapeQueries. The reproduction lines are:
>
> {code:java}
> ant test -Dtestcase=TestXYMultiPolygonShapeQueries
> -Dtests.method=testRandomMedium -Dtests.seed=F1E142C2FBB612AF
> -Dtests.multiplier=3 -Dtests.slow=true -Dtests.badapples=true
> -Dtests.locale=el -Dtests.timezone=EST5EDT -Dtests.asserts=true
> -Dtests.file.encoding=US-ASCII{code}
> {code:java}
> ant test -Dtestcase=TestXYMultiPolygonShapeQueries
> -Dtests.method=testRandomMedium -Dtests.seed=363603A0428EC788
> -Dtests.multiplier=3 -Dtests.slow=true -Dtests.badapples=true
> -Dtests.locale=sv-SE -Dtests.timezone=America/Yakutat -Dtests.asserts=true
> -Dtests.file.encoding=UTF-8{code}
>
> I dug into the failures and there seem to be due to numerical errors in the
> GeoUtils.orient method. The method is detecting intersections of two very
> long lines when it shouldn't. For example:
> Line 1:
> {code:java}
> double ax = 3.314395000050712E38;
> double ay = -1.4151510014141656E37;
> double bx = 3.4028234663852886E38;
> double by = 9.641030236797581E20;{code}
> Line 2:
> {code:java}
> double cx = 3.4028234663852886E38;
> double cy = -0.0;
> double dx = 3.4028234663852886E38;
> double dy = -2.7386422951137726E38;{code}
> My proposal to prevent those numerical errors is to modify the shape
> generator to prevent creating shapes that expands more than half the float
> space.
>
>
>
>
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