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https://issues.apache.org/jira/browse/LUCENE-3582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13153197#comment-13153197
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Yonik Seeley commented on LUCENE-3582:
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We don't really support NaN as a value in Lucene in general I think. I know
that our sorting (priority queue) methods don't support NaN, and this is why
FunctionQuery has the following code:
{code}
// Current Lucene priority queues can't handle NaN and -Infinity, so
// map to -Float.MAX_VALUE. This conditional handles both -infinity
// and NaN since comparisons with NaN are always false.
return score>Float.NEGATIVE_INFINITY ? score : -Float.MAX_VALUE;
{code}
> NumericUtils.floatToSortableInt does not sort certain NaN ranges correctly.
> ---------------------------------------------------------------------------
>
> Key: LUCENE-3582
> URL: https://issues.apache.org/jira/browse/LUCENE-3582
> Project: Lucene - Java
> Issue Type: Bug
> Reporter: Dawid Weiss
> Assignee: Uwe Schindler
> Priority: Trivial
> Fix For: 4.0
>
> Attachments: LUCENE-3582.patch
>
>
> The current implementation of floatToSortableInt does not account for
> different NaN ranges which may result in NaNs sorted before -Infinity and
> after +Infinity. The default Java ordering is: all NaNs after Infinity.
> A possible fix is to make all NaNs canonic "quiet NaN" as in:
> {code}
> // Canonicalize NaN ranges. I assume this check will be faster here than
> // (v == v) == false on the FPU? We don't distinguish between different
> // flavors of NaNs here (see http://en.wikipedia.org/wiki/NaN). I guess
> // in Java this doesn't matter much anyway.
> if ((v & 0x7fffffff) > 0x7f800000) {
> // Apply the logic below to a canonical "quiet NaN"
> return 0x7fc00000 ^ 0x80000000;
> }
> {code}
> I don't commit because I don't know how much of the existing stuff relies on
> this (nobody should be keeping different NaNs in their indexes, but who
> knows...).
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